Laser assisted cold spray of aluminum alloy 6061: Experimental results

Abstract

Laser-assisted cold spray (LACS) is investigated for its potential to improve the mechanical properties of cold spray deposits made by using nitrogen as the gas that carries the powder. High strength cold spray deposits are typically achieved by using the more expensive and resource limited helium. In this work, a laser collocated with the spray spot was used in nitrogen CS operations and the porosity, adhesion strength, tensile strength, and fatigue performance of aluminum alloy 6061 (Al6061) were examined. Using the laser improved all the performance metrics. By increasing the spray spot temperature from 180°C to 455°C, the porosity of the deposit reduced to 0.24 % from 1.73 %. The adhesion strength was increased from 18.4 MPa to 76.6 MPa. The tensile strength was increased from 34.3 MPa to 167.6 MPa, and the elongation was increased from 0.07 % to 15.58 %. It was shown that using laser heating during deposition increases the residual stress in the deposit, but its effects can be counteracted by using a hotplate beneath the substrate. Fatigue testing showed that fatigue performance was largely driven by tensile strength. These results are discussed in the context of in-situ temperature data and metallographic analysis. Analysis indicates these improvements are due to the combined effects of material softening, improved bonding between particles, and various heat treatment modalities.