Effect of austempering on microstructure and mechanical properties of a GCr18Mo steel

The microstructure and mechanical properties of a GCr18Mo steel were investigated. The martensite/lower bainite (BL/M) duplex structure with various BL volume fractions ( f B L ) or that full of BL were produced by austenitizing at 870 °C, quenching in nitrates at 230 °C and holding for different times. The steels with such structures exhibit higher strength–toughness than that of full martensite. When f B L is approximately 37.5% obtained by holding for about 60 min, the duplex-structured steel gives rise to the best combination of mechanical properties.