Plasma nitriding of AISI 2205 steel: effects of surface mechanical attrition treatment and chemical etching

Abstract

In the present study, surface mechanical attrition treatment (SMAT) and plasma nitriding were conducted on AISI 2205 steel. SMAT was effective in enhancing the surface hardness of the steel by about 80%. The influence of SMAT on the corrosion behaviour of the steel was studied in a 3.5 wt-% NaCl solution. Due to the stable and thicker passive layer, improved corrosion resistance was observed for the SMATed steel. However, nitrogen diffusion during plasma nitriding was impeded by the improved passivation, especially for the lower duration (30 min) of chemical etching/cleaning (i.e. sputter cleaning in hydrogen plasma) of the specimen's surface. Furthermore, high chemical etching duration (120 min) resulted in improved surface hardness and nitriding kinetics.

Keywords:

• SMAT
• Duplex stainless steel
• Corrosion
• Nitriding
• Passivation
• Chemical etching

Acknowledgements

We would like to thank Dr R. Kadam and Mr P. Mungole of Kalyani Centre for Technology and Innovation, Bharat Forge Ltd., Pune, India, for their cooperation in SEM and EBSD experiments. One of the authors, Mr Atul Gatey, would like to thank Bharat Forge Ltd. for providing scholarship to do PhD on a related topic. The authors would like to thank MRC, M.N.I.T. Jaipur, for their cooperation in using XRD and GA-XRD characterisation. We would like to thank C. O. E. Pune and N. I. T. K., Surathkal, India for their co-operation in conducting research work and Bhat Metals Research Pvt. Ltd, Pune, India for conducting the plasma nitriding cycles.