用扫描电镜和透射电镜观察X20CrMoV12.1耐热钢在545℃长期运行后的微观组织结构变化,研究了不同运行时间后材料的缺口疲劳强度和硬度.结果表明:经过高温长期运行后,X20CrMoV12.1钢的组织明显退化,其显微组织由原来的马氏体板条结构和弥散分布的细小碳化物逐步转变为亚晶粒和分布在晶界上的粗化球形碳化物组织;随着在高温下运行时间的增加,耐热钢的显微硬度和疲劳强度逐渐降低.其原因是基体中固溶体主要合金元素Cr,Mo,V发生贫化,固溶强化效果降低,沿晶界分布的粗化球形碳化物弱化了材料晶界强度,从而导致X20CrMoV12.1耐热钢高温服役寿命下降.
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