晶粒细化对放电等离子烧结TC4合金微动磨损性能的影响

Effect of Grain Refinement on the Fretting Wear Properties of Spark Plasma Sintered TC4 Alloy

结合高能球磨和放电等离子烧结制备出具有粗晶组织、粗细晶双尺度组织和超细晶组织的TC4合金;采用球-盘微动磨损装置对比研究了这3种显微组织TC4合金在干摩擦条件下的微动磨损性能,分析了晶粒细化对TC4合金摩擦磨损性能的影响。结果表明：随着晶粒的逐步细化,TC4合金的摩擦系数和磨损率逐渐降低。这主要是因为晶粒细化导致TC4合金硬度逐渐提高,并引起磨损机制的转变。粗晶TC4合金的磨损机制为严重的粘着磨损、疲劳剥层磨损和氧化磨损;而双尺度和超细晶TC4合金的磨损机制以磨粒磨损为主并伴随着轻微的粘着磨损和氧化磨损。超细晶TC4合金拥有最高的硬度（HV为4560 MPa）,在载荷30 N下具有最低的摩擦系数（～0.76）和磨损率（1.89×10^-4mm^3·N^-1·m^-1）,说明晶粒细化有助于提高TC4合金的摩擦磨损性能。

Coarse-grained（CG）, bimodal-structured and ultrafine-grained（UFG） TC4 alloy were fabricated by high-energy ball-milling and spark plasma sintering.Fretting wear tests under dry sliding condition were carried out on a ball-on-disc wear apparatus to investigate the effect of grain refinement on the friction and wear properties of TC4 alloy.Results show that the finer the microstructure, the lower the coefficient of friction and the wear rate would be.This is mainly attributed to the improvement of hardness as well as the transformation of wear mechanisms as a result of grain refinement.Severe adhesion, delamination and oxidation are responsible for the wear of CG TC4 alloy, while the wear mechanism turns to be abrasive wear accompanied by mild adhesion and oxidation in the case of bimodal-structured and UFG TC4 alloy.The UFG TC4 alloy exhibits the highest hardness（HV） of ～4560 MPa with the lowest friction coefficient（～0.76） and wear rate（1.89×10^-4 mm^3·N^-1·m^-1） under the applied load of 30 N, suggesting that grain refinement shows positive effects on friction and wear properties of TC4 alloy in current study.