Specific Wear Rate Research Articles

Mechanical properties and biocompatibility of multilayer systems based on amorphous SiN:H/SiCN:H layers on Ti6Al7Nb titanium alloy

Surfaces of metallic implants that replace diseased joints are bound to degrade over time under constant mechanical wear and corrosion, caused by the presence of biological fluids. Production of wear particles and toxic metal ions that follows can undermine both implant stability and patient’s health. To counteract this process multiple surface modifications have been proposed in scientific literature, ranging from simple nitriding to protective layers (e.g.: DLC, CN:H) and multilayer systems. This work presents a combined approach to outlined issue, using multi-staged plasma deposition with SiCN:H layer as a key component, realized using the MW CVD (Microwave Chemical Vapour Deposition) system. The study covers chemical characterization by EDS and FTIR analysis and measurements of relevant functional parameters, such as hardness, Young’s modulus, coefficient of friction, specific wear rate and wettability. Additionally, biocompatibility of modified surfaces are tested on MG-63 cells using Alamar Blue assay, flow cytometry and alkaline phosphatase (ALP) assay. Chemical and microscopic studies revealed amorphous cauliflower-like microstructures that have proven to be hydrogenated SiCN/SiN structures. The obtained layers are turned out to be biocompatible (>70 % of cell survival rate), additionally layers based on amorphous SiCN:H boost ALP activity due to combination of their chemistry and mechanical properties.

Analyzing the impact of TiO2 filler on the wear characteristics of flax fiber-reinforced epoxy composite using the Taguchi approach

Purpose This study aims to investigate the impact of titanium oxide (TiO2) filler on the coefficient of friction (COF) and specific wear rate (SWR) in flax fiber reinforced epoxy composites (FFRCs) under abrasive wear conditions utilizing the Taguchi approach. The primary objective is to enhance wear resistance and promote the development of sustainable materials for various applications. Design/methodology/approach Epoxy/flax composites with varying TiO2 filler content (0–8 wt%) are fabricated through the hand layup method. Subsequently, wear testing is conducted following ASTM G99-05 standards. The Taguchi design of experiments (DOE) and analysis of variance (ANOVA) are utilized for statistical analysis. Findings Results indicate a significant improvement in abrasive wear properties with the incorporation of TiO2 filler. The COF is found to be most influenced by the normal load (55.19%), followed by grit size, wt% TiO2 filler and sliding distance. SWR is found to be most influenced by the grit size (42.92%), followed by wt% TiO2, normal load and sliding distance. Notably, the Taguchi model aligns well with experimental results, demonstrating its efficacy in predicting the abrasive wear behavior of FFRCs. Originality/value This research introduces a novel hybrid composite that combines TiO2 filler and flax fibers, showcasing their potential to enhance the tribological properties of epoxy composites. The study offers valuable insights into optimizing abrasive wear test variables in natural fiber-reinforced composites using Taguchi DOE and ANOVA, crucial for improving the performance of sustainable materials in engineering applications.

Impact of Relative Humidity on the Formation of Low-Frictional Interface and its Continuity in Tribological Systems with Hydrogenated Carbon Nitride Coatings

The impact of relative humidity on the formation of low-frictional interface in hydrogenated carbon nitride (CNx:H) coatings sliding against Si3N4 balls and the formation continuity was elucidated through friction tests conducted in both air and nitrogen atmospheres with controlled relative humidity levels. In air atmosphere, a carbonaceous tribolayer with a transformed structure from the initial CNx:H was formed on Si3N4 at less than the critical humidity that existed in 1.0–3.0% RH, resulting in low friction (μ < 0.05) and a low specific wear rate of the balls (< 2 × 10–9 mm3/N·m). In contrast, this tribolayer failed to form above 3.0% RH. In nitrogen atmosphere, within the 0.25–1.0% RH range, the tribolayer continued to form concurrently with wear progression, maintaining low friction for over 50,000 cycles. However, in less than this humidity range, the lifetime of low friction was limited owing to the tribolayer’s structural alteration. Thus, relative humidity influences not only the formation of the low-frictional interface but also the formation continuity. On the CNx:H friction surface, hydrogen, hydroxyl, and oxygen groups from environmental water and oxygen molecules continued to chemisorb owing to tribochemical reactions on the uppermost few nanometers during continuous low friction in a nitrogen atmosphere, while hydrogen content of CNx:H desorbed. This study experimentally confirmed the critical role of controlling relative humidity in tribological systems using CNx:H coatings to achieve low friction and improve its durability of low friction through the continuous formation of the low-frictional interface.

