Effect of Quenching Process on Microstructure and performance of High-Boron High-Speed Steel

ABSTRACT The effects of quenching process on microstructure and hardness of High-Boron High-Speed Steel (HB-HSS) containing 0.4%C-6.0%Cr-4.0%Mo-1.0%V-1.0%Si-0.5Mn-x%B-y%Al (x=1.0, 1.5, 2.0, y=1.0, 2.0, 3.0) were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Rockwell hardness tester. The experimental results indicate that the quenching microstructure of HB-HSS consists of α-Fe, M2(B, C), M7(B, C)3 and a few of M23(C, B)6 。With the increase of quenching temperature, the net structure of borocarbides is damaged and the borocarbides are evenly distributed in the matrix. When the quenching temperature is 1050 °C, the Rockwell hardness of HB-HSS increases with the increase of boron content. The Rockwell hardness of HB-HSS decreases with the increase of aluminum content. When the quenching temperature is 1050 °C, the aluminum content is 1.0% and boron content is 1.0%-2.0%, the combination of the microstructure and the hardness of HB-HSS is the best.