A newly developed FeCrMoCBWNb coating was deposited on 65Mn steel substrate by arc-spraying. The impact of applied loads and sliding speeds on the wear behavior of the Fe-based coating was ...investigated under dry sliding conditions on a ball-on-disk tribometer. The coating exhibited a dense nano-crystalline structure featuring a grain size of around 19.70 nm and a porosity of 1.50 %. The coating's nano-hardness (H) and reduced elastic modulus (Er) were 9.81 and 209.45 GPa, respectively. The coating displayed superior wear resistance compared to the 65Mn substrate under all dry sliding wear conditions, attributed to the higher ratios of H/Er, H3/Er2, H2/2Er and the η value. Under the different applied loads, the coatings’ wear mechanism was delamination, abrasive, and oxidative wear, while under different sliding speeds, the coatings' wear mechanism was mainly fatigue delamination and oxidative wear. Upon analysis of the worn surfaces, tribo-oxide films that formed as a result of flash temperature on the contact surfaces minimized the coating's wear rate. The FeCrMoCBWNb coating also possesses a higher wear resistance against abrasive particles than the 65Mn substrate, and it's a good prospect for commercial use for wear protection in tiller blades.
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•The wear rate of the coatings increased with load and decreased with speed.•The mechanical properties and flash temperature influenced the wear behavior.•The main wear mechanism of the coatings was mainly abrasive and delamination.•The coating can be used to enhance wear resistance of tiller blades.
This work investigates the possibility of doping Si and Sn solid solution components (separate/simultaneous incorporation) into Ti3AlC2 to provide desired mechanical properties and tribological ...self-adaptability over a broad temperature range. The specimens are sintered at 1450 °C for 2 h in a vacuum environment with a pressure of 30 MPa. The phase composition, mechanical properties and tribological characteristics sliding against Al2O3 counter balls over a wide temperature range from room temperature to 800 °C are investigated. The results demonstrate considerable lattice distortion together with significant solid solution strengthening effects in quinary solid solutions. The friction coefficients of the four solid solutions are discovered to be temperature-sensitive from the distinguished variation tendencies in the wide temperature range. The wear rates exhibit a comparable tendency with test temperature that the values are two orders of magnitude lower at 600−800 °C than those at RT−400 °C. The noticeably lubricant tribofilm is responsible for the decreased wear rate at elevated temperatures. The distinct tribological behaviors of the quaternary and quinary solid solutions are ascribed to the characteristics of the self-generated oxides.
•A-site doping MAX solid solutions were synthesized by hot-pressing.•The Vickers hardness and strength were increased due to the lattice distortion.•The reduced wear rate at high temperatures is benefit from the tribo-film.•The distinct friction behaviors are ascribed to the features of produced oxides.
The durability of industrial components exposed to high temperatures can be increased by depositing high-velocity air-fuel (HVAF) sprayed Cr3C2-based coatings. The uniform embedding of wear-resistant ...Cr3C2 within an oxidation-resistant binder matrix allows HVAF-sprayed Cr3C2-based coatings to be widely used in high-temperature environments. However, consolidating these coatings demands an optimum particle velocity and temperature combination, primarily dependent on the spray torch design. Understanding the role of spray torch variants with altered combustion chamber and nozzle designs is essential, which might influence the coating (splat) formation mechanism and the resultant wear performance. Accordingly, Cr3C2–25NiCr and Cr3C2–30NiCrMoNb were sprayed using different HVAF torches (high-power AK06 and low-power AK05-ID (inner diameter): generate different energy (thermal + kinetic) output) to understand the role of the binder as well as the torch design. The deposited coatings were comprehensively compared based on splat morphology, microstructure, mechanical properties, room and high-temperature erosion and sliding wear behavior. Subsequently, a detailed post-wear analysis was performed to decipher the associated wear mechanism. As inferred from the results, Cr3C2–25NiCr coatings deposited through a high-power AK06 spray torch displayed preferable microstructure, properties and superior wear resistance. The study also offered new insights into HVAF-ID torch-deposited coatings.
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•The spray torch design significantly influenced the coating microstructure and properties.•AK06 spray torch deposited coatings with desirable microstructure and properties.•Regardless of testing conditions, AK06 sprayed coatings offered lesser wear rates.•Cr3C2–25NiCr coatings displayed comparatively better erosion/sliding wear resistance.•Heat-sensitive and challenging geometries could be coated using an AK05-ID torch.
