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Laser additive manufacturing of IN625 coating protects the metal substrate effectively, especially in corrosive and abrasive environments. This study investigates the microstructure of IN625 coating, analyses the coating's tribocorrosion behavior in 3.5 wt% NaCl, and reveals the failure mechanism. The results show that wear significantly enhances corrosion. As the condition changed from unworn to tribocorrosion under a load of 10 N, the passive current density (i pass) increased from 6.01 × 10−6 to 1.10 × 10−4 A/cm2, but the occurrence of wear paradoxically elevates the pitting potential due to surface damage and solution disturbance. The micro-galvanic corrosion between dendrites and interdendrites, between Laves/Al 2 O 3 phases and the IN625 matrix, as well as macro-galvanic corrosion between worn and unworn areas, directly accelerate the degradation of the IN625 coating. Meanwhile, the dynamic damage and regeneration of the passive film caused by corrosion accelerates the wear as well. [Display omitted] • IN625 coating prepared by laser additive manufacturing technology. • Differences in pure mechanical wear and tribocorrosion behavior were compared. • Wear significantly increases the i pass but paradoxically elevates the E p. • Connecting the microstructure of IN625 coating to the tribocorrosion mechanism. [ABSTRACT FROM AUTHOR]

Erosion-corrosion is a complex problem causing severe damage of austenitic stainless-steel equipment used in phosphoric acid production. Herein, time-resolved analyses of the acoustic emission (AE) signal together with the corrosion potential and weight loss were performed to online monitor and evaluate the dynamic degradation and depassivation of the 904L stainless steel under the effect of abrasive SiC particles. Important insights into the erosion-corrosion process are gained from the analysis of the AE waveform and its parameters. The characteristic root mean square (RMS) voltage and acoustic energy of AE signals revealed the self-healing difficulty of the passive film, of which the waveform of AE signals showed the appearance of imperfect continuous high intensity waveform, ranging from 0.1 to 0.4 mV. Evaluation of the average frequency spectrum showed that the amount of SiC particles alters the damage mechanism from AE events dominated by ploughing to AE events driven by micro-cutting. This suggests that the imperfect continuous waveform is possibly a precursor to the emergence of new acoustic sources (burst type): sudden jumps of chips from the cutting lips. This response resulted in a quasi-linearity in the mass loss of the alloy with the respective acoustic response at high particle loading (24 g L−1). The non-linear erosion-corrosion behavior suggests that the depassivation-repassivation events are dependent. These results render the combined AE and electrochemical analysis an effective sustainable approach for the online investigation of the synchronously changing erosion and corrosion rates. [Display omitted] • The dynamic evolution of stainless-steel degradation under erosion-corrosion conditions was unraveled. • Combined acoustic emission (AE) and corrosion potential measurements revealed the extension of surface depassivation and the difficulty of self-healing of the passive film. • At higher SiC loadings, the AE signals showed a high-intensity imperfect continuous waveform. • Analysis of the frequency spectrum and surface morphology demonstrated that the amount of SiC alters the surface damage mechanism. • Weight loss data and acoustic emissions signals are nicely correlated during erosion-corrosion. [ABSTRACT FROM AUTHOR]

The article presents a study of tribocorrosion resistance of AISI 420 steel in extracts of allium cepa (onion juice). The tests were conducted for 3 variants of heat treatment and two ball pressures of 4.5 and 14 N on a ball-on-plate test stand. For all AISI 420 martensitic steel specimens tested in tribocorrosion tests, a clear friction-corrosion synergy effect was found, ranging from 30 to 60 % of total tribocorrosion wear. The lowest mechanical wear was found for samples after low-temperature tempering at 200 °C (54 HRC). Under tribocorrosion conditions, samples after medium-temperature tempering at 400 °C (51 HRC) were more resistant to wear. The results of the tests were used to make an onion-cutting blade, which found industrial application in one of the food industry factories. • Tribocorrosion tests were performed in the extracts of allium cepa of AISI 420 steel. • Specimen with different properties as a result of tempering temperatures were tested. • The highest hardness does not provide the best resistance to tribocorrosion process. • A model of tribocorrosion in the extracts of allium cepa was formulated. [ABSTRACT FROM AUTHOR]

Ni-W composite coatings that are applied using electrodeposition exhibit excellent mechanical strength, corrosion resistance and wear resistance and are a substitute for hard chrome because they involve fewer environmental hazards than regular chromium plating processes. This study determines the effect of process parameters, such as current density (5, 10 and 15 A/dm2) and SiC concentration (0.5, 1.0 and 1.5 g/L), on the chemical composition, structure, mechanical properties and corrosion resistance of electrodeposited Ni-W/SiC composite coatings and determines the interaction between the mechanical behavior and the electrochemical reactions that occur during corrosion and friction. The experimental results show that there are no cracks on the surface of the coating and that the surface roughness increases as current density increases. As the content of W and SiC particles in the composite coating increases, the hardness and corrosion resistance of the coating increase because of solid solution strengthening and nano-ceramic particle dispersion strengthening. In order to verify the protective performance of the coating in complex environments, a ball-on-disk abrasion tester and a potentiostat are used to determine the tribocorrosion behavior of the Ni-W/SiC composite coating against the sliding of the Al 2 O 3 counter-body. In 3.5 wt%NaCl solution and at +600 mV, the corrosion and wear characteristics of composite coatings that are produce using different process parameters are determined. Analysis of the synergistic effects of corrosion and friction shows that the wear component (△W wear) is 3–5 times greater than the corrosion component (△ Wcorr), which is the main cause of coating damage. The greater the hardness of the coating, the less mass is lost for the wear component (△W wear). The results show that the operating parameters for producing ideal Ni-W/SiC composite coatings are a SiC particle concentration 1.0 g/L and a current density of 10A/dm2. These settings give the best wear resistance in corrosive environments. • SiC nanoparticle-enhanced Ni-W/SiC composite coatings are produced using electrodeposition. • Ni-W/SiC composite coating exhibits good tribocorrosion resistance due to its high hardness and corrosion resistance. • The synergistic wear and corrosion of electrodeposited Ni-W/SiC composite coatings in 3.5 % NaCl solution is determined. [ABSTRACT FROM AUTHOR]

In heat exchanger applications, the random vibration due to fluid excitation can cause mechanical wear between tubes and supports. In corrosive environments, the synergy between wear and corrosion can make wear more severe. Therefore, this paper focused on the effects of excitation amplitude and excitation force ratio (drag force/lift force) on fretting wear and corrosion of 316L stainless steel under random impact-sliding conditions. The results showed that as the excitation parameters increased, the friction coefficient and total wear amount would increase, the open circuit potential (OCP) decreased and the polarization curve self-corrosion potential shifted negatively. All synergistic coefficients in this paper were greater than 1, indicating that there was an obvious positive synergy between wear and corrosion. In the fretting wear and corrosion process, pure wear always played a dominant role. Under impact-sliding conditions, as the excitation force increased, the rate of wear-promoted corrosion increased from 3.0 × 10−7 to 2.0 × 10−6 g/h, an increase of 6.67 times. However, the rate of corrosion-promoted wear decreased from 1.1 × 10−6 to 2.0 × 10−7 g/h, a decrease of 5.5 times, showing a certain self-limiting property. The total synergy rose slowly with the increase of excitation parameters. The wear mechanism of materials under impact is characterized by adhesive wear, while under impact-sliding conditions, the wear mechanism involves abrasive wear and corrosion wear. • This paper explores the wear mechanism and the synergy between wear and corrosion. • As the excitation parameters increase, the total wear volume loss increases. • The wear mechanism under impact and impact-sliding is adhesive wear and abrasive wear respectively. • All synergistic coefficients are greater than 1, pure wear plays a dominant role in wear and corrosion. • The effect of corrosion in promoting wear decreases as the excitation force increases. [ABSTRACT FROM AUTHOR]

