Effect of annealing on the microstructure and erosion performance of cold-sprayed FeAl intermetallic coatings

FeAl intermetallic coatings were prepared by cold spraying of mechanically alloyed metastable Fe(Al) powder assisted with post-spray annealing treatment. The microstructure evolution and erosion performance of the coatings annealed at different temperatures were investigated and the erosion mechanism of the intermetallic coatings was examined through the surface morphology and cross-sectional microstructure of the eroded coatings. After annealing at 650 °C, the heterogeneous feature in the as-sprayed coating was evidently modified. With annealing temperature rising to 950 °C and 1100 °C, the interfaces between the particles in the coating completely disappeared. The erosion rate of the coating at the erosion angles of both 30o and 90o decreased with the increase in the annealing temperature. It was found that the erosion resistance of the intermetallic coating annealed at 1100 °C was three times higher than that of the as-sprayed coating. The weight loss of the as-sprayed coating with low cohesion at erosion angle of 90° was attributed to particle spalling off. The weight loss of the annealed intermetallic coatings with enhanced cohesion was attributed to microcutting and ploughing of erosive particles.