Damage-tolerant, hard nanocomposite coatings enabled by a hierarchical structure
Faculty of Computing, Health and Science
School of Engineering (SOE)
A novel hierarchical structured coating was prepared on a pure titanium substrate by a double cathode glow discharge technique. This coating consisted of a 1 μm thick C40-structured MoSi2 outer layer with an average grain size of 5 nm and an underlying MoSi2/Mo5Si3 layer having a gradient, bimodal microstructure, in which C40-structured MoSi2, with an average grain size of 5 nm, is embedded within an intergranular region of D8m-structured Mo5Si3, with an average grain size of 40 nm. The ratio of Mo5Si3 to MoSi2 increased gradually away from the outer surface. Compared with a monolithic MoSi2 coating, the hierarchical structured coating exhibited a marked increase in toughness, while maintaining its hardness.