Post-Processing of Cold-Spray Deposits of Copper and Iron

Abstract

Abstract Layers of high-purity copper and iron produced by cold gas-dynamic spraying have been thermally processed to induce recrystallization and grain growth. In the case of copper deposits, the as-sprayed structure could be "pinned" by arrays of Cu2O particles present on the surfaces of the feedstock powder, however copper powders of higher purity and sphericity yielded sprayed structures which could be annealed to induce recrystallization and grain growth. The higher purity copper compacts exhibited a morphological change in fracture from a brittle, intraparticle mode in the as-deposited condition, to a ductile, "cup-and-cone" morphology in the annealed condition. For compacts produced from water atomized iron, annealing at sub-critical temperatures produced recrystallization and grain growth as found with copper, and thermal processing in the austenitic region resulted in altogether new and coarser grain structures upon cooling. Ease of thermal processing of cold-sprayed materials may offer additional processing routes for engineered surfaces and functional devices produced in this manner.