Influencing the properties of materials through a heat treatment is restricted when this treatment is done under normal atmosphere.
These limits are defined by:
- Chemical reaction of the hot material surface with oxygen (oxidation) or other components of the surrounding air.
- Inclusion of gas molecules from the surrounding gas into the material surface.
Through the use of an inert gas it is possible to prevent oxidation, however, the other potential influences remain. Only the complete removal of all gases out of the furnace atmosphere will prevent any reaction of the material with the ambient.