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Atomistic simulations performed with a family of model potential with tunable hardness have proven to be a great tool for advancing the understanding of wear processes at the asperity level. They have been instrumental in finding a critical length scale, which governs the ductile to brittle transition in adhesive wear, and further helped in the understanding of the relation between tangential work and wear rate or how self-affine surfaces emerge in three-body wear. However, so far, the studies were mostly limited to adhesive wear processes where the two surfaces in contact are composed of the same material. Here, we propose to study the transition from adhesive to abrasive wear by introducing a contrast of hardness between the contacting surfaces. Two wear processes emerge: one by gradual accretion of the third body by detachment of chips from both surfaces and the other being a more erratic mixed process involving large deformation of the third body and removal of large pieces from the soft surface. The critical length scale was found to be a good predictor of the ductile to brittle transition between both processes. Furthermore, the wear coefficients and wear ratios of soft and hard surfaces were found to be consistent with experimental observations. The wear particle is composed of many concentric layers, an onion-like structure, resulting from the gradual accretion of matter from both surfaces. The distribution of sizes of these layers was studied, and it appears that the cumulative distribution of hard surface's chip sizes follows a power law. [ABSTRACT FROM AUTHOR]

Wear failure of cutting inserts is the main form of failure that occurs when cutting difficult-to-machine materials at high speeds. To obtain cutting inserts with outstanding tribological properties, multilayered cubic boron nitride (cBN) and nanocrystalline diamond (NCD) coatings (cBN/NCD) were prepared on WC-6 wt% Co tool substrates. The tribological properties of the multilayered cBN/NCD coatings were studied at different temperatures, and the results showed that the coefficient of friction (COF) and wear rate of the coatings were closely interrelated to the temperatures, and the COF gradually decrease and the wear rate gradually increase as the temperature increased from room temperature (25 °C) to 600 °C. The COF and wear rate of the multilayer coatings at 600 °C were ∼0.05 and 8.43 × 10−6 mm3/(N⋅m), respectively. The wear resistance of the cBN/NCD coatings was higher than that of TiAlN coatings and PcBN tool materials by more than 3 and 4.5 times, respectively. The high-temperature wear failure modes of the multilayered cBN/NCD coatings were abrasive wear, diamond graphitization, and BN hydrolysis. Coating wear accelerated when pores were formed on the cBN surface of a multilayered cBN/NCD coating due to the low nucleation density of diamond. These results would guide the application of cBN/NCD-coated cutting tools in high-speed cutting processes. [ABSTRACT FROM AUTHOR]

This study investigated the microstructure and tribological performance of TiO 2 coating prepared through the plasma-spraying of TiO 2 on an aluminum alloy (ZL109) surface. Box–Behnken design was employed to calculate the optimal spraying parameters (spraying current: 439 A, spraying voltage: 129 V, and Ar flow rate: 117 m3/h). High-temperature tribological characteristics (T = 120 °C) were examined under varying loads (F = 100 N, 120 N, and 140 N). The scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis results revealed that the coating porosity decreased from 3.31 % to 0.31 % with the increase in the spraying voltage from 120 V to 130 V. Both powder and coating exhibited consistent elemental composition (Ti, O) and phase composition (TiO 2 , TiO, Ti 2 O 3). During the spraying process, part of the powder was oxidized. The average coefficient of friction of the coatings varied from 0.05 to 0.08, and as the load increased, the wear mechanism of the coating changed from abrasion to adhesive wear and oxidation. [ABSTRACT FROM AUTHOR]

By incorporating the dual ceramic elements TiB 2 /B 4 C, we investigated their impact on the mechanical properties, thermal properties, and friction performance of copper-based powder metallurgy materials, and elucidated the friction wear mechanism. Additionally, machine learning algorithms were employed to predict the friction coefficient and stability coefficient. The conclusions are as follows:With the increase in the TiB 2 /B 4 C ratio, the trend of mechanical properties initially increases and then decreases, with the optimum ratio being 5:3 for TiB 2 and B 4 C, exhibiting superior mechanical properties. Moreover, B 4 C enhances the thermal conductivity of copper-based friction materials more effectively than TiB 2. In terms of overall friction performance, the ratio of TiB 2 to B 4 C at 5:3 yields better frictional properties. The primary components of the friction surface friction film are CuO, Cu 2 O, Fe 2 O 3 , and B 2 O 3 , transitioning from a ceramic film to a metallic film as the TiB 2 /B 4 C ratio increases. The friction wear mechanism shifts from abrasive wear to severe fatigue wear as the TiB 2 /B 4 C ratio increases, accompanied by oxidative wear. Furthermore, an AdaBoost algorithm model was developed to effectively predict the friction coefficient and stability coefficient, with accuracies of 0.9993 and 0.8739, respectively. [ABSTRACT FROM AUTHOR]

The FeCoCrNiMn high-entropy alloy coating reinforced with WC particles was fabricated on 45# steel using plasma surfacing technique. A comprehensive characterization was conducted to investigate the friction and wear behavior of the coating at various temperatures. Results demonstrated that this coating exhibited exceptional wear resistance at room temperature (RT). However, it experienced slight decomposition of WC particles and oxidation corrosion at 400 °C, resulting in a degradation of its wear resistance. The WC decomposition and oxidation corrosion were aggravated at 600 °C, inducing a stronger oxidation corrosion wear effect, and thus led to a more severe wear of this coating. However, these oxidation products provided considerable lubrication effect resulting in a continuous decrease in friction coefficient, from 0.49 at RT to 0.44 at 400 °C, and reached a lower value of 0.16 at 600 °C. The potential oxidation corrosion wear and lubricating mechanisms of this coating at evaluated temperatures were discussed systematically. [ABSTRACT FROM AUTHOR]

This paper reports a new nondestructive noncontact method of sensing surface roughness, particularly the surface undulation produced in the plowing stage of wear. This method involves inductance measurement. It is fast, provides global information and is suitable for real-time monitoring, but it is limited to electrical conductors. This amounts to structural self-sensing. Ultramild abrasive wear primarily in the plowing regime, with areal weight loss ≤ 0.075 g/cm2 and ≤ 0.040 g/cm2 for steel and aluminum, respectively (i.e., thickness loss ≤ 0.30 mm and ≤ 0.48 mm for steel and aluminum, respectively), is effectively sensed by this method. The inductance measurement involves two electrical contacts (clips) and an LCR meter (2 kHz). The inductance increases monotonically with increasing degree of wear primarily in the plowing regime, beyond which it does not increase further. This is due to the sensitivity of the inductance to the surface undulation, as expected from Faraday's law. Longitudinal wear (wear performed in the inductance measurement direction, i.e., direction along the metal bar length) and transverse wear (wear performed along the direction perpendicular to the inductance measurement direction) give similar weight loss. However, the fractional increase in inductance due to wear is greater for transverse wear than longitudinal wear, as expected from Faraday's law. Hence, the inductance method can discern the surface undulation direction, i.e., the wear direction, but the weight loss method cannot. The fractional increase in inductance due to wear is greater for steel (magnetic) than aluminum (not magnetic). However, magnetic character is not required for the sensing. [ABSTRACT FROM AUTHOR]

