Effect of different adhesive strength on strength on fatigue properties of thermally sprayed steel with Co-based self-fluxing alloy

摘要

Rotational bending fatigue tests were carried out on medium carbon steel (s35C) with a thermally sprayed Co-based alloy coating. The effects of different adhesive strength on the fatigue strength and fracture mechanisms of fused specimens are investigated. Fusing treatment was performed in vacuum furnace, electric furnace, and with induction heating system. When the specimens are fused in vacuum and electric furnaces at 1373K for 4hours, the diffusion layer is formed between coating layer and substrate providing strong adhesive force. As a result, fatigue strength of fused specimens is remarkably increased in comparison with substrate and blasted ones. This implies that the high durability of sprayed coating contributes effectively on the improvement of fatigue strength. On the other hand, the specimens fused with an induction heating system show a reduction of porosity and increment of the elastic modulus and tensile strength compared with substrate. However, since its adhesive strength is low, it leads to the delamination of the coating from the substrate during fatigue tests. As a result, fatigue strength of induction-heating-fused specimen becomes almost the same as that obtained in fatigue tests where substrate alone was used. Therefore, performance of fusing treatment in vacuum and electric furnace demonstrates effectiveness in the improvement of fatigue strength for thermally sprayed materials.