不同温度下等离子渗氮后TC4钛合金的摩擦磨损性能

Tribological properties of TC4 titanium alloy treated by plasma nitriding at different temperatures

采用等离子渗氮技术提升TC4钛合金的耐磨性并探究最优渗氮温度。利用LDM 1-100型等离子渗氮设备,在650,700,750,800,850℃和900℃温度下对TC4钛合金进行渗氮处理,保温时间均为10 h。利用光学显微镜、扫描电子显微镜、白光三维形貌仪、X射线衍射仪和显微硬度计分别对不同温度渗氮试样的微观组织结构、表面形貌、表面粗糙度、相结构和硬度进行表征。利用CETR UMT-3型多功能摩擦磨损试验机测试等离子渗氮后TC4钛合金的摩擦学性能。结果表明:TC4钛合金表面显微硬度和粗糙度随温度升高而增大,在900℃渗氮后TC4钛合金表面显微硬度达到了1318HV 0.05,约为基体(360HV 0.05)的4倍。硬度的升高是由于渗氮后试样表面形成了硬质氮化物相(TiN和Ti2N相),且随着渗氮温度升高氮化物的含量增加。相较于低温渗氮(低于750℃)的试样,850℃和900℃渗氮试样的承载能力显著提升。与原始TC4试样相比,渗氮处理后试样的磨损体积显著降低。当渗氮温度为850℃时,试样磨损体积为未处理试样磨损体积的1.2%(1 N),3.0%(3 N)和62.2%(5 N),试样的耐磨性提升更为显著。

The wear resistance of TC4 titanium alloy was improved by plasma nitriding and the optimum nitriding temperature was investigated.TC4 titanium alloy was nitrided at 650,700,750,800,850℃and 900℃with LDM1-100 plasma nitriding equipment respectively,the temperature holding time is 10 h for each nitriding treatment.The microstructure,surface morphology,surface roughness,phase structure and hardness of nitrided samples at different temperatures were characterized by optical microscope,scanning electron microscope,white light three-dimensional topography instrument and microhardness tester.The tribological properties of TC4 titanium alloy after plasma nitriding were tested by CETR UMT-3 multifunctional friction and wear tester.The results show that the surface microhardness and roughness of TC4 titanium alloy increase with the increase of temperature.After nitriding at 900℃,the surface microhardness of TC4 titanium alloy reaches 1318HV 0.05,which is about 4 times as high as that of the substrate(360HV 0.05).The increase of hardness is due to the formation of hard nitride phases(TiN and Ti 2N phases)on the surface of nitrided sample and the nitride content increases with the increase of nitriding temperature.The load-carrying capacity of nitrided samples at 800℃and 900℃is significantly higher than that of nitriding samples at low temperatures(below 750℃).Compared with the original TC4 sample,the wear volume of the nitrided sample significantly reduces.When nitriding temperature is 850℃,the wear volume of the nitrided sample is 1.2%(1 N),3.0%(3 N)and 62.2%(5 N)of that of the untreated sample,and the improvement of wear resistance of the sample is the most obvious.