This work aims to understand the tribological behavior of cBN-WC-10Co composites subjected to the dry reciprocating sliding wear. The tribological behavior was characterized by the coefficient of ...friction (CoF) and the specific wear rate. The wear test was designed and performed on the composites against SiC ceramic ball at an ambient temperature, and the SEM morphologies for both of the composites and SiC ceramic ball were measured to reveal their tribological behavior. It was found that the cBN-WC-10Co composites was worn out in two manners, i.e., abrasive wear and oxidation wear, and the abrasive wear was dominant. The cBN particles in the composites were worn out by polishing, fracturing and pulled-out. It was also found that (1) adding cBN particles improved the wear resistance of cBN-WC-10Co composites greatly in comparison with that of the WC-10Co cemented carbides; (2) reducing particle sizes in cBN-WC-10Co composites reduced the specific wear rate when the normal load was below certain value (50 N); while using large particle sizes showed better wear resistance when the normal load was continuously increased. The wear of SiC counter body was much severer when against cBN-WC-10Co composites in comparison with that against WC-10Co cemented carbides. This was due to the fact that the cBN particles in the composites acted as micro cutting edges to wear SiC ceramic.
The study of metal-ceramic sliding wear is important as it occurs in many industrial mechanical systems. The friction behaviour and self-lubricating mechanism of low alloy martensitic steel during ...reciprocating sliding wear against the WC ceramic ball under an ambient atmosphere and at room temperature were investigated. The reciprocating sliding wear process was characterised using a commercial friction and wear testing machine and a scanning electron microscope. The results showed that there was a self-lubricating phenomenon during reciprocating sliding wear between the experimental steel and the tungsten carbide ceramic ball, and the friction coefficient decreased to 0.3 from 0.53. This is attributed to the high hardness of the subsurface, the lubricating effect of the surface oxide film, and the removal mechanism of layer-by-layer peeling. The evolution of the friction coefficient corresponded to the change in the wear mechanism. During the initial stage of sliding wear, adhesive wear was the primary wear mechanism, while fatigue spalling occurred during steady-state wear. In addition, during the self-lubricating process, the wear growth rate of the experimental steel decreased correspondingly, and the wear surface roughness also showed a decreasing trend.
●The reciprocating sliding between the experimental steel and WC ceramic was studied.●Reciprocating sliding experiments of various stages were designed.●There was a self-lubricating phenomenon during the reciprocating sliding.●The COF decreased to 0.3 from 0.53 owing to self-lubricating mechanism.
Low alloy wear-resistant martensitic steels are increasingly prevalent in moderate-to-high temperature applications in machinery. In this study, the reciprocating sliding wear behavior of a designed ...low alloy martensitic steel (herein called HTP) against silicon nitride has been investigated within the temperature range of 300–500 °C and compared to similar results for another wear-resistant steel (NM400). A commercial high temperature friction and wear tester was used. The evolution of the microstructure and properties of HTP and their influence on the wear process was investigated as a function of temperature. Results have shown that as the tempering temperature was increased to 500 °C, the wear depth was significantly reduced. This is attributed to increasing the strength and hardness by 25%. As a result, high temperature wear resistance of the HTP was increased by a factor of 1.7 times relative to alloy NM400. By delaying the decrease of dislocation density and carbide precipitation during the tempering of the martensite, the transformation of microstructure from tempered martensite to tempered sorbite could be hindered, thereby improving the thermal strength of the HTP alloy's matrix. The material removal mechanisms was observed to change from fatigue spalling and abrasive wear to oxidative wear and plastic deformation when the temperature was increased from 300 °C to 500 °C.
•The sliding wear of low alloy wear-resistant steel at 300–500 °C was studied.•High tempering stability of HTP steel improved the wear resistance at 300–500 °C.•Wear resistance of HTP steel was increased to 1.7 times relative to NM400 at 500 °C.•The wear mechanism of low alloy wear-resistant steel changed with temperature.
