700℃超超临界锅炉材料617B合金铸态组织及均匀化工艺

Microstructure and homogenization of as-cast 617B alloy for 700℃ ultra-supercritical boilers

利用光学显微镜、扫描电镜和能谱分析对采用真空感应熔炼和保护气氛电渣重熔双联工艺生产的617B合金电渣锭进行组织分析、析出相和元素偏析情况研究.依据残余偏析指数模型通过Dictra热力学软件计算提出七种不同的均匀化制度,并结合均匀化后的组织分析和热模拟压缩试验,确定了617B合金的最终均匀化制度.结果表明:经双联工艺生产的617B合金电渣锭中存在枝晶和元素偏析,其中Mo和Ti是主要的偏析元素;电渣锭组织的晶内存在较多的块状碳化物,表现为多种碳化物共生生长.经过1210℃保温48h均匀化处理后,枝晶和元素偏析基本消除,晶内的块状碳化物部分溶解,且均匀化后的合金表现出良好的塑性.

The microstructure and microsegregation of nickel-based superalloy Inconel 617B ingots produced by vacuum induction melting and electroslag remelting were studied by optical microscopy, scanning electron microscopy, and energy dispersive X-ray spec-troscopy. Their kinetic homogenization curves were calculated by Dictra software through the residual segregation parameter model. Based on the theoretical results, seven homogenizing treatments were tested. Microstructure analysis and thermal compression test with a Gleeble 1500 machine were used to verify the effect of homogenizing treatment. It is found that dendrites and element segregation ex-ist in the ingots, and Mo and Ti are the principal segregated elements. The main precipitated phases in the ingots are different kinds of primary carbides which tend to symbiotic growth. After homogenization at 1210 ℃ for 48 h, this segregation can almost be eliminated, the phase of intragranular carbides dissolves to the matrix, and the ingots exhibit excellent workability.