Laser cladding of high strength aluminium alloy 7075 powder on a 7075 substrate for repair of damged components

Laser cladding is a surface engineering technique that has been employed in this investigation to develop a repair technique for high strength aluminium alloy components. High strength aluminium alloys are used in a variety of situations due to their good combination of high strength and low density. Repair of such components has the potential for cost savings for both the defence and aerospace sectors. Aluminium alloy 7075 powder was laser clad onto a substrate of 7075 and the character of the microstructure in both the clad layer and heat affected zone was evaluated. It was found that the fine precipitates that provide the strength in this class of alloy had grown and coalesced due to the heat supplied by the laser and weakened the heat affected zone from a structural point of view. A solution heat treatment and T6 aging procedure was applied to restore the strength in this region. After the heat treatment, hardness traverse profiles revealed that the hardness in the clad layer was lower than that of the substrate. This was attributed to the evaporation of magnesium and zinc during cladding and the higher concentration of iron in the powder forming an insoluble phase with zinc and magnesium in the clad layer. Both of these factors ultimately reduce the volume of the strengthening phases.