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Today, parts made by additive manufacturing (AM) methods have found many applications in the medical industry, the main reasons for which are the ability to custom design and manufacture complex structures, their short production cycle, their ease of utilization, and on-site fabrication, leading to the fabrication of next-generation intricate patient-specific biomedical implants. These parts should fulfill numerous requirements, such as having acceptable mechanical strength, biocompatibility, satisfactory surface characteristics, and excellent corrosion and wear performance. It was known that AM techniques may lead to some uncertainties influencing part properties and causing significant evaluation conflicts in corrosion outcomes. Meanwhile, the corrosion and wear behavior of additively manufactured materials are not comprehensively discussed. In this regard, the present work is a review of the state-of-the-art knowledge dedicated to reviewing the actual scientific knowledge about the corrosion and wear response of additively manufactured biomedical components, elucidating the relevant mechanism and influential factors to enhance the performance of AM-manufactured implants specifically for the physiological human body fluids. Furthermore, there is a focus on the use of reinforced composites, surface engineering, and a preparation stage that can considerably affect the tribocorrosion behavior of AM-produced parts. The improvement of tribocorrosion performance can have a key role in the production of advanced AM implants and the present study can pave the way toward facile production of high-throughput AM biomedical parts that have very high resistance to corrosion and wear. [ABSTRACT FROM AUTHOR]

Variations in the corrosion behavior of biomedical NiTi alloys in Cl− containing and acidic environments present a problem with their biological implantation. The objective of this research was to evaluate the synergy of the microstructure, the corrosion behavior, and the biocompatibility of novel continuous-cast NiTi alloys and to compare them with commercial NiTi alloys. The two alloys have a practically identical nominal chemical composition, but they differ in production technology. The continuous casting technology involved vacuum induction melting of the basic components and vertical continuous casting, while the commercial NiTi alloy was produced through a process of casting, hot rolling, and forming into square shapes. The microstructure was revealed to determine the surface area and size of grains. The corrosion of a commercial nickel–titanium alloy and one prepared by a novel continuous casting method in acidic and chloride-containing solutions was studied via analytical and electrochemical tests. Localized corrosion characteristics related to oxide properties, when exposed to 9 g L−1 NaCl solution, were examined with focused ion beam analysis and subsequent microchemical analysis of the formed corrosive products. Corrosion potential over time and the oxide film resistance were analyzed using linear polarization measurements. To obtain a preliminary estimate of biocompatibility, human fibroblast cells were used in indirect contact, i.e., alloy conditioning medium. The continuous casting method resulted in a reduction in the average grain size in comparison to the commercial sample and better corrosion stability of the sample in an acidic environment. Also, in a solution of 9 g L−1 NaCl the commercial sample showed high values for the corrosion current density (jcorr = 6 μA cm−2), which indicated low corrosion resistance, while the continuous casting sample possessed much better corrosion stability and lower values for the corrosion current density (jcorr = 0.2 μA cm−2). In line with that, elemental analysis of the corroded surfaces showed higher Cl− ion deposition over the surface layer of the commercial sample, suggesting local oxide breakdown. Moreover, NiTicc reached a value three times higher for polarization resistance (Rp = 270 kΩ cm2) over time in comparison to the commercial sample (Rp~100 kΩ cm2). Biocompatibility evaluation showed that human fibroblast cells exhibited altered metabolic activity. An MTT assay showed that cells' mitochondrial activity dropped below that of control cells in the presence of both materials' supernatants. [ABSTRACT FROM AUTHOR]

When serving in the marine environment, the corrosion of metals is inevitably affected by marine environmental factors, especially dissolved oxygen. This will affect the service life of metal in the marine environment. In this paper, a friction- and wear-testing machine, an electrochemical workstation, and a dissolved oxygen/temperature control system are employed to systematically study the influence of dissolved oxygen (DO) content on the tribo-corrosion characteristics of Monel 400 alloy in seawater. The results show that the DO content has a remarkable effect on the tribo-corrosion behavior of Monel 400 alloy. The corrosion of Monel 400 alloy increases with the increase in DO content, leading to the thickness of corrosion product increasing at higher DO contents. The corrosion product is mainly composed of Ni(OH)2, Cu2O, CuO, and Cu(OH)2. While the corrosion of Monel 400 alloy further affects the wear rate of the alloy, when the corrosion is inhibited, the change of DO content has no effect on the wear rate of Monel 400 alloy. In addition, the inhibition influence of corrosion on mechanical wear is found, which is attributed to the excellent lubrication performance of corrosion products. [ABSTRACT FROM AUTHOR]

This review of the tribocorrosion of coatings and surface modifications covers nearly 195 papers and reviews that have been published in the past 15 years, as compared to only 37 works published up to 2007, which were the subject of a previous review published in 2007. It shows that the research into the subject area is vibrant and growing, to cover emerging deposition, surface modification and testing techniques as well as environmental influences and modelling developments. This growth reflects the need for machines to operate in harsh environments coupled with requirements for increased service life, lower running costs and improved safety factors. Research has also reacted to the need for multifunctional coating surfaces as well as functionally graded systems with regard to depth. The review covers a range of coating types designed for a wide range of potential applications. The emerging technologies are seen to be molten-, solution-, PVD- and PEO-based coatings, with CVD coatings being a less popular solution. There is a growing research interest in duplex surface engineering and coating systems. Surface performance shows a strong playoff between wear, friction and corrosion rates, often with antagonistic relationships and complicated interactions between multiple mechanisms at different scale lengths within tribocorrosion contacts. The tribologically induced stresses are seen to drive damage propagation and accelerate corrosion either within the coating or at the coating coating–substrate interface. This places a focus on coating defect density. The environment (such as pH, DO2, CO2, salinity and temperature) is also shown to have a strong influence on tribocorrosion performance. Coating and surface modification solutions being developed for tribocorrosion applications include a whole range of electrodeposited coatings, hard and tough coatings and high-impedance coatings such as doped diamond-like carbon. Hybrid and multilayered coatings are also being used to control damage penetration into the coating (to increase toughness) and to manage stresses. A particular focus involves the combination of various treatment techniques. The review also shows the importance of the microstructure, the active phases that are dissolved and the critical role of surface films and their composition (oxide or passive) in tribocorrosion performance which, although discovered for bulk materials, is equally applicable to coating performance. New techniques show methods for revealing the response of surfaces to tribocorrosion (i.e., scanning electrochemical microscopy). Modelling tribocorrosion has yet to embrace the full range of coatings and the fact that some coatings/environments result in reduced wear and thus are antagonistic rather than synergistic. The actual synergistic/antagonistic mechanisms are not well understood, making them difficult to model. [ABSTRACT FROM AUTHOR]

Alumina ceramics are widely used to fabricate the insulating tubes of vacuum electronic devices. The long-term stress borne by ceramics during service may lead to failure, so it is of great significance to investigate the mechanical reliability of ceramics. Annealing is a commonly used step in the processing of an alumina ceramic, which may affect its mechanical performance. Herein, the effects of inter-granular crystalline phase induced by annealing on the service reliability of a 95% alumina ceramic are studied, and the mechanisms are analyzed by material characterizations. Moreover, the service life of annealed ceramics is predicted through theoretical calculation. The crystallization of inter-granular glassy phase results in the decreased fracture strength of the alumina ceramic, but increases its long-time service reliability. The existence of inter-granular crystalline phases is responsible for the increase of flaw tolerance and corrosion-resistance of the alumina ceramic, and therefore the alleviated static fatigue can be obtained after annealing. Furthermore, the reliability of the annealed ceramic-Kovar alloy composite joints is analyzed, in which the stresses induced by brazing may lead to cracks in the alumina ceramic. In summary, this work discusses the influence of the crystallization of inter-granular glassy phase on the mechanical performance of alumina ceramics, which is of great value for developing ceramics with excellent mechanical reliability. [ABSTRACT FROM AUTHOR]

