固溶处理对K447A高温合金碳化物组织的影响

利用场发射扫描电镜分析了K447A合金在不同固溶+相同时效处理下碳化物的组织及析出行为。结果表明,铸态K447A合金中初生碳化物为MC型,呈块状、骨架状和汉字状,分布于枝晶间和晶界上;热处理后初生MC碳化物呈破碎状,表面形成一层γ'相包覆层,在热处理过程中,初生MC碳化物的成分发生变化,TaC、TiC、WC等初生碳化物发生了分解,HfC受影响程度最小;热处理后初生MC碳化物附近的枝晶间和残余共晶区域析出大量以HfC为主的细小弥散分布的颗粒状二次MC碳化物,1185 ℃固溶2 h+870 ℃时效20 h时,二次MC析出量最多。

Effect of solution treatment on microstructure of carbide in K447A superalloy

Microstructure and precipitation behavior of carbides in K447A alloy under different solution treatments were analyzed by scanning electron microscopy(SEM). The results show that primary carbides in the as-cast K447A alloy are of the MC type, in the form of blocks, skeletons and Chinese characters, and are distributed between dendrites and grain boundaries. After heat treatment, primary MC carbides are broken, and a layer of γ' phase coating layer is formed on the surface. During heat treatment, the composition of the primary MC carbides changes, and the primary carbides such as TaC, TiC, and WC are decomposed, and HfC is least affected. After heat treatment, a large number of fine and dispersed granular secondary MC carbides dominated by HfC precipitate in the interdendritic and residual eutectic regions near the primary MC carbides. When solution-treated at 1185 ℃ for 2 h and aged at 870 ℃ for 20 h, the amount of secondary MC precipitation is the largest.