CoCrMo has been used as an implant material for a long time due to its excellent combination of strength, corrosion resistance and biocompatibility. The formation of a thin passive oxide film on the surface of the material plays a crucial role in its performance. This passive film can be ruptured during contact between two surfaces, but usually reforms in short timescales. However, the reformation of the film depends on the availability of oxygen in the surrounding fluid. The oxygen level in human tissue, cartilage and synovial fluid, around which the implant is situated, is much lower than that in laboratory testing under open-air conditions. Moreover, the local oxygen concentration and pH values in the body vary from patient to patient, depending on the patient's health condition and other factors, which leads to variation in the corrosion resistance of metallic implants. Therefore, an implant that performs well at one time may still experience an undesirable level of corrosion at another. Thus, evaluation of the tribocorrosion of implant materials carried out in open-air conditions does not reflect the actual process the implants undergo once in the body, particularly if there is irritation due to injury or surgery. In this study, we investigate the tribocorrosion behaviour of CoCrMo in bioactive solutions under fully aerobic to anaerobic conditions with varying loads/contact pressures. The anaerobic condition leads to a reduction in wear rate and a reduction in the extent of tribofilm formation but does not have an appreciable effect on friction. The mechanisms are discussed in detail. • Anaerobic conditions lead to lower wear rates in the sliding of CoCrMo alloys lubricated by bovine serum solution. • The presence of a surface oxide in open-air sliding leads to greater surface strain than under anaerobic conditions. • Anaerobic conditions led to greater dissolution of Mo into the lubricant than in open-air conditions. • In open-air the wear debris was mainly a Cr based oxide; in anaerobic conditions debris was a complicated Cr rich structure. [ABSTRACT FROM AUTHOR]

NiTi alloy is widely used in extreme working conditions due to its pseudoelasticity, shape memory effect and wear resistance. In this study, the NiTi alloy coating (Ni49.8Ti50.2 (at%)) was fabricated by high-frequency induction heating. The coating was well-formed on the surface of cemented carbide YG8 and converted to crystalline after aging treatment. The results of 70h erosion wear experiments carried on the rotary erosion wear test device showing that the erosion wear amount of the coating was reduced by 93 % compared with that of YG8, resulting from the deformation recovery effect. Moreover, the main erosion wear mechanism of the coating was micro-cutting and ploughing. This study can provide technical support and theoretical basis for preparing of NiTi alloy coating and erosion wear resistance. • The coating was prepared using high-frequency induction heating technology. • The coating has better erosion and wear resistance at different test temperatures. • The ability of recoverable deformation improves the erosion wear resistance of the coating. [ABSTRACT FROM AUTHOR]

An Inconel 690 alloy tube acting as a steam generator tube has been widely applied in the second and third generations of nuclear power plants using pressurized water reactors. However, its entire service process is always accompanied by high-temperature and high-pressure (HTHP) liquid medium corrosion and various fretting mechanical damage behaviors. This study first immerses the Inconel 690 alloy tube in HTHP corrosive medium for different lengths of time (0, 4, 8, and 12 h); then, a fretting tribo-corrosion test rig is used to investigate the effect of different fretting mechanical parameters on the surface damage mechanism and electrochemical dynamic response of each test sample. Results show that the corrosion rate of the Inconel 690 alloy tube has significantly increased after being treated by HTHP immersion corrosion, which is mainly due to the pre-existing corrosion products. • 1.HTHP immersion corrosion duration influence alloy tube's fretting tribo-corrosion behaviors was investigated. • Electrochemical corrosion dynamic response of the fretting surface was studied. • Interactive effect between fretting wear and electrochemical corrosion was investigated. [ABSTRACT FROM AUTHOR]

The (AlCoCrFeNi) x /(WC–10Co) 1- x , (x = 100 wt%(HW1), 75 wt%(HW2), 50 wt% (HW3)) composite coatings are fabricated on 3Cr13 martensite stainless steel using high velocity oxy-fuel (HVOF) spraying technology, and the tribocorrosion experiment is carried out in artificial seawater. The tribocorrosion mechanism of the coatings and counterbody are analyzed. Particularly, the synergistic effect of corrosion and wear is explored using the ASTMG119. The introduction of WC-10Co improve the microhardness of the composite coatings, but decrease their corrosion resistance, which are due to the galvanic corrosion of the WC-10Co and HEA. Notably, the results of synergistic effect show that the corrosion of the HW1 coating has an inhibitory effect on wear. The volume loss of tribocorrosion increase with the introduction of WC-10Co, with the HW3 coating experiencing a volume loss of only 46 % compared to that of 3Cr13. The HW1 coating mainly suffers from abrasive wear, surface fatigue wear and adhesive wear. The main wear mechanism of the HW2 and HW3 coatings are abrasive wear, while the fatigue wear is enhanced with the participation of WC-10Co. And the counterbody of the three coatings mainly suffers abrasive wear. • The dense (AlCoCrFeNi) x /(WC–10Co) 1- x composite coatings are prepared by HVOF spraying technology. • The tribocorrosion experiment of the coatings and 3Cr13 are carried out in artificial seawater. • The synergistic effect of corrosion and wear is evaluated using the ASTMG119. • The galvanic corrosion of the WC-10Co and HEA coating is investigated. [ABSTRACT FROM AUTHOR]

The Ti6Al4V alloy is extensively utilized in critical marine equipment components due to its low density, high specific strength, and exceptional corrosion resistance in marine environments. However, its low hardness and inadequate wear resistance pose challenges in meeting the urgent demand for prolonged service life of relative motion friction pairs under complex wear and corrosion conditions. As a newly developed lightweight friction pair material, hardened 60NiTi is considered highly desirable owing to its combination of high hardness, high compressive strength, and excellent corrosion resistance. Nevertheless, the tribocorrosion properties of 60NiTi compared to those of Ti6Al4V are not yet fully comprehended. The present study conducted a series of sliding wear tests using a ball-on-plate configuration in artificial seawater environment to compare the response of 60NiTi with Ti6Al4V. In order to gain a comprehensive understanding of the factors contributing to the divergence in tribocorrosion response between both materials, further analysis was performed on the wear track subsurface and transfer film using focused ion beam-scanning electron microscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy respectively. The 60NiTi demonstrates significantly enhanced wear resistance in artificial seawater compared to Ti6Al4V, attributed to its combination of high hardness and excellent corrosion resistance. However, Ti6Al4V exhibits a lower friction coefficient (∼0.30) than 60NiTi (∼0.45) due to the formation of a stable transfer film primarily composed of SiO 2 , Al(OH) 3 , and Al 2 O 3. • The wear-accelerated corrosion resistance of 60NiTi surpasses that of Ti6Al4V. • The tribocorrosion loss of 60NiTi is lower than that of Ti6Al4V by an order of magnitude. • The wear form of Ti6Al4V and 60NiTi exhibit distinct differences during the tribocorrosion. • The lubricating film can be generated when Si 3 N 4 ball slides against Ti6Al4V disc in seawater. [ABSTRACT FROM AUTHOR]

Tribocorrosion tests were performed on the Cast and SPS Ni20Cr alloys sliding against Si 3 N 4 in 3.5 wt% NaCl solution to investigate the grain size effect on the synergy of corrosion and wear. An appealing result was that the SPS alloy with finer grains exhibited less intense corrosion-induced wear, but more severe wear-induced corrosion, compared to the coarse-grained Cast alloy. The mechanism responsible for the significant difference was attributed to the composition and microstructure of the tribo-layer influenced by grain refinement. The finer grain structure facilitated the rapid replenishment of thicker Cr-rich tribo-layer, while meanwhile the dense layer exhibited high hardness and greatly reduced the wear rate of SPS alloy. • Tribocorrosion behaviors of the Cast and SPS Ni20Cr alloys were investigated, focusing on the grain size effects. • The SPS alloy with finer grain structure displays lower wear rate and COF during tribocorrosion. • The SPS alloy exhibit less intense corrosion-induced wear, but more violent wear-induced corrosion. • The rapid replenishment of thicker and denser Cr-rich tribo-layer greatly reduces the wear rate of SPS alloy. [ABSTRACT FROM AUTHOR]

To suppress the corrosion and wear of cylinder liner of marine diesel engine burning low sulfur fuel, potassium borate/graphene lubricant additive was prepared by plasma assisted ball milling. Tribological tests were conducted by simulating operating condition of diesel engine to evaluate the anti-friction/wear and anti-corrosion properties of potassium borate/graphene additive. The effect of additive on cylinder liner corrosion and wear was verified by bench test of diesel engine. The results of tribological tests indicated tribochemical reaction occurred on the surface of the cylinder liner-piston ring and generated a tribochemical film composed of graphene, FeO, Fe 2 O 3 , Fe 3 O 4 , B 2 O 3 and Fe 2 B with anti-friction/wear and anti-corrosion properties. Bench test shown that potassium borate/graphene additive had good anti-friction/wear and anti-corrosion functions, and reduced fuel consumption and exhaust emissions of the engine. • The cylinder liner, piston ring, cylinder oil and cylinder oil residue obtained from the vessel of "Han Ren" were used as experimental lubricating oil and experimental materials.The cylinder liner, piston ring, cylinder oil and cylinder oil residue obtained from the vessel of "Han Ren" (Type of vessel: general cargo ship. Power source: diesel engine. Type of the application engine: MAN B&W 6S42MC7) were used as experimental lubricating oil and experimental materials. • The anti-friction/wear and anti-corrosion properties of PB/GN in cylinder oil and cylinder oil residue under different working conditions were studied by using disk-pin friction pair to simulate the reciprocating movement of cylinder liner and piston ring of marine diesel engine burning low sulfur fuel. • The suppression effect of PB/GN on cylinder liner wear and corrosion under diesel engine combustion condition were verified by bench test. • The anti-friction/wear and anti-corrosion mechanism of the additive was studied by surface analyses (SEM, EDS, Raman and XPS) of the worn surface under different load and different temperature. [ABSTRACT FROM AUTHOR]