Castor seed oil, as an important biomass fuel, has attracted extensive attention worldwide due to inclusive applications. Castor seed screw mechanical extraction is in fact seed shear damage and oil output. Seed shearing mechanism has been investigated with a developed tribometer. Influences of pressing load, shearing speed, roller roughness were analyzed. Castor seed structural damage was in‐situ observed with optical microscope, and in‐depth analyzed with Scanning Electron Microscopy and Energy Dispersive Spectroscopy. The results reveal that shear interaction can be divided into three stages: coat damage, transition shearing and endosperm oil output. Seed shear mechanism includes coat peeling, endosperm plowing, tissue transferring and oil lubrication. High pressing load leads to more damage of coat and endosperm, causing more oil to flow out. With shearing speed increasing, coat is easily peeled, obvious endosperm shear plowing and oil lubrication happened in contact area. Coat damage by high roughness leads more oil output. Castor oil enters the contact area and work as lubricant, leading to the decrease of friction resistance. [ABSTRACT FROM AUTHOR]

In our previous work, we find that the ethylene glycol (EG) is transferred to amorphous carbon or graphene during sliding under the effect of the tribochemical reactions; herein, in this work, we control the concentration of the modified Al2O3 nanoparticles in the EG solution in order to modulate the tribological properties of the tribosystem sliding in the mixed lubricant consisting of the modified Al2O3 nanoparticles and EG. The tribological tests show that the concentrations of the modified Al2O3 nanoparticles ranging from 0 to 1.0 wt% in the mixed lubricant are helpful for obtaining low wear rate due to the formation of graphene‐like materials induced by tribochemical reactions. On the other hand, when the concentration reaches 1.5 wt.%, the tribosystem exhibits high coefficient of friction (COF) and wear rate, which is attributed to the formation of reunited groups consisting of the modified Al2O3 nanoparticles and graphene‐like materials. This investigation should give a positive guidance for the design of the mixed lubricant with excellent lubrication properties. [ABSTRACT FROM AUTHOR]

Impact-sliding caused by random vibrations between tubes and supports can affect the operation of heat exchangers. In addition, a corrosive environment can cause damage, accelerating the synergism of corrosion and wear. Therefore, the focus of this work was the impact-sliding fretting tribocorrosion behavior of 316L heat exchanger tubes at different halide concentrations. A device system incorporating the in situ electrochemical measurements of impact-sliding fretting corrosion wear was constructed, and experiments on 316L heat exchanger tubes in sodium chloride (NaCl) solution with different concentrations (0.0, 0.1, 0.5, 1.0, 3.5, and 5.0 wt%) were carried out. The synergism between wear and corrosion was also calculated and analyzed. The wear and damage mechanisms were elucidated by correlating the corrosion-wear synergism, morphologies, and material loss rates. The results indicated that the stable wear stage occurred at approximately 9–12 h, after which the corrosion current increased with the expansion of the wear area. As the halide concentration increased, the scale of damage on the wear scars gradually decreased, changing from being dominated by cracks, delaminations, and grooves to being dominated by scratches, microgrooves, and holes. There was an obvious positive synergism between wear and corrosion. The material loss was dominated by pure mechanical wear and wear enhanced by corrosion, but corrosion enhanced by wear contributed more than tangential sliding fretting corrosion. The total mass loss increased gradually in the range of 0.0–0.5 wt% and decreased in the range of 0.5–5.0 wt%. Large-scale damage enhanced by corrosivity and small-scale damage reduced by lubricity dominated the material loss at low and high concentrations, respectively. [ABSTRACT FROM AUTHOR]

The effect of contact load and relative displacement on tribo-corrosion interaction of parallel steel wires of main cable in the suspension bridge was investigated in this study. A self-made tribo-corrosion test bench was employed to conduct tribo-corrosion tests of parallel steel wires in 3.5% (wt%) NaCl solution and deionized water under different contact loads and different relative displacements. The friction coefficient and wear coefficient of wires were presented. Electrochemical corrosion behavior (Tafel polarization curves, Nyquist diagram, and equivalent circuit diagram) was characterized by electrochemical analyzer. Wear morphology was observed by scanning electron microscope. Wear volume loss and corrosion-wear interaction were quantitatively demonstrated by high-precision weighing balance. The results show that the electrochemical corrosion ability of the steel wires increases with the increase of the contact load or relative displacement. The increased contact load or relative displacement increases the volume loss of corrosion-wear and pure wear, but decreases the wear coefficient. The wear mechanisms in 3.5% NaCl solution are adhesive wear, abrasive wear, and corrosive wear as compared to adhesive wear and abrasive wear in deionized water under different contact loads. The wear mechanisms of parallel steel wires are slightly different under different relative displacements. But the main wear mechanisms are similar to that under different contact loads. The interaction effects of corrosion and wear produced by the contact load and relative displacement are all the synergistic effects. [ABSTRACT FROM AUTHOR]

Growth defects such as pores during preparation restrict the service life and wide applications of CrN coating. To improve the corrosion and tribological behaviors of CrN coatings, in this work, the parylene C (PC)/CrN duplex coatings with different CrN layer thicknesses were fabricated, combining chemical vapor deposition and physical vapor deposition technologies. The surface morphologies and chemical bonds of as-deposited coatings were investigated by scanning electron microscopy and x-ray photoelectron spectroscopy, respectively. The corrosion and wear behaviors of the CrN coatings without and with PC layers in the seawater environment were evaluated using an electrochemical workstation and a tribometer, respectively. The results showed that the surface of the PC film was relatively compact, which was well bounded to the CrN layer. The corrosion current density of the PC/CrN duplex coating is low to 10−9 A/cm2, which is reduced by one order of magnitude compared to the single CrN coating. As the thickness of the CrN layer increases, the corrosion potential of the PC/CrN duplex coating decreases and the corrosion current density slightly increases, which may be ascribed to the increased defects of the CrN layer, which debased the corrosion resistance. Furthermore, the steady friction coefficients of PC/CrN duplex coatings are all below 0.05, which are significantly lower compared to the single CrN coatings. The lowest wear rate of the PC/CrN duplex coating is approximately 1.31 × 10−6 mm3/N m, presenting excellent wear resistance. Compared to the single CrN coating, the dense PC film can not only seal the pores and other defects on the CrN surface, but also prevent the permeation and penetration of corrosive seawater inside the coating, which contributes to the superior corrosion resistance of the PC/CrN duplex coating. The low friction and high wear resistance of the PC/CrN duplex coating could be ascribed to the self-lubricating property, the PC film, and its good protective performance as a surface layer, as well as the generation of CaCO3 and Mg(OH)2 lubrication components during the wear process. In summary, the PC films can remarkably improve the corrosion and tribological performance of the CrN coating. The excellent corrosion resistance and wear resistance of the PC/CrN duplex coating make it a good candidate material for applications in marine environments. [ABSTRACT FROM AUTHOR]