Purpose: This empirical study aims to investigate the erosion wear performance of two different 3D-printed materials (acrylonitrile butadiene styrene [ABS] and polylactic acid [PLA]) with various micro textures. The two different textures (prism and square) were created over the surfaces of both materials by using the 3D-printed technique. Design/methodology/approach: The erosion experiments on both materials were performed by using Ducom Erosion Jet Tester. Erosion tests were performed at four different impacting velocities (15, 30, 45 and 60 m/s) with the four different particle sizes (17, 39, 63 97 µm) at the impact angles (30°–90°) for the time duration of 5, 10, 15 and 20 min. The two different textures prism and cone were used for performing the erosion experiments. Taguchi's orthogonal L16 (mixed level) was used to reduce the number of experiments and to determine the impact of these parameters on erosion wear performance of both 3D-printed materials. Findings: The PLA with cone texture was found to be best (against erosion) than the ABS cone and prism textures due to their high hardness (68 HV). Also, the average signal to noise (S/N) ratio for PLA and ABS was measured as 56.4 and 44.4 dB, respectively. As the value of the S/N ratio is inversely proportional to the erosion rate, the PLA has the least erosion rate as compared to the ABS. The sequence of erosion wear influencing parameters for both materials was in the following order: velocity > erodent size > texture > impact angle > time interval. Originality/value: Both PLA and ABS with different micro textures for erosion testing were studied with Taguchi's optimization method, and the erosion mechanisms are well analyzed by using scanning electron microscopy and Image J techniques. [ABSTRACT FROM AUTHOR]

The service performance of polycrystalline cubic boron nitride (PcBN) tools undergoes significant changes due to the deep space environment to the structure and wear behaviors of PcBN. In this paper, the effect of cryogenic treatment (CT) was studied to investigate the physical and tribological behaviors of PcBN. The hardness and wear resistance of PcBN are improved but wear forms are not affected, which are abrasive wear. The shedding of cBN played the role of micro-cutting edges, carving furrows on surfaces. As the CT duration increases, the wear rate of PcBN decreases from 2.56 × 10−8 mm3/N mm to 1.61 × 10−8 mm3/N mm for sliding against Si 3 N 4. When PcBN slid Al 2 O 3 , the lowest wear rate is 1 × 10−8 mm3/N mm which the decline reached 34 %. Due to discrepancies in physical and mechanical properties, Si 3 N 4 and YG8 balls exhibit abrasive and adhesive wear, and Al 2 O 3 shows fatigue wear. Until the fatigue failure appeared, Al 2 O 3 exhibited the lowest wear rate of 2.30 × 10−9 mm3/N mm. Among three materials, the wear rate of Si 3 N 4 was the highest. By calculating the wear rate ratio of the materials, it was concluded that the optimal removal efficiency was achieved for Si 3 N 4 and YG8 when CT duration is 24 and 48 h, respectively. [ABSTRACT FROM AUTHOR]

The wear and friction characteristics of the CuSn10P1 copper alloy are influenced by various factors, including the sliding velocity and applied force. An investigation has been conducted to examine the influence of various loads and sliding velocities on the wear characteristics of the thixoextruded copper alloy. The annealed alloy exhibits a homogeneous distribution of the solid phase, and a liquid island presents in the solid phase. The major phases consist of α-Cu, Cu41Sn11, and a few Cu3P phases. The average coefficient of friction (COF) is between 0.6 and 1.0. SEM-EDS and three-dimensional topography instruments were used to analyze the surface topography and wear rate of reciprocating wear. When the sliding velocity was 5 mm/s, the wear rate increases from 0.07 mm3/Nm to 0.226 mm3/Nm as the load increases from 3 N to 9 N, in accordance with Archard's dry wear law. The worn surface exhibited groove, granular, and layered debris, and the predominant characteristics of the wear were abrasive wear and delamination wear. As the load increased, there was a transition from abrasive wear to delamination wear. [ABSTRACT FROM AUTHOR]

This study utilized ion implantation to modify the material properties of silicon carbide (SiC) to mitigate subsurface damage during SiC machining. The paper analyzed the mechanism of hydrogen ion implantation on the machining performance of SiC at the atomic scale. A molecular dynamics model of nanoscale cutting of an ion-implanted SiC workpiece using a non-rigid regular tetrakaidecahedral diamond abrasive grain was established. The study investigated the effects of ion implantation on crystal structure phase transformation, dislocation nucleation, and defect structure evolution. Results showed ion implantation modification decreased the extension depth of amorphous structures in the subsurface layer, thereby enhancing the surface and subsurface integrity of the SiC workpiece. Additionally, dislocation extension length and volume within the lattice structure were lower in the ion-implanted workpiece compared to non-implanted ones. Phase transformation, compressive pressure, and cutting stress of the lattice in the shear region per unit volume were lower in the ion-implanted workpiece than the non-implanted one. Taking the diamond abrasive grain as the research subject, the mechanism of grain wear under ion implantation was explored. Grain expansion, compression, and atomic volumetric strain wear rate were higher in the non-implanted workpiece versus implanted ones. Under shear extrusion of the SiC workpiece, dangling bonds of atoms in the diamond grain were unstable, resulting in graphitization of the diamond structure at elevated temperatures. This study established a solid theoretical and practical foundation for realizing non-destructive machining at the atomic scale, encompassing both theoretical principles and practical applications. [ABSTRACT FROM AUTHOR]

To address the issues of abrasive wear, impact wear, and soil adhesion that can lead to wear failure and excessive operational resistance in agricultural soil touching parts during farming. This study focuses on UHMWPE composites, modified by filling Nano‐SiC as a hard phase filler and XNBR as an elastic filler. These fillers were dispersed into the UHMWPE matrix through melt blending technology to create a high‐performance composite material for the surface protective material of soil touching parts. The study discovered that by adding hard and elastic fillers to the UHMWPE matrix, the density, hardness, flexural modulus and thermal stability of the materials were all increased. Specifically, the density increased by 5.67% and the flexural modulus increased by 107%. In the block on ring wear test the volumetric wear rate decreased by 98%, while in the mortar wear test the mass wear rate decreased by 64.64%. Additionally, the contact angle on the surface of the specimen after mortar erosion and wear increased to 102.76°, 18% higher than that of pure UHMWPE. These results demonstrate that the modified fillers can improve the abrasion and plastic deformation resistance and hydrophobic desorption of UHMWPE. UHMWPE composite material, serving as the surface protection for soil touching parts, resolves the issues of abrasion of soil abrasive particles and excessive soil adhesion resistance on these parts. This significantly prolongs the service life of soil touching parts of agricultural machinery and improves the operational efficiency and economy. Highlights: Research on nanoparticles and elastomer‐modified composite materials.Research has shown the enhancement of UHMWPE composite materials by Nano‐SiC.XNBR improves the plastic deformation resistance of UHMWPE composites.Effects of Nano‐SiC and XNBR on the desorption behavior of composite materials.UHMWPE composites reduce soil contact wear and soil adhesion. [ABSTRACT FROM AUTHOR]

