Residual stress profiles of nitrided austenitic AISI 316 are shown in the graph. On nitriding, huge compressive stresses are present in the γN layers. Like the hardness and composition distributions, the stress profiles exhibit an abrupt drop when the substrate interface is approached.
For nitriding potentials higher than that of KN = 2.49 (60% NH3), stress relaxation occurs toward the surface in such a way that a compressive stress maximum is present within the expanded austenite zone. Stress relaxation can be attributed to local crack formation, grain pushout, and grain rotations leading to texture changes, indicating that the volume expansion caused by the dissolution of nitrogen into the austenite lattice is partly accommodated plastically.
Volume 4D, Heat Treating of Irons and Steels ⇒ Heat Treated High-Alloy Steels ⇒ Low-Temperature Surface Hardening of Stainless Steel ⇒ Gaseous Low-Temperature Surface Hardening of Austenitic Stainless Steel
