Wear最新文献

Single-crystal silicon carbide (SiC) has poor machinability because of its low fracture toughness, and surface modification has become the first choice for SiC polishing to obtain a high removal rate and a smooth surface. However, the removal mechanism of SiC after modification remains unclear. In this study, diamond scratching experiments were performed on 4H–SiC after oxidation under two conditions. To reveal the material removal mechanism, the scratch morphology and subsurface defects were analysed using Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The results showed that oxidation improved the scratch depth and critical depth for ductile removal, resulting in a smooth scratch surface with low damage. However, weak oxidation increased the median crack length and exacerbated the subsurface damage. The SiO_xC_y, C = O, C–O–C, and Si–O–Si functional groups produced during oxidation reduced the hardness and improved the machinability of the 4H–SiC substrate. On the other hand, strong oxidation reduced the generation of surface cracks, tearing, and spalling, and weakened the propagation of subsurface median cracks. These results prove that ultrasonic-assisted photocatalytic oxidation provides high removal efficiency and defect control, providing a new approach for the synergistic polishing of SiC substrates.

Ti–6Al–4V alloy has become a crucial raw material in aerospace and other industries owing to its exceptional mechanical properties. However, it is also a typical difficult-to-machine material, and its removal process and mechanism have been widely investigated by scratch testing. Nevertheless, the inherent non-rotational symmetry of the Vickers indenter introduces a crucial parameter, i.e., the angle λ between the indenter edge and the scratch direction, which affects not only the mechanical response of materials but also its surface formation mechanism during scratch. This study systematically characterized the micro/nano scratch characteristics of Ti–6Al–4V alloy under three typical angles λ (0°, 22.5°, 45°) as well as various normal forces and scratch speeds. The coefficient of friction (COF), scratch depth, scratch width, residual scratch morphology, and specific scratch energy were comparatively analyzed. Finite element simulations confirmed that the direction of material flow changed with the change in angle λ. The corresponding deformation mechanisms during scratch were discussed accordingly. The results revealed a significant influence of the angle λ on the scratch behaviors and surface quality of Ti–6Al–4V alloy.

This study investigated the tool wear behavior of white alumina (WA) and seeded gel (SG) abrasive wheels in the ultrasonic vibration-assisted creep feed grinding (UVACFG) of nickel-based single-crystal alloy. The abrasive wheel wear characteristics were examined, and their effects on the grinding force, temperature, and surface quality were evaluated. Finally, the wheel wear mechanism in the UVACFG was discussed by analyzing the intermittent cutting behavior and wear patterns of a single grain. Experimental results indicated that the workpiece material adhesion and pore-clogging were the main wear patterns of abrasive wheels without ultrasonic vibration. In contrast, these were adequately mitigated after introducing ultrasonic vibration, and the main wear pattern for both wheels became the grain fracture. The WA wheel in the UVACFG experienced reduced radial wear by around 60.7 % in the initial wear state, 40.2 % in the stable wear state, and 25.3 % in the rapid wear stage, respectively, compared to the conventional grinding (CG). The intermittent cutting behavior of SG grains caused by high-frequency vibration promoted the micro-fracture capacity and ensured the coolant entered the grinding zone sufficiently, which reduced the grinding force and temperature by up to 63.2 % and 46.7 %, respectively, and meanwhile introduced the defects of high bulges and slight plastic deformation on the workpiece surface.

The mechanisms of material transfer in aluminum forming processes at high temperatures have remained a contentious tribological issue. This study aims to investigate the transfer mechanisms in the initial and grow-up stages of 6082-T6 aluminum alloy against commercial Arc-DLC coating under lubricant-free forming conditions. The warm and hot upsetting sliding test (WHUST) was used as the tribological test. It was conducted with two sliding configurations: the full sliding test to study the evolution of aluminum transfer and the short sliding test with a 2-mm sliding distance to observe the initiation of aluminum transfer. Furthermore, the effect of different sliding speeds, 0.5 and 5.0 mm/s, and initial temperatures of the specimen, 300 °C–500 °C, on the phenomenon of aluminum transfer was examined. Experimental results found that the aluminum transfer on the Arc-DLC coating in the initial stage of all cases was mainly caused by mechanical plowing. However, in the grow-up stage, the aluminum transfer could be dominated by mechanical plowing and/or adhesive bonding, depending on contact conditions. The different transfer mechanisms caused variations in the coefficient of friction and surface characteristics on the friction track. It led to the skewness Ssk could be an indicator to differentiate the transfer mechanisms.