The polymer‐based acetabular cup prosthesis, a vital component of hip replacement surgery, significantly contributes to the recovery of patients afflicted with osteoarthritic conditions. Nevertheless, the current clinical usage of polymer acetabular cup prostheses commonly encounters the challenge of balancing wear resistance and oxidation resistance, significantly impacting both their lifespan and patients′ quality of life. Consequently, researchers have persistently enhanced the attributes of polymer acetabular cup prosthetic materials. These enhancements, including irradiation and filler modifications, are intended to concurrently bolster both the wear and oxidation resistance of the prosthesis materials. This comprehensive approach aims to address wear‐associated clinical complications like osteolysis and oxidative brittleness, ultimately extending their in vivo service life. For this reason, this paper retrospectively discusses the progress of research on the modification of polymer acetabular cup prosthesis materials for high wear and oxidation resistance and explores potential design methods for optimising artificial acetabular cup materials, with a view to providing new ideas for extending the service life of artificial joint implants. [ABSTRACT FROM AUTHOR]

Highlights This study emphasizes the significance of stacking sequence and hybridization of glass, carbon, kevlar and basalt fibers to enhance the mechanical characteristics and the overall wear response of polymer composites. The carbon layer on the outside of the composite exhibited higher ultimate tensile and flexural strengths. The abrasive wear of fabricated hybrid composites is also explored by performing experiments using Box–Behnken design approach. The pin‐on‐disc tester is utilized to do the wear test by varying composite type, sliding distance, and sliding velocity, with specific wear rate (SWR) serving as the response parameter. Regression analysis is performed to predict SWR using control and response parameters derived from experimentation. A novel firefly algorithm technique is adopted to determine the optimal process parameter combination. By utilizing optimized parameters (430 m, 10.5 m/s, and the CKBG4BKC stacking sequence), the SWR is considerably reduced to 16.82 × 10−5 mm3/Nm. Scanning electron microscopy on the worn‐out wear surface reveals enhanced interfacial bonding, fiber breakage and plowing as the fundamental wear mechanism. This work provides insight into hybrid composites for constructing aircraft and automobile body structures, where they provide an optimal blend of strength, sustainability, and structural performance. Hybrid composite: Stacking sequence impacts on mechanical and abrasive wear. Box–Behnken design: Applied on stacking order, sliding distance and velocity. Utilizing metaheuristic firefly algorithm to enhance specific wear results. Optimal parameters: 430 m, 10.5 m/s, and CKBG4BKC stacking sequence. Lightweight, high‐strength, cost‐effective, and sustainable hybrid composites. [ABSTRACT FROM AUTHOR]

In this paper, a modified theory of critical distance (TCD) method (i.e., Gradient‐TCD method) is proposed, which combines fatigue parameter gradient and the TCD, to estimate fretting fatigue life of dovetail joints. The advantage of Gradient‐TCD method lies in utilizing the gradient parameters to effectively characterize the local effect zone caused by fretting, thereby enabling the determination of a suitable critical distance length independent of material fatigue parameters. The reliability and predictive capability of the method is validated through experimental results. Furthermore, this method demonstrates insensitivity to mesh size, resulting in an 83.6% reduction in computational time while maintaining the predictions within the two‐times scatter band. The novel Gradient‐TCD method may provide an efficient and reliable approach for fretting fatigue life prediction, which holds promise for evaluating complex full‐scale fretting problems. [ABSTRACT FROM AUTHOR]

In this paper, the morphological, micromechanical and tribological characteristics of the Ti-6Al-4V ELI alloy after thermal oxidation (TO) were identified. TO was carried out at temperatures of 848 K, 898 K and 948 K over a period of 50 h. Microscopic examination revealed that an increase in temperature resulted in an improved uniformity of coverage and an increased oxide grain size. Micromechanical tests showed that TO of the Ti-6Al-4V ELI alloy led to an increase in hardness and deformation resistance. Following oxidation, a decrease (by approximately 10–22%) was observed in the total mechanical work of indentation, Wtotal, compared to the as-received material. The formation of protective oxide films on the Ti-6Al-4V ELI alloy also led to the improvement of tribological characteristics, both when tested under dry friction conditions and in Ringer's solution. The sliding wear resistance increased with an increase in the oxidation temperature. However, a greater degree of wear reduction (by approximately 30–50%) was found for the lubricated contact in comparison with the dry friction tests. Surface roughness also increased with the increase in temperature. [ABSTRACT FROM AUTHOR]

Aluminium finds wide application in mechanical engineering due to its low density and corrosion resistance. In this research, aluminium was subjected to two different metal forming technologies—cold forging (upsetting) and equal channel angular pressing (ECAP)—to obtain improvement in its exploitation properties. Parallel to changing mechanical properties by using these two processes, there was a change in the microstructure of the material. The resulting microstructures were examined using an optical microscope. A different treated aluminium was subjected to erosion wear in various time intervals. Wear testing was conducted for two different impingement angles causing abrasive wear and impact wear. The erosion mechanisms were examined by scanning electron microscopy. These results showed that there is no statistically significant difference in erosion wear for different states at the same impingement angle. However, the difference is noticeable at different wear angles. The significance of the difference in wear of the samples treated with the forging and ECAP techniques was validated by statistical analysis with tests of different sensitivities. The results of the t-test showed that ECAPed samples present a statistically significant difference in the loss of mass due to variations in erosion angle during the 30, 45, and 60 min wearing. A substantial difference in the change in sample mass is also visible for the forged state worn for 60 min. [ABSTRACT FROM AUTHOR]

Mixing involves blending raw rubber or masticated rubber with additives using a rubber mixer, which is the most critical process in rubber production. The internal mixer, as the most important mixing equipment, experiences rotor wear during prolonged operation, affecting the gap between the mixer rotor and the chamber wall. This wear reduces mixing effectiveness, weakens filler dispersion, and ultimately impacts rubber performance. In recent years, as research on multi-walled carbon nanotubes (MWCNTs) and nanomaterials has deepened, their broad application prospects have become increasingly apparent. The objective of the present study is to understand and quantify rotor wear in rubber blends during the mixing process as influenced by multi-walled carbon nanotubes. This study found that with the increase in MWCNT content, the proportion of abrasive wear rises, while the proportion of corrosive wear decreases, leading to reduced overall wear. Compared to rubber without MWCNTs, the Payne effect decreased by 6.78%, 9.57%, 13.03%, 20.48%, and 26.06% with the addition of 1 phr, 3 phr, 5 phr, 7 phr, and 9 phr of MWCNTs, respectively. The friction coefficients between the rubber and metal increased by 6.31%, 8.57%, 25.43%, 39.31%, and 47.61%, while the metal wear rate decreased by 9.08%, 10.73%, 13.41%, 17.46%, and 25%. Conversely, the friction coefficients were reduced by 19.39%, 22.42%, 33.94%, 66.06%, and 76.36%. [ABSTRACT FROM AUTHOR]

With the increase in train speed and axle weight, the quality and service life of the rail (U71Mn steel) are more demanding. Aiming at the excellent properties of nickel/nickel-based alloys and ceramic materials, this paper prepares TiC/Ni45 composite coatings for rail repair by in-situ synthesis of ceramic phases using laser cladding technology. The effects of in-situ synthesized TiC on the physical phase, microstructure, microhardness and wear resistance were investigated and discussed in detail. The results show that the reaction of in-situ synthesized TiC can proceed positively, and the microstructure of the cladding layer mainly consists of the segregation of Cr, TiC particles, and substrate phase. With the increase of nickel-coated graphite and titanium powder, the average microhardness value of the cladding layer increased, and the average friction coefficient and wear volume decreased. When the mass fraction of (Ti + C) reaches 15 wt%, the average friction coefficient of the cladding layer reaches the minimum value. When the mass fraction reaches 20 wt%, the average microhardness of the cladding layer reaches 2.65 times that of the substrate, and the wear mechanism is transformed from mainly adhesive wear to abrasive, oxidative, and fatigue wear. [ABSTRACT FROM AUTHOR]

