1.1210 | C53E induction hardened (incorrectly)

The images show the induction-hardened edge zone of a piston rod, which we can divide into three zones.

• Zone 1:
  Near the surface, a homogeneous austenite was only just missed upon heating. The martensite formed from former pearlite grains is light brown and finely needled (plate martensite). The martensite formed from former ferrite grains is coarsely needled and dark in color (lancet martensite or massive martensite / “soft martensite”). The diffusion time for the carbon in the gamma was too short, so that the martensite structure resembles a steel with approx. 0.2% C content. In the center of these zones, even free ferrite is preserved. Thus, the heat treatment was insufficient.
• Zone 2:
  Here we are in the 2-phase region (alpha+gamma) of the iron-carbon diagram (G-S-P). The pearlite grains have been transformed into austenite and quenched to martensite. The ferrite, on the other hand, did not change its lattice type and remained intact.
• Zone 3:
  The core microstructure consists of ferrite and pearlite. Locally, the ferrite is still slightly acicular (Widmannstätten arrangement).