The drawbacks of commonly used metallic biomaterials like the release of toxic ions for the CoCrMo alloy and poor wear resistance for Ti-based alloys make it necessary to find a better metallic material as a new candidate for orthopaedic applications. In this work, different characterisation techniques were employed to investigate the relevance of a recently suggested TiNbTaZr HEA for orthopaedic applications. TiNbTaZr exhibited excellent mechanical properties and outstanding electrochemical behaviour. However, no significant enhancement in tribocorrosion wear behaviour is observed of TiZrNbTa over Ti6Al4V alloy, but the two materials exhibit different in-situ repassivation behaviour during tribocorrosion testing. A new approach of using the electrochemical noise EN technique in tribocorrosion investigation and data analysis is suggested. • TiNbTaZr HEA does not exhibit better tribocorrosion behaviour when compared with the cheaper and readily available Ti6Al4V alloy. • Using wavelet transform WT in electrochemical noise technique EN data analysis could be a useful and promising approach in detecting tribocorrosion mechanism. • A relation between the COF and depassivation/repassivation process during tribocorrosion is observed. [ABSTRACT FROM AUTHOR]

Cashew Nut Shell Liquid (CNSL) has been explored in several applications within the sustainability principles and circular economy of agro-industrial product waste. To understand the anticorrosive and lubricant properties of CNSL solutions, a multi-faceted approach, incorporating electrochemical analyses, immersion test, tribological measurements, and tribochemical characterization was carried out for mild steel AISI 1012, stainless steel AISI 420 and Aluminium Alloy 6061. Electrochemical analyses reveal a positive impact of CNSL, inducing a shift in corrosion potential to more positive values and a decrease in corrosion current, indicating effective corrosion inhibition for stainless steel and aluminium alloy. In mild steel, CNSL exhibits a mixed-type inhibition with efficiency increasing in correlation with oil concentration. The lubricating properties of CNSL are evident according to the coefficients of friction (COF) obtained and the elastohydrodynamic lubrication regime observed during tribological tests. Tribochemical tests demonstrate a reduction in wear and an improvement in tribocorrosion behavior under sliding conditions. CNSL emerges as a promising tribocorrosion mitigator, demonstrating multifaceted benefits. The concentration-dependent effects highlight the need for optimization in specific applications, particularly for passive materials. CNSL not only inhibits corrosion through film formation but also provides effective lubrication, reducing friction, wear, and chemical-mechanical degradation. This research contributes valuable insights to corrosion science. It proposes practical applications for CNSL in diverse industrial contexts, showcasing its potential as an environmentally friendly and sustainable solution for tribocorrosion challenges. • The influence of Cashew Nut Shell Liquid (CNSL) on the tribocorrosion behavior across three metallic alloys (mild steel, stainless steel, and aluminium) is explored. • Electrochemical analyses, immersion test, tribological measurements, and tribochemical characterization was carried out for AISI 1012, AISI 420 and AA6061. • CNSL exhibited a positive impact on corrosion inhibition for stainless steel and aluminium alloy, inducing a shift in corrosion potential to more positive values and a decrease in corrosion current. • CNSL demonstrated lubricating properties according to the coefficients of friction (COF) obtained and the elastohydrodynamic lubrication regime observed during tribological tests. • CNSL emerges as a promising tribocorrosion mitigator, demonstrating multifaceted benefits. [ABSTRACT FROM AUTHOR]

Gate valve is one of the most common design concepts in onshore Oil & Gas installations. This equipment is composed of a wedge-shaped obturator that performs linear sliding movements during activation. Fluid sealing is achieved through metallic contact between the surfaces of the gate and seat components. Metal surfaces are commonly hardened by heat treatment or coated with Stellite 6 alloy by plasma-transferred arc welding (PTAW). The application of high-velocity oxygen fuel (HVOF) coatings on these surfaces for wedge-gate valves has not yet been foreseen. In addition, comparative studies on the tribological performance of technical surfaces used in onshore wedge-gate valves are also scarce. Therefore, this study presents the results of tests performed on specimens using a ball-on-flat tribometer with linear reciprocating sliding, simulating a gate valve tribosystem in operation: flat (gate) and ball (seat). Martensitic stainless steel 13Cr was used with the contact interfaces under the following conditions: (A) heat treated, (B) Stellite 6 coating by PTAW, (C) Stellite 6 coating by HVOF, and (D) tungsten carbide coating by HVOF. The flat/ball tribological pairs investigated were A/B (TRIM 8), B/B (TRIM 5), C/B, and D/B. The coefficient of friction (COF), surface wear, and wear mechanisms were comparatively evaluated. The results showed that the newly proposed surfaces (C and D) are promising alternatives to reduce material consumption and improve the performance of valves in operation according to the application requirements. • Ball-on-flat test were carried out for tribological surfaces of gate valves. • Tribological performance of HVOF spray coating in surfaces of gate valves. • Adhesive wear and material pull-out in martensitic stainless steel were identified. • Adhesion, transfer film formation and abrasive wear occurred in Stellite 6. [ABSTRACT FROM AUTHOR]

To improve the nitrogen-expanded crystalline structure, tribological and anti-corrosion properties in industrial field, nitrogen atoms were incorporated into 65Mn steel by plasma nitriding. In this study, 65Mn steel was processed using a plasma nitriding method at 600 °C for the improvement of tribocorrosion resistance. The structural evolutions, chemical elements and chemical bonds of obtained nitrided sample were investigated using a scanning electron microscope, electron dispersive spectroscopy and X-ray photoemission spectroscopy, respectively, and the effects of normal load on the coefficient of friction and wear rate in 0.1 mol/L Ca 3 (PO 4) 2 solution were investigated using a reciprocating ball-on-plate wear tester. The polarization and electrochemical impedance spectroscopy of nitrided sample in Ca 3 (PO 4) 2 solutions were conducted using an electrochemical workstation. The results show that the average coefficients of friction of nitrided samples are decreased from 1.047 to 0.420, and the corresponding wear rates are ranging from 6.274 to 11.250 under the normal loads of 2–10 N. The presence of nitrided layer originated from the plasma nitriding process plays roles of the high hardness and excellent tribocorrosion resistance. The wear mechanism is a combination of abrasive wear and adhesive wear, which is attributed to the formation of hard nitrides. Moreover, the corrosion resistance of nitrided sample is improved by the formation of passive film and the band gap energy of Fe 4 N. • The tribocorrosion and electrochemical properties of plasma nitrided 65Mn steel are improved by LR. • The charge transfer resistance of plasma nitrided 65Mn steel is larger compared with the original 65Mn steel. • The tribocorrosion and corrosion models of nitrided 65Mn steel are revealed by the DFT calculation. • The enhancement of wear and corrosion properties is attributed to the Fe 4 N phases with larger band gap energy. [ABSTRACT FROM AUTHOR]

A five-day erosion-corrosion study was conducted to investigate the effect of particle concentration on surface roughness of AISI 1018 steel elbows. Tests were performed in a flow loop containing 10, 20 or 30 wt.% particle concentration and saturated potash brine at a slurry flow velocity of 4 m/s. Optical profilometry analysis showed that surface roughness was higher at the entry region of the elbows than those of the middle and exit regions. Scanning electron microscope images of the worn surfaces revealed the presence of gullies and islands on the entry regions at low particle concentration, but ridges and valleys were formed on the middle and exit regions at higher particle concentrations. In general, results showed that surface roughness, mass loss and hardness at the exit regions increased with increasing particle concentration. Image 1 • Effect of solid particle on surface roughness and hardness of an elbow was studied. • Average surface roughness of the elbow entry region was higher than the exit. • Ridges and valleys formed on the elbow inner wall at high particle concentration. • Impingement of particles on the elbow work hardened the surface. • Work hardening increased resistance to erosion-corrosion attack. [ABSTRACT FROM AUTHOR]

