The abbreviation PM in HSS-PM does not refer to the alloying constituents of the high speed steel, but to the method of manufacture. The liquid steel melt is atomized by means of nitrogen. The powder is then hot isostatically pressed (so-called HIP process) and then brought into the respective shape by forging and rolling as in conventional steel production. The advantages of steel result from the more uniform and finer carbide distribution (carbide = hard materials in steel). This makes the material easier to machine. In application, however, it is still wear-resistant and has a high hot hardness.
Nitrocarburization is a thermochemical diffusion process. Nitrogen, carbon, and a very small number of oxygen atoms diffuse onto the surface of steel or other ferrous alloys. This forms a surface compound layer and a diffusion layer.
