Microstructure of the nitride layer of AISI 316 stainless steel produced by intensified plasma assisted processing

Nitrided austenitic 316 stainless steel produced by intensified plasma assi sted processing has been studied by transmission electron microscopy (TEM), high-resolution TEM, and image simulation techniques. Cross-sectional TEM studies showed that the nitride layer is composed of a single phase that wa s found to possess a simple cubic structure. This nitride is produced by in troducing one N atom into one of the interstitial sites of the octahedra wi thin the unit cell of the gamma-austenite. The lattice constant of the nitr ided simple cubic structure was determined to be a = 3.78 Angstrom, which i s expanded by about 5.4% from that of austenite. Stacking faults, antiphase domains, and antiphase domain boundaries in the nitride layer were observe d using dark-field and high-resolution TEM imaging. The evolution of the ni tride phase seems to be preceded by lattice expansion and formation of stac king faults due to the presence of N and is consistent with the observed la ttice constant reduction with depth. (C) 2000 American Institute of Physics . [S0021-8979(00)06019-9].