Laser-induced gradient microstructure enables superior fretting resistance in graphene/Ti coatings at elevated temperature

Ti60 titanium alloy are easily prone to damage in high-temperature fretting conditions, leading to crack initiation and propagation. Fabricating protective coatings is an effective way to enhance the performance of titanium alloy components. Thus, in this work, a graphene reinforced titanium coating with gradient microstructure is designed and fabricated by laser cladding and remelting. The contribution of gradient microstructure on mechanical and high temperature fretting performance is in-depth illustrated. Results show that the coatings exhibit a distinct gradient microstructural distribution with α-Ti and in-situ TiC phases along the building direction. The width of α-lath formed under low laser energy density is only 1/3 of that formed under high energy density. The G1 coating (with gradually decreasing laser energy density along the building direction) has the highest surface microhardness and the best fretting damage resistance among three types of coatings. The excellent fretting damage resistance is related to the random crystallographic orientation on the top layer of the G1. The coordinated deformation of multiple slip systems effectively prevents stress concentration and crack initiation. In addition, the columnar crystals at the bottom provide sufficient toughness support. The synergy between strength and toughness enables the G1 coating to exhibit optimal high-temperature fretting resistance. This research helps to optimize the design of anti-fretting damage coatings for high-temperature titanium alloys applications.