Samples of AISI 52100 bearing steel were treated by using laminar plasma quenching methods with three optimized process parameters: input power, scanning speed, and scanning distance. The influence of process parameters on the surface morphology and quenching depth of AISI 52100 bearing steels was explored, as well as the influence on their microstructure and microhardness. Furthermore, the surface wear resistance was tested by using a reciprocating wear testing machine. The results showed that samples with a lower surface roughness and a deeper hardened layer could be obtained by treating with the combination of input power 10.6 kW, scanning speed 500 mm/min and distance 20 mm. Microstructure analysis indicated that finer acicular martensite formed at the surface layer. The microhardness analysis shows that the hardness was improved by 20%, and the wear volume was reduced by 37.7%. The treated AISI 52100 bearing steel sample only had some furrow-like abrasive wear, while the untreated sample had more spalling pits in addition to furrow-like wear. The excellent anti-wear performance could be attributed to the hardness of cryptocrystalline martensite, which formed a hardened layer on the surface of the material. Therefore, the plasma quenched AISI 52100 bearing steel exhibited excellent wear resistance, which could effectively improve the service life of the bearing steel and has broad prospects in the field of surface modification. [ABSTRACT FROM AUTHOR]

This study investigates the fretting wear resistance of Inconel 718 fabricated by laser-powder bed fusion (L-PBF) based additive manufacturing (AM) process. A set of the L-PBF processed coupons were subjected to homogenization followed by double aging heat treatment cycles to achieve hardness comparable to wrought material. Material characterization using optical microscopy, scanning electron microscopy (SEM) and x-ray diffraction techniques revealed a fine grained and textured microstructure in AM as-built samples. Point contact (ball-on-flat) fretting wear tests conducted under ambient conditions showed that AM as-built samples had the least wear resistance with a wear coefficient of 15.64 × 10−9 MPa−1 and a higher average coefficient of friction (COF) of 0.75. The wear resistance of the AM samples was found to be improved after heat treatment with the reduced wear coefficient of 10.35 × 10−9 MPa−1 and COF ranged between 0.60 and 0.70. The fretting loops, COF plots and SEM analysis on worn surfaces show that when the applied normal load is low (1N), the operating regime is gross slip regime and the corresponding wear damage is abrasion for all samples. When the load increases to high level (3N), a combined wear mechanism of delamination, adhesion and abrasive wear operating under partial slip regime is predominant with a considerable amount of subsurface cracking. The effect of heat treatment is seen as beneficial in terms of reduction in wear, COF and sub-surface crack which is attributed to improved hardness. [ABSTRACT FROM AUTHOR]

In this work, effect of multi-axial room temperature forging process on scratch and wear characteristics of Al-7.3 and Al-12.1Si alloys with varying cumulative strains was investigated. Al-7.3 and Al-12.1Si alloy ingots were remelted in a furnace and then poured into a preheated die to produce a cast sample of the desired shape and dimension for the MAF process. These samples were subjected to solution heat treatment before forging Scratch test was conducted to measure the scratch resistance of unprocessed and MAF-processed samples. Dry sliding wear tests were performed on a tribometer (pin-on-disk) at ambient temperatures. MAF-processed materials exhibited better scratch and wear resistance compared to as-cast materials. After MAF, wear mechanisms in both alloys shifted from adhesive and delamination wear to a combination of abrasive and a lesser amount of adhesive wear. Moreover, the degree of delamination significantly decreased after MAF-process. Improved scratch and wear resistance is mainly due to increased microhardness via refinement and improved uniformity in the redistribution of eutectic silicon as well as the strain hardening of the aluminum phase. [ABSTRACT FROM AUTHOR]

High-temperature wear tests on molybdenum–tungsten–vanadium steel were conducted using a universal mechanical high-temperature friction and wear testing machine. The experimental results reveal the evolutionary mechanism of high-temperature friction in the oxide layer of the steel. The oxidation wear of the test steel occurred at 700 °C with the evolution of characteristic monolayer tribo-oxidation layers on the frictional surface. The frictional oxide underwent oxide initiation - lateral growth of massive oxide - formation of frictional oxide layer - local intrusion of oxide layer into substrate - local penetration of oxide lateral growth contact. The frictional oxide evolutionary process was accompanied by a shedding of the frictional oxide surface. Carbides in the test steel prevented the tribo-oxidation layer from invading the matrix. The unique evolutionary characteristics of the tribo-oxidation layer are essential factors affecting the mechanism of maintaining slight oxidative wear. [ABSTRACT FROM AUTHOR]

Agglomerated Diamond (AD) abrasives were prepared using a ceramic bond and microfine single-crystal diamond (SCD). Lapping experiments were conducted to investigate the lapping performance and wear mechanisms of AD abrasives. The processing mechanisms of AD abrasives on sapphire wafers were revealed through friction and wear experiments and Power Spectral Density (PSD) methods. The results show that compared to W3 SCD, the material removal rate (MRR) of AD abrasives increased by 89.1 %, while the surface quality of the processed sapphire wafers was similar. Under the polyurethane lapping discs, AD abrasives achieved an MRR of 3.62 μm/min and a surface roughness (Ra) of 15.3 nm. The sapphire surface lapped with AD abrasives was the smoothest, with the PSD curve of the surface profile showing less noticeable layering, and the PSD values of the surface profile in the same frequency domain space were relatively the lowest. During the lapping process, the wear mechanisms of AD abrasives were identified as abrasive wear and micro-fracture. Under the impact and compression between the workpiece and the lapping discs, the fine SCD particles on the surface of the abrasives would wear and detach, and the network structure of the ceramic bond would fracture, exposing the fine SCD particles embedded in the bond to the surface, thus renewing and self-sharpening the cutting edges. • Agglomerated Diamond (AD) abrasives with multi-edge cutting and micro-fracture characteristics were prepared and used for loose-abrasive lapping of sapphire wafers. • The lapping properties and wear mode of AD abrasives were investigated. • The processing mechanism of AD abrasive is revealed through friction wear test and Power Spectral Density (PSD) analysis method. [ABSTRACT FROM AUTHOR]

To enhance the wear resistance of 300M ultra-high-strength steel, a Ni45/Cr3C2/nickel-packed MoS2 composite coating is fabricated using laser cladding technology. The impact of varying laser power on coating properties is investigated. Results show that MoS2 partially decomposes during laser cladding, forming new sulfide lubricating phases, CrxSy, and NiS, while Cr3C2 partially decomposes to create new reinforcing phases, Cr23C6, and Cr7C3. Reinforcing phase and lubricating phases are mainly distributed in the surface of 1100W coating. The surface hardness of the 1100W coating reaches 509 HV0.5, with an average hardness of 508.65 HV0.5, both surpassing those of the 800W coating (surface hardness of 477 HV0.5 and average hardness of 502.88 HV0.5). Wear rates for the 1100W and 800W coatings are 0.29 and 0.21 times that of the 300M steel substrate. Primary wear mechanisms for the 300M steel substrate include severe adhesive wear, abrasive wear, and oxidative wear; for the 1100W coating and 800W coating, predominant mechanisms are abrasive wear and oxidative wear. With frictional wear progression, peeling of lubricating phases and hard particles leads to increased friction coefficients of 1100W coating. Conversely, due to its superior toughness, the 800W coating displays a more stable friction coefficient and lower wear rate. [ABSTRACT FROM AUTHOR]