A novel plasma-facing NdB6 particulate reinforced W1Ni matrix composite: Powder metallurgical fabrication, microstructural and mechanical characterization

Tungsten (W) is one of best candidate metal for plasma-facing materials (PFM), especially due to its high melting temperature and neutron absorption capability. However, converting W into bulk PFM is hard because of its high melting point. This problem can be solved by adding metallic sintering aids with low melting points. In this study, W matrix with 1 wt% Ni aid was reinforced by adding NdB6 particles (1, 5, and 10 wt%). It can be introduced as a novel potential PFM, thanks to its low volatility and high neutron absorbability. The ceramic and composite powders produced via mechanochemical synthesis and mechanical alloying were examined in terms of composition, particle size, crystallite size, and lattice strain. Samples sintered via pressureless sintering (PS) and spark plasma sintering (SPS) were microstructurally analyzed by using an X-ray diffractometer (XRD), a scanning electron microscope (SEM) attached with an energy dispersive spectroscope (EDS), and mechanically analyzed in terms of microhardness and wear behavior. Based on the results, W2B and WB phases emerged in the SPS'ed W1Ni-5NdB6 and PS'ed./SPS'ed W1Ni-10NdB6 composites. SPS'ed W1Ni-10NdB6 composite had the highest hardness value and the lowest specific wear rate. The SPS'ed W1Ni-5NdB6 composite showed fewer surface damages and higher irradiation resistance as compared with other samples after exposure of He+ irradiation.

Microstructure and mechanical properties of in-situ SiO2-reinforced mechanically alloyed CoCrFeNiMnX (X= 5, 20, 35 at.%) high-entropy alloys

The CoCrFeNiMnX (X = 5, 20, and 35 at.%) alloys, reinforced with 5 at.% SiC powder, were prepared by mechanical alloying and spark plasma sintering. This preparation method resulted in microstructural refinement of the FCC solid solution grains, while the SiC addition reacted with residual oxygen to form homogeneously distributed ultrafine SiO2 particles. Additionally, the alloys contained Cr7C3 carbides, which were significantly larger than the SiO2 particles and enriched with the alloy's elements, including Mn. Among the tested materials, the reinforced CoCrFeNiMn20 alloy exhibited the highest hardness and compressive yield strength (CYS), achieving 392 ± 9 HV30 or 476 ± 3 HVIT1 and 1024 ± 18 MPa, respectively. This alloy also maintained superior CYS (956 ± 35 MPa) even after 100 h of annealing at 800 °C. The reduction in CYS after annealing was smallest for the CoCrFeNiMn5 alloy (35 MPa) and increased with higher Mn content, highlighting Mn's significant role in diffusion-related processes. At elevated temperatures (600 and 800 °C), the CoCrFeNiMn5 alloy had the highest CYS of 190 ± 33 MPa, while the CoCrFeNiMn35 alloy had the lowest at 80 ± 6 MPa. This trend was also observed in wear rate tests, where the CoCrFeNiMn5 alloy had the lowest specific wear rate coefficient of 3.54 ± 0.09 × 10-4 mm³ N⁻1 m⁻1. This was due to matrix softening and oxide lubrication without significant spalling. Thus, the CoCrFeNiMn5 alloy demonstrated superior mechanical properties and wear resistance under various conditions, making it a promising candidate for applications requiring high strength and durability.

