Fatigue and delamination of 6061 aluminum cold spray on a similar wrought substrate

Abstract

Fatigue crack growth and fracture of a thick 6061 aluminum cold spray coating on 6061-T6 aluminum substrate were studied through in-situ observation of fatigue crack growth through the coating to the interface in notched four-point bend samples. Mode I cracking was observed through the coating before delamination at the substrate. Crack tip strain fields during the delamination event were plotted with DIC. Interfacial steady-state strain energy release rates were measured using the bimaterial four-point bend solutions by Charalambides. The interfacial crack primarily spread cleanly along the coating/substrate interface, with a post-fracture surface morphology containing a wavy structure with an amplitude on the same order of magnitude as the cold spray particle diameters. The in-situ video of crack propagation and coating-substrate delamination provides lessons for improving the coating-substrate interfacial toughness and thus expands use cases for structural cold spray applications