NiTi alloy is widely used in extreme working conditions due to its pseudoelasticity, shape memory effect and wear resistance. In this study, the NiTi alloy coating (Ni49.8Ti50.2 (at%)) was fabricated by high-frequency induction heating. The coating was well-formed on the surface of cemented carbide YG8 and converted to crystalline after aging treatment. The results of 70h erosion wear experiments carried on the rotary erosion wear test device showing that the erosion wear amount of the coating was reduced by 93 % compared with that of YG8, resulting from the deformation recovery effect. Moreover, the main erosion wear mechanism of the coating was micro-cutting and ploughing. This study can provide technical support and theoretical basis for preparing of NiTi alloy coating and erosion wear resistance.

This work has focused on contact mechanisms between Inconel 718 blades and a NiCrAl-bentonite abradable – a combination commonly used in the hot end of aero-engine compressors, where a transition to high forces and blade wear has been observed in certain contact conditions. In the first set of tests the effects of blade length and rig arrangement were investigated through testing on two different rigs. The purpose was twofold: establishing a connection to the previous research performed on the slower of the two rigs, and developing a general understanding of the effects of these two parameters on results. It was demonstrated that both rig stiffness and blade length in the considered range did not have a strong effect on the likelihood of transition of a test to the aforementioned high wear regime. The higher speed rig was then used to investigate the progression to high contact forces and blade wear in more detail by performing tests at speeds of 200 m/s and 280 m/s, with three incursion rates considered at each speed. Test to test variability was similarly investigated by performing five repeats for each test condition. Two distinct contact modes were observed – one where forces remained low and no blade wear occurred, and another where forces progressively increased until blade wear initiated and forces stabilised at significantly higher values than in the case of low force tests. These contact modes were explained through interaction between the incursion rate and rate of abradable fracture. The results have shown that an increase in incursion rate has increased the likelihood of the high-force contact mode, and an increase in blade tip speed decreased it. The inherent randomness of the abradable spraying process was demonstrated to lead to variability in material properties for nominally similar samples, and in turn the transition in contact mode was in essence probabilistic in nature. This variability also highlighted the importance of performing repeats when contacts with sprayed abradable materials are considered.

Current study reports the dry sliding wear behavior of Fe₅₇Cr₉Mo₅B₁₆P₇C₆ (at. %) fully amorphous bulk metallic glass (BMG) and in situ BMG composites, synthesized via spark plasma sintering. Fully amorphous alloy and in situ amorphous-crystalline composites containing various amount of crystallinity with a relative density > 98% were fabricated via optimized sintering conditions. Effect of in situ induced crystalline phase content on wear behavior and wear mechanism was investigated. In situ crystallization of intermetallic phases such as Fe₅PB₂, Fe₂B and Cr₂B led to significant increase in the hardness of the composite samples up to 15.1 GPa from 10.1 GPa in the case of fully amorphous sample. Increase in crystallinity in the studied Fe-based amorphous-crystalline composites was found to have a positive effect on wear performance. In the BMG sample with completely amorphous phase, sliding wear induced debonding of the sintered particles along with surface oxidation. However, in the case of amorphous-crystalline composite samples, sliding wear caused the formation of oxide rich tribolayer that resulted in lower coefficient of friction and significantly lower wear rates compared to the fully amorphous sample. Coefficient of friction values assumed more than 50% decrease in the case of 20% amorphous composite sample in comparison to the fully amorphous sample. Wear rates of the current Fe-based amorphous-crystalline composite samples were found to be in the order of 10⁻⁷ mm³/N.m, which are relatively lower compared to the recently reported Fe-based BMGs.