Ni–B–TiO2 composite coatings were elaborated by conventional and novel methods. While the first one was designed using TiO2 powder, the second was prepared by adding TiO2 sol in the bath solution. A ...comparative study between both coatings was performed in terms of microstructure, adhesion strength and wear resistance. To achieve a systematic study, various characterization tests were carried out, including Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), microhardness test, progressive load scratch test, reciprocating sliding test and multi-pass scratch test. The results showed that the TiO2 structure (crystalline or amorphous) has extensively changed the microstructure of Ni–B matrix. Furthermore, it was proven that the novel process provided superior scratch response and better wear resistance of the Ni–B deposit since it offers a compact structure. Nevertheless, the traditional method yielded to porous one, thus leading to mediocre mechanical properties of the same coating.
The staggering running of the modern electrified railways in the horizontal plane was simulated to study how the stagger affects the friction and wear properties of the pure carbon strip in the ...present work. The reciprocating sliding distance A of the carbon strip is defined and used to show the degree of the stagger in this work. A series of friction and wear tests were carried on a high-speed block-on-ring tester at different reciprocating sliding distances A. The test results indicate that both the friction coefficient f and the wear rate Ws of the pure carbon strip are affected by A. The arc discharge energy increase with increasing A, especially when the bigger reciprocating sliding distance of the carbon strip A is bigger than 30 mm. Based on SEM image and EDX image, the mechanical wear is mainly consisting of the adhesive wear and the surface scratch, and the mechanical wear reduces but the erosion wear increases with increasing A at high sliding speed with electric current of 250 A. There are delamination wear, oxidation and Cu transfer at the two limit positions of the reciprocating sliding of the carbon strip. Keeping good contact of the contact pairs at two limit positions of the reciprocating sliding is a direct way to reduce the delamination wear of the pure carbon strip.
•The experimental tests were carried on the high-speed wear tester under the condition of the sliding speed from 200 km/h to 300 km/h with electric current of 250 A.•New influence factor, reciprocating sliding distance of the contact strip A is investigated.•New friction and wear properties of the contact strip were presented in the process of electric sliding at different reciprocating sliding distance.•The wear mechanisms are changed with increasing reciprocating sliding distance.•Delamination wear of the carbon strip is close related to the reciprocating sliding distance with electric current.
Depth-dependent hardness variation of dimethylamine borane-reduced electroless Ni-5 wt-%B deposits has been examined using the nanoindentation technique. The deposits were characterised using ...ICP-OES, FESEM, XRD and DSC for evaluating the composition, morphology, structure and phase transformation behaviour, respectively. Coatings were also analysed for hardness and wear resistance. The surface of the as-plated deposit exhibits a typical nodular morphology. DSC traces show the presence of a single exothermic peak at 313°C conforming to its phase transformation. X-ray diffraction pattern of as-prepared deposit contains a mixture of amorphous and sharp microcrystalline nickel peaks. Heat-treated coating exhibits improved hardness and wear resistance. Depth-dependent nanohardness profile of as-deposited film neither obeys Nix-Gao nor the Lam-Chong model of indentation.
B-doped diamond has become the ultimate material for applications in the field of microelectromechanical systems (MEMS), which require both highly wear resistant and electrically conductive diamond ...films and microstructures. Despite the extensive research of the tribological properties of undoped diamond, to date there is very limited knowledge of the wear properties of highly B-doped diamond. Therefore, in this work a comprehensive investigation of the wear behavior of highly B-doped diamond is presented. Reciprocating sliding tests are performed on micro- and nanocrystalline diamond (MCD, NCD) films with varying B-doping levels and thicknesses. We demonstrate a linear dependency of the wear rate of the different diamond films with the B-doping level. Specifically, the wear rate increases by a factor of 3 between NCD films with 0.6 and 2.8 at. % B-doping levels. This increase in the wear rate can be linked to a 50% decrease in both hardness and elastic modulus of the highly B-doped NCD films, as determined by nanoindentation measurements. Moreover, we show that fine-grained diamond films are more prone to wear. Particularly, NCD films with a 3× smaller grain size but similar B-doping levels exhibit a double wear rate, indicating the crucial role of the grain size on the diamond film wear behavior. On the other hand, MCD films are the most wear-resistant films due to their larger grains and lower B-doping levels. We propose a graphical scheme of the wear behavior which involves planarization and mechanochemically driven amorphization of the surface to describe the wear mechanism of B-doped diamond films. Finally, the wear behavior of the nucleation surface of NCD films is investigated for the first time. In particular, the nucleation surface is shown to be susceptible to higher wear compared to the growth surface due to its higher grain boundary line density.
