瞬时液相焊接高温合金接头的显微结构表征

Microstructure characterization of transient liquid phase bonding superalloy joints

瞬时液相焊接(TLP连接)是一种极具应用价值的高温合金连接和修复方法。本文对1230℃下使用Ni-Cr-B中间层对镍基高温合金Mar-M247进行瞬时液相焊接的接头进行了显微结构表征,研究了由非等温凝固区(NSZ)、等温凝固区(ISZ)和扩散影响区(DAZ)组成的接头组织和沉淀相析出行为。研究结果表明:NSZ中析出相主要为M_(23)(C,B)_(6)和γ/γ′组成的共晶组织,其中伴生少量块状MC碳化物;与NSZ相邻的ISZ则由γ/γ′相组成;DAZ中的主要析出相为颗粒状和针状M_(5)B_(3)型硼化物,并伴生少量长直鱼骨状和不规则块状的M_(5)B_(3)型硼化物。更长的焊接保温时间会更有利于等温凝固过程,对样品进行焊后热处理可使接头组织更加均匀。

Transient liquid phase(TLP)bonding is a promising joining and repairing process of Ni-based superalloys.In this paper,the microstructure of the TLP bonded joints of Mar-M247 with Ni-Cr-B amorphous interlayer at 1230℃was systematically characterized.The microstructure and precipitation behavior of the joints composed of non-isothermal solidification zone(NSZ),isothermal solidification zone(ISZ)and diffusion affected zone(DAZ)were studied.The results show that the main precipitated phases in NSZ are eutectic structures composed of M_(23)(C,B)_(6) andγ/γ′,accompanied by a small amount of block MC-type carbides.The ISZ adjacent to NSZ is composed ofγ/γ′.The main precipitated phases in the DAZ are granular and acicular M_(5)B_(3)-type borides,and a small amount of long straight fishbone-like and irregular block-like M_(5)B_(3) borides are dispersed.More sufficient holding time in bonding process is conducive to the isothermal solidification process.Post bond heat treatment could be considered to be an effective method for removing these precipitated phases.