Corrosion resistance of duplex treated AISI H11 steel

Nitriding treatment is widely used to increase the wear and corrosion resistance of steel components. The characteristics of the modified layers, as phase composition and thickness, can be changed by varying the treatment parameters. As the working conditions become more and more severe, nitriding treatment is not always able to achieve a satisfying improvement of the performances. In these cases, a duplex treatment can be performed, by combining a pre-nitriding treatment with a following deposition of a ceramic coating. As already reported in the literature, the improvement of the wear resistance of duplex coated samples is marked when it can be achieved a good adhesion between the modified layers. Particularly, a better bonding of the PVD coating to the nitrided substrate was observed when nitriding treatment produces a modified layer consisting of the diffusion layer only. The aim of this work is to study the corrosion behaviour of duplex coated AISI H11 steel samples. For comparison, morphological and microstructural analysis, microhardness measurements and corrosion tests were carried out also on untreated, nitrided and simply PVD coated samples.