激光熔覆(WC+W_2C)_p/Ni基合金复合涂层的微观结构特征

Microstructure of laser clad(WC+W_2C)_p/Ni based alloy composite coatings

运用XRD、SEM及显微硬度试验等手段研究了激光熔覆Co包铸造(WC+W2C)p增强Ni基合金复合涂层的微观组织特征,分析了Co包铸态(WC+W2C)p在激光熔覆过程中的冶金行为.研究结果表明:在激光熔覆过程中,(WC+W2C)p的Co包覆层完全熔化,(WC+W2C)p本身也发生部分溶解,其稳定性随W2C/WC比增大而降低;当熔池凝固时,(WC+W2C)p在涂层中的分布主要受激光熔池中存在的强烈对流和颗粒/凝固前沿相互作用所控制;依赖于局部成分,涂层中形成变成分的η1-M6C(M=Co、W、Ni)型碳化物,优先分布在(WC+W2C)p表面;涂层基体的典型组织由分布在γ-Ni+M23C6为主加硼化物Ni4B3、Ni3B和碳化物M7C3的伪多元共晶中的η1-M6C组成.

Microstructure of laser clad Co covered(WC+W 2 C)powders/Ni-based alloy composite coatings has been investigated by XRD,SEM and microhardness measurement .Behavior of Co covered(WC+W 2 C) p dur-ing laser cladding has also been analyzed.Results show that Co cover of the(WC+W 2 C) p powders was melt-ed away and mixed with the laser melt,partial dissolution of(WC+W 2 C) p powders also occurred during laser cladding,and the stability of the powders was associated with the W 2 C/WC ratio.While laser melt pool so-lidifies,the(WC+W 2 C) p distribution in the composite coating is primarily controlled by the strong convec-tion in the laser melt pool and the interaction between the powders and the solidification front.Depending on local elemental concentrationsη 1 -M 6 C type(M=Co,W,Ni )carbides with varying compositions form in the coating,preferably on the surface of(WC+W 2 C) p or in close vicinity to them.Solidified microstructure of laser melt differs widely throughout the coating,and the typical microstructure is composed ofη 1 -M 6 C car-bides distributed in a multi-component pseudoeutectic,which predominantly consists ofγ-Ni +M 23 C 6 ,to-gether with borides Ni 4 B 3 ,Ni 3 B,and carbide M 7 C 3 .