A scanning electron microscopy study of carbides in high-speed steels

This paper discusses investigations made using scanning electron microscopy to examine deeply etched specimens and electrolytically extracted carbides of as-cast high-speed steels. It is shown that eutectic carbides appear in three types of eutectic morphologies. A carbide wall exists around type I skeleton eutectic, and growth steps are evident on the top of carbide platelets of the lamellar type II eutectic. Type III generally develops a thick plate or bar form. The delta-eutectoid carbide attains a bunched fiber shape. Increasing molybdenum and decreasing tungsten leads to a change of eutectic carbide from skeleton to platelike and fiberlike morphologies. Vanadium not only promotes the formation of MC carbide, but also the formation of M2C carbide. it was noted to be unfavorable to the formation of M6C carbide, and increasing the vanadium content results in an increase in the size of eutectic and eutectoid carbides