Bushing wear is regarded as the main cause of Variable Stator Vanes (VSV) mechanism failure in compressor airflow control systems. In order to examine the bushing health status, a new tribometer was designed to evaluate the bushing frictional performance under various working conditions. These include high temperature, changing axial load, and reciprocating rotation. The prototype apparatus was validated in real-world operation conditions. Results indicate that key test environment parameters were well controlled during the operation. Bushing made of SP2515, SCP5050 and SCP50094 were tested at 364 °C. It is found that transfer films were formed because of polyimide adhesion on the spindle contacting surface. Furthermore, the wear coefficient of the special contact configuration was derived. Assessment based on frictional torque and wear resistance, SP2515 demonstrated the best tribological performance though polyimide is not applicable in the testing temperature. • A new tribometer was designed to evaluate the frictional performance of the bushing under the similar working conditions. • The reciprocating rotation was achieved by the sinusoidal reciprocating motion mechanism. • Description of a fast heating system with the ceramic heater rollers and cooling fan. • The wear coefficient of reciprocating rotation between a cylinder and a cylindrical ring was derived. [ABSTRACT FROM AUTHOR]

In the aluminium processing industry, the tribo-corrosion of a metal by molten aluminium or its alloys is an urgent problem, as the removal of the corrosion products leads to material losses and even failure. Therefore, a novel Fe-15.3 wt % Cr-3.1 wt % B-6.2 wt % Mo alloy was designed, and its interfacial morphologies and tribo-corrosion behaviour in molten aluminium at 750 °C under different experimental rotation speeds and loads were systematically investigated to understand the effect of molten aluminium via the ring-on-block test (the counter-body, which was 50% of the sliding couple, was produced by Si 3 N 4). The results show that the designed alloy exhibits better tribo-corrosion resistance than H13 steel does (for example, at a load of 10 N and a rotation speed of 300 mm s−1, the volume loss rate of the novel Fe-15.3 wt % Cr-3.1 wt % B-6.2 wt % Mo alloy is 87.5% lower than that of H13 steel) due to the protective capability of the M 2 B-type (M = Fe, Cr, Mo) boride. The scanning electron microscopy (SEM), X-ray diffractometer (XRD), electron probe microanalyses (EPMA) and transmission electron microscope (TEM) analyses of the tribo-corrosion interface indicated that the tribo-corrosion of the designed alloy in molten aluminium involved physical, chemical and mechanical processes. The wear-induced mechanical effect exacerbated the tribo-corrosion interface via the initiation and propagation of micro-cracks. Meanwhile, the wear-intensified mechanical effect resulted in the failure of the M 2 B-type boride, which in turn facilitated matrix corrosion and accelerated tribo-corrosion. • The M 2 B-type (M = Fe, Cr, Mo) borides play an important role in the corrosion-wear process of Fe-15.3 wt % Cr-3.1 wt % B-6.2 wt % Mo alloy in molten aluminium. • The tribo-corrosion process of the designed alloy mainly involves corrosion of the matrix, destruction and removal of Fe-Al corrosion products and the failure of boride phases. • The tribo-corrosion resistance of the designed alloy is mainly dependent on the interface structure. • Intensified wear-induced mechanical effect accelerates the destruction of the boride phases and Fe-Al corrosion products. [ABSTRACT FROM AUTHOR]

Erosion-corrosion degradation in oil and gas pipelines is a significant problem, and a change in flow geometry can significantly enhance rates of degradation. In this study, a 3D printed 90° elbow, integrated into a flow loop, was developed to evaluate erosion-corrosion of X65 carbon steel along both the inner and outer internal portions of the bend in an aqueous carbon dioxide (CO 2)-saturated environment containing sand particles. Designing representative geometries capable of measuring rates of corrosion, erosion and their synergistic interactions, can be challenging and currently no designs have been reported in literature that effectively integrate the required measuring techniques to determine local degradation rates throughout the component. To elucidate the individual contributions to overall erosion-corrosion degradation rates, gravimetric and electrochemical measurement techniques were used to quantify degradation rates at multiple locations in the flow geometry, with the specimen design also enabling the possibility of completing acoustic emission measurements to detect particle impacts. The design of the elbow is presented and erosion-corrosion tests were conducted to determine the magnitude and individual contributions of erosion, corrosion and erosion-corrosion interactions at a flow velocity of 6 m/s in a CO 2 -saturated, pH 4, 60 °C, 2 wt% NaCl solution containing 1000 mg/L of sand particles. • A 90° elbow is designed and 3D printed for erosion-corrosion testing. • Experiments conducted in conditions representative of field conditions. • Twelve carbon steel specimens are flush-mounted into the elbow for measurement. • Integrated measurement techniques enable multiple wear mechanisms to be quantified. • Erosion, corrosion and synergistic degradation is quantified at different locations. [ABSTRACT FROM AUTHOR]

The erosion-corrosion behavior of X65 pipeline steel was studied using a novel designed ring pair electrical resistance sensor (RPERS) array in conjunction with linear polarization resistance (LPR) measurement within a flow loop containing 3.5 wt% NaCl solution with 1 wt% silica sand under 0.1 m/s, 0.5 m/s, 1 m/s, 1.5 m/s flow rates. The initiation of erosion-corrosion could be well captured and the individual contributions of erosion and corrosion on the total metal loss could be accurately measured and evaluated by the sensor system. In combination with computational fluid dynamics (CFD) simulation, the influences of the inhomogeneous distribution of the flow field on the localized erosion-corrosion around the pipe circle was studied. It is found that severe erosion-corrosion prefers to occur around the high sand concentration area under high flow rate conditions. The accuracy of LPR method was studied when localized corrosion appeared on the steel surface. Based on the theoretical derivation and the experimental results, it is found that LPR measurement could effectively reveal the general corrosion rate when the electrochemical kinetic parameters of the anodic and cathodic sites are similar. • An RPERS array in conjunction with LPR measurement was developed for the detecting and monitoring of erosion-corrosion. • A general form of the linear polarization resistance was derived. • The individual metal loss rate induced by both corrosion and erosion can be on-line monitored. • The influence of the inhomogeneous distribution of the flow field on erosion-corrosion was revealed. [ABSTRACT FROM AUTHOR]

This work carried out a systematic analysis to help understanding how surface roughness and relative orientation between surface topography and direction of abrasive entrainment can affect particle dynamics during both pure microabrasion and microabrasion-corrosion. For that, tests were carried out in AISI 304 austenitic stainless steel test specimens using a recently developed microabrasion-corrosion tester. A 3D load cell ensures controlled application and measurement of forces during the tests. For the microabrasion tests, a slurry composed of small (ϕ=2.5 µm) silica particles dispersed in distilled water at a concentration of 20wt% was employed, whereas for the microabrasion corrosion tests the distilled water in the slurry was substituted by a corrosive solutions in distilled water (1 N H 2 SO 4). Potentiodynamic curves varying from cathodic potentials into the transpassive region were obtained within the course of duration of each microabrasion-corrosion test. The specimens were ground using two different SiC papers (#80 and #4000) to vary their surface topography and were tested with the grooves oriented perpendicular and parallel to the direction of rotation of the ball. Although the effect of surface topography was slight under pure microabrasion conditions, it was more significant under microabrasion-corrosion conditions. It was proposed that under microabrasion conditions, the formation of a low friction passive layer on the specimens made particle entrainment more difficult and therefore the relative orientation between surface topography and ball rotation had a stronger effect on the amount of abrasives that entered the contact, affecting wear rates. Grooves parallel to the rotation of the sphere increased wear rates under microabrasion-corrosion conditions when compared with grooves oriented perpendicular to the contact. Parallel grooves also resulted in higher passivation currents than perpendicular grooves, probably due to more severe damage to the passive layer caused by more abrasives into the contact [ABSTRACT FROM AUTHOR]

Nickel is widely used as a coating material in electroplating because of its good corrosion and wear resistance even at high temperature. Tribocorrosion has been identified as one of the main degradation mechanisms of nickel. This study evaluated the tribocorrosion behavior of pure nickel in citrate buffer solution (pH 4.5) under controlled mechanical, chemical and electrochemical conditions as well as wear of pure nickel in dry condition sliding against alumina or zirconia balls, respectively. The results showed that the wear of nickel was higher in passive domain due to wear accelerated corrosion compared to that in the cathodic domain. Surprisingly, both alumina and zirconia were worn by nickel in tribocorrosion condition under passive potentials as well as in dry condition. However, in the cathodic domain, negligible wear was observed on the alumina and zirconia balls. The formation of mixed nickel and aluminum/zirconium oxides was proposed as the wear mechanism of alumina and zirconia. • Nickel wears alumina and zirconia in both tribocorrosion and dry condition. • The wear of the ceramics was found to be dependent on the electrochemical condition. • The wear mechanism of the ceramics was proposed as the formation of mixed oxide. [ABSTRACT FROM AUTHOR]

