K. Sakata, Fujikikosan Corp., Kitakyushu, Japan; K. Nakano, H. Miyahara, Kyushu University, Fukuoka, Japan; Y. Matsubara, Kurume National College of Technology, Dazaifu, Japan; K. Ogi, Oita National College of Technology, Oita, Japan
This paper describes a microstructure control for wear resistance improvement of Co-based (Co-Cr-W-B-Si) self-fluxing alloy coating by diffusion treatment. A thermal analysis of the alloy specimen was performed to decide the diffusion treatment condition, and to clarify the stable phases at high temperature. The diffusion treatment of thermally sprayed Co-based alloy coatings on steel substrate were carried out at 1373K to 1418K for 600s to 7200s under an Ar atmosphere. The microstructural variations of coating and bonding interface were investigated in detail. A proper diffusion treatment arose two kinds of precipitates in Co-based matrix. EPMA and XRD analyses revealed these precipitates a chromium boride dissolving cobalt and a wolfram boride containing cobalt and chromium. The size of each precipitate became larger with increasing treatment temperature and time. The coating with a proper size of precipitates showed a superior wear resistance.
Summary: The diffusion treatment of thermally sprayed Co-based alloy coatings on steel substrate were carried out at 1373K to 1418K for 600s to 7200s under an Ar atmosphere. The microstructural variations of coating and bonding interface were investigated in detail. A proper diffusion treatment arose two kinds of precipitates in Co-based matrix. EPMA and XRD analyses revealed these precipitates a chromium boride dissolving cobalt and a wolfram boride containing cobalt and chromium. The size of each precipitate became larger with increasing treatment temperature and time. The coating with a proper size of precipitates showed a superior wear resistance.
