Production, characterization and evaluation of protective Cr oxide coatings against metal dusting

Cr oxide/Cr thin films have been deposited on HK40 steel substrates in order to evaluate their behavior under metal dusting conditions. The films were produced by reactive magnetron sputtering under various conditions of oxygen flow, work pressure, power and bias voltage to find the optimum deposition conditions to form an adequate dense structure with good adhesion to the substrate. The coatings were extensively characterized by scanning electron microscopy, x-ray diffraction and atomic force microscopy. The most promising structures were subjected to metal dusting conditions in a thermobalance (TGA) to evaluate their response to this type of corrosion. The results indicate that lower applied power and slowly graduated feeding of oxygen resulted in coatings with less residual stresses, higher density and better adherence. The TGA experiments showed an improvement in resistance to metal dusting of the coated samples compared to an uncoated one.