PTFE matrix composites reinforced with α-Al2O3 fillers are considered a gold standard polymeric solid lubricant. α-Al2O3 PTFE exhibits ultra-low wear rates (k ∼10−8 mm3/Nm) when sliding against steel ...in the presence of water vapor. Mechanochemical interactions involving the breaking of PTFE chains, and subsequent oxidation in the presence of water vapor helps promote growth of interfacial films that are strongly bound to the sliding interface. In the absence of moisture, wear rates of α-Al2O3 PTFE can increase by as much as three orders of magnitude, underscoring its importance to ultra-low wear behavior. A similar increase in wear rates of α-Al2O3 PTFE in humid environments has recently been observed when sliding against brass counter surfaces, though reasons for this increase remain unclear. These findings suggest that mechanisms of ultra-low wear not only rely on ambient humidity but are also strongly dependent on the counter surface chemistry. In the present work, we test the hypothesis that counter surface chemistry drives alumina PTFE wear by systematically investigating the wear of an α-Al2O3 PTFE composite against brass and aluminum substrates within the context of the morphological and mechanochemical evolution of the sliding interface. Wear tests are conducted under reciprocating, dry sliding conditions. Results presented in this work offer insights on mechanochemical mechanisms that drive wear of α-Al2O3 PTFE against brass and aluminum, and provide a framework for developing strategies for controlling wear.
•Dry sliding wear of α-Al2O3 PTFE increases when sliding against brass and aluminum, relative to steel by nearly three orders of magnitude.•Spectroscopic analysis suggests increase in wear is due to partial oxidation of PTFE, resulting in less strongly bound interfacial films.•Preconditioning of polymer pins is explored as a viable route for recovering ultra-low wear against non-ferrous substrates.
This paper provides a comprehensive characterisation of HVOF- and HVAF-sprayed Cr3C2–25wt.% NiCr hardmetal coatings. One commercial powder composition with two different particle size distributions ...was processed using five HVOF and HVAF thermal spray systems.
All coatings contain less Cr3C2 than the feedstock powder, possibly due to the rebound of some Cr3C2-rich particles during high-velocity impact onto the substrate.
Dry sand-rubber wheel abrasive wear testing causes both grooving and pull-out of splat fragments. Mass losses depend on inter- and intra-lamellar cohesion, being higher (≥70mg after a wear distance of 5904m) for the coatings deposited with the coarser feedstock powder or with one type of HVAF torch.
Sliding wear at room temperature against alumina involves shallower abrasive grooving, small-scale delamination and carbide pull-outs, and it is controlled by intra-lamellar cohesion. The coatings obtained from the fine feedstock powder exhibit the lowest wear rates (≈5x10−6mm3/(Nm)). At 400°C, abrasive grooving dominates the sliding wear behaviour; wear rates increase by one order of magnitude but friction coefficients decrease from ≈0.7 to ≈0.5. The thermal expansion coefficient of the coatings (11.08x10−6°C−1 in the 30–400°C range) is sufficiently close to that of the steel substrate (14.23x10−6°C−1) to avoid macro-cracking.
•Particle abrasion involves coarse abrasive grooving and pull-out of coating fragments.•Particle abrasion resistance depends on inter- and intra-lamellar cohesive strength.•Sliding wear at R.T. involves moderate abrasion, carbide pull-out and adhesive wear.•At 400°C, sliding wear rates increase due to more severe abrasive grooving.•Lower friction at 400°C than at R.T. is due to graphite clusters in the wear debris.
The purpose of this research was to investigate the potential use of Cu–Ti3AlC2 composites sliding against a Cu–5%Ag alloy as a viable electrical contact couple. Sliding friction and wear tests were ...conducted in the presence of an electric current using a custom-designed block-on-ring wear testing apparatus. The electrical current density was 0–15 A/cm2 along with an apparent contact pressure of 1.25–7.5 N/cm2 and sliding velocities ranging from 2.5 to 15 m/s. The results indicate that friction coefficient, wear rate, and contact voltage drop measured for the sliding couple increases with an increase in the electrical current density. As the apparent contact pressure increases, the contact voltage drop of Cu–Ti3AlC2 composites increases gradually, while friction coefficient and wear rate first decrease and then increase. With an increase in the sliding velocity, the friction coefficient of the sliding pair decreases and the contact voltage drop increases gradually, while wear rate decreases first, then increases. Adhesive wear and arc erosion wear proposed as the main wear modes. A lubricating film was observed to form on the wear surfaces under each test condition, and that film apparently improves the tribological properties of the sliding couples.
•The electrical sliding wear properties of Cu–Ti3AlC2 composites rub against Cu–Ag alloy are studied.•Effect of electrical current density, apparent contact pressure and sliding velocity are studied systematically.•Lubricating films are formed at each contact condition and improve the tribological properties of the material.•Two main mechanisms for electrical sliding wear of Cu–Ti3AlC2 composites are presented.
