Development of Al oxide PVD coatings against metal dusting

Al oxide thin films were deposited on 304L stainless steel substrates to investigate their potential as protective coatings in metal dusting environments. Deposition of the films was carried out by d.c. reactive magnetron sputtering varying feeding mode of O₂ flow and application of a Cr interlayer. The response to metal dusting of coated and uncoated substrates was evaluated by thermogravimetry in an atmosphere of CH₄+H₂+residual oxygen at 1073 K for 20 h. The results indicated that these types of coatings can effectively protect the 304L steel in these conditions. The protection was associated to good adhesion provided by the Cr interlayer and the role of the Al oxide as a barrier for diffusion. Improvement of the present coatings can be achieved within magnetron sputtering deposition techniques.