Mechanical and Corrosion Behavior of Titanium Cold Spray for Repair of Engineering Components

Cold spray technology shows great promise for repairing engineering components, particularly in extending the life cycle of titanium (Ti) materials. This study presents proof-of-concept for the cold spray repair of Ti by depositing thick layers of commercially pure titanium on a more highly alloyed substrate. We evaluated the corrosion resistance and mechanical properties using multiscale hardness testing, examining the impacts of coating cohesion, decohesion, and porosity. Two types of cold sprayed Ti coatings were analyzed: one from Armstrong powders with a porous, irregular morphology, and another from hydride-dehydride powders with an angular-blocky morphology. The angular powders achieved porosity below 1%, while the irregular powders had ~1.1% porosity. Although the irregular powders reached higher in-flight particle velocities, their internal porosity hindered densification. The dense structure of angular powders facilitated better kinetic energy dissipation through plastic deformation, resulting in a higher hardness at low loads. Whereas in irregular powders, a portion of the energy is expended in closing pores. The lower porosity and greater cohesion strength for the coating with angular powders led to improved corrosion resistance and hardness at high loads. These findings highlight the significant role of powder morphology on the mechanical and corrosion behavior of Ti cold spray coatings.