A study on the feasibility of laser annealing to relieve residual stresses in cold spray coatings

Abstract

This paper investigates the effect of laser annealing on residual stresses in cold spray (CS) coatings. Residual stresses can compromise the material properties of the deposited materials, and potentially cause delamination; thus it is essential to understand and reduce these residual stresses where possible. The deposition of single tracks of copper onto aluminium substrates was examined. A novel method of in-situ monitoring of residual stresses during the CS process was developed, using a bondable rectangular strain gauge rosette. A standardised substrate fixing method was designed to ensure consistent and repeatable CS tests, where the in-situ strains were recorded during both the CS and laser annealing process. The experimental results proved that laser annealing is a potential in-process treatment method for relieving residual stresses within a CS coating, when compared to a standard furnace stress relieving cycle. However, results indicated that stresses are reintroduced due to the high cooling rates of the substrate.