A study of microstructure and performance of cast Fe-8Cr-2B alloy.

The effects of quenching temperature on microstructure and hardness of cast Fe-8Cr-2B alloy containing 0.3 wt% C, 2.0 wt% B, 8.0 wt% Cr, 0.6 wt% Si, and 0.8 wt% Mn were investigated by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Rockwell hardness and Vickers microhardness testers. The experimental results indicate that the as-cast microstructure of cast Fe-8Cr-2B alloy consists of M2B (M = Fe, Cr), M7(C, B)3, α-Fe, and γ-Fe. The dendritic matrix composed of lath martensite mixed with a small amount of retained austenite, and the netlike boride M2B distribute in the grain boundary. After quenching between 950 °C and 1100 °C, the netlike eutectic boride are broken up and a new phase-M23(C, B)6 which is distributed in the shape of sphere or short rod-like are precipitated from the matrix. Both the macrohardness and microhardness of specimens increase with the increasing quenching temperature. At about 1050 °C, the hardness reaches the maximum value. However, when the temperature exceeds 1050 °C, the hardness will decrease slightly. With the increase of tempering temperature, the hardness of cast Fe-8Cr-2B alloy quenching from 1050 °C decreases gradually and its impact toughness increases slightly. Crusher hammer made of cast Fe-8Cr-2B alloy quenching from 1050 °C and tempering from 300 °C has good application effect, and its service life improves by 150-180% than that of high manganese steel hammer. [ABSTRACT FROM AUTHOR]