正火温度对含钛高铬耐热钢显微组织和性能的影响

Effect of normalizing temperature on microstructure and properties of high chromium heat-resistant steel with titanium

采用光学显微镜、X射线衍射、扫描电镜和透射电镜研究了正火温度对不含钛和含钛（0.14wt%）高铬马氏体耐热钢显微组织和力学性能的影响。结果表明：在1000-1150℃范围内,随正火温度的升高,不含钛的钢晶粒明显长大,而含钛钢晶粒大小基本不变;经不同温度正火和750℃高温回火处理后,两种钢的洛氏硬度值均随正火温度的升高先增后减,在1100℃正火处理时达到峰值,含钛钢的洛氏硬度均略低于不含钛的钢。1100℃×1h正火处理＋750℃×1h高温回火处理后,含钛钢在晶界上存在尺寸约为2μm的TiC颗粒,在马氏体板条界附近区域内分布有高密度纳米TiC析出相。蠕变过程中裂纹易于在大颗粒TiC的界面处形核导致含钛钢的高温蠕变性能降低。

Effects of normalizing temperature on microstructure and properties of the high Cr martensitic heat-resistant steels without Ti and with 0. 14wt% Ti were studied by the optical microscope, XRD, SEM and TEM. The results show that the austenite grain coarsens obviously with increasing normalizing temperature from 1000 ℃ to 1150℃ for the steel without Ti, but it doesn＇t grows for the steel with 0. 14wt% Ti. After normalizing and tempering heat treatment, hardness increases with increasing normalizing temperature below 1000 ℃ followed by a decreases above 1000 ℃ for the both steels, and the steel with 0. 14wt% Ti has a lower hardness than the steel without Ti. Both large TiC particles with a size of about 2 μm distributed in grain boundaries and dense nano-sized TiC particles in grain and martensitic lath boundaries were found in the steel with 0. 14wt% Ti after normalizing at 1100 ℃ for 1 h and tempering at 750 ℃ for 1 h. The creep crack is prone to nucleate at the interface between matrixes and the large TiC particles resulting in the decrease of the high temperature creep property.