The aim of this study is to provide insights into the performance of copper-based brake pads used in high-speed trains and contribute to a more predictable braking system by leveraging mathematical and artificial intelligence (AI) models. The wear behavior of Cu-based brake pads in high-speed trains was investigated using a pin-on-disc test setup under different speeds, temperatures, and loads with a constant sliding distance. Additionally, mathematical and AI models were developed to predict the friction coefficient and wear rate values obtained from the experiments. This innovative approach initiates a significant discussion in line with a current need, and the sharing and publication of the obtained results are currently essential to address the knowledge gap in this field. The results revealed that an increase in temperature led to an increase in both the friction coefficient and wear rate. Conversely, an increase in load resulted in a decrease in both the friction coefficient and wear rate. The transition from abrasive wear to adhesive wear occurred due to the softening of copper between friction surfaces, leading to material transfer. According to the results obtained from the models, both the artificial neural network (ANN) and multiple regression models demonstrated comparable accuracy, predicting the friction coefficient with approximately 94% accuracy in both cases, indicating reliable predictions. For the wear rate, the models achieved approximately 90% and 92% accuracy, respectively. [ABSTRACT FROM AUTHOR]

Chemical strengthening of glass represents a standard technology for fabricating damage‐resistant protective covers. Still, little attention has been paid to modifications in the tribological properties of ion‐exchanged glass surfaces. This work reports on scratch testing of a chemically strengthened alkali‐borosilicate thin glass. Diffusive Na+/K+‐ion exchange produces a residual surface compressive layer with compressive stress of 200–340 MPa and layers depths between 16 and 50 µm, depending on exchange temperature and treatment time. This leads to notable changes in the surface mechanical properties, such as an increase in surface Young's modulus, indentation, and scratch hardness. Surprisingly, the Na+/K+‐ion exchange is shifting the onsets of scratch‐induced microcracking and microcracking to lower normal loads. The accelerated buildup of lateral indentation stress in glasses with high scratch hardness was found to be responsible for the lower threshold loads of microcracking and abrasive wear in chemically strengthened alkali‐borosilicate thin glass. [ABSTRACT FROM AUTHOR]

It is widely acknowledged that fluidelastic instability (FEI), among other mechanisms, is of the greatest concern in the flow-induced vibration (FIV) of tube bundles in steam generators and heat exchangers. A range of theoretical models have been developed for FEI analysis, and, in addition to the earliest semi-empirical Connors' model, the unsteady model, the quasi-steady model and the semi-analytical model are believed to be three advanced models predominant in the literature. The unsteady and the quasi-static models share the merits of having explicit fluid force expressions and ease of being implemented but require more experimental inputs, whereas the semi-analytical model requires fewer parameters due to its analytical nature but is hard, if not prohibitive, to derive explicit fluid force expressions. Since the fluid force formulations set in the core of development of FEI models, the understanding and in particular the implementation of the semi-analytical model has been impaired by the nonexistence of explicit fluid force expression. This issue becomes more profound in time-domain analysis whereby the simple harmonic assumption is discarded. Here we report a new semi-analytical time-domain (SATD) FEI model with explicit fluid force expressions. The new model allows a consistent frequency-domain stability analysis and more importantly a truly time-domain response analysis. The theory was validated by calculating linear stability thresholds of two typical tube array patterns and comparing against reported experimental data. We then present a nonlinear time-domain analysis of a single loosely-supported tube with piece-wise linear stiffness. The nonlinear and nonsmooth dynamics was probed in details by utilizing various techniques, playing an emphasis on characterizing and distinguishing the chaotic vibration. We found that the system follows a quasi-periodic route to chaos. Such an in-depth study of the nonlinear dynamics of tubes in crossflow has never been reported in the context of SATD model. Our results enrich the theory and provide a different approach for linear and nonlinear dynamics of tube bundles, which are essential for the subsequent fretting wear analysis. • A new formulation on semi-analytical time-domain model for fluidelastic instability of tube bundles. • The formulation has explicit fluid force expressions. • Linear frequency- and time-domain analysis are validated against available experimental and theoretical results. • Nonlinear dynamics behavior of a loosely-supported tube is probed based on the new formulation by using various techniques. • The route to chaos of the system is found through quasi-periodic to chaos. [ABSTRACT FROM AUTHOR]

Titanium and its alloys have been recognized as biocompatible materials since decades although these materials can at times show wear, corrosion and thrombosis leading to various health complications. Surface coating has been found to be one of the effective techniques to overcome this issue in-vitro as well as in-vivo. In this paper, thin film coating of zirconia (ZrO 2) on Ti6Al4V is reported using pulsed laser deposition (PLD) technique at elevated substrate temperatures ranging from room temperature to 800 °C (TiZr800). The morphology, composition, wettability and average surface roughness of the samples were analyzed by scanning electron microscope, Raman spectrometer, water contact angle (WCA) and profilometer, respectively. Adhesion between film and substrate was qualified using Elcometer. The tribological studies were performed in ball-on-disc against ZrO 2 counterpart, the electrochemical potential analysis was done in simulated body fluid to replicate body environment and the hemocompatibility test was evaluated on the basis of human whole blood adsorption and distribution of Red Blood Cells (RBCs) on the samples. The results revealed an increase in WCA and film adhesion with increased substrate temperature. At 800 °C, formation of zirconium carbide, a relatively harder material, was observed due to diffusion of substrate carbon into ZrO 2 film, as confirmed by the Raman analysis. In comparison to pristine, TiZr800 sample showed a reduction in wear rate from 3.5 × 10−3 mm3/Nm to 1.1 × 10−3 mm3/Nm indicating improved resistance of the sample against abrasive wear. Further, drop in I corr from 4.96 × 10−7 A/cm2 to 2.75 × 10−7 A/cm2 resulted in a 44 % increase in corrosion protective efficiency of the sample coated at 800 °C. Additionally, a 4.5 fold increase in RBC counts was observed on TiZr800 sample. Therefore, it is inferred that while ZrO 2 coating can improve overall surface properties of Ti–6Al–4V, additional benefits can be obtained by performing PLD at higher substrate temperatures, more so when the temperature is such as to promote formation of ZrC in the coating. [ABSTRACT FROM AUTHOR]

As a crucial part in micro-electromechanical manufacture, local ultra-precision processing of highly ductile copper is expected to be realized by fluid jet polishing (FJP), which widely utilized in optical elements. Since copper exhibits different wear behavior from stiff and brittle material, there is currently no abrasive wear prediction model applicable for copper to investigate the polishing mechanism. This research reveals that the copper material removal is dominated by deformation wear rather than cutting wear through abrasive jet impact experiments and localized wear scars analysis. A three-dimensional gas-liquid-particle triphasic wear model for copper in FJP is developed by considering impact energy and wear mechanism simultaneously. Ultimately, validation assessments at various working pressures and impingement angles achieve the goodness-of-fit up to 0.92–0.97 in quantitative comparison between simulations and experimental measurements, which demonstrate the wear prediction ability of the proposed model. This investigation facilitates a better understanding of copper wear mechanism and provides theoretical guidance for FJP process optimization. [ABSTRACT FROM AUTHOR]