The complicated interplay between microstructure and tribo‐corrosion behavior has long been an intriguing problem in the field of advanced materials engineering. In this study, the effects of different laser energy densities (LEDs) on the surface morphology, microstructure, and tribo‐corrosion behavior of Ti–6Al–4V produced using laser powder bed fusion (LPBF) technology are systematically investigated. The surface morphology and microstructure of the specimens are characterized in detail using various characterization techniques such as optical microscopy, scanning electron microscopy, and X‐ray diffraction. Additionally, a self‐assembled friction–corrosion equipment is employed to evaluate the tribo‐corrosion behavior of the samples at different LED settings. In the results, it is shown that the LED has a significant effect on the surface morphology, microstructure, and tribo‐corrosion behavior of the Ti–6Al–4V. Increasing the LED leads to reduced surface roughness, weakened keyhole and segregation phenomena, more distinct β grain boundaries, and coarser acicular α phase. Moreover, the tribo‐corrosion behavior initially improves and then declines with increasing LED. Furthermore, tribo‐corrosion product and mechanism of the Ti–6Al–4V alloy prepared by LPBF are revealed. This study is of great significance for understanding the relationship between the microstructure and tribo‐corrosion behavior of Ti–6Al–4V manufactured by LPBF. [ABSTRACT FROM AUTHOR]

When introduced into the body, the implant interacts with biological environment and may suffer corrosion. In addition, when this implant is submitted to friction, it may degrade by tribocorrosion due to the simultaneous action of corrosion by the body liquid and mechanical wear. Both corrosion and tribocorrosion are connected to the presence of proteins that cover the surface implant. The latter plays an ambiguous role on corrosion since dozens of contradictory papers pointed out their beneficial or detrimental effect. After its introduction into the body, the implant should form a direct interface with bone through structural and functional connection. The osseointegration and the strength of interfacial bond depend on surface properties of the implant, namely, its topographical and physico-chemical properties. In addition, since bone cells are sensitive to the species produced during the implant corrosion, when corrosion occurs, this may lead to impact osseointegration and to cause implant loosening. There is a strong connection between corrosion and osseointegration, both of which are worth discussion. That is the object of the present narrative review where we will discuss: (1) corrosion and tribocorrosion of titanium alloys used as biomaterials paying particular attention to the influence of proteins, (2) the effect of implant roughness and surface energy on osseointegration. [ABSTRACT FROM AUTHOR]

Tribocorrosion, a research field that has been evolving for decades, has gained renewed attention in recent years, driven by increased demand for wear- and corrosion-resistant materials from biomedical implants, nuclear power generation, advanced manufacturing, batteries, marine and offshore industries, etc. In the United States, wear and corrosion are estimated to cost nearly USD 300 billion per year. Among various important structural materials, passive metals such as aluminum alloys are most vulnerable to tribocorrosion due to the wear-accelerated corrosion as a result of passive film removal. Thus, designing aluminum alloys with better tribocorrosion performance is of both scientific and practical importance. This article reviews five decades of research on the tribocorrosion of aluminum alloys, from experimental to computational studies. Special focus is placed on two aspects: (1) The effects of alloying and grain size on the fundamental wear, corrosion, and tribocorrosion mechanisms; and (2) Alloy design strategies to improve the tribocorrosion resistance of aluminum alloys. Finally, the paper sheds light on the current challenges faced and outlines a few future research directions in the field of tribocorrosion of aluminum alloys. [ABSTRACT FROM AUTHOR]

The current review gives an insight into high-entropy alloys (HEAs) as a new possible binder material for the tungsten carbides, heavy tungsten alloys, and titanium carbo-nitride (Ti(C,N)) based cermet composites. The existing binder materials (for instance, Co, Ni, etc.), produced by powder metallurgy methods, have limited tool bits performance and short service life while mining applications; however, replacing existing binders with more accurate binder material is still a great challenge for researchers. Therefore, the present review is explicitly and precisely dedicated to the finding of the HEAs-based binder materials for the WC hard metals, heavy tungsten alloys, and Ti(C,N) cermet composites to produce high-performance drill bits associated with higher service life in the mining and cutting operations by improving the mechanical properties and tribo-corrosion performance. In this review, the performance of the HEAs over conventional binder materials has been compared and discussed concerning hardness, fracture toughness, oxidation, and tribo-corrosion resistance. The HEA-based binders showed low transformation kinetics and a lack of solubility as compared to the conventional binder. Hence, after optimising the composition, microstructures, properties, and costs of the HEAs-based binder materials, it can be estimated that in the upcoming year, the HEAs-based binder may replace the conventional binder. [ABSTRACT FROM AUTHOR]

Electroless nickel-boron coatings present outstanding properties such as high hardness, excellent wear resistance and uniform coating, and thus they are considered to be alternative to toxic hard chrome coatings. However, they contain lead that is toxic and used as stabilizer in the plating bath. This study aims to investigate the tribocorrosion behaviour of lead-free electroless nickel-boron coatings. In the present research, several tests were carried out to investigate the behaviour of these coatings under both dry and tribocorrosion reciprocating sliding wear against alumina balls, at room temperature. The open circuit potential (OCP) method was used to determine the degradation mechanism of the coatings. The results of the tribocorrosion and dry wear tests showed that the performance of coatings was very different from each other. A steady state for the coefficient of friction (COF) is achieved during the tribocorrosion test, whereas the constant production of debris and their presence in the contact implied an increase in COF with distance during the dry wear test. The wear mechanisms of these coatings also presented variations in these tests. It was found that the wear area calculated from tribocorrosion is lower (56 µm2) than the one from dry sliding test (86 µm2). [ABSTRACT FROM AUTHOR]

A failure analysis of API X52 steel pipeline was conducted. The investigation included complete material characterizations using tensile and hardness testing, optical microscope, SEM, and EDS. The main failure occurred in the downstream pipe located near the welded joint at the elbow outlet instead of elbow which was interesting. The main mechanism of failure was found to be erosion-corrosion mechanism that caused breakdown of the protective FeCO3 film, thinning of the downstream pipe, and finally failure. It is believed that the erosion-corrosion was induced by sand impingement due to turbulent flow that was promoted by sudden change in the flow cross section between the elbow inlet and upstream pipe and poor welding quality of joint at the elbow outlet. [ABSTRACT FROM AUTHOR]

Several leaks appeared in a mild steel (MS) pipe jet nozzle installed in a direct impact test rig after a few months of operation in erosive flow at the Centre for Erosion–Corrosion Research. The locations of perforation leaks were primarily upstream, but severe wall thinning was also noticed adjacent to the exit section. In this paper, a failure analysis was carried out on the leaking of a pipe jet nozzle, and the results are discussed in detail. The investigation carried out includes visual observation, scanning electron microscopy, 3D scanning, energy-dispersive spectroscopy, and laser profilometry measurements. In addition, numerical simulations based on computational fluid dynamics (CFD) and the discrete phase model (DPM) were conducted to investigate the root cause of the failure of leaks in the pipe jet nozzle. Further CFD-DPM simulations were performed on three different pipe jet designs for liquid–solid flow conditions, and were compared to find an alternative design to prevent the failure of the pipe jet nozzles. It was found that the increase in turbulence along with multiple impacts of particles on the wall generate leaks and cracks in the pipe jet nozzle. Moreover, the CFD-DPM showed a five-fold reduction in the maximum erosion rate; this was observed in the replacement of failed pipes with the proposed alternative nozzle pipe design featuring a chamfer reducer section. The CFD-DPM analysis of all geometric configurations showed that alteration of reducer section design has the greatest impact on erosive wear mitigation. [ABSTRACT FROM AUTHOR]

