稀土含量对Ti6Al4V钛合金等离子渗氮层组织和摩擦学性能的影响

目的研究稀土含量对Ti6Al4V钛合金表面等离子体渗氮层结构和性能的影响。方法运用等离子表面改性技术对Ti6Al4V(TC4)钛合金进行等离子渗氮处理,渗氮过程中通入不同含量的稀土作为催渗剂,以获得钛合金表面强化层。利用金相显微镜和扫描电子显微镜(SEM)观察渗氮层组织,用X射线衍射仪(XRD)分析渗层相组成,用能谱仪(EDS)检测渗层的化学成分,用维氏显微硬度计测量渗层的显微硬度,用球-盘式摩擦磨损试验机和三维轮廓仪检测渗层的摩擦磨损性能。结果TC4钛合金表面等离子渗氮层结构包括表面化合物层(主要成分为δ-TiN)和扩散层(主要为N原子扩散形成的N-Ti固溶体),加入稀土可以促进N原子向基体的扩散,提高渗氮速度。渗层厚度增加,硬度和耐磨性能提高,扩散层使钛合金基体与化合物层之间的硬度梯度更加平缓。当稀土通入速率为60 mL/min时,渗层厚度可达155μm,表面硬度为1275HV0.05,摩擦系数降到0.27,磨损率明显降低。结论钛合金等离子渗氮过程中加入稀土可以有效提高渗速,改善渗氮层硬度,提高材料表面的耐磨性能。

Effect of Rare Earth Content on the Microstructure and Friction Properties of Ti6Al4V Alloy by Plasma Nitriding

The work aims to investigate the influence of rare earth content on the structure and properties of Ti6 Al4 V alloy by plasma nitriding.Plasma nitriding of Ti6 Al4 V(TC4)titanium alloy was carried out by plasma surface modification technology.Rare earth with different contents were introduced as accelerating agents in the nitriding process to obtain strengthening layer on titanium alloy surface.Microstructure and phase composition of nitrided layer were observed and evaluated by SEM and XRD.Chemical components were detected by EDS.Microhardness was tested by Vickers microhardness tester.The friction and wear properties of the infiltration layer were tested by ball-disc friction and wear tester and threedimensional profiler.The structure of plasma nitrided layer on TC4 alloy surface consisted of compound layer(δ-TiN phase)and diffusion layer(N-Ti solid solution mainly formed by diffusion of N atoms.).Rare earth could promote the diffusion of N into the matrix during nitriding process,thus increasing the nitriding speed,the thickness,the microhardness and the wear properties.The diffusion layer could smooth the hardness gradient between the titanium alloy matrix and the compound layer.When the flow rate of the rare earth content was 60 mL/min,the thickness of the nitride layer reached 155μm and the surface mircohardness was 1275 HV0.05.The friction coefficient was reduced to 0.27,and the wear rate was obviously reduced.The addition of rare earth elements in the plasma nitriding process can effectively increase the penetration rate and improve the hardness and the wear resistance of the nitriding layer.