A study of the microstructure and wear of high speed steels
The present work describes the successful extraction of the secondary hardening carbides of high speed steels, which allowed the identification of these carbides by crystalloqraphic, and microanalysis techniques. The secondary hardening carbide of high speed steels was found to be the-cubic M2C carbide and not the MC carbide as previously claimed. The secondary kic carbide was found to precipitate in the over-tempered state well beyond peak hardness. The sequence of secondary carbide precipitation has been determined. The relation between wear resistance and hardness of high speed steels has been found to be non-linear due to microstructural changes at and beyond peak hardness. However, primary carbides of the MC and M6C types of carbides were found to be stable during tempering, of these steels. It has been shown that the primary carbides did not contribute to the wear resistance of steels tempered to peak hardness. -However, the primary carbides were found to contribute to the wear rate of over-tempered steels due to their abrasive role.