Austenitic stainless steel 304 is widely used in various applications due to its mechanical strength, toughness, and, most importantly, its corrosion resistance. However, machining this material presents significant challenges, primarily due to its high tendency for work hardening and generation of elevated temperatures. In the cutting process, this temperature rise can result in premature tool wear, leading to a reduction in their lifespan. To address these issues, cutting fluids are typically applied. Although this component offers advantages, it also contributes to environmental pollution, health risks, and significant costs, including disposal.Therefore, this study introduces an Internally Cooled Tool (ICT) method aimed at reducing the heat generated during machining. In this study, an analysis of tool life and wear was conducted to evaluate the effectiveness of ICTs compared to conventional machining methods during the turning of austenitic stainless steel 304 using double-coated tools (AlCrN on TiAlN, PVD (Physical Vapor Deposition)). Additionally, the use of ICTs in combination with lubrication (hybrid machining Minimum Quantity Lubrication (MQL) + ICT) was also investigated. The study covered five machining atmospheres (ICT, ICT + MQL, dry, wet, MQL). Cutting conditions were kept constant, including cutting speed (vc = 400 m/min), feed rate (f = 0.1 mm/rev), and depth of cut (ap = 0.5 mm). Scanning electron microscopy (SEM) analyses were conducted to examine the wear mechanisms and types present in each condition, along with statistical tests such as analysis of variance and Tukey tests to validate the experiments. The results indicated that ICTs (ICT and ICT + MQL) showed a longer tool life compared to dry machining and MQL techniques, while the wet machining method did not demonstrate significance compared to this technique. The observed wear mechanisms included abrasion, adhesion, and diffusion, with abrasion being the predominant mechanism. In summary, it was found that the durability of the inserts was directly related to coating adhesion, as coating detachment quickly led to the end of the insert's lifespan.

MoS₂–Sb₂O₃ coating is commonly used as solid lubricant for titanium alloys, but the wear-resistance performance is still limited. Core-shell annealed nanodiamond (AND) particle is used as reinforcement for MoS₂–Sb₂O₃ coating on Ti6Al4V substrate treated by plasma electrolytic oxidation (PEO) and laser surface texturing (LST). The incorporation of AND particles into the MoS₂–Sb₂O₃ coating results in a 39 % decrease in friction and significantly reduces wear on the composite coating. Structural transformation of AND particles to amorphous carbon and graphitic structure promotes the densification of top-layer coating, enhancing lubrication and wear-resistance. Change of contact stress by PEO-LST promotes the formation of dense tribofilm and re-orientation of MoS₂. This study has implications for the development of solid lubrication coatings for aerospace applications through functional nanomaterials and targeted designed surfaces.

The study involved plasma arc transfer welding (PTAW) for preparing coatings of Inconel 625 alloys that contained different amounts of nano-sized hafnium carbide (nano-HfC) particles. The impact of nano-HfC on the microstructure evolution and mechanical properties of PTAWed Inconel 625 were investigated. The research reveals that nano-HfC decomposes during the high-temperature plasma arc process and then react with O element to generate nano-HfO₂. These HfO₂ can serve as nucleation sites for MC carbides, which restricts the growth of secondary dendrite arms, leading to a more disordered grain growth direction. Simultaneously, the decomposition of HfC can increase the C/Nb ratio of the matrix, effectively suppressing Laves phase formation while encouraging the development of MC carbides. Compared with IN625, the wear rate of composites at room temperature and 600 °C were decreased. Notably, at 600 °C, the wear rate of the coating with 0.5 wt% HfC is the lowest among all the samples, as reflected by a noteworthy reduction in wear rate of 50 %. This is mainly attributed to the refinement of γ matrix, reduction of Laves phase as well as precipitation of the fine-sized MC carbides. This work illustrates that adding nano-HfC is an effective way to improve the wear resistance of the PTAWed Inconel 625.