The behavior of TiVN on the tribological and mechanical properties of titanium, as well as its biocompatibility for use as a biomaterial, is studied. The coatings are deposited using direct current magnetron sputtering on titanium substrates, with varying deposited power of titanium and vanadium on the surface layer. During the process of obtaining the TiVN coating, TiN and VN are deposited as interlayers to enhance the adhesion between the coatings and the substrates. The average thickness of the obtained coatings is 1.2 μm. The chemical characterization, nanohardness tests, and tribocorrosive behavior are evaluated using potentiodynamic polarization tests., A pin-on-disk wear test was used to study the tribocorrosion behavior of the coating systems and determine their synergistic behavior. The coupling with potentiodynamic polarization tests improved the corrosion resistance of the system from 2.76 μ to 1.86 μA. Notably, there was a significant enhancement in corrosion resistance, with average corrosion current values of 2.54 μA/cm2 and a coefficient of friction of 0.35. Additionally, hardness values of 15.6 GPa were observed, compared to 4.51 GPa for the substrate., As the working power for each element was increased. As well as exhibiting good behavior in the relationship between wear and corrosion for TiVN1 to TiVN4 coatings, there was an antagonistic-synergistic behavior observed for the TiVN5 to TiVN8 coatings. Additionally, the biocompatibility of the ternary systems was evaluated, and the samples incubated in the TiVN coatings showed good cell viability. [ABSTRACT FROM AUTHOR]

To promote the utilization of Mo 2 NiB 2 –Ni cermet under sulfuric acid drew corrosion conditions, it is essential to elucidate the resistance mechanism of these cermets to sulfuric acid corrosion. In this study, the corrosion behavior of Mo 2 NiB 2 –Ni cermets with different Ni content in 90 wt % H 2 SO 4 solution at 110 °C was investigated, and the corrosion resistance mechanism was analyzed. The results reveal that the corrosion weight losses and corrosion rates of the cermets decreased with increasing Ni content. Mo 2 NiB 2 –Ni cermets with higher Ni contents exhibited improved corrosion resistance. This improvement can be attributed to the generation of a considerable amount of NiSO 4 corrosion products from the Ni binder phase corroded by H 2 SO 4 , which led to the subsequent formation of a large-scale, flat, and dense corrosion products layer with a certain thickness. This effectively prevented further erosion of the inner matrix and improved the corrosion resistance of the cermet. Additionally, the electrochemical results indicate that the corrosion product layer hindered the passage of electric charges through the layer, which inhibited the corrosion reaction. [ABSTRACT FROM AUTHOR]

Erosion-corrosion resistance is a critical factor in the service life extension of metallic structural materials in front of complex flow and solid impingement. To improve the erosion-corrosion resistance, a CrN/Cr gradient coating was fabricated on carbon steel by the double glow plasma alloying technique. The CrN/Cr gradient coating mainly consists of the CrN phase and (Fe, Cr) metal phase. Debye rings from the X-ray pattern illustrated that the coating was under a compressive stress of 868 MPa. Residual stress and fine toughness of the gradient structure enhanced its adhesion strength, endowing it with the potential to accommodate strains caused by external forces. The potentiodynamic polarization test illustrated that the addition of solid particles and the increase in flow velocity severely weakened the protective ability. The mass loss rate results illustrated that the synergistic effect made the greatest contribution to the erosion-corrosion damage of the CrN/Cr gradient coating, while its proportion increased as the flow velocity increased. Compared to the substrate, the gradient structure of the coating facilitated interruption of the sharp interfaces, thereby reducing the deformation mismatch and enhancing the damage tolerance of the coating. [ABSTRACT FROM AUTHOR]

This work investigates the influence of altered engine oil on the tribological performance, focusing in particular on wear and interconnected tribofilm formation. For this purpose, Zinc dialkyldithiophosphate (ZDDP) additivated engine oils of different degradation levels, produced in an artificial oil alteration process, were used in tribometer tests with a nitride steel piston ring against a grey cast iron cylinder liner model contact. Parameters were chosen to simulate the boundary and mixed lubrication regime typical for the top dead centre conditions of an internal combustion engine of a passenger car. Wear of the cylinder liner specimens was continuously monitored during the tribometer tests by the radio-isotope concentration (RIC) method, and tribofilms were posteriorly investigated by X-ray photoelectron spectroscopy (XPS). The results clearly show that the steady-state wear rates for experiments with altered lubricants were significantly lower than for the experiments with fresh lubricants. XPS analysis on the formed tribofilms revealed a decrease in sulphide and an increase in sulphate states for altered oils evaluated at 120 °C oil temperature, correlating with a decrease in steady-state wear rate. This finding emphasizes the role of sulphate species in the tribofilm formation process and its anti-wear capabilities, in contrast to the sulphide species and the (poly-)phosphate species, as outlined in most of the ZDDP literature. Moreover, the RIC signal that represents the amount of wear in the engine oil showed a decrease over time for specific altered lubricants and test conditions. These "negative" trends in the wear signal are remarkable and have been identified as an incorporation of wear particles from the lubricant into the tribofilm. This finding is supported by XPS results that detected an iron-oxide layer with a remarkably similar quantity within the tribofilm on the surface. Based on these findings, an assessment of the minimum film formation rate and particle incorporation rate was achieved, which is an important basis for adequate tribofilm formation and wear models. [ABSTRACT FROM AUTHOR]

In modern aviation production, innovative hard-to-machine materials with unique physical and mechanical properties are being used increasingly. When processing such materials, the weakest link in the technological chain of production is the metal-cutting tool. In this paper, to improve the efficiency of the blade cutting of heat-resistant alloys, we propose the use of nanostructured multilayer wear-resistant coatings with subsequent laser processing of the cutting surfaces of the end milling cutters according to various schemes. In this case, an increase in the wear-resistant properties of the cutting edge by 15%–20% is provided due to the formation, at high temperatures, of secondary structures with increased wear resistance and a reduction of the temperature and force loading of contact processes. Methodologically, the work was carried out in several consecutive stages: the first stage was the determination of effective grades of wear-resistant coatings obtained via various installations with their subsequent laser processing during the «SharpMark™ Fiber» installation; at the second stage tribotechnical tests were carried out during the tribometer and adhesion installation; and in the third stage wear-resistant, temperature-force tests were carried out using milling machines in various cutting modes. According to the results of the field tests, the tool durability period was increased by 15%–20%. [ABSTRACT FROM AUTHOR]

The effective diffusion of hydrogen in a cylindrical geometry, mimicking a pipe with a coating defect, was investigated by modelling and verified experimentally. Analytical solutions for the extreme cases of no hydrogen uptake and constant hydrogen uptake were developed. Simulations showed less than 5% error, when compared to two well-documented reference cases for diffusion. The intermediate case of modelling kinetic controlled hydrogen uptake was investigated and the effects of time, position, effective diffusion coefficient, corrosion protection current density and their binary interactions, were reported. Modelling results show, that certain parameter combinations such as effective hydrogen diffusion coefficients between 10−11 - 10−9.5 m2 s−1, particularly in combination with a hydrogen uptake j H of more than 0.1 A m−2, may lead to locally increased hydrogen concentrations in the material. • Cathodic corrosion protection can lead to accumulation of hydrogen in the material. • Corrosion protection current densities from ISO norms may already lead to H accumulation. • Analytical model for diffusion in cylidrical geometry developed, including coating defect areas. • Influence and interplay between parameters such as time, position, diffusion, and kinetic hydrogen uptake quantified. • Simulations verified against experiments as well as limiting special cases and show good agreement. [ABSTRACT FROM AUTHOR]

