Plasma-nitrided AISI-316 stainless steel examined by scanning electron microscopy and secondary ion mass spectrometry

Samples of the austenitic stainless steel AISI 316 nitrided at low temperat ure in a low-pressure r.f, plasma have been examined by scanning electron m icroscopy (SEM) and secondary ion mass spectrometry (SEM), with a view to d etermining the composition of the treated surface layer. With suitable samp le preparation SERI can provide clear images of details of the treated laye r that facilitate a relatively direct measurement of layer thickness. We sh ow explicitly that the sputter rate in a SIMS depth profile is constant for this material. Hence the depth scale can be easily calibrated, so that SIM S is a convenient method of measuring the thickness of the treated layer, T he SIMS depth profile suggests that the small proportion of carbon in the a lloy is pushed ahead by the incoming nitrogen and piles up at the interface between the treated layer and the hulk material. The sputter yields of the main components of the alloy vary differently with the concentration of ni trogen, whereas that of carbon appears to be unaffected by nitrogen concent ration. (C) 1999 Elsevier Science S.A. All rights reserved.