Influence of spraying parameters on cold gas spraying of iron aluminide intermetallics

Abstract

Cold spraying was used to build up coatings of ordered Fe40Al intermetallics, which are a kind of alloys which are being proposed for high temperature applications. The spray experiments were performed with chemically ordered powder feedstock of different size distributions to study influences from impact velocities. Stainless steel and Ti grade 1 substrates were used to investigate influences of the mechanical and physical properties of the substrate material. While coatings on stainless steel are mostly dense with good cohesion, those on titanium show some cracks perpendicular to the coating substrate interface. That might be due to the larger difference in the thermal expansion coefficients between the titanium substrate and the iron aluminide. Regarding the influence of spraying parameters, it has been found for both substrate materials, that when spraying the first layers, a uniform almost linear decrease in the coating thickness is observed when increasing the spraying distance. By increasing the number of spray layers, the increase in thickness asymptotically approaches a saturation limit. Thicker coatings were obtained on stainless steel substrates than on Ti substrates.