New insights into the coating/substrate interfacial bonding mechanism in cold spray

A new theory was proposed to explain the interfacial bonding mechanism of hard Ni coating,onto soft Al substrate. The experimental results indicate that the metal-to-metal contact and the consequent metallurgical bonding at the coating/substrate interface were absent in the single particle depositing but could be achieved in the full coating deposition. Based on this, it is proposed that the particle peening effect breaks the cracked oxides that remained at the coating/substrate interface into nano-pieces and promotes further deformation of materials. Thus, the pores caused by the bridge-like oxides at the interface are filled and the discontinuous metal-to-metal contact is achieved. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.