Effect of heat treatment processes on the microstructure and mechanical properties of 00Cr13Ni5Mo super martensitic stainless steel (SMSS)

The effects of quenching and tempering temperatures on the microstructure and mechanical properties of super martensitic stainless steel (SMSS) 00Cr13Ni5Mo were studied. The SMSS after heat treatment is composed of martensite (α phase) and a small amount of austenite. When the quenching temperature is 930 °C, with the increase of tempering temperature, the enrichment of Ni in martensite leads to the formation of reverse austenite, the content of martensite phase decreases from 84.9 % to 80.0 %, and the average grain size increases from 23.23 μm to 27.07 μm. When tempering at 580 °C, the content of martensite phase decreases from 80.0 % to 83.7 % with the increase of quenching temperature. The average grain size increased from 25.23 μm to 35.01 μm. When the quenching temperature is 930 °C, the hardness and yield strength of SMSS decrease, and the hardness and yield strength are the highest at 530 °C, which are 275 HV and 873 MPa. The plasticity increases first and then decreases, and the plasticity is the best at 580 °C. The elongation and reduction of area were 22.87% and 71.41%. These changes in mechanical properties are mainly related to the content of martensite and reversed austenite in the microstructure. The tensile strength and elongation of SMSS under different process conditions were compared. The results show that when the quenching temperature is 930 °C and the tempering temperature is 580 °C, the comprehensive performance of SMSS is the best, reaching 18700 MPa•%. This value is 31% higher than that of forgings. Finally, the formation mechanism of reversed austenite was discussed, and the strengthening model of SMSS 00Cr13Ni5Mo was established.