Protective coatings against metal dusting

Metal dusting is a corrosion process that occurs in highly carburizing atmospheres. It represents significant economical losses in the petrochemical, iron reduction, and heat treatment industries. In the present work, PVD coatings of Cr adhesion layers + protective chromium oxides have been applied to HK40 substrates and their response to metal dusting measured by thermogravimetric analysis. Coatings were produced by reactive magnetron sputtering under different processing conditions. For the adhesion layer, the effect of power and surface roughness on the quality of the adhesion layer was analyzed. In the case of the oxide deposit, the composition of the reactive (Ar + O2) mixture was varied. Thermogravimetric analysis of uncoated and coated samples was carried out in carburizing conditions. The microstructure of the samples was analyzed by scanning electron microscopy + energy dispersive analysis and X-ray diffraction. The results indicate that the quality of the coatings, particularly their density and adhesion, are more important than the thickness of the layer deposited for effective protection against metal dusting.