正火对高Cr马氏体耐热钢组织和性能的影响

通过光学显微镜、透射电镜(TEM)及扫描电镜(SEM)分析，研究了正火处理对高Cr马氏体耐热钢显微组织、力学性能及断裂机理的影响.结果表明，900~970℃正火后，晶粒尺寸十分细小，在10μm以下.1060~1200℃正火晶粒尺寸迅速增长，1060℃正火晶粒尺寸约为33μm.经过1060℃×2h正火+760℃×3h回火热处理后，室温和600℃高温拉伸屈服强度分别达到535MPa和380MPa，综合力学性能优良，而1060℃长时间正火对力学性能并无明显影响.1060℃×2h正火+760℃×3h回火热处理后得到破碎的晶粒细小回火马氏体组织，晶界上200~300nm M₂₃C₆和晶内5~50nm MX型弥散析出有效地阻碍位错运动，进而提高了材料力学性能.

Effect of Normalizing on Microstructure and Properties of High Chromium Martensitic Heat Resistant Steels

Effect of normalizing heat treatment on microstructure， mechanical properties and fracture mechanism of high Cr martensitic heat resistant steel was investigated by optical microscopy， transmission electron microscopy (TEM) and scanning electron microscope (SEM) analysis. The results show that after normalizing at 900~970℃， grain size is very small which is less than 10μm. After normalizing at 1060~1200℃， grain size increases rapidly which is about 33μm at 1060℃. After normalizing at 1060℃ for 2h and tempering at 760℃ for 3h， the excellent mechanical property can be achieved where the tensile yield strength at room temperature and high temperature at 600℃ is about 535MPa and 380MPa， respectively; while a longer normalizing time at 1060℃ has no obvious effect on mechanical property. Moreover， after normalizing at 1060℃ for 2h and tempering at 760℃ for 3h， mechanical properties can also be improved effectively by the fine grains of the tempered martensite， the precipitate of M₂₃C₆with its size of 200 ~ 300nm at the grain boundaries and the MX dispersion with its size of 5~50nm inside grains.