Amorphous metallic thin films show great promise for applications where mechanical and chemical attack coexist due to their excellent wear, corrosion, and tribocorrosion resistance. In this research, the effect of scratching frequency on amorphous Al-Mn thin film were studied in simulated seawater by varying the scratching frequency from 0.05 to 1 Hz in reciprocal motion. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied to characterize the microstructure before and after tribocorrosion testing. Post-tribocorrosion topography measurement was performed using non-contact optical 3D profilometer. It was found that the total tribocorrosion rate, including both mechanical and chemical wear, increased with increasing scratching frequency. Mechanical wear increased with scratching frequency, mostly related to an increment of coefficient of friction and real contact area. On the other hand, chemical wear tend to increase with scratching frequency, most likely due to faster repassivation kinetics at lower frequency. Cross-sectional TEM analysis shows that the disordered surface layer primarily consists of aluminum oxide where manganese is completely absent. • Increasing sliding frequency led to higher tribocorrosion rate, friction coefficient, and surface current of Al-Mn. • Both chemical and mechanical wear increased with increasing frequency. • Anodic current in the wear track during tribocorrosion increased monotonically with frequency, but not linearly. • The subsurface of Al-Mn remained amorphous after tribocorrosion. • A uniform oxy-gen rich layer was observed on the wear track. This layer is highly non-uni-form away from the wear track. [ABSTRACT FROM AUTHOR]

Electrical contacts are basic components of electrical systems. They are applied in various conditions, which can influence the lifetime of the electrical contacts significantly. Fretting corrosion is one of the main failure mechanisms of electrical contacts with micro-motion. During this operation, the coating on electrical contacts is worn, generating wear debris. If the coating consists of non-noble material, for instance tin, which is a widely used coating material for electrical contacts, the wear debris will be oxidized and subsequently form an electrically highly resistant oxide layer after long-term service. Two decisive factors for the lifetime of electrical contacts are the number of cycles of motion and the time required to form this thick oxide layer. In many power semiconductor components, the housing is firstly pumped to vacuum condition, and then filled with nitrogen. The higher degree of vacuum leads to a substantially reduced amount of oxygen, a lower oxygen partial pressure and a longer mean free path of oxygen molecules, which retards the oxidation process. Therefore a remarkable improvement of fretting corrosion behavior is theoretically expected. The subject of this study is to investigate the effects of atmosphere and vacuum on fretting corrosion behavior. In order to investigate the fretting corrosion performance and the lifetime of these tin coated electrical contacts, a series of wear and fretting corrosion tests are conducted under various degrees of vacuum. The correlation between the lifetime of electrical contacts and pressure is analyzed. The results indicate that with an increasing degree of vacuum, the lifetime of electrical contacts in fretting tests is, as expected, prolonged. • The higher vacuum level leads to a remarkable improvement in fretting corrosion behavior of tin coated electrical contacts. • A relationship between the oxygen partial pressure and the lifetime is proposed based on theoretical derivation and then verified by the experimental data. • The lifetime can be significantly influenced by the vacuum condition. • It is possible to predict the lifetime of tin coated electrical contacts under various vacuum conditions. • The common model of fretting corrosion can be validated quantitatively by the results of this study. [ABSTRACT FROM AUTHOR]

Oil and gas companies apply different methods to limit erosion-corrosion of mild steel lines and equipment during the production of hydrocarbons from underground geological reservoirs. One of the frequently used methods is limiting the flow velocity to a so-called "erosional velocity", below which it is assumed that no erosion-corrosion would occur. Over the last 40 years, the American Petroleum Institute recommended practice 14E (API RP 14E) equation has been used by many operators to estimate the erosional velocity. The API RP 14E equation has become popular because it is simple to apply and requires little in the way of inputs. However, due to a lack of alternatives and its simplicity, the API RP 14E equation has been frequently misused by it being applied to conditions where it is invalid, by simply adjusting the empirical c -factor. Even when used within the specified conditions and associated applications, the API RP 14E equation has some limitations, such as not providing any quantitative guidelines for estimating the erosional velocity in the two most common scenarios found in the field: when solid particles are present in the production fluids and when erosion and corrosion are both involved. A range of alternatives to the API RP 14E equation that are available in the open literature is presented. Some of these alternatives overlap with API RP 14E, while others go beyond its narrow application range, particularly when it comes to erosion by solid particles. A comparison between the experimentally obtained and calculated erosion by different models is presented. The erosional velocity calculated by some of the models was compared with that estimated by the API RP 14E equation. • The origin of the API RP 14E erosional velocity equation remains unclear. • The API RP 14E Eq. cannot be used in various conditions by just varying the c-factor. • The API RP 14E Eq. provides no quantification when solids or corrosion is expected. • Most alternatives to the API RP 14E focus on velocity limits in the presence of solids. • For erosion-corrosion velocity limit, no reliable model exists in the open literate. [ABSTRACT FROM AUTHOR]

In this paper, the degradation mechanisms of the ceramic and the metal in Titanium/Zirconia pairs for biomedical applications were analyzed. To do that, an experimental set-up with well-controlled mechanical and chemical conditions was used based on a unidirectional ball-on-disk tribometer coupled to a potentiostat. Tribocorrosion tests were carried out in artificial saliva at different applied potentials, this is, different chemical conditions of the surface. Wear damage of the titanium/zirconia pair was influenced by the properties and the behavior of wear debris in the contact. Under passive conditions metallic and oxidized titanium particles (formed by the cyclic removal of the passive film and subsequent repassivation) were smeared and mechanically mixed within the contact forming compacted wear debris through which the loading was carried out. Properties and amount of oxidized titanium lead to low wear at low passive conditions (OCP) and higher wear at high passive conditions. Zirconia did not suffer any damage under all the studied conditions and oxidized titanium was transferred to the ball at anodic applied potentials. • Zirconia wears titanium depending on electrochemical conditions. • Cathodic potentials lead to plastic deformation of asperities on titanium. • Wear debris at open circuit potential supports mechanical loading and reduces wear. • Zirconia does not wear when sliding against titanium in artificial saliva. [ABSTRACT FROM AUTHOR]

Accurate friction-slip modelling is particularly important for locomotive traction and rail damage studies. This paper compares friction-slip measurement results from a hand operated (HO) tribometer and a twin disc tribomachine on AS60 rail. The results were used to calibrate traction coefficient-slip curves using the Modified Fastsim contact model. The differences between the two friction measuring instruments including scale, speed, and rail cleaning effect influenced the friction coefficient and slip value at which the friction peak occurred. The proposed equalisation technique was able to match the HO tribometer traction coefficient-slip curve with the tribomachine curve while preserving most of the Modified Fastsim contact parameters. • Friction-slip behaviour is characterised for locomotive traction and rail damage. • Friction measurements using tribomachine and hand-operated tribometer are compared. • Tribomachine and hand-operated tribometer results implemented in Modified Fastsim. [ABSTRACT FROM AUTHOR]

This study investigates the microstructural, mechanical, and tribological characteristics of 17–4 PH stainless steel specimens produced through Additive Manufacturing (AM) techniques, namely Selective Laser Melting (SLM) and Fused Filament Fabrication (FFF), in comparison to conventionally wrought steel (W). The wear test carried out on the samples were pin-on-disk, ball-on-plate and lubricated pin-on-disk. The counter part was an alumina ball with a diameter of 3 mm. The wear scar was less pronounced on lubrication test than in dry conditions for all samples. The coefficients of friction (COFs) were higher in dry conditions (in the order of 10−1) than in lubrication conditions (in the order of 10−2). Moreover, the wear rate had a significant reduction under lubrication conditions (in dry tests are in the order of 10−7, while lubrication conditions led to results in the order of 10−9). Additionally, FFF and SLM exhibited remarkably low wear rates in comparison to the wrought sample showing a superior dry and lubricated wear behaviour. AM allows for comparable or improved properties, despite slightly lower hardness due to retained austenite/delta ferrite and reduced precipitates. That significant improvement enhances the appeal of AM for high-performance components, particularly for small production runs and complex geometries being a promising and efficient technology for diverse industries. [Display omitted] • 17–4 PH SS produced by additive manufacturing. • Wear behavior of SLM and FFF 17–4 PH SS is compared to conventional. • Tribological behavior in dry and lubricated conditions is studied. • Improved tribocorrosion resistance is found for AM produced 17- 4 PH SS. [ABSTRACT FROM AUTHOR]

