摘要
粉末冶金高温合金中原始粉末颗粒边界组织(PPBS)由碳化物和少量碳氧化物组成。采用SEM、TEM以及AES等研究了粉末颗粒内、表面上以及合金中PPB上碳化物的结构和组成,依据热力学和扩散理论分析了Hf消除原始粉末颗粒边界组织(PPBS)的微观机制。结果表明:快速凝固粉末颗粒表面形成含有Ti、Nb、Cr、Mo、W的MC型亚稳定碳化物MC′,在HIP过程中粉末颗粒表面上的MC′相转变成稳定的MC相,以及粉末颗粒内的Ti、C元素向烧结颈处扩散,HIP后在粉末颗粒边界上形成富Ti和Nb的MC型碳化物(Ti,Nb)C。加入微量Hf后,在粉末颗粒内形成了更多更稳定的含Hf的MC型碳化物(Ti,Nb,Hf)C,C、Ti被"绑定"在碳化物(Ti,Nb,Hf)C中,抑制了C、Ti向烧结颈处扩散,从而抑制了MC型碳化物在粉末颗粒边界上的析出。
The precipitates at prior particle boundary （PPB） are composed of carbide and small amount oxycarbide or oxide in PM superalloys.The composition and structure of carbide inside the powder,on the powder surface and on the PPB were investigated by SEM,TEM,AES techniques,etc.The mechanism of Hf eliminating prior particle boundary structure （PPBS） was discussed according to thermodynamics and diffusion theory.The results show that metastable MC type carbide MC＇ rich in Ti,Nb,Cr,Mo and W elements forms on powder surface during atomization,the metastable MC＇ carbide will transform into stable MC carbide during hot isostatic pressing （HIP） process.Ti and C inside powder particles will diffuse to sintering neck during HIP process,then stable MC carbide （Ti,Nb） C will form on powder particle boundaries.When micro-element Hf is added in,more and more stable MC type carbides containing Hf precipitate within powder particles,which means C and Ti elements are bound in （Ti,Nb,Hf） C carbides,suppressing the diffusion of C and Ti to sintering neck,and finally the precipitation of MC type carbides is inhibited.
出处
《粉末冶金工业》
CAS
北大核心
2014年第5期1-7,共7页
Powder Metallurgy Industry
基金
国家重点基础研究发展计划项目(2010CB631204)
