高Cr铁素体耐热钢高温热循环过程的组织演化规律

Microstructure Evolution of High Cr Ferritic Heat-Resistant Steel in High Temperature Thermal Cycle

为探究高Cr铁素体耐热钢高温热循环过程的组织演化规律,通过采用光镜与透射电镜显微组织分析方法,对高Cr铁素体耐热钢单次和二次高温热循环加热后基体组织和沉淀相的演变规律展开研究,从而为第4类裂纹萌生微观机制的研究提供试验依据.结果表明:高温热循环加热后,奥氏体相分数都随着峰值温度的增高呈现先增加后降低的趋势,在峰值温度1,100,℃处达到最大;M_(23)C_6碳化物在峰值温度达1,100,℃后全部溶解,而MX碳化物在峰值温度达1,300,℃后才全部溶解,且MX的尺寸在不同热循环过程中基本保持不变;马氏体板条宽度随着峰值温度的升高而增加;沉淀相的溶解和δ-铁素体的形成对基体的硬度有明显影响.

To explore the microstructure evolution of high Cr ferritic heat-resistant steel in high temperature thermal cycle,high temperature thermal cycle test was carried out. By using optical microscopy and transmission electron microscopy（TEM）,the evolution of matrix and precipitate of high Cr ferritic heat-resistant steel in single high temperature thermal cycle test and double high temperature thermal cycle test was systematically studied,which provides the experimental basis for the study of initiation micro mechanism of the fourth welding crack. The results show that during high temperature thermal cycle test,the fraction of the austenite phase increases first and then decreases with the increase of thermal cycle temperature,reaching the maximum at the peak temperature 1 100 ℃.The M_（23）C_6 carbonitrides all resolve at the peak temperature 1 100 ℃,while the MX carbonitrides all resolve at the peak temperature 1 300 ℃,and their sizes in different high temperature thermal cycle tests have remained unchanged.The widths of martensite increase with the increase of thermal cycle temperature.The dissolution of precipitate and the formation of δ-ferrite have an important effect on the hardness.