Particle-based simulation of cold spray: Influence of oxide layer on impact process

Abstract

High-speed cold spraying of micro-particles, at temperatures well below their melting point, impinging on desired substrates is a useful emerging additive process. One principal element believed to dramatically influence the bonding strength and final coating quality of many metallic cold-spray deposits is the native oxide layer on the surface of the impinging particles and substrate. Here, smoothed-particle hydrodynamics (SPH), a mesh-free, particle-based method, is used to simulate cold-spraying, including the action of oxide layers in the deposition and bonding processes. The effect of increasing particle impact velocity on oxide breakup and subsequent bonding is studied. Particle/substrate bonding is quantified via metallic interaction at the interface and found to continuously improve with increasing velocity well beyond the critical velocity. The coefficient of restitution is also calculated for different oxide layer thicknesses on the particle and the substrate. The effects of particle diameter and oxygen content on the impact process are reported and compared to results from the literature. The particle-based simulation approach is found to reproduce experimentally characterized trends in oxide content effect and provide insight into the mechanisms of oxide breakup during bonding.