Characterization of surface cratering and particle deformation during high speed microparticle impact events

Simple-to-use damage models are important in predicting the outcome of high speed particle impacts for high speed vehicles traveling in particle laden flows. Such models largely hinge upon experimental data from well-characterized single-impact events. In this study we developed and applied an experimental system to systematically examine surface cratering and particle deposition driven by high speed micrometer particle impacts onto Aluminum 6061-T6 substrates and Inconel 718 substrates. Monodisperse ferrous sulfate particles 1.8 and 6.2 micrometer in diameter were accelerated using a converging-diverging nozzle to achieve varying impact velocities in the range of 0.29–0.84 km s^-1 as measured by laser Doppler velocimetry. Post-mortem surface characterization was carried out using a combination of atomic force microscopy and scanning electron microscopy. For the aluminum samples, we then utilize traditional non-dimensional groups to develop scaling relationships between crater size, particle size, velocity and incident angle. Measurement results are found to agree with data from previous studies at higher impact velocities, but notably with a sharper slope between dimensionless crater size and dimensionless impact energy, indicative of a non-negligible amount of particle elastic rebound influencing the outcome of the impact process. In addition, in contrast to crater formation observed on aluminum, equivalent impacts onto Inconel 718 led to no discernible crater formation and instead adhesion and deformation of the impacting particles.