时效热处理对选区激光熔化成形18Ni300摩擦磨损性能的影响

Effects of Aging Heat Treatment on Friction and Wear Behaviors of Selective Laser-melted 18Ni300

目的通过研究选区激光熔化(SLM)成形18Ni300时效热处理前后摩擦磨损性能及磨损机制,为SLM技术在模具中易磨损部位的应用提供理论支撑。方法采用扫描电镜对热处理前后试样进行微观组织观察,采用X射线衍射仪对原始粉末和试样进行物相分析,并测试试样时效热处理前后的硬度、密度和抗拉强度,采用球盘摩擦磨损试验机测试在不同载荷下时效热处理前后试样的摩擦磨损行为,采用3D轮廓仪和扫描电镜对磨损后试样和磨球表面进行观察,并对磨损区域进行能谱分析。结果时效热处理后试样“鱼鳞状”熔道组织弱化,主要为板条状马氏体组织。原始粉末及成形后试样的物相主要为马氏体,原始粉末和时效热处理后试样中含有少量残余奥氏体。时效热处理后试样硬度由37.6HRC升高到54.4HRC,密度变化不大,抗拉强度由1107 MPa升高到2031 MPa,伸长率由14.4%降低至4.5%。随着摩擦磨损试验载荷的增大,时效热处理后试样摩擦因数降低,体积磨损率增大,但均低于热处理前试样。结论当载荷为10 N时,磨损机制主要为磨粒磨损;当载荷为15 N时,磨损机制过渡到氧化磨损和黏着磨损;当载荷为20 N时,主要为黏着磨损。

The work aims to study the friction and wear properties and wear mechanism of 18Ni300 steel formed by selective laser melting(SLM)before and after aging heat treatment,so as to provide theoretical support for application of SLM technology in easily worn parts of die.The microstructure of samples before and after heat treatment were observed through scanning electron microscope.The phases of raw powder and samples were analyzed through X-ray diffraction.The hardness,density and tensile strength of samples before and after heat aging treatment were tested.The friction and wear properties of as-deposited and aging treated samples were tested with ball-on-disk apparatus.The worn surface of samples and counter balls were observed and analyzed through 3D profilometer,scanning electron microscope and energy dispersive spectrometer.After aging heat treatment,the“fish-scaled shape”molten path microstructure of samples was weakened,which was mainly lath martensite.The mainly phase was martensite in raw powder and samples.Slight retained austenite were detected in raw powder and aging treated samples.After aging heat treatment,the hardness raised from 37.6HRC to 54.4HRC,the tensile strength raised from 1107 MPa to 2031 MPa,the elongation decreased from 14.4%to 4.5%,where the density changed little.With the increase of the testing load,the friction coefficient of aging treated samples decreased,the volume wear increased,and they were both lower than as-deposited samples.The wear mechanism is mainly abrasive wear under the load of 10 N,and turned to oxidative wear and adhesive wear when the load is 15 N;when the load is 20 N,the wear mechanism transforms to adhesive wear.