Cold sprayed MCrAlY + X coating for gas turbine blades and vanes

• Cold spray technique has been considered for gas turbines coatings deposition.
• The process parameters have been selected from previous experience with Ni base alloys.
• The obtained coatings are evaluated and compared with conventional bond coats.

The feasibility of depositing an MCrAlY + X coating via cold gas dynamic spray (CGDS), also called cold spray, was considered as an alternative to traditional thermal spray solutions where there is concern regarding the relatively high costs of the standard processes. The effect of the particle size distribution on the process deposition efficiency was assessed by using two powder size ranges. The properties of the cold spray deposited material, as well as the density and the quality of the bond with the substrate, were evaluated in the as-sprayed condition and after post-deposition heat treatment. The coated samples were exposed to high temperature oxidation at various typical in-service temperatures and for different durations to analyse the high temperature behaviour of the cold sprayed coating in terms of Al-rich β phase depletion rate. After exposure, the oxidised samples were characterised by optical and scanning electron microscope. All coatings from this study were benchmarked against those deposited using standard techniques, already widely characterised. Cold spray seems a promising alternative to the standard deposition routes, although further work is necessary, especially on samples that also incorporate a TBC top coat.