Characterisation of duplex layer structures produced by simultaneous implantation of nitrogen and carbon into austenitic stainless steel X5CrNi189

Plasma immersion ion implantation has been used for simultaneous implantati on of carbon and nitrogen into austenitic stainless steel X5CrNi189 at 400 degrees C. Duplex layer structures are formed with a nitrogen-rich layer cl ose to the surface and a carbon-rich layer at greater depth. The influence of different gas compositions on the structure and phase composition of the layers is examined and compared with results from pure nitrogen and methan e. The results provide further information about 'expanded austenite' (S-ph ase) which is formed during the low temperature nitriding of austenitic sta inless steels. (C) 2000 Elsevier Science S.A. All rights reserved.