The influence of nitrogen on the structure and properties of Fe–10Cr–N and Fe–10Cr–1Mo–N steels after tempering in the temperature range of 650–750 °C

The influence of nitrogen on the structure and properties of the Fe–10Cr–N and Fe–10Cr–1Mo–N ferritic steels after tempering in the temperature range of 650–750 °C was studied. Before selecting tempering temperatures, the investigation of precipitation processes during continuous heating of the quenched steels (studied here) was carried out using non-isothermal dilatometry and TEM. For better understanding of the observed phenomena, thermodynamic calculations were performed using the Thermo-Calc™ programme. Change of nitrogen content shifts the temperature of the maximum length change rate, which correspond to Cr2N or (Cr, Mo)2N and M23C6 precipitation processes at higher temperatures. The decrease of tensile strength, yield point, and hardness with tempering temperature rise in steels with higher nitrogen contents is less intensive. It was observed that the deterioration of impact toughness, elongation, and the reduction of area becomes more evident after increase of the nitrogen content.