Bearing life calculation is a well-researched and standardized topic for rotating operation conditions. However, there is still no validated and standardized calculation for oscillating operation, only different calculation approaches. Due to the increasing number of oscillating rolling bearings, for example, in wind turbines, industrial robots, or 3D printers, it is becoming more and more important to validate one of these approaches or to formulate a new one. In order to achieve this goal, the damage mechanisms for oscillating operating conditions must first be analyzed in more detail by means of experimental investigations. The open question is whether fatigue is the relevant damage mechanism or whether wear damage, such as fretting corrosion or false brinelling, dominates. The present work therefore shows under which oscillation angle and frequency fatigue occur in oil-lubricated cylindrical roller bearings. [ABSTRACT FROM AUTHOR]

Ti3SiC2/Cu composites were prepared using spark plasma sintering technology, and the effect of the velocity–load bivariate on the tribological behaviors of the Ti3SiC2/Cu-45# steel tribo-pair at 800 °C was investigated. The physical change and frictional chemical reaction during the friction process were analyzed based on the morphology characterization and frictional interface phases. The related friction and wear mechanism model was established. The results showed that the influence of velocity and load on the tribological performance of the Ti3SiC2/Cu-45# steel tribo-pair was not monotonically linear. When both the velocity and load were large, the coordinated effect of the two led to a low friction coefficient (0.52). At 800 °C, the velocity mainly affected the exfoliation and re-formation of the oxide film on the wear surface of the Ti3SiC2/Cu-45# steel tribo-pair, while the load affected the extrusion and fragmentation of the oxide film on the wear surface of the tribo-pair. In the friction process, frictional oxidation was the main influencing factor for the formation of the oxide film. When the velocity and load were small, the main frictional oxide consisted of SiO2−x and a small amount of CuO. When the velocity reached 1 m/s and the load reached 3 N, the oxide film was partially broken down and flaked off, and the matrix of the Ti3SiC2/Cu composite was exposed and oxidized, at which time the oxide film was composed of SiO2−x, TiO2, CuO, and Fe2O3. Under the synergistic effect of the velocity–load–temperature field, the friction and wear mechanism of the Ti3SiC2/Cu-45# steel tribo-pair changed from abrasive wear to frictional oxidation wear with the increase in velocity and load. [ABSTRACT FROM AUTHOR]

Precision processing of monocrystalline silicon presents significant challenges due to its unique crystal structure and chemical properties. Effective modeling and simulation are essential for advancing the understanding of the manufacturing process, optimizing design, and refining production parameters to enhance product quality and performance. This review provides a comprehensive analysis of the modeling and simulation techniques applied in the precision machining of monocrystalline silicon using diamond wire sawing. Firstly, the principles of mathematical analytical model, molecular dynamics, and finite element methods as they relate to monocrystalline silicon processing are outlined. Subsequently, the review explores how mathematical analytical models address force-related issues in this context. Molecular dynamics simulations provide valuable insights into atomic-scale processes, including subsurface damage and stress distribution. The finite element method is utilized to investigate temperature variations and abrasive wear during wire cutting. Furthermore, similarities, differences, and complementarities among these three modeling approaches are examined. Finally, future directions for applying these models to precision machining of monocrystalline silicon are discussed. [ABSTRACT FROM AUTHOR]

Refractory high-entropy alloys have great application potential in aerospace and shipbuilding due to their excellent properties, such as high-temperature strength and corrosion resistance. However, due to the vast difference in the melting point of the constituent elements, the formability of the traditional sintered and cast refractory high-entropy alloy parts still has defects. Previous studies added the remelting step under low energy density to obtain a more uniform element distribution, but this inevitably brought challenges to the molding efficiency of the parts and the molding design of complex shapes. In this study, macro-defect-free MoNbTaW RHEA bulks were fabricated on pure titanium substrates by the laser metal deposition technique. The mechanical properties and microstructure morphology of the samples were examined. The powders and various parts of the samples were characterized and analyzed by scanning electron microscopy, energy dispersive spectrometer, and X-ray diffraction. The average yield strength of the alloy was 1320.16 MPa, the average compressive strength was 1855.11 MPa, and the average fracture strain was 15.92%. The average hardness of the top layer was 846.4 HV. The average coefficient of friction for the top layer region of the sample was 0.164219. The wear form was mainly abrasive wear. [ABSTRACT FROM AUTHOR]

Worldwide, light water reactors (LWRs) have been using zirconium (Zr)-based alloys for the cladding of the uranium dioxide fuel for more than 6 decades. Zr alloys oxidize rapidly in the presence of water and steam at temperatures > 450°C; therefore, they do not respond well to scenarios of loss of coolant accidents. There is a global effort by nuclear materials technologists to find more robust or stronger cladding materials for LWRs. One option is to use an iron-chromium-aluminum (FeCrAl) alloy since they have excellent resistance to high temperature oxidation and superior mechanical properties at LWR operation temperatures. Results show that (1) FeCrAl alloys have better mechanical properties than Zr alloy and are orders of magnitude more resistant to creep at temperatures higher than LWR normal operation conditions. (2) FeCrAl alloys have better resistance to fretting wear than Zr alloys at the normal operation conditions of LWRs. [ABSTRACT FROM AUTHOR]

High-entropy nitride AlCrNbSiTiN coatings were deposited by RF magnetron sputtering at different bias voltages. The structure, mechanical properties and water vapor corrosion resistance of the coatings were systematically studied. The coatings exhibit a face-centered cubic (FCC) structure, while achieving a hardness up to 35.8 GPa. The main wear mechanisms of the coatings are adhesive wear and oxidation wear. After 200 h of water vapor corrosion, the content of O in the coatings is 4.30 at.%. [ABSTRACT FROM AUTHOR]

CrN and diamond-like carbon (DLC) coatings are deposited on the surface of 431 stainless steel by the direct current magnetron sputtering technique. The surface morphology, micro-structure, hardness, friction, and wear properties of CrN, CrN/DLC and multi-layer composite DLC coatings are investigated by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, nanoindentation tester, scratch tester, and friction and wear tester. The results show that the surface of the single CrN coating is very rough for the columnar crystal structure with preferred orientation. When it serves as inner transition layers to form the composite DLC coatings, the surface gets much smoother, with reduced defects. The friction and wear results indicate that the composite DLC coatings exhibit lower coefficients of friction, and better wear and corrosion resistance in dry friction, deionized water, and seawater. In the dry wear and friction process, the single CrN coating is easily worn out, and severe friction oxidation and furrow wear both appear with a friction coefficient of 0.48. But the friction coefficient of a CrN coating in seawater is reduced to 0.16, and friction oxidation and wear loss are further reduced with water lubrication. The CrN/DLC coating has excellent tribological performance in three test concoctions and has the lowest friction coefficient of 0.08 in seawater, which is related to the higher sp3 bond content, density (1.907 g/cm3) and high degree of amorphization, contributing to high hardness and a self-lubrication effect. However, due to the limited thickness of CrN/DLC (1.14 µm), it easily peels off and fails during friction and wear in different testing conditions. In multi-layer composite DLC coatings, there are more sp2 bonds with decreased amorphization, high enough thickness (4.02 µm), and increased bonding strength for the formation of different carbides and nitrides of chromium as transition layers, which gives rise to the further decreased average friction coefficient and the lowest wear loss. Therefore, the CrN coating alone has good wear resistance, and, as with the inner transition layer with a DLC coating, it can effectively improve the overall thickness and the bonding strength of the multi-layer films by optimizing the chemical compounds of DLC coatings. These results provide experimental support and reference for the design and selection of surface coatings for 431 stainless steels in different working conditions. [ABSTRACT FROM AUTHOR]

