Search

Cold spraying of hard Fe particles onto soft Al substrates increases the mechanical energy supplied to the interface of the two metals compared to previous Al coatings on Fe substrate. As a result, the irregular interfacial morphologies found in this study were on a larger scale. As in the case of the soft particle/hard substrate system, roll-up features that perfectly encapsulated the Fe particles were found, but their structure was larger and complicated. When the Fe/Al interface was investigated further, it was found to be amorphous. This amorphous layer had a composition gradient, which indicates intermixing on an atomic scale. As could be expected from the enhanced mechanical energy of the Fe particle/Al substrate system, the amorphous layer was also thicker than that of the reversed system. Cold spraying is an ambient-temperature processing technique that involves materials that can be plastically deformed, and therefore, an analogy can be found with the cold rolling (cold welding) of two metal sheets or wires, where similar interfacial characteristics are found. Hence, the mechanisms of bonding and interface formation can be thought of as similar.