不同压力对 TC4 钛合金真空脉冲渗氮的影响

目的采用不同压力对TC4钛合金进行真空脉冲渗氮处理,提高其表面硬度及耐磨性。方法通过金相显微镜、X射线衍射仪、显微硬度计及耐磨试验机分析渗氮硬化层的组织与性能。结果 TC4钛合金经过真空气体渗氮处理后,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。渗氮压力太低,表面氮化物数量较少,氮化物层较薄;随渗氮压力的增大,表面氮化物数量增多,表面硬度及耐磨性增加。压力为0.015 MPa时,氮化物层表面硬度最大,表面硬度为1100~1200HV,有效硬化层深度为50~60μm。渗氮压力继续增加,表层组织变得疏松,表面硬度及耐磨性开始降低。结论选择合适的渗氮压力和表面氮浓度进行真空脉冲渗氮,可以提高钛合金表面硬度,改善耐磨性。

Influence of Different Pressure on Vacuum Pulse Nitriding of TC4 Titanium Alloy

ABSTRACT:Objective Vacuum pulse nitriding treatment at different pressure was applied to TC4 titanium alloy to improve sur-face hardness and wear resistance. Methods The microstructure and properties of hardened layer were analyzed by metallurgical microscopy, X-ray diffraction (XRD), microhardness tester and wear testing machine. Results The surface composite modified layer composed of TiN, Ti2 AlN and Ti3 Al was obtained by vacuum nitriding treatment of TC4 titanium alloy. Low nitriding pressure led to the low number of surface nitrides and the low thickness of the nitriding layer. With the increase of pressure, the number of nitrides increased, the surface hardness and wear resistance also increased. The surface hardness reached the maximum value at 0. 015 MPa. The surface hardness of nitrided TC4 titanium was 1100~1200HV, and the thickness of the effective hardened layer reached 50~60 μm. With further increase of nitriding pressure, the microstructure became loose, the surface hardness and wear resistance began to decrease. Conclusion Vacuum pulse nitriding treatment under suitable pressure and suitable concentration of N could increase the surface hardness of titanium alloy and improve its wear resistance.