The present investigation addresses the mechanical properties, wear behaviour, and high-temperature oxidation of cermets and hardmetals based on either Ti(C,N) or WC and a metal binder based on Fe15Ni or Fe15Ni10Cr. This study also includes a commercial-grade WC-Co for comparative purposes. The production of these materials involved a powder metallurgy and sinter-HIP processing route under identical conditions. It is found that WC-based materials have superior mechanical properties, including hardness, fracture toughness, transversal rupture strength (TRS), and wear response, compared to Ti(C,N)-based materials. However, the latter show better oxidation behaviour than the former. Notably, WC-FeNi exhibits a higher hardness and TRS than the commercial-grade material (an increase of 7% and 9%, respectively). The difference in wear behaviour is due to the difference in wear mechanisms. In this regard, cermets wear through a tribolayer of Ti and Fe oxides, while hardmetals primarily wear through abrasion from ploughing. Thus, hardmetals exhibit a lower coefficient of friction (COF) and wear rate than cermets. Furthermore, Ti(C,N)-based materials form a protective layer of TiO2, which enhances their integrity and reduces mass gain. The addition of Cr to the FeNi binder only appears to have a clear effect on the TRS of the materials. [ABSTRACT FROM AUTHOR]

Particle diameters and jet pressure in abrasive water jet (AWJ) are significant jet properties which deserve a better understanding for improving AWJ machining performance. Some influence factors have been verified regarding nozzle wear in abrasive water jet polishing application. A three-dimensional model of a nozzle is established to analyze the influence of internal multi-phase flow field distribution, which is based on Euler-Lagrange methodology. With the increase of jet pressure, the erosion rate decreases; with the increase of the diameter and mass flow rate of the erosion particles, the erosion speed increases as well. When the diameter of the outlet is worn to 1.6 mm, the pressure on the work piece caused by the abrasive water jet increases by more than double compared to the non-worn nozzle; when the diameter of the nozzle outlet is worn to 1.6 mm, the shear force is 2.5 times higher than the shear force when the diameter is 1.0, which means that the jet force is divergent when the diameter is 1.6 mm, and the damage of the work piece is very serious. The obtained results could improve polishing efficiency on the work piece, extend nozzle lifetimes, and guide the future design of AWJ nozzles. [ABSTRACT FROM AUTHOR]

This study examines the effects of different addition levels of tungsten (W) content on the microstructure, corrosion resistance, wear resistance, microhardness, and phase composition of coatings made from FeCoCrNiAl high-entropy alloy (HEA) using the laser cladding technique. Using a preset powder method, FeCoCrNiAlWx (where x represents the molar fraction of W, x = 0.0, 0.2, 0.4, 0.6, 0.8) HEA coatings were cladded onto the surface of 45 steel. The different cladding materials were tested for dry friction by using a reciprocating friction and wear testing machine. Subsequently, the detailed analysis of the microstructure, phase composition, corrosion resistance, wear traces, and hardness characteristics were carried out using a scanning electron microscope (SEM), X-ray diffractometer (XRD), electrochemical workstation, and microhardness tester. The results reveal that as the W content increases, the macro-morphology of the FeCoCrNiAlWx HEA cladding coating deteriorates; the microstructure of the FeCoCrNiAlWx HEA cladding coating, composed of μ phase and face-centered cubic solid solution, undergoes an evolution process from dendritic crystals to cellular crystals. Notably, with the increase in W content, the average microhardness of the cladding coating shows a significant upward trend, with FeCoCrNiAlW0.8 reaching an average hardness of 756.83 HV0.2, which is 2.97 times higher than the 45 steel substrate. At the same time, the friction coefficient of the cladding coating gradually decreases, indicating enhanced wear resistance. Specifically, the friction coefficients of FeCoCrNiAlW0.6 and FeCoCrNiAlW0.8 are similar, approximately 0.527. The friction and wear mechanisms are mainly adhesive and abrasive wear. In a 3.5 wt.% NaCl solution, the increase in W content results in a positive shift in the corrosion potential of the cladding coating. The FeCoCrNiAlW0.8 exhibits a corrosion potential approximately 403 mV higher than that of FeCoCrNiAl. The corrosion current density significantly decreases from 5.43 × 10−6 A/cm2 to 5.26 × 10−9 A/cm2, which suggests a significant enhancement in the corrosion resistance of the cladding coating. [ABSTRACT FROM AUTHOR]

This article presents the results of abrasion wear resistance tests of wear-resistant steel and surfacing under laboratory conditions and natural operation. Abrasion wear resistance determined on the basis of the study by determining geometrical characteristics of the alloying additives using computer image analysis methods, as well as examining the changes occurring on the surface of the workpieces and their wear intensity. Based on the results obtained from laboratory tests, it was noted that AR steel exhibited 14 times greater wear than the padding weld. This wear is affected by alloy additives, which, for the padding weld, are chromium additives. The microstructure image shows that soil mass had a destructive effect mainly on the matrix of the material, whereas in the areas with high concentrations of chromium precipitates, this effect was significantly weaker. The operational test results showed that within the area of the tine subjected to hardfacing, the material loss was lower than that for the same area of the tine in the as-delivered state. For the hardfaced tine, a 7% loss of volume was noted in relation to the operating part before testing and following the friction process. However, for the operating part in the as-delivered state, this difference amounted to 12%. [ABSTRACT FROM AUTHOR]

Background: Despite the large variety of retainer wires available, no studies could be found comparing the micromechanical properties and surface roughness of different retainer wires. Such characteristics affect the survival of the fixed retainer in terms of both fracture resistance and resistance to debonding from the tooth. Therefore, the aim of the present study was to examine and compare those characteristics in popular retainer wires. Methods: six different popular orthodontic retainer wires were subjected to instrumental indentation based on the Oliver and Pharr method. The geometric surface structure was analysed using a non-contact profilometer. Results: stainless steel wires had a higher hardness and a higher elastic modulus compared to titanium wires and white gold chain. The titanium wire and the white gold chain showed much more roughness than other wires. Conclusions: stainless steel wires are the most resistant, considering both the shape retention capacity and the ability to resist abrasive wear. The titanium wire showed the lowest hardness and, thus, the highest susceptibility to deformation. Bond-a-braid, Retainium and Orthoflex white gold are more resistant to fracture than other steel wires. Titanium wire and chain retainer wires have more roughness, which is a great advantage in terms of mechanical adhesion to composite materials. [ABSTRACT FROM AUTHOR]

