Features of surface nitriding revealed by Mossbauer spectroscopy

Two different nitriding surface treatments of austenitic stainless steel have been studied: gaseous nitriding in a NH3-H-2 mixture performed at temperatures between 700 and 900 degrees C and nitrogen ion implantation with different dose rates between 5 x 10(16) to 1.5 x 10(17) N-2(+) ions cm(-2) and different current densities between 1 to 5 mu A cm(-2). The microstructure of the coating was studied by X-ray diffraction and Mossbauer spectroscopy. The discussion emphasizes the role of thermodynamical equilibrium conditions at high temperatures and of the process parameters at low temperatures on the phases which constitute the layer.