Residual Stress Development in Cold Spray Coatings: Insights from Curvature Measurements and Finite Element Analysis

The analysis of residual stresses in coatings is crucial for evaluating their service life and performance. In thermal spray processes, the interplay between thermal and kinetic energy influences the residual stress state. High-temperature processes, such as plasma spraying and arc spraying, generate significant quenching stresses, typically tensile in nature. In contrast, high-velocity processes, such as High-Velocity Oxy-Fuel (HVOF) spraying, introduce compressive stresses due to particle pinning effects. Cold spray, a solid-state deposition technique where particles adhere via plastic deformation at relatively low temperatures, is expected to produce predominantly compressive residual stresses. However, recent in-situ curvature measurements have revealed cases where tensile residual stresses unexpectedly develop in cold-sprayed coatings.

This study aims to quantify and understand the residual stress evolution in cold spray coatings through a combined approach of in-situ curvature measurements and finite element modeling. Coatings of copper and stainless steel were deposited onto various substrate materials under different process conditions, allowing for a systematic investigation of the interaction between impact dynamics, layer buildup, and post-deposition cooling. The analysis of soft and hard material combinations under varying kinetic energy conditions highlights the role of thermal mismatch stresses relative to pinning-induced compression. Microstructural evaluations further corroborate the observed stress states, providing insight into the mechanisms governing stress evolution in cold spray.

By drawing comparisons with established stress measurements in conventional thermal spray processes, this study presents strong hypotheses regarding the origin of tensile stresses in cold spray. The findings contribute to a deeper understanding of residual stress development in high-velocity deposition methods and offer guidance for optimizing process parameters to achieve desired stress states.