Ti6Al4V合金激光熔覆Ni基自润滑涂层的组织和性能

Microstructure and properties of laser clad Ni-based self-lubricating coating on Ti6Al4V alloy

利用光纤激光器在Ti6Al4V合金基体表面制备了Ni25为基体和Ni包MoS_(2)为润滑剂的Ni基自润滑涂层,通过FESEM、XRD、硬度测试仪和摩擦磨损试验机研究了熔覆层的显微组织、物相组成和摩擦性能。结果表明,熔覆层表面主要以“花瓣”状组织以及少量的树枝晶组成,界面处的组织主要是以树枝晶为主,还有少量的等轴晶粒。熔覆层中形成了NiTi、NiTi_(2)等金属化合物以及其它一些化合物,这些强化相的形成有效地提高了熔覆层的表面硬度,由基体的180〜200 HV0.3提高到了表层的430~530 HV0.3。同时随着Ni包MoS_(2)含量增加,表层的硬度会有所下降。此外,当MoS_(2)加入量为5%和10%时摩擦因数较大,加入量达到15%时摩擦因数有所降低,同时,熔覆层的磨损率也从5%时的7.49×10^(-7) mm^(3).N^(-1).m^(-1)降低到15%时的3.29×10^(-7) mm^(3)•N^(-1)•m^(-1).

Ni-based self-lubrication clad layers consisting of Ni25+Ni-coated MoS_(2) were fabricated on Ti6Al4V alloy by using fiber laser.The microstructure,phases composition and friction performance of the clad layers were studied by means of field emission scanning electron microscopy(FESEM),X-Ray diffraction(XRD),and friction and wear tester.The results show that the clad layer surface mainly consists of petaloid and a little dendrites,while the microstructure at the clad-layer/substrate interface is mainly dendritic with a small amount of equiaxed grains.Intermetallic compounds such as NiTi and NiTi2 and some other compounds are formed,which can improve surface hardness of the clad layers effectively and make the hardness change from 180-200 HV0.3 of the substrate to 430-530 HV0.3 of the surface layer.Meanwhile,the hardness decreases somewhat with the increase of amount of the Ni-coated MoS2.Besides,the frictional coefficient of the clad layers with adding 5% and 10% MoS2 is larger,and it decreases somewhat when the addition is 15%.The wear rate of the clad layers also decreases from 7.49× 10^(-7) mm^(3)•N^(-1)•m^(-1) at 5% addition to 3.29 × 10^(-7) mm^(3)•N^(-1)•m^(-1) at 15% addition.