回火温度对高Cr马氏体耐热钢组织与性能的影响

利用光学显微镜(OM)、透射电镜(TEM)、扫描电镜(SEM)及电子探针(EPMA)等手段，系统研究了不同回火温度下9%Cr马氏体耐热钢的组织及力学性能变化.结果表明:回火后位错网络化、析出相形态、板条马氏体破碎化等是影响力学性能变化的主要因素.正火并760℃回火后在室温和550℃条件下抗拉强度分别达到657和556MPa，0℃冲击功达到285J，此回火温度下实验钢具有最佳综合力学性能.700， 820，850℃回火，韧性大幅降低.高温服役条件下不发生粗化的MX相弥散分布在铁素体和马氏体中，与马氏体高温回复形成的亚稳态多边形结构有效提升耐热钢抗高温蠕变性能.

Effect of Tempering Temperature on Microstructure and Mechanical Properties of High Cr Martensitic Heat Resistant Steel

The microstructure and mechanical properties of 9% chromium martensitic heat resistant steel tempered at different temperature were investigated with the OM，TEM， SEM and EPMA．The results showed that the dislocation network，precipitation phase and lath martensite fragmentation after tempering were the main factors for the variations of mechanical properties. It was found that after normalizing and tempering at 760℃， the test steel had an excellent integrated mechanical properties， where the tensile strength at room temperature and 550℃ reached 657MPa and 556MPa， respectively， and the impact absorbing energy at 0℃ reached 285J. Tempering at 700， 820 and 850℃， promoted a substantial reduction in toughness. Under a high temperature service， the MX phase was dispersed uniformly in the ferrite and martensite without coarsening， and metastable polygonal structure was formed during the recovery of martensite at high temperature. Such combination of substructure and dispersed distribution can effectively enhance the high-temperature creep resistance of this heat-resistant steel.