Challenges of laser cladding Al7075 Alloy with Al-12Si alloy powder

Compared to conventional arc-welding processes commonly used to repair aluminium (Al) components, laser cladding involves lower overall heat input, less part distortion and narrow heat affected zones (HAZ). With the development of high power lasers, it has become an attractive technology for the refurbishment of high value-added structural airframe components in commercial and military aircrafts, especially those made of hard-to-weld heat treatable Al alloys. A series of cladding trials was performed on Al7075-T6 alloy substrates using an Al-12Si alloy powder as the filler repair material because of its high corrosion resistance and a high power Nd:YAG laser. The effects of laser operating parameters such as laser power, substrate scan rate, powder feed rate and increment between cladding tracks on the clad characteristics, e.g. height, depth and dilution, were investigated. Results are described, showing how the process conditions were optimized to reduce the clad depth, dilution and HAZ, while minimizing the formation of porosity in the clad during solidification. Clad samples were produced without liquation cracks in the HAZ, and despite the unavoidable formation of decorated grain boundaries near the fusion zone, the tensile strength of selected claddings was acceptable, within 5% of that of the parent metal, while ductility was low but similar to the parent metal.