Microstructural, mechanical, and sliding wear characterization of an Al90Cu4Fe2Cr4 spray-formed alloy

In this work, the microstructure and sliding wear behavior of a spray-formed Al90Cu4Fe2Cr4 (at%) alloy was studied. Mechanical properties under compression and Vickers microhardness were also evaluated. The microstructure of the spray-formed material consisted of an α-Al matrix reinforced with two complex intermetallic phases, λ-Al13Fe4 and Al13Cr2, which are binary based intermetallic structures, with significant amounts of the other elements of the alloy. The dry-sliding wear resistance of the composites was evaluated using a pin-on-disk test configuration, with normal loads ranging from 10 to 20 N and sliding velocities of 0.05–0.2 m.s−1. Alumina spheres were used as counter-bodies in these tests. The samples exhibited a high sliding wear resistance and showed almost no variation in the specific wear rates for all test parameters used, with values ranging from 7×10−4 to 8×10−4 mm3/N.m. The coefficient of friction also remained almost constant, around 0.4, and the main wear mechanism was the delamination of intermetallic particles. The results indicate an improved dry-sliding wear resistance at high normal loads compared to previously fabricated Al-matrix composites reinforced with quasicrystals and complex intermetallic phases. The mechanical properties of this alloy, fabricated in a single-step process, was in the same range as found for previous studies, of Al-matrix reinforced with micron-sized quasicrystals and intermetallics, prepared by more complex processing techniques. The simplicity of the one-step preparation process used in this study contributes to the development of more efficient and cost-effective tribological materials for various applications.

A comparative investigation on the surface characteristics of AISI 304 and AISI 1045 steel influenced by turning combined with ball burnishing

Burnishing is a popular superfinishing procedure in the manufacturing industry that induces plastic deformation to the finished product by the application of a highly polished and hardened deforming element known as a burnishing tool. Research work on the burnishing process is numerous. However, the reports containing the comparative investigations are lacking. In this work, the effect of ball burnishing parameters namely penetration depth, burnishing spindle speed, and number of passes has been compared and analyzed on AISI 1045 and AISI 304 steels with respect to surface roughness, hardness, wear resistance, and corrosion resistance. Results indicate that the combination of a feed rate of 0.12 mm/rev, spindle speed of 160 rpm, and penetration depth of 0.025 mm with four passes generated minimum surface roughness (AISI 1045). However, maximum surface hardness is obtained with a feed rate of 0.12 mm/rev, spindle speed of 160 rpm, and at 0.085 mm penetration depth under one pass (AISI 304). The lowest specific wear rate is achieved with a feed rate of 0.12 mm/rev at a spindle speed of 160 rpm and a penetration depth of 0.085 mm in one pass (AISI 304). The burnishing process influenced both materials, AISI 304 and AISI 1045, under varying parametric conditions. The maximum reduction in surface roughness is 68.1% for AISI 304 and 79.3% for AISI 1045, while surface hardness improves by 27% for AISI 304 and 22% for AISI 1045. Additionally, the burnishing process reduces the specific wear rate by 49.3% for AISI 304 and 45.4% for AISI 1045. The refinement of grains during the burnishing process enhances corrosion resistance compared to the unburnished surface.

Investigation of Microstructure, Mechanical, and Tribological Behavior of Nano‐Y2O3, TiO2, ZrO2‐Dispersed W–Ni–Nb–Mo–Zr Alloys Fabricated by Spark Plasma Sintering

