Combined laser shock and micro-compression approach to the mechanical behavior of powders for cold spray

The simulation of particle impact is a key for the understanding of cold spray. This type of simulation typically involves the Johnson-Cook model. However, few data only are available for powders when submitted to cold spray conditions. In this study, an approach based on the use of a laser shock was therefore developed in addition to micro-compression testing to characterize the mechanical behavior of powders. From subsequent FEM simulation of the test, the static coefficients in the Johnson-Cook model could be identified. For the dynamic part of the model, a portable test bench was developed using a laser shock to accelerate a single particle, namely LASHPOL (LAser SHock POwder Launcher). The velocity of LASHPOL’ed particles, measured using high-speed imaging, ranged from 10² m.s^-1 to 10³ m.s^-1 typically. In addition, image analysis of particles before and after the impact was developed, together with FEM simulation, to determine coefficients related to strain rate hardening in the Johnson-Cook model. The combination of the two testing methods resulted in a mechanical characterization for powders. This approach is expected to become a powerful industrial tool for developing and/or controlling powders tailored for cold spray.