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4748 |
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Wednesday, May 11, 2016, Yellow River Hall 9:00 AM Automotive Industry |
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Application of cold spraying for contact reactive brazing of Mg alloy to steel |
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Hong Li* / Beijing University of Technology, P.R. China Hai-jie Nie / College of Materials Science and Engineering, Beijing University of Technology, China Wei-min Long/ State Key Laboratory of New Brazing Material and Technology, Zhengzhou Research Institute of Mechanical Engineering, China Zhuo Chen/ College of Materials Science and Engineering, Beijing University of Technology, China |
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The cold-sprayed coatings can be widely applied not only as protective coatings but also functional coatings. Its potential for welding applications is prepare coatings as intermediate filler layers in brazing or TLP diffusion bonding processes. In the present study, samples of magnesium alloy AZ31B were coated by cold spraying with a powder of pure copper. Then coated magnesium samples were brazed to 08F steel in vacuum furnace using contact reaction brazing (CRB) technology with deposited Cu coatings as an intermediate layer. The microstructure of the coated and brazed samples was investigated. The results show that the pure copper powder could be very well deposited on the substrate by cold spraying. The coated magnesium samples of low oxygen content could be well brazed in vacuum atmosphere. The holding time influenced the dissolution of Cu coatings, as well as the eutectic reaction between Cu coating and magnesium substrate. The initial thickness of Cu coatings was 50µm while the brazed seam has a thickness of 300µm after eutectic reaction. Mg-Cu eutectic phase has good wettability on steel with only a few pores in brazed seam. Within a certain range, the shear strength of brazed AZ31B/08F steel joints showed a trend of increasing firstly and then decreasing as the heating temperature and holding time increased. Maximum shear strength 37MPa was gained at brazing temperature of 530 and holding time of 60 min for brazed AZ31B/Cu coating/08F steel joint. |