W–Ni–Nb–Mo–Zr alloys with 1.0 weight% (wt%) Y2O3 (alloy A), TiO2 (alloy B), ZrO2 (alloy C) dispersion synthesized by mechanical alloying for 20 h have been subjected to spark plasma sintering at 1150 °C with 65 MPa pressure and 5 min holding time. X‐ray diffraction analysis reveals the occurrence of intermetallics (W2Zr, NiNb, Ni10Zr7, MoNi), which improves the strength of the alloys. Field‐emission scanning electron microscopy analysis shows that the grain size of alloy A is less compared to alloy B and C. Energy‐dispersive spectroscopy reveals the presence of oxides at the matrix interface. Maximum % relative sintered density, ultrahigh hardness, excellent compressive strength, % compressive strain at the maximum compressive load of 99.5%, 20.42 GPa of 2.55 GPa, 9.7%, respectively, have been recorded for alloy A. Maximum texture intensity of 1.5 is recorded for alloy A which supports the superior mechanical properties. The specific wear rate of alloy A is around 2.78 times less compared to alloy C. The crystal structure transformation of ZrO2 from monoclinic to tetragonal after sintering deteriorates the mechanical properties and wear resistance in alloy C. The article also reports the operative wear mechanism in the studied oxide dispersion‐strengthened alloy.

Enhancing mechanical properties and tribological performance through boron carbide hybridization in Novolac matrix graphite composites under dry sliding condition

This study extensively investigates the effects of 10 wt% graphite reinforcement and varying B4C content (1 wt%, 2 wt%, 4 wt%) on the properties of Novolac matrix polymer composites prepared by mechanical milling-assisted hot pressing. The microstructures, wear surfaces, wear debris, and fracture surfaces of the produced polymer composites were examined using SEM and EDS. The density measurements were conducted according to the Archimed’s principle. Their tribological behavior was evaluated with a reciprocating ball-on-flat sliding wear test at 50 N, 75 N, and 100 N loads. After the wear tests, surface topography was analyzed in 3D with an optical profilometer. The results indicated that composites with 2 wt% B4C had the lowest specific wear rate and the highest wear resistance.

Effects of liquid lubricants on the surface characteristics of 3D-printed polylactic acid

In this study, 3D-printed Polylactic acid (PLA) specimens were manufactured and polished using various lubricants to assess their surface, friction, and wear characteristics. After polishing, the surface roughness decreased by approximately 80% compared with that before polishing, except when acetone was used as the lubricant. In particular, under deionized (DI) water and acetone lubrication conditions, the friction coefficient decreased by 63% and 70%, respectively, whereas the specific wear rate decreased by 88% and 83%, respectively, compared with the unpolished specimens. In the case of dry polishing, adhesion, friction, and wear increase owing to surface damage. Ethanol and IPA polishing resulted in hydrolysis and increased friction, but slightly decreased wear rates. The surface of the specimen polished with acetone dissolved and became very rough. Only the surface polished with DI water exhibited hydrophobic properties. When acetone and DI water were used as lubricants, the surface adhesion force, adhesion energy, friction coefficient, and wear rate were lowest. The finite element analysis results showed that the polished surface exhibited stable contact pressure and friction force, while the unpolished surface showed large fluctuations in contact pressure and friction force owing to the laminated pattern. These results suggest that the polishing process is crucial for improving the surface characteristics and mechanical performance of 3D-printed PLA parts.

Enhanced tribological performance of MoS2 and hBN-based composite friction materials: Design of tribo-pair for automotive brake pad-disc systems

This research comprehensively analyzes the friction and wear behavior of composite friction materials when dry sliding against grey cast iron and laser-clad nickel-based (LC1) and iron-based (LC2) alloy discs. The composite friction materials (P1, P2, P3, P4, P5, and P6) under investigation contain graphite, MoS2, and hBN-based solid lubricant synthesized through the powder metallurgy technique. Tribological tests were conducted using a pin-on-disc configuration to simulate the dynamic interaction between the composite materials and the laser-clad grey cast iron discs. The tests were performed at a 60 N load, 6283.19 m sliding distance, and 2.094 m/s sliding velocity under dry sliding conditions. The results provide valuable insights into the effectiveness of MoS2 and hBN-based solid lubricant composites in reducing friction and wear when in contact with iron and nickel alloy-based laser-clad grey cast iron surfaces. The study elucidates the mechanisms governing tribological behavior, including the formation of friction plateaus and the role of laser-clad counter-discs in reducing wear. The specific wear rate of the nickel-based laser-clad counter disc (LC1) and iron-based laser-clad (LC2) system improved by 63.76 % and 48.32 %, respectively, compared to the conventional grey cast iron disc system when using the hBN-based pin (P6). Additionally, the specific wear rate of the hBN-based pin was 38.49 % lower than the conventional graphite-based pin when sliding against the grey cast iron counter-disc. Artificial Neural Network (ANN) was used to validate the wear rate of the best-performing tribological pair, namely the hBN-based pin (P6) and LC2 counter discs, through supervised learning.

