查看更多>>摘要：The hard particles in particle-reinforced aluminum matrix composites significantly increases tool wear during friction stir welding (FSW), resulting in the shortage of tool life. In this study, SiCp/Al composites are used as the research object, and the tool wear experiment in friction stir welding is carried out by using high-speed steel pin and high-speed steel + AlCrN coated pin. A new method for calculating tool wear based on hydrodynamic pressure is proposed, and the tool pin wear prediction model is established and verified by experiments. The results show that the wear rate of AlCrN coated pin is very low at the beginning, indicating that AlCrN coating can extend the tool life to a certain extent. However, the wear rate of the tool will increase significantly after the coating is worn away. Through the analysis of the surface wear morphology of the pin, it is found that the main mechanisms of tool wear in the friction stir welding of SiCp/Al composites are the micro ploughing and micro cutting of SiC particles.
查看更多>>摘要：Fretting and corrosion of metallic medical devices are significant degradation mechanisms that impact performance. Multi-asperity contact surfaces undergo a progressive engagement-damage-redistribution process distributed over the nominal contact surface, implying that relatively short-lived fretting contact engagements of individual asperities are a central element to fretting corrosion processes in modular taper junctions of total hip replacements. In this work, the contact mechanics of single asperity hard-metal surfaces under small scale reciprocal sliding (SSRS) between two contacting surfaces in air and solution (i.e., tribocorrosion), typically less than 100 μm cyclic motion are presented and discussed for Ti-6Al-4V, CoCrMo, and 316L SS alloys. Characteristic scaling factors, based on asperity radius, hardness, and modulus, for characteristic stress and a dimensionless asperity radius are presented based on the interaction between elastic and plastic contact mechanics. The contact and tribological interactions of a 17 μm radius spherical diamond asperity was used to explore damage effects on these alloys in both air and phosphate buffered saline. The volume abraded, depth of penetration, extent of plastic deformation and oxide debris formation were captured as functions of cycles, load, and solution presence/absence. Damage was analyzed and quantified using digital optical microscopy, atomic force microscopy and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The results were analyzed with ANOVA statistics (α < 0.05). The extent of damage follows CoCrMo < Ti-6Al-4V < 316L SS. The wear characteristics varied significantly between alloys with more plastic deformation associated with CoCr and more shearing particle and ribbon formation present for Ti-6Al-4V and 316L SS. Solution immersion did not significantly increase volume loss for any alloy but did increase the amount of released and embedded oxide debris for 316L SS. Titanium also exhibited oxide debris generation and embedding. Importantly, significant (<5 μm) penetration depths were obtained after 100 cycles, indicating that single asperities, continuously engaged with metal under very low loads, rapidly generate extensive debris and plastic deformation.
查看更多>>摘要：TiB_2-TiC-based cermets are expected to replace cemented carbide in the cutting and finishing of ferrous alloys, steel, aluminum, copper, and other nonferrous metals owing to their excellent wear resistance and cutting performance. In this study, the tribological behaviors and wear mechanisms of TiB2-TiC-based cermets with different WC contents were investigated by sliding the specimens against a cemented carbide ball. As the WC content of the TiB_2-TiC-based cermets increased from 0 to 25 wt%, the wear rate and friction coefficient first increased and then decreased. Cyclical changes were observed in fatigue, adhesive, and abrasive wear. Explanatory mechanisms were proposed for these phenomena. This is the first comprehensive study on the effect of the WC content on the tribological properties of these important composites.
查看更多>>摘要：This study investigates the mechanism of wear damage of human tooth enamel by applying reciprocating impact-sliding wear tests. Two sliding loads (20 N, 49 N) were applied. In general, greater the load, greater the wear damage. The wear tracks could be divided into the impact part and the sliding part, and the wear characteristics of enamel were different between two parts. Impact wear in the impact part displayed plastic deformation, quasi-plastic deformation and brittle fracture. Sliding part with abrasive wear exhibited microscale cutting and plowing processes. The impact motion was the main cause for the loss of enamel in the early stage which led to higher wear rate and a larger enamel loss. The sliding movement was the main reason for the loss of enamel in the later stage of the experiment which led to a steady wear rate and moderate material loss.
查看更多>>摘要：In this study, a comparison of the wear resistance of AlCrN, AlTiN, TiAlN, TiCN, and CrN PVD coatings deposited on hard-metal WC-Co wood milling cutters was performed. Real industrial application experiments were performed for the milling of oak wood. During the tests, the roughness of the machined oak wood surface was inspected, and the cutter wear was measured after the experiments. Thickness, hardness, roughness, and coefficient of friction of the coatings were determined. It was found that deposition of CrN, AlCrN, and TiCN coatings could improve the wear resistance of the investigated cutter by factors of 3, 1.9, and 1.7, respectively. The performance differences and wear mechanisms were described in detail based on the properties of the coatings.