Friction modifier (FM) in the rail/wheel applications is a special lubrication material that could be applied between the top of rail and the tread of wheel. The application of FM brings many benefits to the wheel-rail interface such as reducing noise, alleviating wheel-rail wear and mitigating corrugation. Viscosity is an important parameter to reflect fluid properties of FM materials. In this study, FM samples with different viscosities were prepared by changing the content of sodium carboxymethyl cellulose (CMC). The tribological and rheological performance of these FM samples were explored using the twin-disc testing machine and rotational rheometer. Furthermore, the relationship between the tribological and rheological results were tried to establish. The results showed that the increase in the content of CMC could increase the viscosity of FM and enhance the solid-like characteristic of FM, which could help FM reduce coefficient of adhesion (COA) level and wheel-rail damage. For the FM material developed in this study, the rational applying amount and the range of viscosity were about 15 μL/time and 200 Pa·s to 400 Pa·s, respectively, considering the factors of wheel-rail adhesion, wear, potential waste and pumping process in the practical application. • The prepared FMs can realize the adhesion control and wear alleviation. • High viscosity FM showed a solid-like property due to dense molecular grids. • Performance of FMs with different viscosity varies from the application amount. • The rational application amount and viscosity are about 15 μL/time and 300 Pa s. [ABSTRACT FROM AUTHOR]

In the biomedical industry, the AISI 316L steel has been widely used due to its biocompatibility and low cost. However, an undesired effect of the wear and corrosion influenced by operational conditions is the reaction of the tissue to the metal, generated by replacements of the biomedical components such as screws and fixing plates. In this work, the evolution of the chemical species formed on the surface of the borided and non-borided AISI 316L steels during wet sliding conditions using a simulated body fluid (SBF Hank's solution) was investigated with the aim to improve the wear performance of the AISI 316L steel exposed to a boriding process. The results revealed that the specific wear rate of the borided AISI 316L steel was ∼3 times lower than that of the non-borided AISI 316L steel under the same wet sliding conditions. Also, the corrosion and wear resistance of both steels are related to combinations of reaction productions such as B 2 S 3 , Cr 2 O 3 , and Fe 2 O 3 during sliding wear by the formation of a passive layer, according to the results obtained by XPS, which reduced the specific wear rate. Finally, adhesive, abrasive, and tribo-oxidative wear modes were observed in both steels, with grooving, material agglomeration, plastic deformation, and passive film as the main wear mechanisms. [Display omitted] • Chemical species formed under wet sliding wear test of borided and non-borided AISI 316L steels were evaluated by the XPS technique. • Tribochemical reactions protect the surface against wear. • B 2 S 3 , Cr 2 O 3 , and Fe 2 O 3 chemical species evolved over the surface during wet sliding wear. • A tribocorrosion effect promotes a different behavior of the chemical species than only the effect of corrosion. • Hank's solution provides a boundary lubrication regime between tribopairs. [ABSTRACT FROM AUTHOR]

Erosion-corrosion is a major factor contributing to material loss and reduced useful life of hydro-transport equipment. The combined effect of erosion and corrosion is responsible for high degradation rates. In oil sand mining, materials from different classes are used for various applications depending on the severity of degradation. In this research, we assessed the erosion-corrosion characteristics of four uniform materials (pipeline and abrasion-resistant steels) as well as five materials containing varying types and quantities of carbide (chrome white iron and WC-based overlay). The materials underwent erosion-corrosion testing within a slurry container (comprising 3.5 wt% NaCl + 35 wt% natural silica sand) at a temperature of 45 °C. Under the test conditions, it was found that matrix wear influences the extent of carbide degradation for all carbide-containing materials. To provide good erosion-corrosion resistance, the surrounding matrix that supports the carbide must have sufficient wear and corrosion resistance. This study also identifies the dominant wear mechanisms for both uniform and carbide-containing materials. • Tungsten carbide-based overlays demonstrate outstanding erosion-corrosion resistance, outperforming plain carbon steel by 21 times. • Enhanced erosion resistance is attributed to higher carbide volume fraction and larger carbide size, particularly observed in hyper-eutectic white iron. • Synergy accounts for over 40 % of the total material loss across all evaluated materials, with hyper-eutectic white iron showing a more significant erosion-corrosion synergy effect. • The study offers valuable insights into the wear mechanisms of erosion-corrosion, emphasizing the impact of matrix degradation around carbides. [ABSTRACT FROM AUTHOR]

Refractory high-entropy alloys (RHEAs) have superior mechanical performance at high temperature, excellent wear resistance and corrosion resistance. They are promising candidates for applications in marine equipment, which warrants further studies in tribocorrosion. The TiZrHfNb-based RHEAs were prepared and their phase, microstructure and hardness were examined. The tribocorrosion behaviors of TiZrHfNb-based RHEAs against Si 3 N 4 balls under OCP and −0.4V Ag/AgCl conditions in 3.5 wt% NaCl solution were investigated and compared with dry sliding. The results show that TiZrHfNb-based RHEAs are of single BCC structure and the hardness increase with lattice distortion. The addition of Ta and Mo in TiZrHfNb-based RHEAs can effectively improve their corrosion and wear resistance, which is attributed the formation of passivation film and increase of hardness. The wear and corrosion of TiZrHfNb-based RHEAs under −0.4V Ag/AgCl condition is slightly higher than that under OCP condition. The tribocorrosion involves both electrochemical and mechanical interaction, and the TiZrHfNb 1.83 Mo 1.83 shows the best tribocorrosion property. • TiZrHfNb-based refractory high-entropy alloys were prepared by arc-melting. • The tribocorrosion behavior of TiZrHfNb-based RHEAs was investigated. • Addition of Ta and Mo can effectively improve their corrosion and wear resistance. • TiZrHfNb 1.83 Mo 1.83 RHEA shows the best tribocorrosion property. [ABSTRACT FROM AUTHOR]

Abstract The eroded surface of 2205 duplex stainless steel after liquid-solid jet impingement can be divided into three regions according to the severity of erosion-corrosion damage. The erosion-corrosion behavior for different local eroded regions was investigated using surface profile and potentiostatic polarization measurements. The results show that the critical flow velocity of these three regions is 13 m/s, 11 m/s and 15 m/s, respectively. The region with a lower critical value is more sensitive to erosion-corrosion damage with the increase of jet flow velocity showing much higher erosion-corrosion damage. The combined effect of impact angle and impact velocity of solid particles is the main reason causing the difference of critical flow velocity for different local eroded regions. Highlights • The critical flow velocity (CFV) in different local eroded regions was studied. • The relationship between exposed area of a sample and CFV behavior was studied. • The effect of impact angle and impact velocity on CFV behavior was discussed. [ABSTRACT FROM AUTHOR]

Abstract Corrosive wear is a form of material degradation that is known to occur on equipment and components that handle suspended solids in aqueous solutions. This surface deterioration process is generally enhanced when the fluids contain chlorides that are acidic in nature. Such environments are encountered in many applications, one such example being the minerals processing industry. High chromium white cast irons are widely used in many engineering applications as they extend the service life beyond that of stainless steels. In this work, the corrosive wear of austenitic stainless steel UNS S31600 and martensitic stainless steel UNS S42000 are compared with high chromium white cast irons (27WCI and 37WCI) by using a submerged jet technique at perpendicular incidence. The testing medium consisted of 3.5% NaCl liquid solution (pH 7 and pH 3) with suspended silica sand particles. The post-test methodology characterised the material loss within the directly impinged zone and turbulent zone where abrasive damage is involved. In neutral conditions, the presence of chromium carbides in white cast irons provided benefits, whilst in the acidic conditions, the austenitic structured materials (for stainless steels and white cast irons) suffered lower overall material loss compared with the martensitic structured materials. Highlights • The high hardness was linked to the optimum erosion-corrosion resistance in neutral pH solution. • In acidic environment, the corrosion resistance was the driving force for achieving high erosion-corrosion performance. • The enhanced erosion due to corrosion was an important factor for materials ranking in both neutral and acidic conditions. [ABSTRACT FROM AUTHOR]

