Carburization at the inert gas annealing
Carburization of the case is an enrichment of carbon in the surface area of the material. Favoring factor is for example a furnace atmosphere with a high potential at carbon atoms. This can be a high adjusted amount of CO-gas in the composition of the protective gas. A diffusion of carbon, out of the material, is usually prevented by the protective gas. The contrary effect, a diffusion of carbon into the material, can arise at too high CO concentration. This fact can be used positively, for aimed weak carburization of e.g. workpieces, to achieve an a little higher surface hardness at the later quenching and tempering. Not all materials react in a similar manner.
