Effect of Microstructural Evolution on Mechanical Properties of Secondary Hardening Low‐Carbon High‐Alloy Bearing Steel

Abstract

The hierarchical martensite structure of secondary hardening low‐carbon high‐alloy bearing steel at different solution temperatures is characterized in detail, and the effect of microstructural evolution on mechanical properties of the experimental steel is studied. The results show there are a large number of micron‐M6C at the boundary of the prior austenite grain when the solution temperature is 1,000–1,025 °C, which is conducive to hinder the growth of the prior austenite grain and produces smaller packets that improve the yield strength of the material. At the same time, such micron‐M6C is prone to stress concentration when the material is subjected to an external force load, which can severely reduce the material toughness. The M6C completely dissolves into the matrix when the solution temperature exceeds 1,050 °C, and the packets size grows rapidly with the prior austenite grain size. At this point, the effect of packets on yield strength no longer dominates, and the rate of decrease in yield strength tends to be gradual. Under the comprehensive function of the micron‐M6C‐remelting, the martensitic blocks refinement, the increased number of the Σ3 grain boundaries, and the growth of cracks can be hindered, and the toughness of material can be improved accordingly.