Effects of vanadium addition on formation of carbides of high carbon high speed steel

摘要

The effects of vanadium, from 1 to 10 mass %, on the formation of carbides of as cast high carbon high speed steels containing 1.6 and 2.1 mass % C were investigated by SEM, TEM and EDS analyses In the 1 % V steels, M{sub}7C{sub}3 and M{sub}6Ctype eutectic carbides formed on the primary austenite boundary. In the 3 % V steels, V-rich MC type eutectic carbide was found to exist. In steels with V above 3 % the amount of MC carbide increased while those of M{sub}7C{sub}3 and M{sub}6C decreasedwith increasing V content. In both the 8 % and 10 % V steels, primary MC and eutectic M{sub}3C carbides were observed. Carbon content influenced the start and finishing temperatures of the eutectic reaction and the microstructure, i.e. both thetemperatures decreased and the length of needle-like eutectic carbides became longer in the 2.1 % C steels. While the hardness of the steels with V below 5 % did not change with V content, it began to drop suddenly in the steels with V above 8 % due tothe existence of ferritic matrix.