Applicability of Coatings to Control Metal Dusting

Abstract We have performed a long term comparative study between five wrought and three centricast materials, both as-is, and in coated condition. Two commercially available coatings were applied to each different alloy. One coating was aluminum based with a chromium rich intermediate layer. The other coating was nickel rich with substantial amounts of silicon and aluminum. Both types of coating were of good quality, and did not show (micro)defects. The coated and bare alloy samples were exposed in a high pressure metal dusting atmosphere, and characterised based on mass loss, pit depth, pit size and pit density at regular intervals. The results indicate that a properly applied coating can boost the metal dusting resistance of low chromium alloys to a level comparable with alloy 693, for which generally no metal dusting attack is observed. Finally, the effect of micro cracks on the coating performance was assessed.