BEHAVIOR OF NUCLEATION AND GROWTH OF CARBIDE LAYERS ON ALLOYED CARBIDE PARTICLES IN SUBSTRATES IN SALT BATH CARBIDE COATING

In salt bath immersion carbide coating, the effect of alloyed carbides in substrates is significant from the scientific and industrial points of view. This is because carbide layers grow by chemical bonding between carbon atoms in substrates and carbide forming elements in the baths, and by continuous supply of carbon atoms from substrates. It is concluded, from the use of substrates with very coarse carbide particles, that carbide growth behavior is highly dependent on combinations of species of the coating carbides and carbide particles in substrates. This can be explained in terms of the free energy for carbide formation of both coating carbide elements and substrate carbide elements.