Wear最新文献

In laser powder bed fusion (LPBF), processed H13 tooling has a broad application prospect in the mold and die industry. In practice, however, it is often impossible to obtain hot wear resistance and compressive residual stresses which constrain its development, affecting hence the wear performance and service life. Under these conditions, substrate preheating is an effective way to reduce thermal stress and defects of H13 for tooling applications. This research paper emphasizes the main characteristics of preheating temperature and its chief induced properties on microstructure and wear behavior of LPBF-processed H13 steel. The elevated preheating temperature altered the microstructure, increasing hardness and wear resistance. Under low applied loads, better wear resistance was attributed to high hardness and tribo-oxide layer formation. Whereas under high applied loads, it was dominated by the increased hardness due to strain hardening.

A wear-resistant composite material based on aluminum bronze with an addition of tungsten and tungsten carbide particles is developed using a combined wire- and powder-feed additive electron beam technology. The wear tests conducted under dry sliding conditions at room and elevated temperatures demonstrate a significant increase in wear resistance without any significant changes in the friction coefficient. Specifically, the composite with a particle content of 10 % exhibits an average wear rate 1.6 times lower compared to that of pure aluminum bronze, while the composite with a particle content of 20 % shows a 3.9-times wear rate reduction. The wear of the steel counterfaces during the composite sliding remains close to the values observed in a similar process for pure bronze.

In magnetorheological (MR) fluid polishing, high magnet speed releases abrasive particles from the finishing region, reducing their grip on the ferromagnetic chain structure and triggering the process to stall. Enhancing polishing efficiency necessitates developing a new composite magnetic abrasive (EIP-Al₂O₃) through microwave sintering. EIP-Al₂O₃ has favourable soft magnetic effects when it comes to its structure, phase composition, magnetic, and rheological properties. Chemo-mechanical magneto-rheological finishing (CMMRF), a developed hybrid-finishing method, aims to thoroughly evaluate CMA's performance. CMA attains a defect-free Al-6061 surface with R_a ∼79 nm and MRR ∼0.379 mg/min. CMAs outperforms simply mixed abrasives (SMA) by a significant 25 % increase in R_a and a remarkable 60 % increase in MRR. CMAs emerges as an effective solution for combating tool aging effects at high rotational speeds.

This study successfully prepares iron-based oil-containing materials with connected porous structures using TiH₂ and nylon 66 short fibers as pore-forming agents. The dehydrogenation of TiH₂ can produce large pore cavities and the nylon 66 short fiber with a highly regular shape has a unique advantage in pore channel production. Compared to the iron-based specimen without the pore-forming agent, the oil content of the iron-based specimen with the two pore-forming agents increases by 33.86 %. The tribologica23ee3l properties of the iron-based oil-containing materials under dry and self-lubricated sliding conditions are evaluated using the MM-200 ring-block sliding tribometer and the HDM-20 end-face friction and wear tester, respectively. Special emphasis is given to the effect of pore structures on wear patterns. The results showed that the material's surface is subjected to significant shear failure under dry sliding conditions, leading to the closure of pores due to plastic deformation during the initial sliding. The connected pore structure is a non-dense region, allowing shear damage to occur in the deeper subsurface of the matrix and increasing the material's wear rate. Under self-lubricated conditions, the connected pore structure facilitates the rapid release of lubricating oil, improves the initial lubrication state, and delays pore closure. As compared with dry friction, the wear rate can be reduced by two orders of magnitude under self-lubricating conditions. At a sliding speed of 0.46 m/s, an appropriate load (about 900 N) can enhance the material's ability to continuously and rapidly supply oil.

Polycrystalline diamond (PCD) wear is a classic issue limiting the widespread use of PCD circular saw blades, impairing the final cost and productivity. However, previous studies have rarely focused on the wear of PCD layers of saw teeth considering the vibration effect. Hence, this study aimed to elucidate the wear behavior and impact breakage characteristics of PCD teeth in sawing hard aluminum alloys. Sawing experiments were conducted, while vibration signals and force signals were captured in real-time. Then, wear morphologies of different zones of the PCD tooth were finely characterized and studied by SEM. The results suggested that the main wear types of cutting edges are abrasion, chipping, and adhesion. The abrasive wear was found on the cutting edges, side edges, rake faces, and flank faces. Interestingly, the breakage in chipping zones is mostly marked by grain spalling and cleavage fracture due to binder strength limitations. Adhesive wear occurs in wear zones by EDS analysis. A schematic of the impact wear evolution mechanism is given to explore in detail the wear morphologies of PCD layers. The wear behavior and morphological characterization of the PCD layer are finely discussed considering impact load and sawing factors (e.g., adhesive chips). This study sheds insight into the wear behavior of PCD teeth and guides the design of PCD layers.

The tribological properties of high-entropy alloys (HEAs) have been extensively studied in recent times but majority of the investigations have been limited to sliding wear behaviour and 2-body abrasive wear. There has been limited research on the three-body abrasive wear behaviour across different stress regimes. In this study, HEAs with different microstructures (FCC, FCC + secondary phases and BCC) were fabricated by systematic addition of Al, Ti and Mo to an FCC phase CoCrFeNi HEA and subjected to three-body abrasion. The abrasion resistance of different HEAs under low and high stress abrasion were measured using ASTM G65 and B611 methods, respectively. Under low stress, abrasion resistance increased with hardness for dual phase HEAs and BCC HEAs. Interestingly, the abrasion resistance of single phase FCC HEAs was comparable to the much harder dual phase HEAs. This was attributed to the formation of work-hardened sub-surface layer in the FCC alloys and a ploughing dominated wear mechanism on the surface. Further, the severe plastic deformation under high stress abrasion in the FCC HEAs resulted in the formation of a sub-surface layer with a nano-crystalline structure with high hardness. However, the dual phase HEA with 13 at.% Al showed the lowest wear loss under high stress abrasion due to the combined effect of hardness provided by the BCC phase and the ability of FCC phase to undergo work-hardening and accommodate plastic deformation.