During reciprocating sliding of the Cu and Cu–Al alloys, we found that the characteristics of subsurface morphological patterns are intimately linked to dynamic recrystallization (DRX) structure ...generated by sliding. With the decreasing DRX grain size, the pattern changes from vortical to laminar feature at about 0.5 μm. The reciprocating sliding motion is favorable for producing morphologically vortical pattern and the DRX structure, while the occurrence of these processes is rare under unidirectional sliding. Additionally, the samples under unidirectional sliding exhibit higher wear resistance than those under reciprocating sliding, which may facilitate the development of delaminating tribolayer. The present results shed new insight into the relationship between morphological pattern, microstructure and wear behavior of materials under different sliding modes.
•A transition of subsurface morphological pattern exits at a DRX grain size of 0.5 μm.•Reciprocating and unidirectional sliding influence the subsurface morphological pattern and DRX structure differently.•The samples under unidirectional sliding exhibit higher wear resistance than those under reciprocating sliding.
The literature is controversial in relation to the influence of wear debris on tribological behaviour. Some works have shown that the presence of debris is fundamental to the formation of a ...protective tribolayer, thus reducing friction, whereas others showed that the presence of wear debris could contribute to increase friction coefficient due to the energy spent dragging them into the contact. This work aims to study the influence of the presence of wear debris, simulated by Al2O3 particles, on the tribological behaviour of an aluminium-steel pair under reciprocating sliding contact. Special emphasis is given to the particle size (0.05 µm, 0.1 µm, 1 µm and 10 µm). The particles were dispersed in distilled water (2 wt.%) as the source of debris. Reference tests were carried out solely in the presence of distilled water. The addition of alumina particles contributed to a significant reduction in friction coefficient, in particular for the largest particles (diameter ϕ=10 µm). When the larger particles were added, it was possible to observe the formation of a tribolayer on the sample surface leading to a gain of mass. In opposition, the wear rate of the counter body increased when large particles were added and the wear tracks showed strong evidence of abrasive wear. This suggests that hard and large wear debris, incorporated in the tribolayer formed on the samples, can act as hard protuberances, leading to abrasive wear of the counterbodies. When small particles were added, friction was still reduced when compared with the reference test, but the reduction of the friction coefficient was less significant. Small particles reduced the steel counter body wear rate and did not affect significantly the wear rate of the aluminium samples. It is proposed that small debris can get entrapped in the surface irregularities of the specimens and therefore participate less in the formation of the tribolayers.
•Al2O3 particles with varying average sizes were used as model wear debris.•Large particles formed a protective tribolayer, reducing friction and wear.•Large particles induced high wear rates and abrasion on the counterbodies.•Small particles had little effect on friction and wear.•The ratio Sq by debris size defined a transition from passive to active debris.
To explore the microstructure response to repeated sliding of materials showing stress-induced martensitic (SIM) transformation, we have investigated the microstructure evolution of solutionized ...Ti-51.5 at.% Ni introduced during the dry sliding against the GCr15 sphere at room temperature. It was found that B19′ was the dominant phase in the worn subsurface of solutionized case exhibiting extremely low martensitic transformation start (Ms) temperature (lower than −120 °C) and reverse transformation finish temperature (Af=−3.4°C), albeit amorphous structure observed in the topmost layer. Remarkably, nanotwins and faulting were experimentally revealed to contribute to the special microstructure. Moreover, particles of R phase were also discovered. The elementary mechanisms illustrated will be essential for the future modelling of the tribologically deformed layer of the alloys.
•The microstructure responses of the solutionized Ti-51.5 at.% Ni to sliding wear have been analyzed by TEM.•Martensite (B19′ and R) was retained at room temperature albeit Af=−3.4°C.•Amorphisation was ascribed to faulting in B2 and nanotwins accumulation in B19′.
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