Prediction of specific wear rate of Al7050-12 wt% ZrO2 composite using box-behnken design approach

Prediction of specific wear rate of Al7050-12 wt% ZrO2 composite using box-behnken design approach

Machine learning assisted study of phase and properties in cobalt-free AlCrxCuFeNi2 high-entropy alloys

The application of machine learning (ML) accelerates the discovery of new materials, the prediction and optimization of properties, and the analysis of the correlation between structure and properties. The design, characterization, and mechanical properties of the novel AlCrxCuFeNi2 cobalt-free high-entropy alloys (HEAs) were investigated in this study. Through the experimental validation combined with the predictive K-nearest neighbor model (KNN) and the extreme gradient boosting model (XGBoost), the influence of Cr content on phase evolution and mechanical behavior were analyzed comprehensively. The results indicate that the optimized KNN and XGBoost models can achieve the 10-fold average cross validation (CV) accuracies of 0.761 and 0.836, respectively. Eight components of AlCrxCuFeNi2 HEAs are selected for experimental verification. The experimental results shows that the microstructures of the eight alloys are composed of FCC + BCC phases, which is agreement with the prediction. With the increase of Cr content, the dendrite morphology becomes finer and the lattice constants increase. The addition of Cr results in the hardness values from 332.4 HV to 447.7 HV and the deviation from the predicted ones is between 5.4 HV and 37.3 HV. It is worth noting that wear resistance is consistent with the change in hardness values, the specific wear rate decreases from 3.152 × 10−4 mm3/Nm to 6.357 × 10−5 mm3/Nm, and when x = 2.0, the wear resistance is the best. This research underscores the efficacy of ML in expediting the discovery and optimization of HEAs, offering valuable insights for promoting materials design and engineering applications.

Copper Alloys Performance in High-Pressure and Low-Velocity Conditions Using a Custom Tribometer

A custom tribometer was developed to measure friction coefficient and temperature in high-pressure, low-velocity conditions, specifically for studying copper alloys used in sliding bearings for heavy equipment. Using this equipment, two commercial alloys were tested to evaluate friction coefficient, specific wear rate, thermal behavior, and subsurface strain. The results, validated through comparison with reference commercial equipment and uncertainty estimates, met acceptable criteria for tribological tests, with an uncertainty estimate value for the friction coefficient of 0.4%. The tribological tests confirmed the importance of solid lubrication in high-lead bronzes and the high wear resistance of Cu-Al-Ni-Fe alloys, which directly influence temperature, subsurface strain, and respective wear mechanisms.

Study on the Wear Behaviour of Aluminium foam Reinforced Glass Fibre Epoxy Composites

Hand layup was used to fabricate the glass fibre reinforced aluminium foam epoxy composites in this study. On the manufactured materials, dry sliding wear experiments were performed. The effect of wearprocess parameters such asapplying load (kg), speed (m/s), and sliding distance (m) on specific wear rate (Ws) was investigatedand the obtained results were compared with neat glass fibre reinforced epoxy composite in this work. The outcome of these results showed that specific wear rate (Ws) of glassfibre epoxy composite containing aluminium foam decreased as compared with neat glass fibre reinforced polymer composites. Experimental results showed that a minimum wear rate of 10.1 �m was attained for the sliding velocity (1.5 m/s), Applied load (2 kg), and sliding distance (1000 m) in the fabricated composite laminates. It was observed thatthe resistance to wear in glass fibre reinforced aluminium foam composite was mainly due to the bond strength between aluminium foam and epoxy.

