Phase composition of diffusion coatings of rare earth metals on steels

Abstract

1. In diffusion saturation of carbon steels with rare earth metals the following phases are formed: α solid solution with a limited cerium concentration, intermetallic compound CeFe5, and unstable cerium carbide CeC2 inclusions in the grain boundaries which are susceptible to hydrolysis. 2. Because of the limited solubility of cerium in the α solid solution it is inadvisable to add excessive amounts of rare earth metals to steels, since it leads to the formation of excess phases containing cerium in the grain boundaries, impairing the physicomechanical properties of the steels.