Surface layer of a work piece with the content of one or more elements being modified compared to the initial composition of the work piece.
This mixed crystal may contain additional precipitations which are formed during slow Cooling. This layer is also referred to as precipitation layer. If there are Intermetallic phases between the element and the base metal, layers may be formed from these intermetallic phases at the surface. These layers are referred to as compound layer. The surface layer under the compound layer is referred to as Diffusion layer. In contrast to the compound layer, the diffusion layer may have a thickness of several tenths of a millimeter.
In surface engineering, the diffusion layer is a layer on metal work pieces which is formed by the diffusion of chemical substances into the base metal.