Determination of “tribological performance working fields” for pure PEEK and PEEK composites under dry sliding conditions

Poly-ether-ether-ketone (PEEK) and PEEK composites are widely used polymers in many engineering applications where dry sliding is required. In this study, the influence of sliding velocity and applied load values on the friction and wear behavior of pure PEEK, 30 wt% glass fiber reinforced PEEK (PEEK-30GF), 30 wt% carbon fiber reinforced PEEK (PEEK-30CF) and 10 wt% carbon fiber+10 wt%graphite +10 wt%poly-tetra-fluoro-ethylene (PTFE) filled PEEK (ie. High (H) pressure (P) and velocity (V) resistant PEEK (PEEK-HPV)) composites rubbing against AISI 304 stainless steel disc was investigated. The experiments were carried out at room temperature under dry sliding conditions in a pin-on-disc wear rig. The applied loads ranged from 30 to 250 N, while the sliding velocities ranged from 1.0 to 4.0 m/s. At these load and velocity ranges, the friction coefficient-wear rate relationship of pure PEEK and composites was established and evaluated. In addition, the operating load-velocity limits of each material were determined and stated. The lowest coefficient of friction and wear rate were obtained in PEEK-HPV, PEEK-30CF, PEEK-30GF composites and pure PEEK polymer, respectively. In addition, it was observed that the coefficient of friction (CoF) decreased and the specific wear rate (SWR) increased with the increase in sliding velocity and applied load in all PEEK materials. The wear rate values of PEEK-HPV and PEEK-30%CF composites are in the range of 10−7 - 10−6 (mm3/Nm), while the wear rate values of pure PEEK and PEEK-30%GF are in the range of 10−6 - 10−5 (mm3/Nm). It was determined that carbon fiber, graphite and PTFE additives added to PEEK polymer as hybrid were very effective in reducing the wear rate of PEEK composite (PEEK-HPV). An adhesive wear mechanism was observed in PEEK-HPV and PEEK-30CF composites both at low load and velocity values and at high load and velocity values.

Densification, microstructure, and wear properties of TiB2-TiC-GNP and TiB2-TiC-BN composites

In this study, TiB2–TiC, TiB2–TiC-GNP, and TiB2-TiC-BN composites were produced via spark plasma sintering (SPS). The densification and sintering behavior, phase and Raman spectroscopy analyses, microstructural properties, Vickers microhardness, and wear behavior of the binary and ternary composites were investigated. The addition of various amounts of TiC to TiB2 resulted in nearly complete densification. The TiB2–TiC-GNP specimens exhibited a relative density of more than 99 %; in contrast, the addition of BN did not contribute to the densification. The Vickers hardness of the GNP-added composites was ∼25 GPa, whereas hBN addition to the matrix decreased the hardness to ∼22 GPa (∼9 % decrease). According to the wear test, the addition of GNPs did not result in a significant change in the TiB2–TiC matrix; however, the addition of hBN increased the specific wear rate of the matrix by ∼100 %. The GNPs did not have a negative effect on the densification, microstructural, or mechanical properties, such as the Vickers hardness and wear resistance. Hence, they were determined to be a more suitable sintering aid for matrix composition than hBN.

Experimental Comparison of Manufacturing Parameters in Automotive Friction Materials

