In the case of unalloyed steels, the crystalline structure ofthe diffusion layer is influenced by the rate of cooling afternitrocarburizing. After rapid cooling in water, the diffusednitrogen remains in solution. If cooling is done slowly, orif a subsequent tempering is carried out, some of thenitrogen could precipitate into iron nitride needles in theouter region of the diffusion layer of unalloyed steels. Thisprecipitation improves the ductility of nitrocarburizedcomponents. Unlike unalloyed steels, part of thediffusion layer of high alloyed materials can be betteridentified metallographically from the core structure, dueto the improved etchability.