Abstract T ribo-pairs experiencing fluctuating operating conditions are expected to have lower useful life compared to those that operate in a steady state condition. The objective of the present study is to gain insight into the wear characteristics of such tribo-pairs operating in dry conditions and to develop a general procedure to reliably predict their useful life. Results are presented based on a series of experiments performed using a ball-on-disk tribometer. The disk is made of brass coated with a black paint to clearly detect the onset of failure defined as the time when the steel ball contacts the brass disk and friction force rapidly fluctuates and becomes erratic. First, experiments are performed at various loads (1 N, 2 N and 3 N) at a constant sliding speed (0.1 m/s), and different sliding speeds (0.05 m/s, 0.1 m/s and 0.2 m/s) at a constant load of 2 N) for establishing the useful life. Following these experiments, fluctuating operating conditions are imposed by varying (i) loading sequence, (ii) sliding speed sequence and (iii) both load and sliding speed in an arbitrary manner. For all these experiments the remaining useful life for the last sequence are determined by considering Miner's constant C = 1 and cumulative power to failure of 103 W. The results revealed that the maximum error between the power generation method and experimental results vary from 2% to 10.3%, while using Miner's constant, the error was substantially higher. Further, the applicability of power generation method is validated for an extreme operating condition for an Al-steel tribo-pair. Finally, a detailed mathematical explanation is provided to illustrate the reason for the advantage of power generation method over Miner's rule. Highlights • Variable loading and sliding speed negatively affects tribo-components wear life. • A method for predicting wear life with variable loading and sliding speed is presented. • Miner's rule drawback in predicting remaining wear life is explained. • Prediction of remaining wear life for variable loads and speeds is experimentally verified. [ABSTRACT FROM AUTHOR]

Abstract Minimization of corrosion loss or corrosion-related loss is highly desirable for enhancing the tribo-corrosion resistance of physical vapor deposition (PVD) hard coatings. Various tribo-corrosion tests against Al 2 O 3 counterparts combined with microscopic examinations, were used to study the tribo-corrosion behaviors of three typical kinds of magnetron sputtered CrSiN coatings. The dense and columnar coating exhibited superior tribo-corrosion resistance, with a lowest specific tribo-corrosion rate of 6 × 10−16 m3/N m and a lowest friction coefficient of ~0.14, where the dominant mechanism was considered as a layer-by-layer mechanical removal and the chemical corrosion was inappreciable. The porous and columnar coating failed for its poor intrinsic corrosion resistance. For the almost column-free coating, brittle fracture leaded to an increase of the corrosion component in the material wear, despite that the coating had the best intrinsic corrosion resistance. The comparison studies demonstrated that the dominant factors of the tribo-corrosion resistance are more complicated than purely mechanical wear or purely chemical corrosion; high compactness, effectively crack-controlled wear, and the dynamic equilibrium of depassivation-repassivation surfaces on the worn are indispensable for the highly tribo-corrosion resistant PVD hard coatings. Highlights • Compare the tribo-corrosion behavior of three kinds of typical CrSiN coatings. • Provide the micro-scale and dynamic examination of the tribo-corrosion process. • Reveal the microstructural effect on the tribo-corrosion mechanism of hard coatings. • Discuss the key factors of the tribo-corrosion resistance for hard coatings. [ABSTRACT FROM AUTHOR]

Abstract Critical flow velocity (CFV) is one of the valid parameters to evaluate the erosion-corrosion performance of passive materials. The comparison of CFV for common passive materials is significant for the engineering applications. This study focuses on the comparison of CFV for different types of stainless steel (SS), including the pearlitic 2Cr13 SS, austenitic 304 SS, 316 SS, 254 SMO SS, and two duplex stainless steels (DSS) (2205 DSS and 2507 DSS) in 3.5 wt% NaCl solution containing 2 wt% silica sand particles using the impingement jet apparatus. Different methods (potentiostatic polarization tests, mass loss measurements and surface roughness measurements) were used to determine the CFV and the values of CFV derived from different methods showed a good consistency. The 254 SMO SS exhibited the highest CFV, followed by 2507 DSS, 2205 DSS and 316 SS, and 304 SS and 2Cr13 SS. Compared with the mass loss method which is normally time-consuming, comprehensive evaluation based on the critical flow velocity and current density at flow velocity higher than the critical value by using potentiostatic polarization tests is more effective and efficient for the material selection for erosion-corrosion. Highlights • The critical flow velocity (CFV) of six stainless steels is compared. • The CFV determined by different testing methods is consistent. • CFV is a valid parameter to evaluate erosion-corrosion behavior of passive materials. [ABSTRACT FROM AUTHOR]

Rain erosion of leading edges of wind turbine blades is caused by repeated high speed liquid droplet impacts, which causes damage in the form of pitting or peeling over time and can lead to a significant reduction in performance if left untreated. Due to an increase in the tip speed of modern wind turbine blades, rain erosion is becoming an increasingly prominent issue. Currently, polymeric coatings are applied to the surface of the wind turbine during manufacture in order to mitigate the issue; however, it has been reported that these coatings are being eroded within the first 2–5 years of the 15–25 year life cycle of the blades. Rain erosion testing of polymer coatings requires prolonged characterisation using expensive bespoke apparatus. The focus of this study is to assess if nanoindentation can conveniently provide sufficient information to characterise the rain erosion resistance of polymeric materials. A range of polymeric materials were first tested in the Whirling Arm Rain Erosion Rig (WARER) to assess their ability to resist rain erosion, while a Nanoindenter G200 was also used to assess their stiffness, hardness, surface roughness, elastic and viscoelastic properties. The results indicated a number of correlations. A reduction in both storage modulus and hardness was seen to be beneficial for rain erosion resistance and materials that resist rain erosion can recover quickly to their original shape in time to resist subsequent impacts. Viscoelasticity was assessed through the fitting of a spring and dashpot model to the nanoindentation data, showing good correlation. This technique also has the potential to experimentally characterise the viscoelastic properties required to create analytical or numerical models to evaluate rain erosion performance. Scanning probe microscopy carried out at various stages of the erosion process showed that the roughness of the polymeric materials increases with erosion time up to critical roughness ( Sa CRIT ), before which no significant mass loss will occur. Furthermore, it was found that the rate at which a polymer is roughened during the incubation period is related to the rate at which it loses mass in the mass loss period, providing an empirical insight into the mechanics of the rain erosion of these materials. [ABSTRACT FROM AUTHOR]

Erosion-corrosion is frequently encountered in pipelines used in potash processing equipment and it may be a severe problem, causing rapid material degradation if the slurry flow velocity and solid concentration are high. In this study, the interaction between erosion and corrosion of 1018 steel 90° elbows (2.54 cm schedule 40 - long radius) was investigated in a continuous flow loop. Experiments were conducted using a slurry consisting of saturated potash brine and silica sand. The effects of solid concentration and flow velocity on erosion-corrosion damage of the steel elbow were investigated. The results indicated that increasing flow velocity and solid concentration increased the mechanical effects of particles on the tested elbows and hence increased the erosion-corrosion rates of the elbows. It was observed that there was a 56% synergy between erosion and corrosion at 2.5 m/s, but the synergy level decreased to 11% at 4.0 m/s. [ABSTRACT FROM AUTHOR]

Tantalum coatings were deposited on Ti-13Nb-13Zr alloy by filtered cathodic vacuum arc deposition in order to improve the alloy's wear and corrosion resistance under load-bearing, biomedical applications. The Ta coating exhibits an amorphous structure, which transforms into a mixture of alpha and beta phases as the substrate is heated to 300 °C during deposition. Tribo-corrosion tests were performed using a ball-on-disk tribometer under simulated joint fluid at 37 °C by sliding the uncoated and Ta-coated surfaces against alumina balls. The Ta coatings showed a significant reduction in the coefficient of friction under these test conditions. The wear rates of the Ta-coated disk surfaces are slightly lower than those of the bare Ti-13Nb-13Zr alloy, while the wear rate of the alumina balls was one order of magnitude higher when it slid against the Ta-coated samples than when it was slid against the Ti-13Nb-13Zr alloy. The wear debris generated from the Ta-coated samples sliding against alumina was comparatively smaller than that generated by the uncoated alloy against alumina. The wear characteristics of the Ta coatings do not favour using such coatings on implant materials. The Ta coatings exhibited a strong capacitive response which is proposed to enhance corrosion protection of the Ti-13Nb-13Zr alloy. [ABSTRACT FROM AUTHOR]

Improvement in wettability and lubricity of water/glycerol base fluid by the synergy of nanoparticles (NPs) and protic ionic liquid (PIL) was experimentally investigated. The hybrid additives were made by combining graphene nanoplatelets or silicon oxide nanoparticles with tert- octylamine oleate PIL. A lubricating sample preparation procedure included ultrasonication, centrifugation and magnetic stirring. Kinematic viscosity, pH, and wettability were evaluated. The tribo-tests were performed on a ball-on-plate reciprocating tribometer. It was observed that NPs alone could not improve the lubricity of the base fluid. However, the lubricity was substantially enhanced by using the PIL additive. Furthermore, the combination of NPs and PIL provided an even better tribological response. The hybrid additives improved wettability and facilitated composite tribo-film formation. • Tert-octylamine oleate improves the wettability of water-based lubricating fluid. • Hybrid additives substantially improved the lubricity of water/glycerol base fluid. • Hybrid additives improved lubricity by forming a composite tribo-film. [ABSTRACT FROM AUTHOR]

