Duplex surface engineering of cold sprayed Ti coatings and physical vapor deposited TiN and TiAlN thin films

The feasibility of a duplex coating based on cold spray technology and magnetron sputtering was evaluated for repair applications requiring a “thin-on-thick” layered structure. Commercially pure angular-shaped Ti particles are fed to cold spray gun and accelerated toward a Ti alloy substrate to deposit thick (~4.5 mm) coatings. TiN and TiAlN thin films are deposited on polished cold sprayed coatings using closed-field unbalanced magnetron sputtering. Microstructure was characterized using electron channeling contrast imaging. Nanoindentation technique was used to evaluate the hardness and elastic modulus of thin films as well as local mechanical properties of cold sprayed coatings. Using scratch testing, adhesion of TiN and TiAlN thin films to cold-sprayed Ti was investigated. Tribological testing was performed on duplex coatings as well as cold sprayed coatings without topcoat using a reciprocating tribometer equipped with an alumina ball counterface. Scanning electron microscopy was used to reveal worn surface morphologies and cross-sectional analysis of the wear track. Friction and wear behavior of thin films were discussed in relation to their mechanical properties, adhesion to cold sprayed interlayer, and cold sprayed coating plastic deformation under tribological loadings.