K418合金激光熔覆Ni-Cr-Ti-Al涂层的组织研究

采用机械球磨法获得混合均匀的Ni-Cr-Ti-Al熔覆材料;并利用CO2激光器在K418镍基高温合金表面制备了不同化学成分的Ni-Cr-Ti-Al涂层;采用光学显微镜(OM)、扫描电子显微镜(SEM)及X射线衍射仪(XRD)等手段探讨了不同成分涂层与基体合金的结合情况。分析比较了Ni,Ti和Al含量对熔覆涂层的组织特征的影响。结果表明,在熔覆过程中,Ti,Al合金元素与Ni相互作用将形成Ni2TiAl,Ni3(Al,Ti),Ni3Ti和NiAl金属间化合物相;Ni-Cr-Ti-Al熔覆涂层以Ni3(Al,Ti)相形成的枝晶组织为主,Ni2TiAl,Ni3Ti及NiAl相分布在Ni3(Al,Ti)枝晶间;其中,Ni66.11Cr7.35Ti14.39Al12.15熔覆涂层形成了TiAl合金与K418合金之间成分和性能的良好过渡,为实现TiAl合金/K418合金异种合金间的扩散连接提供了良好的组织基础。

Microstructures of Ni-Cr-Ti-Al Laser Claddings on K418 Superalloy

Ni-Cr-Ti-Al cladding powders were mixed by using mechanical ball milling technique.Ni-Cr-Ti-Al laser cladding layers with different chemical composition on superalloy K418 were prepared by CO2 laser.By means of optical microscopy(OM),scan electron microscopy(SEM) and Xray diffraction(XRD),microstructures of cladding layers were studied,and micro-hardness was measured.The results show that,during the process of laser cladding,Ni3(Al,Ti),Ni2TiAl,NiAl and Ni3Ti intermetallic compounds are formed resulting from the interaction of Ti,Al and Ni.Microstructures of Ni-Cr-Ti-Al cladding layers are characterized by massive Ni2TiAl,Ni3Ti or NiAl distributing between Ni3(Al,Ti) dendritic.Ni-Cr-Ti-Al laser cladding layer with the chemical composition of Ni66.11Cr7.35Ti14.39Al12.15 is beneficial to the diffusion bonding between TiAl alloy and K418 superalloy.