气体渗氮工艺对NbVTi合金化灰铸铁组织与性能的影响

Effect of gas nitriding process on microstructure and properties of NbVTi alloyed gray cast iron

针对发动机高速重载的发展趋势,对新型NbVTi合金化灰铸铁气缸套材料进行了不同温度的气体渗氮处理。通过光学显微镜、维氏硬度计、摩擦磨损试验机、扫描电镜等手段,研究了NbVTi合金化灰铸铁气缸套表面的气体渗氮工艺对组织性能的影响。结果表明:随着渗氮温度的增加,NbVTi合金化灰铸铁气缸套的渗氮层深度都有所增加,距离表面100μm和130μm处的显微硬度先增后降。在最佳的渗氮温度570℃渗氮后,气缸套尺寸膨胀量在0.010~0.055 mm标准范围内,渗氮层平均厚度约140μm,距离表面100μm扩散区平均硬度达到500 HV0.1以上,可满足高速重载气缸套的使用要求。气体渗氮后,气缸套的摩擦磨损性能得到了大幅提高,随着载荷的增大和速度的增加,磨损率随之增大,其磨损机理由磨粒磨损向粘着磨损转变。

In view of the development trend of high speed and heavy load of engine,a new type of NbVTi alloyed gray cast iron cylinder liner material was gas nitrided under different temperature.The effect of gas nitriding process on microstructure and properties of NbVTi alloyed gray cast iron cylinder liner was studied by means of metallographic microscope,Vickers hardness tester and friction wear testing machine.The results show that with the increase of nitriding temperature,the nitrided depth of NbVTi alloyed gray cast iron cylinder liner is increased,and the microhardness at the depth of 100 μm and 130 μm from the surface is increased first and then decreased.After nitriding at the optimum nitriding temperature of 570 ℃,the cylinder liner size expands in the standard range of 0.010-0.055 mm,the average thickness of nitrided layer is about 140 μm,and the average hardness of the diffusion zone at the depth of 100 μm from the surface is above 500 HV0.1,which can meet the requirements of high speed and heavy load cylinder liner.After nitriding,the friction and wear performance of cylinder liner is greatly improved.With the increase of load and speed,the wear rate increases,and the wear mechanism changes from abrasive wear to adhesive wear.