Tempering of quenched ferritic-austenitic Cr−Ni steel

Summary

• 1. Embrittlement at 475–500°C is due to the enrichment of the grain boundaries of the α-phase in nickel and to the precipitation of small particles of (apparently) the carbonitrile phase.

• 2. Embrittlement at 650–800°C is due to the precipitation of the σ-phase, which forms as the result of the enrichment of the surfaces of the grains of the α-phase in chromium and possibly in nickel. The resulting strengthening is apparently the consequence of directional diffusion of the elements inducing the deformation of the crystal lattice of the α-phase.