PROTECTIVE COATINGS ON HIGH-TEMPERATURE STEEL APPLIED BY PVD DEPOSITION TECHNIQUES

The protection of surfaces against corrosion by thin coatings is a common technique. Nevertheless, coatings deposited by PVD processes are applied due to their mechanical properties (high hardness, high erosion protection etc.) rather than taking advantage of their potential for corrosion protection at high temperatures. The corrosion protection at high temperature by PVD coatings is conditioned by 3 parameters: (i) the thermodynamically stability, (ii) the coating micro structure and (iii) diffusion processes within coating and substrate. These three parameters are discussed during this lecture starting with general considerations about high temperature corrosion, focusing than on PVD processes and the micro structure of the deposited coatings. This micro structure does not only determine the adherence and mechanical properties of the coating, but is also of vital importance for diffusion processes occurring during an eventual high temperature treatment.