Thermal aging of 16Cr-5Ni-1Mo stainless steel - Part 2 - Mechanical property characterisation

Mechanical property characterisation has been carried out on specimens of 16Cr-5Ni-1Mo stainless steel, subjected to various aging cycles. The heat treatment cycles involved solution treatment at 1050degreesC for 1 h followed by heating in the temperature range 400 - 750degreesC for different holding times (1 - 16 h). After heat treatment, tensile, hardness, impact, and creep tests were conducted. Specimens aged at 475degreesC exhibited maximum values of tensile strength and hardness with minimum values of ductility and impact toughness, while specimens aged at 625degreesC had maximum values of impact toughness and ductility. The results were correlated with the microstructural data presented in Part 1 of this study. Softening of the martensitic matrix at 625degreesC occurs as a result of the elimination of internal stresses, the decrease in the dislocation density, and the high volume fraction of austenite which lead to the drop in values of tensile strength and hardness. The results of the study reveal that aging at 550degreesC for 4 h gives the optimum combination of strength, hardness, ductility and toughness for this steel.