Combined Laser Shock and Micro-Compression Approach to the Mechanical Behavior of Powders for Cold Spray

Abstract

In cold spray, particles undergo large plastic deformation upon impact in a rapid dynamic regime (up to 109 s-1) at solid state. The simulation of this impact is key to understanding the cold spray process. In this study, an approach based on laser shock and micro-compression testing was developed to characterize the mechanical behavior of powders and fit parameters of the Johnson-Cook material behavior model. In situ micro-compression particle testing was performed in a SEM equipped with a microindentation stage. From subsequent FEM simulations of the test, static coefficients of the Johnson-Cook model were identified. A laser shock powder launcher (LASHPOL) was also developed to accelerate single particles and measure their corresponding velocity using high-speed imaging. In addition, image analysis of the particles before and after impact, together with FEM simulation, were used to determine strain rate hardening coefficients for the Johnson-Cook model.