In this study, a fixed automotive friction material content was determined and the mechanical and tribological effects of manufacturing parameters on friction materials were investigated. Parameters; pre-forming time (1-3-5 min) and pre-forming pressure (8-10-12 MPa), hot pressing time (5-10-15 min) hot pressing pressure (8-10-12 MPa) and hot pressing temperature (125-150-175 °C), curing time (4-8-12 h) and curing temperature (120-150-180 °C) were determined. The friction test of the produced samples was carried out under 0.551 MPa pressure and 7 m/s rotation speed for 90 min. In addition, the average COF, friction stability, specific wear rate, density and hardness values of the samples were calculated. According to the results obtained, the average COF value increased as the pre-forming time and pressure increased. The lowest specific wear rate among all specimens was calculated as 7.622x10-6 cm3/Nm in PFP-12 specimen. With the increase in hot pressing time, the tribological properties of friction materials improved. The highest friction stability among all samples was calculated as 79.42% in the HPT-15 sample. Although there was an increase in the average COF value with increasing hot pressing pressure and temperature, the specific wear rates increased in these parameters. The highest average COF value among all samples was obtained in the CT-12 sample with a value of 0.553. The specific wear rate increased with the increase in curing time and temperature. The highest specific wear rate among all samples was calculated 10,743x10-6 cm3/Nm in the CTe-180 sample. Finally, it has been suggested that 3 min for pre-forming time, 12 MPa for pre-forming pressure; 15 min for hot pressing time, 12 MPa for hot pressing pressure, and 150°C for hot pressing temperature; and a curing time of 8 h and curing temperature of 150 °C may be sufficient.

Tribological Properties of Laser-Cladded NiCrBSi Coatings Undergoing Friction with Ti6Al4V Alloys

This work aims at reducing abrasion between titanium alloy parts, such as drive shafts and support pairs used in aviation. Three different NiCrBSi coatings, Ni40, Ni50, and Ni60, are prepared on surfaces of Ti6Al4V by laser cladding. The microstructural and mechanical properties of these coatings are analyzed by scanning electron microscope (SEM) and a microhardness tester. The tribological properties of the NiCrBSi coatings undergoing friction with Ti6Al4V are tested using a wear testing machine. The results show that the Vickers hardnesses of the Ni40, Ni50, and Ni60 coatings are 490 HV0.3, 609 HV0.3, and 708 HV0.3, respectively. For the above NiCrBSi coatings, more hard phases are produced with increases in the amounts of Cr in the powders, resulting in increases in the coatings’ hardnesses. The wear test results show that the NiCrBSi coatings could reduce the friction coefficients, which gradually decreased with increases in the coatings’ hardnesses. Both the coating-specific wear rates and the friction pair wear losses initially decreased and then increased. The Ni50 coating and the Ti6Al4V friction pair undergoing friction with the Ni50 coating showed the best wear performance, with a specific wear rate and wear loss of 0.51 × 10−7 mm3/(N·m) and 7.8 mg, respectively. The specific wear rates for Ni50 were only 8.4%, 35.4%, and 37.0% of the Ti6Al4V, Ni40, and Ni60, respectively. In addition, the friction pair wear loss was only 36.4%, 52.5%, and 55.3% of that while undergoing friction with Ti6Al4V, Ni40, and Ni60, respectively. The NiCrBSi coatings prepared on the surface of Ti6Al4V show excellent antifriction and wear resistance properties, providing a viable solution for the design of wear-resistant coatings on load-bearing and non-load-bearing titanium alloy parts.

Cold Spray Deposition of MoS2- and WS2-Based Solid Lubricant Coatings

The cold spray deposition technique has been used to produce a new class of solid lubricant coatings using powder feedstocks of the metal disulfides WS2 or MoS2, either pure or mixed with Cu and Ni metal powders. Friction and cycle lives were obtained using ball-on-flat reciprocating tribometry of coated 304 SS flats in dry nitrogen and vacuum at higher Hertzian contact stresses (Smax = 1386 MPa (201 ksi)). The measured friction and thickness of the coatings were much lower than for previous studies (COF = 0.03 ± 0.01 and ≤1 µm, respectively), which is due to their high metal disulfide:metal ratios. Cu-containing metal sulfide coatings exhibited somewhat higher cycle lifetimes than the pure metal sulfide coatings, even though the Cu content was only ~1 wt%. Profiling of wear tracks for coatings tested to 3000 cycles (i.e., pre-failure) yielded specific wear rates in the range 3–7 × 10−6 mm3N−1m−1, similar to other solid lubricant coatings. When compared to other coating techniques, the cold spray method represents a niche that has heretofore been vacant. In particular, it will be useful in many precision ball-bearing applications that require higher throughput and lower costs than sputter-deposited MoS2-based coatings.