3. Case-hardening steels

3.1 General

Case-hardening treatments (followed by quenching), whose aim is to obtain a very hard martensitic layer (high carbon content) resting on a tough core, are applied to steels whose base carbon content is limited so that the martensite and bainite likely to form in the core retain sufficient ductility; this limit is generally less than 0.25%.

The hardenability of these steels can partially condition the case-hardening depth (but the latter depends above all on the case-hardening conditions). On the other hand, the core strength of the parts depends on it. In fact, limiting the carbon content of the base metal does not allow us to modify the hardening capacity, and it is therefore, within these limits, the structural state that determines the level of...