Effect of Process Parameters on Residual Stresses of Cold Gas Sprayed IN718 Coatings on Large Repair Geometries

Abstract

The residual stresses induced by the various process conditions in engineering components can have a significant impact on their structural integrity and performance. It is essential to ensure reliable control of the mechanical properties of structural components during the repair process, as this directly affects their performance and longevity. Cold gas spray, a solid-state deposition technique, involves the high-velocity impact of fine powder particles onto a substrate, resulting in the formation of a dense, metallurgically bonded coating. The aim of this study is to investigate the suitability of cold gas spraying parameters for the repair of large cavities in components made of Inconel 718. Two sets of parameters, approaching the limits of the spraying facility, have been utilized and analyzed using particle diagnostics. Experimental methodologies involve the characterization of residual stress profiles using techniques such as in situ curvature measurement and the incremental hole drilling method after the cold gas spray repair. Additionally, the microstructure and topography of the as-sprayed repair coatings are demonstrated. The results demonstrate the ability of cold gas spray to successfully fill deep repair cavities and adjust the residual stress state of such repair coatings by varying the processing parameters. Lower residual compressive stresses in the layer were achieved by utilizing gas parameters, wherein the particles impact the substrate at an elevated temperature and at a comparatively reduced velocity. Both conditions exhibited coatings with consistent microstructure, good adhesion and uniform topography without major defects. This research demonstrates the potential of cold gas spray as a viable and efficient repair method for large repair geometries, offering a promising avenue for enhancing the reliability and lifespan of critical engineering structures.