ABSTRACT
References .......................................................................................................................... 469
Heat treatment of components is to date mostly accomplished in gaseous atmospheres, the
more so if plasma and vacuum are regarded as special cases of gaseous atmospheres. In
comparison, heat treatment in solid or liquid media is negligible in numbers. Heat treatment
in gaseous atmospheres falls into two categories: processes with the aim of avoiding a mass
transfer between the gaseous atmosphere and the material, and processes with the aim of
achieving just such a transfer. Mass transfer occurs when there is a difference in the potential
between the constituents of a gaseous atmosphere and those of the microstructure of a
component. The direction of such a mass transfer is determined by the potential difference,
which leaves two fundamental possibilities with regard to the component. One is the intake
of elements of the gaseous atmosphere into the component and the other is the emission of
elements of the component into the gaseous atmosphere. This kind of heat treatment falls
under heat treatment with gas, which is the subject of this chapter. The deposition of
constituents of a gaseous atmosphere onto the surface of a component (coating), which is
not connected with the described mass transfer mechanism, is therefore excluded from the
subject of heat treatment with gas.