The poor tribocorrosion resistance of the Ti6Al4V alloy limits its wide applications in orthopedics. In addition, the tribocorrosion performance and mechanism of the Ti6Al4V alloy are not clear in some clinically specific pathological settings, such as peri-implantitis and diabetes. In this work, the tribocorrosion performances of the Ti6Al4V alloy in simulated body fluids (SBF) containing H 2 O 2 and glucose were investigated to analyze the degradation behavior in the simulated inflammatory and hyperglycemic microenvironment. The tribocorrosion tests were carried out on a tribometer equipped with a three-electrode system electrochemical workstation. The material volume loss of the Ti6Al4V alloy in the high glucose environment (6 g/L) is 3.1 times more than that in the glucose-free environment, while H 2 O 2 does not increase the material volume loss. The continuous corrosion product film on the Ti6Al4V surface in the SBF with H 2 O 2 acts as a lubricant in mechanical wear, while the Ca and Mg-containing mineralized film formed in the high glucose environment increases the coefficient of friction (COF) during sliding. These results suggest that diabetic patients may be at a higher risk of the implant failure due to the tribocorrosion. This finding also provides a valuable reference for the placement of titanium-based implants in specific pathological settings in orthopedics. [Display omitted] • The tribocorrosion behavior of Ti6Al4V is affected by the surface product film. • The corrosion product film on Ti6Al4V in SBF containing H 2 O 2 acts as a lubricant. • The accelerated mineralized film in SBF containing high glucose increases the COF. [ABSTRACT FROM AUTHOR]

To improve the tribocorrosion resistance of 316L stainless steel in acidic media, Fe–Al–Ti coatings were prepared on 316L substrate by self-propagating high-temperature synthesis (SHS) using an aluminothermic reaction. The effects of Ti content on the tribocorrosion behaviors of Fe–Al–Ti coatings in 0.5 mol/L H 2 SO 4 solutions were investigated. The Fe–Al–Ti coatings exhibited a multi-phase microstructure. The open circuit potential (OCP) of the Fe–Al–Ti coatings and 316L substrate decreased significantly with the onset of sliding, indicating a strong wear-corrosion synergistic effect. The hardness and tribocorrosion resistance of Fe–Al–Ti coatings increase with increasing the Ti content. The tribocorrosion volume loss of the Fe–25Al–25Ti coating was about one order of magnitude lower than that of the 316L substrate. The Fe–25Al–25Ti coating was more suitable as a tribocorrosion-resistant material than the 316L substrate. • The Fe–Al–Ti coatings were successfully prepared by the aluminothermic reaction. • Tribocorrosion behaviors and mechanisms of the coatings were investigated systematically. • Selective tribocorrosion of interdendritic phase (Fe 2 Ti) occurred during tribocorrosion. • XPS analysis determined the presence of Al 2 O 3 , TiO 2 and Fe 2 O 3 tribocorrosion protective film. • Fe–25Al–25Ti coating was more suitable as a tribocorrosion resistant material than 316L substrate. [ABSTRACT FROM AUTHOR]

The regular replacement and maintenance of steel pipes used to transport slurry in oil sands mining and extraction continue to represent a major expense for oil sands operations. Pipeline steels such as API 5 L X65 and X70 are the main materials for the slurry transport system. In our previous work, dual-phase stainless steel showed excellent performance in aeriated (high dissolved oxygen) slurries operated at low to moderate velocities involving erosion-corrosion. However, the benefits of using stainless steel diminish as the oxygen in slurry is depleted or at higher slurry velocities at which mechanical properties, particularly deformation energy or strain-hardening capability, of the steel become more dominant. This article reports our recent studies on erosion-corrosion of high manganese steel at different slurry velocities (3.5 m/s and 5.5 m/s) and different dissolved oxygen levels (0.6 ppm and 3.8 ppm). The erosion-corrosion tests were performed at 60 °C in sand-containing slurry (20% vol. silica) with 500 ppm chloride, which simulated common field situation. Characterization of the steel was carried out with optical and scanning electron microscopy, energy dispersive x-ray spectrometry, x-ray diffraction technique, micro-mechanical probe, and electrochemical testing. The performance of the high manganese steel was compared to those of API 5 L pipeline steels commonly used in slurry transport, ASTM A1053 Gr.50 dual-phase ferritic-martensitic stainless steel, and AR400 martensitic hard plate. Results of this investigation demonstrate how the high strain-hardening capability of the high manganese steel produces an outstanding erosion resistance, which is more than two times as high as those of ferritic steels. The results are compared to those obtained through field trials performed in an oil sands coarse tailings pipeline. • High manganese steel exhibits a remarkable erosion-corrosion performance. • Erosion resistance of high manganese exceeds those of AR400 and pipeline steels. • Deformation energy showed the larger influence on the steels erosion resistance. • Field trials of high manganese steel were consistent with laboratory results. [ABSTRACT FROM AUTHOR]

The tribo-electrochemical behavior of AISI 316L has been investigated under tribocorrosion conditions in a 3% NaCl solution and the material damage evolution with time has been analyzed. A numerical contact model based on a Boundary Element Method (BEM) has been developed in order to determine the contact pressure distribution and to quantify the worn material as a function of time. The time dependence of the tribological behavior of the material has been described. At the initial state, the high contact pressures generate a material flow causing an increase in the worn area. After around 300 cycles, the Archard wear model linearly describes the wear evolution with time. The proposed model describes the evolution with time of the wear profiles of the tested material and takes into account the plastic behavior of the material during the first cycles. [ABSTRACT FROM AUTHOR]

Several components in the oil and gas industry are subjected to wear and corrosion. This work evaluated the feasibility of using Diamond-Like Carbon (DLC) coatings in Subsea Safety Control Valves (SSCV), piston and pumps. These are made from API X65 carbon steel and are subjected to wear and corrosive/saline environments. Coatings were deposited using Plasma Enhanced Chemical Vapour Deposition (PECVD). The electrochemical behaviour of Silicon-doped and Hydrogenated DLC films was evaluated before and after wear tests. Film characterisation included nano-indentation, surface roughness, micro-abrasion testing, Raman spectroscopy, atomic force microscopy and scanning electron microscopy. Electrochemical tests and electrochemical impedance was also measured. Sliding wear tests against silicon nitride were conducted with a maximum initial Hertz stress of 150 and 400 MPa under dry and wet conditions. The H-DLC had better wear performance than Si-DLC. The advantages of H-DLC were related to higher hardness increasing the wear resistance; small galvanic coupling between DLC and steel, inhibiting the localised corrosion into the DLC defects; lowest anodic current, suggesting high resistivity to use as a corrosion barrier for steel and the corrosion process on the substrate that did not affect DLC properties (adhesion and wear/ corrosion resistance). [ABSTRACT FROM AUTHOR]

A nanocrystallized surface layer of around 150 µm thickness was created on AISI 304L by nano-scale surface peening. Electron back scattered diffraction (EBSD) has revealed that the upper layer of the nanocrystallized surface was formed by nanosized ferrite grains. However, bottom layer was compounded from martensite and deformed austenite. Tribocorrosion behavior of the nanocrystallized surface against alumina was investigated in a mixture of olive pomace and tap water filtrate. Nanopeened 304L was more sensitive to tribocorrosion under intermittent sliding than continuous one due to depassivation/repassivation phenomena. Mechanical and corrosion wear components were quantified. Tribocorrosion mechanism was dominated by abrasion mechanical removal of the uncovered surface. The wear resistance of AISI 304L surface was markedly improved by treatment. That improvement could be explained by the higher hardness of nanocrystallized AISI 304L. [ABSTRACT FROM AUTHOR]

Ti6Al4V has extensive uses in the marine and biomedical industry. In some of these applications, corrosion is present with additional mechanical wear. Thus, the corrosion, wear and their synergistic properties were investigated in applications where there were specifically induced material property changes, such as in welding. One such welding technique, friction-stir-welding, is a well-suited method for joining plates of the Ti6Al4V alloy. The purpose of the work was to investigate the effect of mechanical wear combined with electrochemical corrosion on the various weld zones of the material in a salt solution. The corrosive properties of the advancing side, retreating side and weld-zone regions of the material were compared to the properties of the parent material. The study showed that, when compared to the parent material, heat-affected zone and the weld zone, the advancing side was found to possess lower wear corrosion properties when compared to the retreating side. In addition, the weld zone was shown to have the lowest material loss per year under tribocorrosion conditions. [ABSTRACT FROM AUTHOR]