chapter  7
60 Pages

Heat Treatment with Gaseous Atmospheres

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

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.