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采用光学显微镜、扫描电镜和透射电镜对1000 MW超超临界发电机组P92钢再热蒸汽管道焊缝区的显微组织及其对蠕变裂纹扩展速率的影响进行了深入的研究。结果表明,试验用P92钢蒸汽管道焊缝区为回火马氏体组织,其组织极不均匀,主要表现在马氏体的回复程度相差较大。马氏体回复程度越低,板条形态保持得越好,板条越细密,蠕变裂纹扩展速率就越小。在焊缝区,原奥氏体晶界、马氏体板条界及亚晶界上主要分布有两种析出相,即富含钨、钼的Laves相和富含铬的M_(23)C_6型碳化物;而在焊缝区晶体内部除有上述两种析出相外,还有富含钒、铌的MX型碳化物,且Laves相总伴生在M_(23)C_6型碳化物处。
The microstructure of weld zone of P92 steel reheat steam pipe of 1000 MW ultra supercritical power plant and its effect on the creep crack growth rate were studied by optical microscope, scanning electron microscope and transmission electron microscope. The results show that the weld zone of P92 steel steam pipe for test is tempered martensite with very uneven microstructure, which is mainly reflected in the difference of martensite recovery. The lower the degree of martensite recovery, the better the shape of the slab retained, the thinner the slats and the smaller the creep crack growth rate. In the weld zone, the former austenite grain boundary, the martensite lath boundary and subgrain boundary, there are mainly two kinds of precipitates, namely Laves phase rich in tungsten and molybdenum and M_ (23) C_6 enriched in chromium Type carbides. In addition to the above two precipitates, there are MX-type carbides rich in vanadium and niobium in the interior of the weld zone, and the Laves phase is always associated with M_ (23) C_6 carbides.