Precipitation behavior of cold sprayed Al6061 coatings

Abstract

Cold spray coating technique is an established technology where deposition of the desired coating is carried out at temperatures below the melting point. Current literature on the application of cold spray technique, particularly using Al-6061 alloy powder was reviewed. In this work, we report the precipitation behavior of the cold sprayed Al6061 coatings in the directly aged (as-deposited and aged) and solutionized aged conditions. Coatings were deposited using a convergent-divergent (De-Laval) nozzle at a pressure of 20 bar and a temperature of 400 °C using air as a carrier gas. The peak hardness of the directly aged coatings (107±3 HV0.3) is similar to the bulk counterpart (110±2 HV0.3). The peak hardness of the directly aged coating is attributed to mixture of highly strained microstructure, fine and coarse grains. Needle-shaped β” (Mg5Si6) precipitates contribute to peak hardness of solutionized aged coatings. The directly aged coatings have not exhibited β” (Mg5Si6) precipitates because of segregation of solute at the cell boundaries, Al-Mg-Fe, and Mg-Si rich particles. There is an improvement in bonding for directly aged coatings, and significant improvement in bonding with solutionized aged coatings.