2. Case-hardening and carbonitriding steels

2.1 General

The choice of steel on which the treatment is carried out is an important parameter with regard to the possibilities of obtaining the structure and, therefore, the properties of the case-hardened or carbonitrided part.

In principle, a case-hardening or carbonitriding steel should have a low carbon content, i.e. less than 0.4%. After treatment, this low value enables good toughness characteristics to be maintained, while at the same time benefiting from good surface properties thanks to the contribution of interstitials during treatment.

Within the carbon range indicated above, the 0.2 to 0.4% C zone is generally reserved for grades intended for carbonitriding, while grades below 0.2% are more particularly attributed to case-hardening....