Thermochemical process for hardening of surface layers.

Hardening of the surface layer takes place due to diffusion of alloy elements [N, C, and (H)]. Table 1 shows the respective treatment substances and the temperatures at which thermochemical hardening is carried out. Table 2 illustrates the properties that can be achieved. The carbonitride layer (s. Carbonitride) obtained in this way increases resistance against adhesion and abrasion, improves the endurance limit and partly also corrosion resistance.

  • Table 1: Major thermochemical processes for hardening of surface layers (according to H. Gräfen)
  • Table 2: Properties of nodular graphite cast iron subsequent to thermochemical treatment (according to H. Gräfen)
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