Electro-plating of aluminum-based composites for eliminating carbides formation in laser welding

Limited success has been achieved in using CO2 and pulsed Nd:YAG lasers to weld certain types of Al-Si/SiC metal matrix composites. However, the problem of the formation of brittle carbide phases at the weld zone remains largely unsolved. In this study, a new laser joining technique has been developed with an aim to avoid the formation of brittle carbide phases. This technique involved brush plating of nickel on aluminum-based composites prior to laser welding. Different plating conditions and laser processing parameters were employed to assess the applicability of this technique. Using an appropriate plating procedure, good metallurgical bond was obtained between the Ni coating and the Al-composite matrix. The results of the EDS analysis showed that by plating a suitable thickness of nickel coating on the joining faces, it was possible to prevent the formation of carbide phases. Microstructural changes at the plating interface were discussed in terms of the coating thickness and the temperature profile of the weld. The welding results also showed that a lower critical power intensity was required to obtain keyhole welding in the Ni-plated samples as compared to the uncoated one.