Bonding probabilities in cold spray deposition of composite blends

Cold gas spraying of metal alloys using single feedstock powder is well described in terms of impact conditions and critical velocities for bonding of similar particles. In contrast, the mechanism of layer build-up in cold spraying of dissimilar powder blends, especially where the particles have significantly different thermomechanical properties, is far from being fully established and has remained an open question. We explore this question by taking W-Cu and Mo-Cu as example blends of significantly dissimilar materials, with potential applications in thermal management systems. The current study aims mainly to provide a comprehensive overview of the electrical, mechanical and microstructural characteristics of the deposits formed under varied feedstock compositions. The experimental data are further interpreted in view of a statistical model for deposition, considering the different deformation behavior as well as the possibly even repulsive chemical interaction of the dissimilar particles. In this way, the model supplies a quantitative description of the observed deposition efficiency as a function of powder size and composition. The paper also discusses the scope of application of the findings and the model to other cold-sprayed composites or single alloy systems. •Dense W-Cu and Mo-Cu coatings produced by cold spraying of powder blends•Composite properties mainly determined by Cu matrix instead of embedded hard phase•Hard phase contents determined by impact statistics and bonding probabilities•Bonding probability grows with velocity ratio η and attractive chemical interaction•Statistical impact model describes composite formation by cold spraying of blends