Influence of substrate geometry on the mechanical properties of copper cold spray deposits

As cold spray (CS) transitions from a coating technology to an additive manufacturing process, the variety of part shape and size is significantly increasing. Simultaneously, the drive to optimize mechanical properties of CS deposits has emerged, especially for structural applications. It has been well documented that particle impact temperature and velocity strongly influence the deposit mechanical properties. While some work has been performed on the effect of substrate temperature on the coating properties, the contribution of substrate geometry to these properties has been neglected. This work studies the effect of substrate material, shape and size on copper CS deposit hardness and tensile properties. The CS deposits are fully characterized in the as-sprayed and heat treated states to understand the origin of the observed variations. Generally, it was found that for similar particle temperature and velocity, deposits that were sprayed on larger parts exhibited lower as-heat treated ductility and tensile strength. This effect is largely attributed to the variation in the substrate temperature developed during deposit build-up, which influences the as-sprayed coating microstructure and resulting as-heat treated ductility and tensile strength. This work has important implications for CS process scale-up from small laboratory size coupons to larger parts.