Coating Technology to Improve the Performance of Resistance Welding Electrodes
PosMAC (POSCO Magnesium Aluminum alloy Coating product) is a ternary alloy coated steel (Zn-3%Mg-2.5%Al) for high corrosion resistance developed. 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. 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) process with different type of WC based powders. 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. HVOF sprayed WC-12Co coating shows promising results in spot and projection resistance welding experiment. 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.