Fracture Toughness of Cold Sprayed Pure Metals

The study of fracture toughness of pure Al, Cu, Ni and Ti deposited by cold spray was performed in order to obtain a fundamental understanding of the damage process and quantify the material performance. Rectangular specimens cut from self-standing deposits with fatigue pre-cracks were tested in three-point bending. The KIC values were obtained from J-R curves following the ASTM E1820 standard. The stress–strain behavior of the tested material was obtained from supplementary four-point bending. The cold spray deposits exhibited significantly lower fracture toughness than the corresponding wrought materials. The reduction was more pronounced for coatings with limited ductility (Ti and Cu), where the fracture toughness reached less than 12% of the wrought counterpart only. The higher ductility coatings of Al and Ni possessed fracture toughness of 18–25% of the wrought reference materials. The performed fractographic analysis revealed inter-particular decohesion as the major failure mode.