间歇渗氮周期对TC4钛合金真空渗氮的影响

Influence of intermittent period on vacuum nitriding of TC4 titanium alloy

为了提高TC4钛合金表面硬度及耐磨性,采用不同的间歇渗氮周期对其进行真空间歇渗氮处理。通过金相观察、X射线衍射（XRD）、显微硬度计和耐磨试验机分析了渗氮层组织与性能。结果表明,TC4钛合金经真空间歇渗氮处理后,形成了由Ti N、Ti2Al N和钛铝金属间化合物Ti3Al组成的复合改性层。间歇渗氮周期较小,氮扩散区较窄,随间歇渗氮周期增加,氮明显向内扩散形成了一定宽度的氮扩散区,渗氮周期为30 min时,表面硬度为1100-1200 HV0.1,有效硬化层深度为60μm,渗氮周期继续增加,氮化物层开始变得疏松,表面硬度和耐磨性开始降低。

Vacuum intermittent nitriding with different period was applied to TC4 titanium alloy to improve surface hardness and wear resistance. The microstructure and properties of hardened layer was analyzed by optical microscopy,X-ray diffraction,microhardness tester and wear testing machine. The results show that a surface composite modified layer composed of Ti N,Ti2 Al N and Ti3 Al can be obtained by vacuum nitriding. Short period will lead to relatively narrow nitrogen diffusion zone. With the increase of period,a certain width of nitrogen diffusion zone can be formed because nitrogen obviously inward diffuse. When nitriding period is 30 min,the surface hardness of nitrided TC4 titanium is 1100-1200 HV0. 1 and the thickness of the effective hardened layer can reach 60 μm. When nitriding period is further rise,the microstructure of hardened layer begin to transform loose,the surface hardness and wear resistance begin to decrease.