Effect of tempering temperature on microstructure and properties of low silicon hypereutectic high chromium cast iron

Abstract

High‐chromium cast iron is a good wear‐resistant material. Its heat treatment regime has an important influence on the evolution of its microstructure and properties. This study investigates the microstructural attributes and properties of Fe–4.0 C–35.0Cr–0.5Si (wt.%) low‐silicon hypereutectic high‐chromium cast iron subsequent to quenching at 1050 °C, followed by tempering at diverse temperatures. The microstructure was examined using optical microscopy, scanning electron microscopy, and X‐ray diffractometry across varied tempering conditions. Furthermore, microhardness and wear resistance were conducted via a microhardness tester and a wear testing machine. The results show that the quenching heat treatment promotes the transformation of the matrix from austenite to martensite, while also promoting the precipitation of secondary carbides of M23C6‐type. The subsequent tempering heat treatment engenders transformations involving retained austenite to martensite, amplifies the precipitation and enlargement of secondary carbides, and induces martensite decomposition. As the tempering temperature increases, primary and eutectic carbides exhibit minimal changes, while the secondary carbide morphology evolves from granular to reticular. The matrix composition predominantly comprises martensite, interspersed with a minor fraction of austenite. It is worth noting that the alloy has the highest hardness and wear resistance after quenching at 1050 °C and then tempering at 400 °C.