Interaction of aluminium with stainless steel during plasma nitriding

An interaction between a stainless steel (AISI 316) substrate holder and an Al 2011 substrate occurred during plasma nitriding at ∼575 °C. The interaction layer formed was ∼100 μm thick, with a hardness of 850 HV and was composed of Al, Cu, Fe, Ni and Cr, suggesting diffusion from the steel holder into the Al substrate. Prior to the plasma treatment the hardness of the Al substrate was 122 HV. While some interaction occurs on heating in the absence of plasma, the presence of plasma under otherwise identical conditions significantly enhances this interaction. The application of a sample voltage bias did not affect the formation of this layer. However, on plasma treatment at lower temperatures (500 °C), no layer was formed.