The oxidation process, which can be done at three different temperatures, is also known as steam temper in some sources.
The main purpose is to create a controlled oxidation film on the material surface. The output of this process is usually 3-5 µm thick iron (II, III) oxide.
It is often applied after nitration and nitrocarburization to gain corrosion resistance to the material.
It is made to prevent liquid metal adhesion in metal injection molds. All other applications are for corrosion resistance in general. It is made to increase the oil holding ability of the surface and the beautiful appearance in parts such as drill bits and milling dies.