In this work, the microstructure and tribological properties of coarse-grained nickel aluminum bronze (NAB) alloys with different ratios of α/β′ phases were studied at room temperature. For revealing the intrinsic tribology behavior, the hard SiC sanding disc with a microhardness of 2400∼2800 HV, almost 10 times higher than that of the NAB alloy, was selected as the counter material. The tribological behavior was investigated using multiscale characterization, including macroscale X-ray diffraction (XRD) and laser scanning confocal microscopy (LCM), microscale scanning electron microscopy (SEM), as well as nanoscale transmission electron microscopy (TEM). The findings reveal that abrasive wear predominates in these samples, with delamination, oxidation, and fatigue wear also present. Notably, the dual-phase alloy exhibits inferior wear resistance compared to the single-phase alloy, attributed to the alternating-wear process of the two phases. Additionally, we observed the in-situ formation of a nano oxide film during the friction process, highlighting its significant role in enhancing the wear resistance of NAB alloys through a self-lubricating effect.

Among the AM processes Laser based Powder Bed Fusion (LPBF) technique offers precise and complex geometric fabrication. However, the microstructural and mechanical properties obtained from LPBF process requires further investigation, especially for IN718 superalloys. In this study, various heat treatments were applied to LPBFed Inconel 718 specimens to examine their effects on microstructure, microhardness and wear behavior. Three different heat treatments, each involving varied solutionizing and ageing steps were incorporated. As-printed specimens exhibited distinct fish scale structures with columnar dendrites. Heat treatments effectively dissolved the Laves phase and precipitated strengthening phases like γ′′ and γ′. Microhardness increased significantly after heat treatments, correlating with the formation of strengthening precipitates. Friction and wear tests showed as-printed specimens exhibited higher wear loss (922 ± 13 μm) and coefficient of friction (COF) (0.511 ± 0.07) due to the presence of Laves phase and softer matrix. Heat-treated specimens demonstrated significantly reduced wear loss (262 ± 5 μm) and COF (0.368 ± 0.01), with HT2 showing the best wear resistance attributed to a homogeneous microstructure. SEM analysis of worn surfaces confirmed abrasive and adhesive wear mechanisms in as-printed specimens, while heat-treated specimens exhibited reduced wear with smoother surfaces.

CoCrMo has been used as an implant material for a long time due to its excellent combination of strength, corrosion resistance and biocompatibility. The formation of a thin passive oxide film on the surface of the material plays a crucial role in its performance. This passive film can be ruptured during contact between two surfaces, but usually reforms in short timescales. However, the reformation of the film depends on the availability of oxygen in the surrounding fluid. The oxygen level in human tissue, cartilage and synovial fluid, around which the implant is situated, is much lower than that in laboratory testing under open-air conditions. Moreover, the local oxygen concentration and pH values in the body vary from patient to patient, depending on the patient's health condition and other factors, which leads to variation in the corrosion resistance of metallic implants. Therefore, an implant that performs well at one time may still experience an undesirable level of corrosion at another. Thus, evaluation of the tribocorrosion of implant materials carried out in open-air conditions does not reflect the actual process the implants undergo once in the body, particularly if there is irritation due to injury or surgery. In this study, we investigate the tribocorrosion behaviour of CoCrMo in bioactive solutions under fully aerobic to anaerobic conditions with varying loads/contact pressures. The anaerobic condition leads to a reduction in wear rate and a reduction in the extent of tribofilm formation but does not have an appreciable effect on friction. The mechanisms are discussed in detail.

Additive manufacturing makes fabricating titanium alloy components directly into their near-net shapes possible, reducing the need for machining. However, post-additive manufacturing machining becomes necessary for immediate design adjustments, dimension alterations, and surface quality enhancement. The inherent thermal effects during additive manufacturing make machining challenging due to altered mechanical properties from their wrought counterpart, including increased strength and hardness with reduced ductility. Textured cutting tools are being widely used to enhance the machinability of superalloys. In this work, micro-pillar type textures, created using Reverse Micro Electrical Discharge Machining (RμEDM) on tungsten carbide inserts, aimed to explore machinability in turning operations on selective laser melted (SLM) titanium alloy. The study investigates micro-pillar interaction with SLM Ti6Al4V in chip behavior, tool morphology, cutting forces, and surface roughness under various cutting fluid strategies. Under Minimum Quantity Lubrication (MQL), textured tools show significant improvements, producing untangled chips with reduced curl radius. A considerable decrease of 38 % in the tool/chip contact area indicates a substantial reduction in the seizure zone, hence a decline in the temperature rise of the cutting tool. Dry conditions show a 20.4 % reduction in flank wear width, suggesting prolonged cutting-edge sharpness due to tool texturing. In MQL conditions, a maximum 28.9 % reduction in feed force is observed, indicating improved frictional conditions at the interface. Additionally, a 10.4 % improvement in surface finish is achieved. The work is summarized by claiming micro-pillar textured tools enhance the machinability of additively manufactured Ti6Al4V demonstrated through improvements in titanium adhesion, cutting-edge sharpness, feed force, and surface finish, particularly MQL conditions.