1.7225 | 42CrMo4 Induction hardened

The approx. 1.5 mm thick, induction-hardened surface layer consists entirely of quite coarsely needled martensite and has a hardness of up to 639 HV0.5. The heat of the induction hardening has not reached the core, and the hardness drops to an average of 288 HV0.5.

The core structure consists of ferrite, molded cementite, residues of undissolved lamellar pearlite and residues of highly tempered martensite, similar to a subheat-hardened structure. Here, therefore, residues of the soft annealed microstructure and isolated pearlite lamellae are still present (pre-tempered condition).

Etching with PAG QT² shows the prior austenite grain boundaries as well as pronounced segregation lines in the core structure.