Influence of the spray trajectories on the residual stress development in cold sprayed deposits

Cold spray additive manufacturing has developed rapidly in recent years as potentially viable technology for structural repair of high-value parts requiring a high integrity of deposited materials. Apart overall strengths, residual stresses are a factor that affects properties and service lifetime. In cold spraying, stresses are to high extent determined by maximum reached deposit temperature and thermal gradients. One option to reduce thermal effects is given by trajectory planning. This study aims to evaluate the effects of different scanning pattern and scanning direction in individual layers by a modelling approach. The thermal history and thermal stresses by different scanning strategies are analysed by a thermomechanical finite element model. The results indicate that different scanning pattern leads to deferent thermal loads and consequently affect the magnitude and distribution of thermal stresses. Also, a more uniform temperature and stress distribution is achievable by changing scanning direction between the layers. Therefore it is important to choose the best scanning strategy to minimize the temperature and thermal gradient over the component leading to less anisotropy in materials layers. The thermomechanical analysis thus could provide an effective way to optimizing the cold spray coating deposition strategy and improve the coating performance.