Micro-arc oxidation is a technique used to modify the surface of metals by anodic oxidation. The process changes the material's surface characteristics to improve its wear, corrosion, and tribocorrosion resistance. Additionally, the technique allows for incorporating elements that contribute to osseointegration when the material is intended for biomedical applications. The main objective of this study is to enhance the surface of the Ti-25Ta binary alloy, which has the best mechanical compatibility among the alloys of the Ti–Ta system, by using the micro-arc oxidation method. The surface treatment was performed to promote the incorporation of calcium, phosphorus, and magnesium, followed by heat treatments to modify the crystalline phases of the coating to increase the hardness of the oxide layer, improving adhesion and wear resistance. The structural and microstructural characterization, performed by X-ray diffraction and microscopy (scanning electron and confocal), showed that ceramic coatings are initially composed of TiO2 (anatase and rutile) and calcium carbonate (CaCO3). Increasing the heat treatment temperature to 600 ℃ induced rutile formation. For temperatures above 600 ℃, the calcination of the CaCO3 compound occurs, forming calcium oxide and calcium titanate in the form of perovskite (CaTiO3). Regarding the morphology, the high temperatures increased the crystallinity, decreased the number of surface pores and thickness of the MAO layer, and increased the hardness value of the coating, consequently improving the wear resistance of the Ti-25Ta alloy. [ABSTRACT FROM AUTHOR]

Introduction: The main aim was to analyse the series of 29 collected cemented Charnley–Muller Alivium retrievals with the meantime in situ of 27 years. In addition, the revision rate of 1425 Alivium prostheses implanted at our institution between 1977 and 1992 was calculated. Materials and methods: The revision percentage of the Alivium cohort was calculated up to 45 years of follow-up and compared to that of all total hip arthroplasties (THAs) implanted in the same period (No. 5535). Metal and polyethylene retrieved components were inspected in 29 cases for wear damage and roughness. Wear particles were retrieved from periprosthetic tissue using digestion protocols and their composition, morphology, and size distribution were investigated. Periprosthetic tissue was analysed histologically. Results: The revision percentage of the Alivium cohort was 16% at 45 years of follow-up. It was comparable to all the THAs implanted at the same time (18%). The shape of polyethylene particles isolated from periprosthetic tissue corresponded to the wear pattern on polyethylene cups. Polyethylene particles were the main wear product, with the majority (68%) of particles smaller than 0.1 µm. Metal particles were rare with two types: CoCr and Cr based. Histological analysis showed that in 14 out of 18 specimens, the metal particles were graded + 1, reflecting that the metal loading in the periprosthetic tissue was low. Conclusions: Our study represents valuable data not reported previously on the survival rate of Charnley–Muller prostheses at 45 years of follow-up and a unique insight into the collected retrievals from the materials' point of view. [ABSTRACT FROM AUTHOR]

This research intends to enhance the tribo-mechanical and corrosion properties of ADC 12 alloys by incorporating marble dust (MD) as a reinforcing element. Composites with varied MD concentrations (0–10 wt%) were fabricated using a squeeze casting process, addressing the limitations of conventional casting techniques. The microstructural analysis confirmed homogeneous MD dispersion within the ADC 12 matrix, facilitating an effective load transfer and solid interfacial bonding. As MD content increased, the experimental density decreased, while porosity increased from 1.22% to 3.97%. Remarkably, adding 4 wt% MD yielded a 20.41%, 17.63%, and 15.75% enhancement in hardness, tensile, and compression strength compared to the as-cast ADC 12. Incorporating MD particles facilitated Orowan strengthening and Hall–Petch strengthening mechanisms, contributing to the observed improvements. The wear rate was reduced by 18.33% with MD content, showing a 17.57% corrosion reduction at 72 h. These outcomes establish the synergistic benefits of ADC 12 squeeze casting with MD reinforcement, delivering superior tribo-mechanical and corrosion properties. [ABSTRACT FROM AUTHOR]

The application of Artificial Neuronal Networks (ANN) offers better statistical accuracy in erosion-corrosion (E-C) predictions compared to the conventional linear regression based on Multifactorial Analysis (MFA). However, the limitations of ANN to require large training datasets and a high number of inputs pose a practical challenge in the field of E-C due to the scarcity of data. To address this challenge, a novel ANN method is proposed, structured to a small training dataset and trained with the aid of synthetic data to produce an E-C neural network (E-C NN), applied for the first time in the study of E-C wear synergy. In the process, transfer learning is applied by pre-training and fine-tuning the model. The initial dataset is created from experimental data produced in a slurry pot setup, exposing API 5L X65 steel to a turbulent copper tailing slurry. To the previously known E-C scenario for selected values of flow velocity, particle concentration, temperature, pH, and the content of the dissolved C u 2 + , new experimental data of stand-alone erosion and stand-alone corrosion is added. The prediction of wear loss by E-C NN considers individual parameters and their interactions. The main result is that E-C ANN provides better prediction than MFA as evaluated by a mean squared error (MSE) values of 2.5 and 3.7, respectively. The results are discussed in the context of the cross-effect between the proposed prediction model and the resulting estimation of relative contribution to E-C synergy, which is better predicted by the E-C NN. The E-C NN model is concluded to be a viable alternative to MFA, delivering similar prediction with better sensitivity to E-C synergy at shorter computation times when using the same experimental dataset. [ABSTRACT FROM AUTHOR]

In order to clarify the difference in corrosion performance between low Cr-containing (3Cr, 5Cr, and 9Cr) tubing material and carbon steel N80 in the Carbon dioxide (CO2) flooding injection and production environment and the range of adaptation, corrosion tests and analysis were carried out in simulated working conditions. In this paper, the electrochemical potentiodynamic testing technology and the weight loss method were used to comparatively analyze the corrosion performance and variation law of three types of tubing materials with different Cr contents in a simulated CO2 flooding-produced water environment under different partial pressure conditions. Additionally, scanning electron microscopy and Energy Dispersive Spectrometer (EDS) analysis were conducted to examine the surface corrosion morphology characteristics and elemental composition of material films under various conditions. The results indicate that the open circuit potentials of 3Cr, 5Cr, and carbon steel N80 were similar under the same experimental conditions. However, the open circuit potentials of 9Cr were relatively high and there was an obvious passivation zone in anodic polarization. Nevertheless, compared to that of 13Cr, the passivation state was unstable, and pitting corrosion continued to expand once it formed. This demonstrates that the corrosion resistance of the material can be effectively enhanced and a stable passivation state can be achieved in the anodic polarization region when the Cr content of the material reaches at least 13%. The service life of materials can be predicted based on their corrosion rate under high temperature and pressure simulation environments. We found that 9Cr materials exhibited good adaptability while 3Cr and 5Cr materials showed poor adaptability. Therefore, it was not recommended to use 3Cr and 5Cr materials. Therefore, 3Cr, 5Cr, and N80 materials will be used at lower partial pressure levels of CO2 (<0.2 MPa). [ABSTRACT FROM AUTHOR]

