Ti6Al4V钛合金表面真空渗氧处理

Vacuum Oxidation Treatment on Ti6Al4V Titanium Alloy

目的在Ti6Al4V钛合金表层制备硬度高、耐磨性好的硬化层。方法结合真空技术,以高纯的O2为介质,在Ti6Al4V钛合金表面制备致密的渗氧硬化层,采用X衍射仪分析渗氧层的相组成,用金相显微镜观察渗氧层和磨痕组织,用显微硬度计测试渗氧层的显微硬度,用MM-U10A端面磨损试验机研究渗氧层的耐磨性。结果渗氧层物相主要由TiO_2、TiO、Ti_3Al及Al_2O_3组成,温度较低时,形成的渗氧层较薄,温度增加,渗氧层厚度迅速增加,硬度及耐磨性也随之增加。温度为760℃时,表面硬度为基体硬度的2.5倍以上,大于750HV,有效硬化层厚度达60μm以上,其磨损失重仅为未渗氧原样的1/4,表面磨痕细密,没有撕裂情况发生,渗氧层保持完整。温度继续增加,氧化物开始聚集长大,渗氧层组织开始变得疏松,硬度及耐磨性开始下降。结论 Ti6Al4V钛合金表面真空渗氧处理可显著提高其表面硬度,耐磨性改善明显。

The work aims to prepare a hard and abrasive hardening layer on the surface of Ti6Al4V titanium alloy. A dense oxygen-diffusing hardening layer was prepared on the surface of Ti6Al4V titanium alloy with pure oxygen working medium gas by taking advantage of vacuum technique. Phase composition of the oxygen-diffusing layer was studied with XRD, oxygen-diffusing layer and grinding crack structure were observed with metallurgical microscope, surface hardness was tested with micro-hardness tester, and wear resistance was analyzed by MM-U10A end-face abrasion tester. TiO2, TiO, Ti3Al and Al2O3 were major phases in the surface layer. The oxygen-diffusing layer was thinner when the Ti6Al4V titanium alloy was oxidized at lower temperature; the layer thickness, hardness and wear resistance increased as the temperature increased; at the temperature of 760 ℃, hardness of the surface exceeded 750HV, over 2.5 times higher than that of the substrate; hardness of the effective hardening layer exceeded 60 μm; weigh loss was only 1/4 that of unoxidized sample; surface friction trace was fine, no surface tearing was observed and the surface oxygen-diffusing layer was intact. The oxide aggregate started to grow and the oxygen-diffusing layer transformed into loose microstructure as the oxidizing temperature further increased. As a result, the hardness and wear resistance decreased. The surface hardness and wear resistance of Ti6Al4V titanium alloy can be significantly improved by vacuum oxidation technique.