中文摘要：

以X20CrMoV12.1耐热合金钢管为研究对象,重点研究了管道材料的显微结构变化,特别是碳化物沉淀相的形态和成分变化,探讨了材料性能变化的微观原因.结果表明：12%Cr耐热合金钢主蒸汽管线在550℃高温条件下经180 000 h长期服役后,材料的组织结构发生明显变化,出现马氏体分解,形成板条亚晶结构,表现出典型的蠕变特征;合金碳化物沉淀相大多分布于晶界和板条亚晶界,且相对于原始态粗化严重;晶界和亚晶界分布的碳化结构是M23C6,晶内相对细小的碳化物结构也大多数是M23C6,另有少量方形片状的富V碳化物MX;M23C6碳化物中合金含量随服役时间的延长明显富集,且分布在不同区域的碳化物不仅形态不同,其化学成分也存在明显差异.长期服役过程中碳化物产生这些演变现象与碳化物的粗化进程相关,并受热力学条件和扩散方式的影响.

英文摘要：

Taking X20CrMoV12.1 heat-resistant steel pipes as the object of study, microstructure changes of the material,especially evolution of the carbide morphology and composition,were studied,while causes leading to variation of material properties analyzed.Results show that after 180 000 h long-term service at 550 ℃,the material microstructure will have great changes： Its martensite structure decomposes,forming lath sub-structure,behaving typical creep characteristics;carbide precipitates distributes on boundary and lath sub-boundary,seriously coarsened,most of which are identified as M_（23）C_6;the majority of finer carbides within the matrix are also M_（23）C_6 except for some tiny V-rich plate-like structure identified as MX;alloy contents in M_（23）C_6 carbide enriches with growing service time;carbides distributed in different zones differ in shape and chemical composition.Above phenomena of carbide evolution might be relative to their coarsening processes,which are dominated by local thermodynamic conditions and diffusion modes.