Adhesion and residual stress state of cold-sprayed Inconel 718 coatings

In recent years, the interest in cold gas spraying has increased due to its potential applications in repair and additive manufacturing. Nevertheless, there are still challenges in understanding the resulting residual stress state of such cold-sprayed forms as well as the adhesion. Traditional coating examination methods like microstructural and micromechanical measurements are limited in scope and depth related to these properties. In this presentation, adhesion tests on Inconel 718 substrates, coated with Inconel 718 powder and prepared with different surface pre-treatments (e.g. grit-blasting, particle blasting), have been carried out to investigate the bonding quality of such cold sprayed coatings. For the same coatings and processes, in-situ curvature measurements via the ICP sensor coupled with in-depth stress analyses using the hole drilling method have been used for characterization. The residual stress state of the Inconel 718 coating, which is generally compressive in nature, could be reduced by adjusting specific process parameters even leading to the tensile residual stress state. For reliable in-situ curvature measurements, a sufficient substrate thickness should be used. The results clearly indicate that the new approach allows a flexible adjustment of a desired stress state in cold-sprayed coatings.