Effect of Quenching Temperature on Microstructure and Properties of Al-Bearing High-Boron High-Speed Steel

Abstract

Microstructure and properties of the alloys could be changed by heat treatment process. In this work, effect of quenching temperature on the microstructure of Al-bearing high-boron high-speed steel (AB-HSS) was investigated by means of optical microscopy, scanning electron microscopy and X-ray diffraction. Hardness and wear resistance of AB-HSS at different quenching temperatures were tested by rockwell hardness tester, microhardness tester and wear tester, respectively. The experimental results indicate that the microstructure of as-cast AB-HSS is mainly composed of pearlite, ferrite, M2B-type boride and M23(C, B)6-type borocarbide. After quenched treatment, the matrix transforms into the martensite and the type of boride has no obvious change. The morphology of boride changes from continuous network and fish-bone to isolate shape and granular distribution. As quenching temperature increases, the hardness of alloy increases. The hardness reaches 65.1 HRC when quenching temperature is 1110 °C. The wear resistance of alloy gradually increases with the increase in quenching temperature. The wear resistance is the best when the quenching temperature reaches 1110 °C.