Plasma nitriding of gradient structured AISI 304 at low temperature: Shot peening as a catalyst treatment

This study involves the capability of severe shot peening (SSP) as a catalyst intake for plasma nitriding process and the probability of reducing the requirement of thermal energy individually on the diffusion of interstitial atoms. To this end, combination of mechanical-thermal energy is run with pure thermal plasma assisted energy. Therefore, SSP is exposed to AISI 304 austenitic stainless steel as a former treatment and gradient structured surface (nanograined zone, ultrafine grain martensite-twin intersections zone and twin densed zone) is created. Then, plasma nitriding at 400 degrees C-4h and 475 degrees C-2h temperature-duration conditions. The condition of 475 degrees C-2h provides the requirements of diffusion individually however former treatment SSP increases the diffusion layer effectively. In contrast, 400 degrees C-4h condition is not adequate for diffusing atoms and white layer formation on the surface. The support of SSP as a mechanical energy triggers the process and white layer and the interstitial atoms diffusion take place influentially.