Effect of heat treatment on microstructure and mechanical properties of Ti-containing low alloy martensitic wear-resistant steel

Effects of quenching temperature and cooling conditions (water cooling and 10% NaCl cooling) on microstructure and mechanical properties of a 0.2%Ti low alloy martensitic wear-resistant steel used for die casting ejector plate were investigated. The results show that lath martensite can be obtained after austenitizing in the range of 860–980 °C and then water cooling. With an increase in austenitizing temperature, the precipitate content gradually decreases. The precipitates are mainly composed of TiC and Ti4C2S2, and their total content is between 1.15wt.% and 1.64wt.%. The precipitate phase concentration by water-cooling is higher than that by 10% NaCl cooling due to the lower cooling rate of water cooling. As the austeniting temperature increases, the hardness and tensile strength of both water cooled and 10% NaCl cooled steels firstly increase and then decrease. The experimental steel exhibits the best comprehensive mechanical properties after being austenitized at 900 °C, cooled by 10% NaCl, and then tempered at 200 °C. Its hardness, ultimate tensile strength, and wear rate reach 551.4 HBW, 1,438.2 MPa, and 0.48×10−2 mg·m−1, respectively.