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6415 |
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HVOF and cold spray coating technology to improve the performance of resistance welding electrodes |
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SangHoon Yoon* / RIST, Republic of Korea Hyung-Jun Kim / RIST, Korea Seo-Jeong Park/ RIST, Korea Gyuyeol Bae/ POSCO, Korea |
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PosMAC (POSCO Magnesium Aluminum alloy Coating product) is a ternary alloy coated steel (Zn-3%Mg-2.5%Al) for high corrosion resistance developed by POSCOs own technology. Generally, the coated steel sheet (PosMAC) has lower weldability due to the reaction between Cu-based electrode and coated layer during resistance welding compared to normal steel sheet. Therfore, PosMAC steel sheet has difficulty in expanding demand for parts requiring welding because of poor weldability. It is considered that the degradation mechanism of welding electrode is the formation and growth of CuZn compound, and inhomogeneous wear resulting in the reduction of the life time of welding electrode. In this study, the coating was produced using HVOF (High Velocity Oxygen Fuel) and cold spray process with different type of WC based powders to improve the life time of welding electrode. The coated and uncoated electrodes were evaluated by measuring the tensile strength in every 100 spot points after spot welding. The final coating electrode was evaluated by projection resistance welding in a dual fan component manufacturer. Compared to cold sprayed coating, HVOF sprayed WC-12Co coating shows promising results in spot and projection resistance welding experiments. As results of the projection welding tests of the coated electrode, the life time of coated electrode is more than 10 times higher than that of the commercial uncoated electrode. |