Intermixing and interfacial morphology of cold-sprayed Al coatings on steel

The microscopic intermixing phenomena at the interface of cold-sprayed, soft Al coatings on a hard steel substrate were investigated. It was found that even though there was no evidence of vortex formation, the high velocity collision of even relatively soft particles of Al can generate a very thin and amorphous Al-Fe intermixed layer that provides full coverage along the interface. Furthermore, a portion of this layer was observed to crack and split to form an embedded layer remote from the interface. Along with the original interface layer, this popped up layer inside the Al coatings can also provide a nucleation point for the formation of intermetallic compounds as well as the original interface layer. A rougher surface can therefore influence the composition of both the popped up and interfacial layers, leading to enrichment of substrate components. (C) 2014 Elsevier B.V. All rights reserved.