To achieve the best quality of laser cladding, selection of suitable powder and process parameters is vital. A series of experiments were performed on a 7075 aluminium alloy substrate clad with Al-Si powder, using a Nd:YAG laser. The laser processing parameters such as laser power, process speed, clad powder feed rate and silicon content in the Al-Si powder all had a significant influence on clad layer quality and microstructure.

Experimental results showed that laser cladding of Al-Si powder on 7075 Al substrate can generally produce metallurgically sound clad layers. However, at lower scan rates, porosity occurred but it reduced with increasing scan rate. Cracking in the clad layer was sensitive to Si content in the Al-Si powder. Cracks were observed in the clad layers where low percentage of Si was present in Al-Si powder. No cracks were observed with high silicon (Al-12%Si) powder. The characteristics of the cracks in the clad layer were similar to hot or liquation cracks in aluminium welds. Laser power had no discernible effect on the presence of cracks and porosity. However, the scan rate had a significant effect on porosity but little effect on crack density.

Topics
Laser materials processing, Chemical elements, Alloys, Materials synthesis and processing
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2004
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