铁基合金激光熔覆组织及高温时效转变的TEM研究

利用ＡＴＥＭ研究了铁基多元合金ＦｅＣｒＷＮｉＣ激光熔覆层的微观组织、亚稳相结构特征以及高温时效时的亚稳相转变机制。结果表明组织为亚共晶组织，即γ＋（γ＋Ｍ７Ｃ３），γ奥氏体为具有较高合金度的过饱和亚稳相，Ｍ７Ｃ３（Ｍ为Ｃｒ，Ｆｅ，Ｗ）为六方结构的Ｃｒ基亚稳合金碳化物。熔覆组织在高温时效时存在两类碳化物形成机制，即亚稳γ中析出Ｍ２３Ｃ６、Ｍ２Ｃ与ＭＣ碳化物以及Ｍ７Ｃ３→Ｍ２３Ｃ６与Ｍ７Ｃ３→Ｍ６Ｃ的碳化物原位转变机制。熔覆组织具有较高的显微硬度并存在显著的二次硬化特征

Microstructural Characterization and Evolution of\=Laser Cladding Fe\|Cr\|C\|W\|Ni Alloys

In situ synthesis of Fe\|Cr\|W\|Ni\|C alloys on a low alloy steel substrate by laser cladding was investigated by analytical electron microscopy with EDAX and PEELS. It was observed that the clad coatings consisted of hypo\|eutectic microstructure, i.e., +(+M\-7C\-3). The \|austenite is meta\|phase with extended solid solution of alloying elements and a great deal of fine structures. The M\-7C\-3 was Cr\|based alloy carbide, with various growth morphologies under laser rapid solidification. After thermally treating, the precipitation of M23C\-6,M\-2C and MC from austenite and in situ transformation of meta\|carbides, such as M\-7C\-3M\-6C and M\-7C\-3M23C\-6 were observed. The microstructure had effect of secondary hardening.