Influence of annealing on microstructure and cavitation erosion resistance of iron-based metallic glass coatings synthesized by HVOF thermal spraying

This study aimed to deposit a novel iron-based metallic glass coating onto 316L stainless steel and analyze the microstructures, phases, mechanical properties, and cavitation erosion resistances of the as-sprayed and annealed coatings. The coatings were annealed at temperatures of 540, 640, and 740 degrees C, resulting in varying crystal contents. As the annealing temperature increased, the amorphous content of the iron-based coatings decreased from 90% to 62%, 35%, and 29%, respectively, while the microhardness increased from 849 HV0.2 to 944, 970, and 860 HV0.2, respectively. The coating annealed at 640 degrees C exhibited the best resistance to cavitation erosion, whereas the coating annealed at 740 degrees C had the poorest resistance. Cavitation erosion always initiated from defects in the amorphous/nanocrystal coatings, such as pores, microcracks, or phase interfaces, and then propagated along these defects, eventually causing the stripping of particles. During cavitation erosion, the wellbound particles fragmented under repeated shocks, and the amorphous phase crystallized into nanocrystals, leading to detachment of particles in small sizes.