To improve the surface properties of austenitic stainless steels, a thick S-phase layer was prepared by using a novel critical temperature nitriding (CTN) process. The properties of the thick S-phase layer were optimized by controlling the process parameters. The microstructures and phase compositions of CTN-treated layers were characterized by the optical microscope, scanning electron microscope and X-ray diffraction, respectively. The surface properties, including corrosion and wear resistance, were systematically investigated by the electrochemical workstation, micro-hardness tester and ball-on-disk tribometer, respectively. The results showed that a thick S-phase layer with a thickness of 18 to 25 μm can be fabricated in a short time by critical temperature nitriding, which represented higher efficiency than conventional low-temperature nitriding. Although the most top surfaces of CTN-treated layers contain massive iron nitrides, there are no precipitates in the inner nitrided layer. The electronic work function calculated by first-principles method has confirmed that those iron nitrides had a slight influence on the corrosion resistance of nitrided layers. The optimized CTN-treated layer exhibited a comparable corrosion resistance and wear resistance as the low-temperature nitrided layer. The CTN process is considered a potentially highly efficient surface modification method for austenitic stainless steels. [ABSTRACT FROM AUTHOR]

The inherent micropores of micro-arc oxidation (MAO) coatings on magnesium alloy often cause poor long-term corrosion resistance. Herein, a low-porosity and high corrosion-resistant 8HQ/LDH/MAO composite coating, comprising a layered double hydroxide (LDH)-doped MAO primer and a top layer of 8-hydroxyquinoline (8HQ) inhibitor film, was deposited onto the magnesium alloy surface. Characterizations such as high-resolution field-emission transmission electron microscopy were performed to observe the synthesized nanoparticles' morphology, size, composition, and structure. Results confirmed the successful synthesis of nitrate ion intercalated MgAl-LDH nanosheets and demonstrated the increase in thickness and denseness of the MAO coating after LDH doping. Based on electrochemical impedance spectroscopy and Tafel curves, the corrosion current density (j corr) of the newly fabricated 8HQ/LDH/MAO composite coating was reduced by about three orders of magnitude. The low-frequency impedance modulus (| Z | ƒ=0.1 Hz) increased by nearly four orders of magnitude compared with that of bare Mg alloy. After 14 days of exposure to the corrosive electrolyte, the composite coating maintained a low j corr , showing significantly enhanced corrosion resistance compared with single MAO coating. These findings demonstrated the synergism of LDH doping with 8HQ sealing to enhance the corrosion protection of MAO coating on magnesium alloy. [ABSTRACT FROM AUTHOR]

This research work highlights the tribomechanical investigations of using a low loading fraction of two ceramics combinations, Alumina (Al2O3) and Silicon Carbide (SiC) as reinforcement for Low-density Polyethylene (LDPE) matrix. The hybrid additives with different weight percentages (0.1 + 0.1, 0.25 + 0.25 and 0.5 + 0.5 wt%) were mixed with LDPE matrix and the degree of homogeneity was controlled using double-screw extruder prior to fabricating the composite samples via the injection molding machine. The nanoparticles fillers were characterized by field emission scanning electron microscope (FESEM), EDX and particle size analyzer to check its morphology, composition and size distribution. Thermogravimetric analyzer (TGA) and melting flow index (MFI) were performed for the fabricated nanocomposites samples. The mechanical properties of the nanocomposite were evaluated by performing tensile test, bending test and Shore-D hardness test, while the tribological performance was investigated using a ball on desk apparatus under different applied loads and sliding times. Moreover, in order to confirm the load-carrying capability of the composite, contact stresses was measured via finite element model using ANSYS software. The results show that the incorporation of low fraction hybrid ceramic nanoparticles can contributed positively in the tribological and mechanical properties. Based on the experimental results, the maximum improvement in the tensile strength was 5.38%, and 8.15% for hardness LDPE with 0.5 Al2O3 and 0.5 SiC, while the lowest coefficient of friction was noticed under normal load of 10 N, which was approximately 12.5% for the same composition. The novel approach of incorporating low fraction hybrid ceramic nanoparticles as reinforcement for LDPE matrix is investigated, highlighting their positive contributions to the tribological and mechanical properties of the resulting nanocomposites. [ABSTRACT FROM AUTHOR]

The present study investigates the application of friction stir processing (FSP) on the degradation (wear, corrosion, and wear-corrosion synergism) response of cold spray additive manufactured (CSAM) 316L SS components. All tribological-based tests were conducted using a reciprocating ball-on-flat configuration in 3.5 wt% NaCl solution. Each degradation response was then correlated with the atomic, microstructural, and mechanical characteristics of the pre-and-post-FSP surfaces. In pure wear conditions, the austenitic phase transformation induced by FSP treatment decreased the frictional response and slightly increased the wear rate compared to the unprocessed CSAM substrate. In pure corrosion conditions, the densified surface enabled by FSP resulted in improved electrochemical resistance and a lessened corrosion rate. In wear-corrosion synergism conditions, the influence of FSP decreased the cumulative wear loss and wear-corrosion synergism of the CSAM substrate. It is believed that the combination of phase change, surface densification, and microstructural refinement induced by FSP are responsible for the improved wear-corrosion resistance. Based on these findings, it can be suggested that FSP is indeed a useful technique to improve the wear, corrosion, and wear-corrosion characteristics of CSAM 316L SS. [ABSTRACT FROM AUTHOR]

Because of the microstructural anisotropy for laser cladding materials, the tribo-corrosion performance can vary significantly with different directions. In this study, one certain Fe-based coating was fabricated by laser cladding. To study the effects of anisotropy, three working surfaces (0°, 45°, and 90° to the building direction) were machined from the laser cladding samples; as-cast samples with an approximately homogeneous structure were prepared as controls. The tribo-corrosion tests were conducted in a 3.5 wt% NaCl solution with varying normal loads (5, 10, and 15 N). The results demonstrated that the 45° surface has superior friction stability, corrosion resistance, and wear resistance. This was directly related to the crystal orientation and grain boundary density. In addition, a refined microstructure may enhance tribo-corrosion properties by increasing deformation resistance and decreasing surface activity. [ABSTRACT FROM AUTHOR]

Anticorrosive coatings for corrosion protection on aluminum alloy remain challenges in high protection efficiency and stability with facile design. Here, a stable superhydrophobic film is successfully prepared on 5052 aluminum alloy (AA5052) by electrodeposition to enhance its corrosion resistance in 3.5 wt% NaCl solution. The contact angle reaches 157° at the electrodeposition voltage of 10 V. Electrochemical tests confirm that it can serve as a highly effective and stable coating for corrosion protection with an inhibition efficiency (η) of 99.1%. The charge transfer resistance of the coated Al alloy increases remarkably from 8.955 kΩ cm2 to 366.1 kΩ cm2. Besides, the superhydrophobic surface shows good stability when it is exposed to air and NaCl solution for a long time. After immersion for 12 days in 3.5 wt% NaCl solution, the superhydrophobic coating still exhibits a low corrosion current density of 3.309 × 10-7A/cm2. The synergy effects of the superhydrophobicity and the Ce3+ endow the coating with remarkably enhancing corrosion resistance. This facile strategy can provide new ideas for designing highly effective and stable anti-corrosion coatings on aluminum alloy. [ABSTRACT FROM AUTHOR]