C. Hernandez-NavarroE. Rodriguez-De AndaE. GarciaJ. E. Gonzalez-Sevilla...
11页
查看更多>>摘要：The tribological performance of the coatings depends on their properties like material, morphology, structure, among others. This work compares the tribological performance of two multilayers films of ceramic/metallic (TaTiN/TaTi) combination with a hierarchical morphology arrangement using DC-magnetron co-sputtering with Ta and Ti metallic targets controlling the sizes of their ceramic-layer thickness on the Ti substrate. These films had the configuration of the nano to microscales (NML) and micro to nanoscale (MNL) layers. The films had the structure combination of c-TaTiN, c-TiN, and α"-TaTi, with higher Nitrogen in the MNL coatings and higher intensity of LA vibrational mode in their Raman spectra. The XPS study showed that the MNL coating presented a higher metallic composition in the top layer than NML. Nevertheless, MNL film had a higher H and lower E* than NML coating due to the stress distribution by the multilayer arrangement. The MNL coatings showed higher elastoplastic deformation and reduced the presence of cracks and fractures of the layers. The Raman spectra of MNL coating presented a higher presence of Ta_2O_5 vibrational modes than the MNL film due to a tribolayer formed by debris accumulation.
查看更多>>摘要：Many reinforcing fillers (particles, fibers, and platelets) can reduce the high wear rate of polytetrafluoroethylene (PTFE) (K～10~(-4) to 10~(-3) mm~3/Nm) by 10-1000 times. However, certain α-alumina particles can produce up to 10,000 times lower wear rate when composited with PTFE (K～1.3 × 10~(-7) - 6.7 × 10~(-8) mm~3/Nm). This ultralow wear behavior was attributed to two mechanisms: tribofilm generation and tribochemistry. However, while reducing the wear rate of PTFE, α-Al_2O_3 can also increase its friction coefficient up to two times (μ～ 0.1 vs 0.2-0.25). This study revealed that the friction coefficient of PTFE-Cr against Brass 260 counterbody is up to three times lower than the ultralow wear PTFE α-alumina against 304 Stainless Steel (μ = 0.08-0.12 vs μ = 0.2-0.25) with up to 200 times lower steady-state wear rate (K～1.4-34 × 10~(-9) mm~3/Nm) than PTFE α-alumina against 304 SS (K～6.7-13 × 10~(-8)), and ～3 × 10~5 times lower than unfilled PTFE. PTFE-Ti (μ = 0.09, Kss = 2.9 × 10~(-8) mm~3/Nm) and PTFE-Mn (μ = 0.12, K_(ss) = 1.2 × 10~(-8) mm~3/Nm) against Brass 260 also performed better than PTFE-α-Al_2O_3 against 304 SS both in reducing wear rate and friction coefficient. The tribofilms created by the PTFE-Cr, PTFE-Mn, and PTFE-Ti composites were evaluated using Scanning White Light Interferometry (SWLI) and Infrared (IR) Spectroscopy. These analyses showed that these composites created thin (500-1500 nm) films on the Brass 260 counterbody and their worn surfaces exhibited new chemical groups (carboxylate salts, hydroxyl groups, and acetate ions). These new chemical groups signal the formation of bonds between the PTFE matrix, filler particles, and the metal counterbody, which protects both the composite and counterbody from wear.
Sam AshworthJ. Patrick A. FaircloughJames MeredithYoshihiro Takikawa...
9页
查看更多>>摘要：Machining of carbon fibre reinforced polymer (CFRP) is abrasive and causes significant tool wear. The effect of tool wear on static flexural strength is investigated, using edge trimming with uncoated carbide and chemical vapour deposition (CVD) diamond coated burr style tools. Edge rounding (ER) criteria along with flank wear are used to observe tool degradation with ER shown to preferentially wear allowing the tool to become cyclically sharper and duller, corresponding to fluctuating dynamometer readings, a novelty for CFRP machining. Areal surface metrics degraded for an uncoated tool due to changes in cutting mechanism, whilst for up to 16.2 m of linear traverse, the coated tool showed limited changes. Tool wear, caused by edge trimming 7.2 m of CFRP, using an uncoated carbide tool, provided a flexural strength reduction of up to 10.5%, directly linking tool wear to reduced mechanical strength.
查看更多>>摘要：The wear damage and aging behavior of natural rubber (NR) nanocomposites are very complex under severe conditions (high load, high-speed wear, or ablation). Little is known about the influence of strong interfacial friction on the high-temperature aging mechanism in the internal of NR nanocomposites. In this study, a set of UMT-TriboLab wear tester was used to study the wear and aging of NR nanocomposites, and to reveal their influence on the internal aging of specimens under severe conditions. Sliding wear tests were carried out with rubber-metal tribopair using a Block-on-Ring configuration. Different from mild wear conditions, the wear mechanism of NR nanocomposites under severe conditions experienced a transition from abrasive wear to adhesive wear. The viscous film formed by the degradation products on the wear surface was found to strongly affect the subsequent wear and aging behavior (wear weight loss, friction coefficient, temperature rise, etc.) of specimens. Layer-by-layer analysis showed that the heat diffusion caused by surface wear resulted in noticeable post-crosslinking in the internal layer of specimens while the oxidation reaction was limited to occur only on the specimen surface.
查看更多>>摘要：This study evaluated the cavitation erosion behaviour of a commonly used material in the marine environment, nickel aluminium bronze (NAB), after exposure to the adhesion of Bacillus sp. biofilm in artificial seawater. Results showed that the biofilm could inhibit the corrosion progress, keeping κ phases intact and subsequently allowing the NAB to retain its cavitation erosion resistance. Detailed discussion about the effect of the biofilm on cavitation erosion behaviour of NAB was presented. Furthermore, the importance of the κ phases for resisting cavitation erosion was evidenced by in-situ SEM, and a correlation of the decrease in hardness and the increase in mass loss during cavitation erosion was built.
NSTL
Elsevier