4. Controlling surface properties: furnaces and atmospheres

4.1 Salt bath furnaces

Salt baths, which generally consist of barium and sodium chlorides, are mainly used to treat small and medium-sized parts, such as standard martensitic steel parts. If salt baths are only used to treat stainless steels, they are neutral to the parts and therefore do not lead to surface deterioration. If other steels are treated in the baths, these are likely to evolve and cause decarburization of the treated stainless steels. The graphite and methyl chloride baths will then have to be rectified, a delicate operation which can lead to a carburizing treatment for the metal if not carried out correctly.