Ti6Al4V alloy has good corrosion resistance due to the formation of the passive oxide films on the surface of Ti6Al4V alloy. However, Ti6Al4V alloy has poor tribocorrosion resistance in the seawater environment. Herein the present work, plasma electrolytic oxidation (PEO) with the electrolyte of glycerol and sodium borate is used to generate PEO coatings on the surface of Ti6Al4V alloy to improve its tribocorrosion properties. The microstructure and tribocorrosion properties of PEO coatings are investigated by using scanning electron microscopy, X‐ray diffraction, and tribometer, respectively. The growth kinetics and the tribocorrosion mechanisms of PEO coatings are discussed in detail. It is shown in the results that PEO coatings deposited on the surface of Ti6Al4V alloy are composed of rutile and anatase phases. The surface hardness and thickness of PEO coatings are enhanced with the increase of the voltage and time. The wear rate of Ti6Al4V alloy with PEO coatings is significantly reduced in artificial seawater. [ABSTRACT FROM AUTHOR]

Cast Nickel Aluminium bronze widely finds its application in marine components because of ease its of fabrication in complex shapes and geometries. The cast alloys are prone to erosion-corrosion failures in the marine environment. To enhance the corrosion resistance of these alloys, surface modification techniques are being used. Friction surfacing is one such newly developed technique which can be employed to improve the erosion-corrosion resistance of cast NAB alloys. In this investigation an attempt has been made to deposit extruded NAB alloy over cast NAB alloy by friction surfacing technique. The influencing process parameters like plunge rate, rotational speed and transverse speed of tool (extruded NAB alloy rod) were mathematically modelled and empirical relationships were developed using response surface methodology (RSM). These parameters were further optimised using Particle Swarm optimization (PSO) to attain the maximum bonding strength. The Ram tensile strength carried on the surfaced alloy had maximum strength of 245 MPa. The mathematically modelled methods provided results nearing to the experimental values. The values were in good agreement with the experimental values with error deviation of 5%. The erosion corrosion property of the friction surfaced NAB alloy improved than the cast alloy. [ABSTRACT FROM AUTHOR]

Stainless steel (SS316L) and titanium alloy (Ti6Al4V) exhibit suitable properties for biomedical applications; however, the tribocorrosion of these materials, which is associated with metallosis, is still a significant concern. This work investigates the effectiveness of DLC smoothing coatings applied to the metals to reduce tribocorrosion and improve cell viability. The study was motivated by many reports of metallosis caused by metal debris in the soft tissues of the body. DLC coatings were produced using the plasma-enhanced chemical vapor deposition (PECVD) technique. The cytotoxicity, genotoxicity, and cell viability of metallic samples with and without DLC coatings were analyzed, considering the chemical composition of the coating and metallic components. The results show that the DLC coatings presented suitable interaction properties and no cytotoxicity or genotoxicity when exposed to the cellular environment, compared with the control group (p < 0.0001). They also demonstrated cell viability, low friction representing a reduction of 80%, and hardness 23–26 GPa, making them ideal for use on fixed implants. It is necessary to control the thickness and roughness of the coating to avoid pinholes and increase the corrosion protection of implants. These DLC coatings with low friction coefficients could facilitate the fixation of implantable pins and screws, including Kirschner wires. [ABSTRACT FROM AUTHOR]

To reveal the influence of passive film on the tribocorrosion behaviour of stainless steel, SUS430 was loaded at 2.0 N or 10.0 N in aqueous solutions with various pH from 1.0 to 10.0. The pure wear behaviour was investigated in the air for comparison. The polarization behaviour, the morphology of the worn or tribocorroded surface, and the depth profiles of the formed groove were measured to discuss the mechanism. The passive state was confirmed at pH = 7.0 and 10.0, but vanished at pH = 1.0 and 2.0. The pure wear in air depended on the applied loads, rather than the sliding time. On the other hand, the tribocorrosion in deionised water was much smaller than the pure wear in air. Under a load of 2.0 N, the tribocorrosion at pH = 1.0 was weaker than pH = 2.0. However, the situation reversed when increasing the load to 10.0 N. The tribocorrosion in neutral and alkaline solutions is considerably smaller than in acid solutions. [ABSTRACT FROM AUTHOR]

To improve the corrosion resistance of 316L substrate and lengthen its useful life in marine environments, Ni-based/WC/Y2O3 cladding layers with different Y2O3 contents were fabricated on 316L stainless steel using laser cladding technology. The influence of Y2O3 additives on the microstructure and properties of the cladding coatings was investigated by using scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, a microhardness tester, an electrochemical workstation and a tribometer. Results show that the metallurgical bonding is well formed between the coating and the 316L substrate. The coating consisted primarily of γ-Ni phase and carbides. Adding an appropriate amount of Y2O3 can effectively refine the microstructure and inhibit the precipitation of the carbide hard phase; in addition, the added rare earth element can promote the solid-solution-strengthening effect of the cladding coatings, thus improving the microhardness and wear resistance of the cladding coatings and their electrochemical corrosion property in 3.5 wt% NaCl solution. The hardness of the Ni-based/WC coatings was substantially higher than that of the substrate, and it was greatest at a Y2O3 content of 1%. The corrosion and wear resistance of Y2O3-modified Ni-based/WC composite coatings are significantly better than those of the composite coating without Y2O3. [ABSTRACT FROM AUTHOR]

Erosion‐corrosion (E−C) is one of the most intense forms of metal degradation observed whenever a static metallic material is in contact with dynamic liquid. Efficiency of industrial plant mainly depends upon the condition of various components of the equipment. Collective mechanism of corrosion and erosion results in severe surface deterioration with heavy material loss due to synergistic effect. Erosion‐corrosion is mainly observed in the pipelines used in oil and gas industries, petroleum industries, heat exchanges and mainly in marine equipment. Free flowing saline water, containing different grades of sand particles adversely affect marine equipment. Numerous reports are available discussing the impact of erosion‐corrosion in chemical industries. Single report documenting all types of prototypes, comparative study of erosion corrosion of various engineering materials and control techniques is highly limited. This review gives vivid account of various types of prototypes, comparative study of erosion‐corrosion of various engineering materials, various factors affecting tribology of system and control techniques is a systematic way. Application of corrosion inhibitors appears to be an effective method to reduce erosion‐corrosion. This review highlights the importance of understanding the mechanism of erosion‐corrosion in industrial equipment and provides a succinct overview of erosion‐corrosion synergism. [ABSTRACT FROM AUTHOR]

Corroded points can act as stress concentrators, usually resulting in the component failure at fewer cycles than was initially projected. Aerators are widely used in waste treatment units for chemical and biological control. Due to the chemically aggressive environment to which these components are subjected, they usually fail due to corrosion in one or more components. Cooling towers are one of the most applied equipment for temperature control in industrial processes. Due to generally hostile environments and operating conditions, this equipment is subject to failures which almost always lead to system imbalance followed by the catastrophic failure of the component. This work investigates the synergic effect of corrosion and fatigue in two separate case studies. In the first, the wear of the mixing shaft of an aerator was investigated. It was observed that the root cause of wear was the corrosion of the dissimilar welded joints in the mixing blades, which suffered the sensitization phenomenon. This sensitization led to the formation of accentuated corrosion pits, which concentrated stresses and led to the failure of the welded joint. After the joint failure, the component was left in an unbalanced state, which resulted in severe wear on the mixer shaft of the aerator. In the second, the failure of a cooling tower fan shaft fracture was evaluated, with the fractured component being compared to an intact one. As means of analysis were employed: metallographic tests on macroscopic and microscopic scales, tensile, chemical composition, hardness tests, and fractography. The results indicated the component failure due to fatigue under low amplitude loading, with corrosion pits as stress intensifiers. [ABSTRACT FROM AUTHOR]

