相同硬度下不同显微组织对TC4 钛合金磨损机理的作用机制OA

This research is systematically conducted to elucidate the dominant role of microstructural configuration in governing the tribological performance of TC4 titanium alloy,following the effective isolation of the macroscopic hardness variable.To achieve this objective,samples with comparable hardness levels(approximately 395HV)but distinctly different microstructural characteristics are meticulously prepared through three distinct processing routes:vacuum arc melting(resulting in an as-cast,coarse microstructure),laser powder bed fusion(producing a fine-grained microstructure with ultrafine grains),and solution treatment followed by aging(yielding a precipitation-strengthened microstructure with finely dispersed secondary phases).A comprehensive tribological evaluation is performed using a ball-on-disc reciprocating sliding tester under varying operational conditions,specifically employing two normal loads(5 N and 15 N)and two sliding frequencies(1 Hz and 3 Hz).Subsequent to testing,detailed surface morphology and subsurface microstructural analyses are carried out utilizing scanning electron microscopy(SEM)and energy-dispersive spectroscopy(EDS)to accurately identify the dominant wear mechanisms and damage progression. The results unequivocally demonstrate that,despite the near-identical bulk hardness,the tribological responses,encompassing the coefficient of friction,wear rate,and damage modes,vary significantly across the different microstructural configurations.Under the relatively mild conditions of 5 N and 1 Hz,the fine-grained sample exhibit the lowest coefficient of friction(0.41).This superior performance is attributed to its homogeneous ultrafine-grained structure,which effectively mitigates stress concentration at the contact surface,promoting more uniform deformation.However,when the sliding frequency is increased to 3 Hz,the precipitation-strengthened sample demonstrates the minimum friction coefficient(0.40),facilitated by the formation of a stable,continuous,and adherent titanium oxide(predominantly TiO2)lubricating layer on its surface,indicating a shift to oxidative wear as the primary mechanism.In stark contrast,under these same dynamic conditions,the fine-grained sample suffers a sharp increase in the friction coefficient(0.58),accompanied by clear evidence of fatigue spalling.This detrimental behavior is linked to the synergistic interaction between inherent process-induced defects(e.g.,minor porosity)and the intrinsically brittle nature of the acicular α′ martensite phase formed during rapid solidification,which accelerates crack initiation and propagation under cyclic loading.Meanwhile,the as-cast sample,with its coarse and thermally unstable microstructure,experiences a predominant transition to severe adhesive wear,characterized by substantial plastic deformation and material transfer onto the counterface. The critical influence of microstructural stability becomes even more pronounced under the high-load condition of 15 N.Here,the precipitation-strengthened sample outperforms the others significantly in terms of wear resistance.Its fine and dense matrix,strengthened by homogeneous precipitates,is proved highly effective in suppressing plastic deformation,impeding crack initiation,and hindering the propagation of cracks,thereby resulting in the lowest wear rate.Conversely,wear in the fine-grained sample is markedly exacerbated by accelerated fatigue crack propagation originating from stress concentrations at microstructural defects.The as-cast sample,plagued by its coarse and mechanically unstable grain structure,undergoes the most severe damage,dominated by extensive adhesion and gross material transfer,leading to the highest wear loss. In conclusion,this study firmly establishes that the"configuration quality"of the microstructure,defined by its homogeneity,stability against deformation and crack growth,and overall integrity(low defect density),is a far more critical and fundamental factor in determining the wear resistance of TC4 titanium alloy than the macroscopic hardness alone.These findings provide vital guidelines for the microstructural design and selection of high-performance,wear-resistant titanium alloy tailored for specific service conditions involving varying stresses,sliding speeds,and environmental factors.