Effects of NbC Powder Addition on Microstructure and Oxidation Resistance of High‐Speed Steel

This study investigates the effects of NbC addition on the microstructure, hardness, and oxidation resistance of high‐speed steel (HSS) rolls. Microstructure of metallography, X‐ray diffractometer, scanning electron microscope, and energy‐dispersive X‐ray spectroscopy analyses reveal that with increasing NbC content (up to 3%), eutectic colonies and carbides are progressively refined, accompanied by continuous hardness improvement. However, excessive addition leads to the formation of coarse NbC phases. Oxidation resistance shows slight enhancement at 0.5% NbC but gradually deteriorates beyond this level, with significant acceleration in oxidation weight gain when exceeding 1.5%. The deterioration of oxidation resistance of HSSs is attributed to the increase in the amount and size of Nb‐rich MC precipitates in the microstructure. The results demonstrate that 1.5% NbC addition achieves an optimal balance between hardness and oxidation resistance, attributed to its optimization effect on the size and distribution of MC carbides.