Ion-nitriding induced plastic deformation in austenitic stainless steel

Lattice parameter measurements in ion-nitrided surface layers of austenitic stainless steel have been performed using x-ray microbeam diffraction on samples with different nitrogen contents as a function of depth and grain orientation, respectively. The lattice expansion observed in the layers as a result of nitriding is anisotropic due to the presence of elastic strains, but the austenite (fcc) structure is largely retained. Parallel to the layer-substrate interface the expanded lattice is highly relaxed which is, along with significant changes in the surface morphology, indicative of plastic deformation in the nitrided zone. (C) 2000 American institute of Physics. [S0021-8979(00)05823-0].