Multi-scale elastic behavior of cold sprayed refractory metal from splat to bulk deposit by integrated experimental and modeling approach

The absence of a scientific understanding of the multi-scale elastic behavior of cold sprayed refractory metal deposits impedes their manufacturing for surface protection against harsh environments. This paper reports an integrated experimental and modeling approach to establish the multi-scale hierarchical nature of elastic modulus of cold sprayed deposits for the first time. At the nanometer length scale, localized structural heterogeneities such as splats and jetting result in a large elastic modulus distribution from 75 to 92% of the wrought metal. These variations persist at the mesoscopic length scales, with the modulus ranging from 62 to 100% of that of wrought metal over 3 to 4 splats. Finite element modeling, built on experimental microstructures and modulus measurements, revealed that at microscopic length scales over 10 to 20 splats, these localized modulus heterogeneities are ‘ironed out’ to 75–82% of wrought values. Finally, at macroscopic length scales over thousands of splats, the bulk elastic modulus of cold sprayed deposits stabilizes at 162 GPa, about 87% of wrought metal. This article thus bridges the gap in scientific knowledge on elastic behavior of cold sprayed hierarchical deposits across orders of magnitudes in length scales and identifies focus areas for future aligned research.