Processing-microstructure-property relationships for cold spray powder deposition of Al-Cu alloys

Abstract

This thesis presents research on the cold gas-dynamic spray process applied to the deposition of aluminum-copper alloy coatings. Cold spray deposition is a process utilized to create corrosion protection coatings and to perform additive repair for aluminum structures. This thesis utilized a series of Al-Cu binary alloy powders, from 2–5 weight percent copper and characterized their chemistry and microstructure. The powders were deposited using the cold spray approach to study the systematic increase of the alloying agent on the deposition process and coating characteristics. Deposition efficiency, critical velocity, coating thickness, hardness, porosity, and microstructure were all characterized as functions of carrier gas pressure, carrier gas temperature and feedstock powder copper composition. This thesis has demonstrated that all of the aluminum copper powders utilized can be successfully deposited via the low-pressure cold spray process with helium as the carrier gas. The copper content of the powders has a direct effect on the volume fraction of Al2Cu intermetallics, and on the coating hardness, while having no measurable effect on critical velocity for deposition or the coating thickness per pass.