Particle Impact Characteristics Influence on Cold Spray Bonding: Investigation of Interfacial Phenomena for Soft Particles on Hard Substrates.

The influence of particle impact temperature and size on adhesion of soft particle/hard substrate material in cold spray has been scarcely studied. While the relationship between particle impact conditions and particle/substrate bonding is commonly established through FEM studies, they typically lack comparison to experimental data. In the current study, characterization was performed by post-mortem observation of removed adhered particles and collected rebounded particles contact surfaces. Observations are correlated to interfacial pressure and temperature using FEM, otherwise impossible to measure in situ. The influence of pressure and its temporal evolution with particle deformation on melting and bonding is evaluated. Evidence of anisotropic particle deformation associated with microstructural orientation and grain geometrical features has been observed. Experimental evidence confirms that the particle south pole experiences restricted deformation as the original powder grain morphology was observed even after impact. Interfacial melt features have been detected and the melt zone generation, propagation, stagnation and regression tracked through FEM have shown important influence on single impact adhesion processes. Observed metallic bonding features and FEM indicate that increasing particle velocity, i.e., decreasing particle size, accelerates particle bonding processes to occur within tens of nanoseconds. Contact compressive pressure and interfacial expansion increase with particle increasing velocity and temperature. [ABSTRACT FROM AUTHOR]