Solid lubricant materials could be used in various extreme conditions owing to the excellent anti‐friction and ‐wear with the low friction coefficient and wear rate. Polyurethane (PU)‐based solid lubricants as one of the widely utilized composite materials had been well‐known by researchers all over the world. PU‐based composite lubricants were commonly segmented into single‐phase lubricants and multi‐phase lubricants via inorganic or organic lubricant additives. What is more, the modified PU by solid lubricants would endow higher tribological performances than that of single‐phase PU‐based lubricants. Based on the multi‐component synergy, the multi‐phase lubricants could significantly improve the PU matrix's lubrication and wear resistance and enhance the comprehensive performance such as corrosion resistance. This paper mainly discussed and summarized the recent development in tribological performances of PU‐based composite lubricants, and explored their prospective research directions. [ABSTRACT FROM AUTHOR]

MXenes, a newly emerging class of layered two dimensional (2D) materials, are promising solid lubricants due to their 2D structure consisting of weakly-bonded layers with a low shear strength and ability to form beneficial tribo-layers. This work aims at evaluating for the first time MXenes lubrication performance and tribofilm formation ability on different metallic substrates (mirror-lapped Fe and Cu discs). After depositing MXenes via ethanol (1 wt%) on the substrates, pronounced differences in the resulting substrate-dependent frictional evolution are observed. While MXenes are capable to reduce friction for both substrates after the full evaporation of ethanol, MXenes lubricating effect on Cu is long-lasting, with a 35-fold increased lifetime compared to Fe. Raman spectra acquired in the wear-tracks of the substrates and counter-bodies reveal notable differences in the friction-induced chemical changes depending on the substrate material. In case of Fe, the progressive failure of MXenes lubrication generates different Fe oxides on both the substrate and the ball, resulting in continuously increasing friction and a poor lubrication effect. For Cu, sliding induces the formation of a Ti3C2-based tribofilm on both rubbing surfaces, enabling a long-lasting lubricating effect. This work boosts further experimental and theoretical work on MXenes involved tribo-chemical processes. [ABSTRACT FROM AUTHOR]

The degradation of materials due to erosion–corrosion occurs on the components that handle particle-laden corrosive slurry. The combined attack of mechanical erosion and corrosion shows increased material loss than the individual action of erosion and corrosion. The synergy accelerates material removal by eroding the corroded surface layer and corroding the surface due to the elimination of the passivating oxide layer by erosion. The synergism of erosion–corrosion is found to be more complex. Further, the coupled effect of mechanical erosion and electrochemical corrosion and the factors influencing erosion–corrosion still needs to be fully investigated. This review aims to provide a general and detailed summary of the interaction between erosion and corrosion of materials for the applications of pump impellers, pipelines for desalination, and oil and gas transportation. Importance is also given to the factors influencing erosion–corrosion, such as erodent particle properties (hardness, size, and shape), slurry properties (particle concentration, pH value, temperature), and flow characteristics (impingement angle, velocity). The various erosion models and the most used apparatus have also been reviewed. [ABSTRACT FROM AUTHOR]

To comply with the high demand for efficient and sustainable lubrications, carbon-based tribofilms and/or nanomaterials have emerged as a potential solution that can resolve the current major shortcomings of phosphorus- and sulphur-rich tribofilms and protective coatings. Although their employment is still in the early stages of realization and research, these tribofilms receive significant interest due to their capability to continuously and in situ repair/replenish themselves during sliding, which has been an ultimate goal of all moving mechanical systems. Structurally, these tribofilms are complex and predominantly amorphous or disordered with/without graphitic domains (e.g., graphene/graphite, onion-like carbon, etc.). Chemically, the compositions of these tribofilms vary significantly with environments, conditions, and material precursors. Yet, the structural properties of carbon-based tribofilms remain largely ambiguous, which precludes a full understanding of the mechanisms underlying the formation and lubrication performance. This review will summarize the current state-of-art research about the in situ carbon-based tribofilms that have been published since the pioneering works. Particularly, this work will highlight the recent approaches to generate these tribofilms, their associated lubrication performance, current understanding of the formation mechanics, common analytical approaches for these tribofilms, and the compatibility of these tribofilms with other additives. Together, the overall outlooks will be drawn, demonstrating the knowledge gaps and proposing further investigation tactics to tackle these emerging issues. [ABSTRACT FROM AUTHOR]

To improve the hardness and wear resistance of an aluminum alloy, Fe-Al intermetallic coatings are synthesized in situ on the surface of aluminum alloys by laser cladding. An x-ray diffractometer (XRD) and a scanning electron microscope are used to characterize the phase and microstructure of the coating. The corrosion resistance, wear resistance, and hardness of the coating were measured by an electrochemical workstation, a reciprocating friction and wear tester, and a Vickers hardness tester, respectively. There are no pores but some microcracks in the coating. The coating structure is composed of a dendrite crystal, a columnar crystal, and an equiaxed crystal. The XRD results show that the Fe-Al coating is mainly composed of body-centered cubic solid solution, FeAl phase, and Fe3Al phase. At the same time, the average hardness of the coating reaches 601.54 Hv0.2, which is approximately 5.9 times that of the substrate (101.8 Hv0.2). Compared with the substrate, the self-corrosion voltage of the coating in 3.5% NaCl solution increased by 0.41 V, the self-corrosion current reaches 1.65 × 10−5 A, and the protection rate increased by 71%. [ABSTRACT FROM AUTHOR]

Machined, etched, blasted, and anodized commercially pure titanium (Cp-Ti) samples were used in this study. The aim of this study is to examine the effects of the most applied surface treatments on Cp-Ti samples, which are preferred for use in biomedical applications, on surface wettability, corrosion, and tribocorrosion behaviors. It was observed that surface morphology had a significant effect on surface wettability. The best wettability was obtained from the anodized sample. In the samples whose corrosion and tribocorrosion performances were examined, it was observed that the highest resistance was obtained from the anodized sample, compared to other samples. [ABSTRACT FROM AUTHOR]

At Mae-Moh power plant, Thailand, superheater tubes, which are exposed to a fly ash environment, often degrade due to solid particle erosion. To extend the service lifetime of the superheater tubes, the high velocity oxy-fuel (HVOF) thermal spray technique is used to deposit a protective coating on the material, SA213-T22 steel. In this work, the solid particle erosion of Stellite-6 and WC-12Co coatings was investigated using erodent particle impingement at angles of 30 and 90°. This was carried out with an average particle size of 60 μm. The erosion behavior of SA213-T22 with and without Stellite-6 and WC-12Co coatings was examined using ductile and brittle erosion modes. The erosion testing resulted in the brittle mode for both Stellite-6 and WC-12Co coatings, while the SA213-T22 without coating indicated the ductile mode. On investigation of the surface morphology, the SA213-T22 steel showed ploughing and microcutting. The Stellite-6 coating showed some evidence of ductile erosion such as lips on the coating surface, different from the WC-12Co coating which showed microcracks and deep cavities. The erosion resistance of the Stellite-6 coating was higher than the WC-12Co coating. This was due to the strength and toughness of the metal matrix composite structure and the low porosity of the coating. [ABSTRACT FROM AUTHOR]