The new design to improve the stability of retained austenite and mechanical properties in super martensitic stainless steel

Abstract

The quenching and partitioning (QP) process has proven to be an effective technique for stabilizing retained austenite (RA). The N element partitioning process has replaced the traditional C element partitioning method, resulting in improved stability of RA in super martensitic stainless steel. To enhance these benefits, an innovative combination of intercritical annealing (A) and QP has been developed, known as the QAP process. This technique utilizes interstitial N atoms and substitutional Ni, Mn atoms to co-stabilize RA, leading to excellent comprehensive mechanical properties. The findings indicate that the QAP samples display a yield strength (YS) that is 75–121 MPa higher than the QP sample. At intercritical annealing temperatures of 500 °C and 550 °C, the QAP steel demonstrates a product of strength and elongation (PSE) of 36.61 GP·% and 31.51 GP·%, respectively, surpassing the QP steel (26.52 GP·%). Furthermore, the presence of secondary martensite increases with higher intercritical annealing temperatures in QAP samples. However, excessive secondary martensite significantly diminishes toughness.