In this paper, the effect of ambient temperature, sliding speed and normal load on friction coefficient and wear mechanism were investigated through end-face testing to simulate the influence of process parameters during hot forming–quenching integrated process. With the increasing ambient temperature, the wear mechanism changes from abrasive wear to adhesive wear and oxidation wear. When the ambient temperature reaches 400 °C, the delamination wear characteristics occur due to the crack propagation caused by thermal stress. The friction coefficient and wear rate increase with the increase in the normal load. When the normal load is 1.8 and 3 kN, because of the generation of a large amount of heat and the increase in the contact area, the peeling morphology appears, and the adhesive wear and oxidation wear are further enhanced with the increase in the temperature. The enhancement of work hardening weakened the adhesion effect due to the high sliding speed. The friction coefficient decreases with the increase in the sliding speed. In addition, the wear rate at 10 r/min and 50 r/min sliding speed are 29.6 and 29.2 mm3/m, respectively. [ABSTRACT FROM AUTHOR]

The study investigated the fretting fatigue behavior of a bridge‐flat component, utilizing a flat specimen with two bridge‐type pads tested under cyclic loading. Numerical simulations were also carried out using the finite element method. Firstly, precise calculations of contact stress were performed with the material's elastoplastic model. Secondly, the stress distribution on the maximum stress cross‐section was extracted, and the stress gradient was computed. Finally, a stress fatigue life prediction model considering the stress gradient was proposed, and the predicted life was compared with the test life. The results of the study revealed that the specimens exhibited high stress gradients at the edges of the contact region during the bridge‐flat tests. In comparison with plain fatigue, fretting fatigue life was significantly reduced. The life prediction model proposed in this paper demonstrated good accuracy for predicting fretting fatigue. [ABSTRACT FROM AUTHOR]

In this article, we use a macro-mesoscopic method to analyze the forced vibration behavior of the SiCf/Ti cantilever beam. The shear-lag model was applied to determine the stress-strain relationship of SiCf/Ti composites with matrix cracking, interface debonding, wear, and failure damages under tension-compression loading. We established the cyclic tension-compression constitutive model of SiCf/Ti composites by considering the evolution laws followed by three injury patterns. From a macroscopic perspective, we use the cyclic tension-compression constitutive model to obtain the stiffness reduction at different stress levels and reduce the stiffness at different stress levels. Finally, we use Ansys software to reveal the forced vibration properties of the SiCf/Ti cantilever beam under different acceleration amplitudes. [ABSTRACT FROM AUTHOR]

Tribooxidation is the main mechanism to adapt the cutting tool to extreme mechanical and thermal loads during high-speed cutting. Wear and tribooxidation processes in the single layer TiAlCrSiYN and multilayer TiAlCrSiYN/TiAlCrN non-stoichiometric coatings on cutting tools after dry cutting with speed of 500 m/min on the running-in and steady wear stages were studied by the set of modern surface analysis methods. The reasonable preference of the multilayer coating comparing to the single layer one was demonstrated. It was established that oxide films with an amorphous-nanocrystalline structure are formed on the surface of the wear hole. Their composition is close to k Cr2O3, TiO2, Al2O3 (sapphire) and Al2O3 · 2(SiO2) (Mullite 1:2). Prospects of yttrium addition in the complex nitride were estimated by quantum chemical calculations, which has shown that such polyvalent metals as Ti+4, Cr+5,6, Y+4, Al+3 in a multicomponent nitride form a very complex spatially organized electronic structure of double and triple bonds with unoccupied π*-orbitals of nitrogen atoms. Quantum-chemical calculations of the oxidation susceptibility of these coatings with Y microadditions confirmed that this element is more inert than chromium and it is predominantly involved in the formation of interatomic bonds with Al, Ti, Cr affecting the mechanical properties of nitride coatings. [ABSTRACT FROM AUTHOR]

The wheel set of a rail vehicle with a disc brake is the basic assembly of a rail vehicle exposed to abrasive wear. From the operational point of view, the wear process of the wheels and brake discs is uneven, which for the carrier involves switching off the vehicle, once when the maximum wear of the discs is reached and again when the wheels wear out. The process of both untying the wheel set from the bogie, dismantling the wheels and discs from the axle is a time-consuming and expensive process, which consequently affects the exclusion of the vehicle from planned traffic. In the article on the basis of brake disc wear results, 3 concepts of bogie management were proposed. The first concerns the bogie rotation, the second and third concepts concern the exchange of bogies with and without rotation. Using the MUZ multi-criteria programming method, the concepts were evaluated and the best one was selected taking into account the evaluation criteria. The aim of the article is to present concepts that reduce the wear of discs brake systems in a multi-unit traction unit using bogie migration under the vehicle. [ABSTRACT FROM AUTHOR]

When tunnel boring machines (TBMs) tunnel in extremely hard rock, it is difficult for the cutter to penetrate the rock, resulting in an excessive cutting load, severe wear, and a short lifespan. The rock-breaking mode of synchronous cutting by an abrasive water jet (AWJ) and a disc cutter is expected to improve the rock-breaking performance. To investigate the cutting features of the new method, a synchronous cutting model is established. The results demonstrate that synchronous cutting can significantly enhance the rock-breaking efficiency and reduce the cutting load compared to single-cutter cutting. Moreover, synchronous cutting results in superior rock-breaking effectiveness compared with precutting kerf cutting, attributed to the overlapping of stress waves. The influence of the AWJ kerf depth and the spacing between the disc cutter and the jet on the rock-breaking performance is studied. As the depth of the AWJ kerf increases and the spacing decreases, the cutting load decreases, while the range of rock damage and stress-wave propagation initially increase and then decrease. When the penetration depth of the cutter, kerf depth and spacing are 6 mm, 15 mm, and 30 mm, respectively, the cutting performance of the synchronous cutting is better than that under other conditions. Highlights: A simulation model of the synchronous cutting of granite by an AWJ and a disc cutter is constructed based on the SPH–FEM coupled algorithm. The dynamic process of rock damage and stress-wave propagation is studied for synchronous cutting by an AWJ and a disc cutter. The rock-breaking characteristics of the single-cutter cutting mode, the precutting kerf mode, and the synchronous cutting mode are comprehensively compared. The influence of the AWJ kerf depth and the spacing between the disc cutter and the jet on the rock-breaking performance are investigated. [ABSTRACT FROM AUTHOR]

High‐vanadium high‐speed steel (HVHSS), known for its exceptional wear resistance, is widely used in industries such as steel production, bearing manufacturing, and the manufacture of cutting tools and high‐end components. To address the need for improved performance under challenging service conditions, the fabrication of HVHSS is investigated using spark plasma sintering (SPS) as an alternative to traditional casting methods. The research focuses on analyzing the microstructural changes in HVHSS samples produced by SPS under various sintering temperatures. These samples are then compared with those of cast HVHSS in terms of their microstructures, mechanical properties, and wear resistance. The study found that at a sintering temperature of 900 °C, the SPS‐fabricated HVHSS achieved a relative density of 98.1%. The fine and evenly dispersed carbides (mainly M7C3 and VC) in the matrix increased the microscopic hardness to 654.1 HV, which is higher than that of the cast sample. Notably, the wear resistance is significantly enhanced, showing increases of 15.48 cm−3 and ≈18% in absolute and relative terms, respectively. These results show that SPS fabrication is a major technique for enhancing the wear resistance and optimizing the microstructure of HVHSS. [ABSTRACT FROM AUTHOR]