Microstructure Evolution and Properties of Nitrogen-Bearing Hypereutectic High Chromium Cast Iron after Quenching

High chromium cast iron (HCCI) is widely used in mining and metallurgy due to its high wear resistance. The purpose of this study is to reveal the effects of different quenching temperatures on the microstructure evolution, hardness and wear resistance of nitrogen-containing hypereutectic high chromium cast iron (HHCCI). The results show that with the increase of quenching temperature, the primary carbides change from hexagonal prism to irregular shape, and the eutectic carbides change from daisy-like and strip-like to larger lumps with a tendency to aggregate and grow. The secondary carbides are mainly transformed from precipitation to re-dissolution, and there are two morphologies of the precipitated secondary carbides. One is block, which is mainly M7C3 type and distributed around primary and eutectic carbides by TEM analysis. The other is short rod-like, of the M23C6 type, which tends to precipitate in the "central" region far away from the eutectic carbide. With the increase of quenching temperature, the hardness and wear resistance of hypereutectic high chromium cast iron show a tendency of increasing first and then decreasing, and quenching at 1050 °C, the specimen shows the highest hardness of 66.0 HRC and the best wear resistance. It was expected to provide reference for the formulation of heat treatment quenching process of nitrogen-containing HHCCI.