Deformation mechanisms in laser-additive carbon atoms-reinforced Ti-based coatings with exceptional high-temperature fretting resistance

High-temperature titanium alloys such as Ti–Al–Sn–Zr-based titanium alloys often suffer severe high-temperature fretting damage when used in aerospace compressors, leading to crack initiation and reducing the service reliability. Therefore, developing reliable protective coatings is imminent. This study used C atom-reinforced Ti-based coatings to achieve high-temperature fretting damage resistance on Ti60 surfaces through laser cladding and re-melting. The contributions of C atoms from graphene to the toughening–strengthening mechanism of fretting damage in the coatings (herein called Gr-Ti coatings) were examined. Results show that C atoms refined the microstructure while the variant selection law of α-Ti was altered. Solid solution of C atoms led to an increase in the c/a ratio of α-Ti, leading to prismatic-slip initiation. Gr75 coating (Ti-based coating with 0.75 wt% graphene) exhibited the best yield strength and strain during micro-pillar compression owing to solid-solution strengthening effects as well as the (0001) <11 2‾ 0> and (101‾ 0) <112‾ 0> multi-slip mechanisms due to the influence of solid solution of C atoms. Additionally, Gr75 exhibited superior resistance to fretting damage under an alternating cycle condition owing to its enhanced microstructure stability and plastic-deformation accommodation capacity during fretting imparted by the C atoms through fine-grain strengthening, solid-solution strengthening, and the promotion of (0001) <11 2‾ 0> and (101‾ 0) <112‾ 0> multi-slip mechanisms. Thus, the study findings provide new approaches to the design of new fretting-resistant Ti-based coatings.