This study aimed to evaluate the microstructure and wear properties of WC-10Co-4Cr, WC-12Co, and WC-17Co coatings on TC4 titanium alloy. The coatings were deposited using high velocity oxygen-fuel ...(HVOF) technique. To analyze the influence of binder phases, the coatings were thoroughly examined using scanning electron microscopy, X-ray diffractometer, microhardness tester, and friction and wear tester. The analysis of the results reveals that the primary phases in all three coatings consist mainly of WC, with smaller quantities of W2C and amorphous phases present. The WC-10Co-4Cr powder demonstrates a relatively even particle size distribution, high degree of sphericity, and rough porous surface, allowing for efficient heat absorption and uniform heat distribution, resulting in a dense coating. Notably, the WC-10Co-4Cr coating exhibits significantly smaller tungsten carbide grain size compared to the other coatings. Moreover, the microhardness of the WC-10Co-4Cr coating, measured at 1377.8 HV0.05, is significantly higher than that of the WC-12Co and WC-17Co coatings, which measured at 1258.8 HV0.05 and 1182.4 HV0.05, respectively. Additionally, the WC-10Co-4Cr coating demonstrates low friction coefficient and wear volume, indicating excellent wear resistance. Subsequently, a comprehensive analysis was conducted to determine the reasons for the relative enhancement in binder performance.
•Preparation of WC-10Co-4Cr, WC-12Co, and WC-17Co coatings on TC4 titanium alloy via ultra short-distance HVOF.•Characterized the morphology of three WC powders and the microstructure of the coatings.•An in-depth analysis was conducted on the effect of binder phases on coating performance.•Tested the microhardness and wear performance of the coatings, and explained their differences.
This paper summarizes the wear behaviour of Al-composites reinforced with ceramic materials. The influence of the mechanical parameters such as applied load, sliding velocity, sliding distance, ...temperature, and counterface hardness; and the material factors such as reinforcement type, size, shape and fraction, on the wear performance of Al-composites have been reviewed and discussed. It has been revealed that these parameters can influence the surface and subsurface behaviour of Al-composites during sliding wear conditions. It has also been observed that the ceramic reinforcements improve the wear resistance of the Al-composites under two-body abrasive or adhesive wear. However, the wear resistance of these composites is similar to the matrix alloy under intermediate load conditions due to three-body abrasive wear. Reduction in wear rate due to formation of oxide layers on the wear surface has also been reported in literature. Literature also reveals that the use of solid lubricant (Gr) particles and hard ceramic particles (SiC or alumina) as hybrid reinforcements can effectively improve the wear properties of the sliding system. The study indicates that the Al-composites especially the hybrid composite can be considered as an outstanding material for design of various automotive components, which require high strength and wear resistance.
High entropy alloys (HEAs) show promise as materials for structural applications, even at elevated temperatures. However, their wear behaviour over a wide range of temperatures has not been ...extensively studied. CoCrFeMnNi and AlxCoCrFeNi HEAs were subjected to pin-on-disc dry sliding wear at temperatures between 25 °C and 900 °C against an alumina ball, and the tribological performance benchmarked against AISI 304 and Inconel 718. A detailed characterisation of the wear tracks using electron microscopy and surface profilometry revealed a transition in wear mechanism from abrasive wear at room-temperature to oxidative and delamination wear above 600 °C. The wear performance of the HEAs, AlCoCrFeNi in particular, is substantially enhanced with increasing temperature, surpassing that of Inconel 718 at 900 °C. The enhanced wear performance of the HEAs above 600 °C is attributed to the formation of a compact oxide scale in the contact region, and relative subsurface strengthening in the form of a fine-grained recrystallised structure containing precipitation hardening phases.
•The wear behaviour of various high entropy alloys up to 900 °C is analysed.•Wear rates of high entropy alloys decreases with increasing temperature.•High wear resistance of AlCoCrFeNi due to alumina scale and σ-phase precipitation.
Dry sliding wear tests of steel disks of various compositions were performed with consideration of the effects of microstructure, shear strain and shear strain rate using a ball-on-disk tester with a ...tungsten carbide ball under ambient atmosphere and room temperature. We found a severe–mild wear transition phenomenon, which we called self-lubrication, and categorized friction behavior into two regimes: a high-friction regime and a low-friction regime. However, self-lubrication occurs only at specific strain levels and rates related to materials with martensite and pearlite structures. We characterized the microstructures of the worn surface, subsurface and matrix and found a thin self-lubricating layer composed of nano-oxide particles with sizes in the range 6–20 nm attached to the surface. The formation of these nano-oxide particles is controlled by lamellar structure (martensite or pearlite) nano-lamination, oxidation and solid-state amorphization during dry sliding. The high density of geometrically necessary dislocations and defects induced by plastic deformation under wear shear strain levels and rates is important in the formation of nano-lamellar microstructures and amorphous oxide. These results both clarify nano-lamellar microstructure solid-state amorphization and oxidation behavior and reveal the mechanism of self-lubricating layer formation observed in this work.
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