Influence of Substrate Temperature on the Structure and Cohesive/Adhesive Strength of Fe–Co–Si–B–Nb Metallic Glass Coating Films Produced by Thermal Spraying

Abstract

The influence of the substrate temperature on the structure, pore distribution and cohesive/adhesive strength of Fe–Co-based metallic glass coating films has been examined. The metallic glass coating films have been produced by a thermal spraying technique using our developed cylindrical nozzle on SS400 substrates. The splat morphology of the sprayed particles changed from an irregular splash to a disk shape at a transition temperature of about 300°C. When the substrate temperature increased to the transition temperature region (300–323°C), the porosity in the boundaries between the sprayed coating films and the substrates decreased. This can be produced by the strong increase in the wettability of the sprayed particles which is accompanied with a morphological change from splashed to disk-shaped particles. At temperatures ranging from 375 to 400°C, the porosity in both the boundary and inside regions decreased, and the volume fraction of the amorphous phase increased with temperature, resulting in a increase in the cohesive/adhesive strength up to about 27 MPa.