Microstructure, microhardness and impact toughness of low pressure carburized PM steels
The effect of low pressure carburizing (LPC) on two low alloyed sintered steels processed according to different
routes to obtain different amounts of open porosity was studied. In presence of an open porosity,
overcarburizing promotes the precipitation of grain boundary carbides in the Cr steel, and the formation of
retained austenite in the Cr free one. In presence of a fully closed porosity LPC results in the formation of a
homogeneous case. Even a slight amount of open porosity causes overcarburizing. In absence of
overcarburizing, impact toughness is typical of a brittle behavior, as expected. However, an unexpected high
toughness is measured in the supercarburized steel containing retained austenite.