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Kinetic roughening of tantalum films during the initial growth stages has been studied by atomic force microscopy, scanning electron microscopy, and dynamic scaling theory. Different from the time-independent scaling behavior for continuous film growth, an intriguing unstable kinetic roughening occurs during island coalescence. In such case, roughness exponent α increases with growth time, accompanied by lower growth exponent β and higher coarsening exponent η. Detailed analysis of film surface morphology and simple phenomenological models suggests that this unstable behavior is related to the pronounced lateral growth of surface islands, which arises from the combined effect of the formation of grain boundary and the covering of heterogeneous substrate surface.

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A strategy integrating structure zone model with dynamic scaling theory was proposed to study the global surface dynamics of polycrystalline Cu films deposited at different homologous temperature Ts/Tm. The evolution of roughness exponent α and growth exponent β reveals a transition from random deposition to surface diffusion dominated smoothening in the lower Ts/Tm regime and then to rapid surface roughening in the higher Ts/Tm regime. In contrast to that of amorphous films, the distinct scaling behavior in higher Ts/Tm regime arises from the change of anisotropic mass transport mechanisms, which could be related to the texture evolution during growth.

The interdiffusion behaviours and oxidation resistance of the NiCrAIY/AI duplex coated specimens during the isothermal oxidation test at 950°C were investigated. It was shown that the NiCrAlY coating system with an AI bondcoat outperformed the NiCrAlY single coating system and the substrate y-TiAl alloy during hot exposure. Analysis techniques such as X-ray diffraction, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to study the phase formation, microstructure and depth distribution of the elements in the coated specimens.The results showed that the NiCrAIY/AI duplex coating system exhibited better oxidation resistance and adhesion strength with the substrate during scratch test. The SEM-EDS profile analyses further showed that the outward Ti diffusion and the inward Ni diffusion were delayed apparently by the AI interlayer, which was also considered as AI source for forming protective a-Al2O3 scale on the NiCrAIY/AI coating surface.

Although several empirical wear formulas have been proposed, theoretical approaches for predicting surface topography evolution during sliding wear are limited. In this study, we propose a novel wear-prediction method, wherein the energy-based Arrhenius equation is combined with a mixed elastohydrodynamic lubrication (EHL) model to predict the point-contact wear process in mixed lubrication. The surface flash temperature and contact pressure are considered in the wear model. Simulation results are compared with the experimental results to verify the theory. The surface topography evolutions are observed during the wear process. The influences of load and speed on wear are investigated. The simulation results based on the Arrhenius equation relationship shows good agreement with the results of experiments as well as the Archard wear formula. However, the Arrhenius equation is more accurate than the Archard wear theory in some aspects, such as under high-temperature conditions. The results indicate that combining the wear formulas with the mixed EHL simulation models is an effective method to study the wear behavior over time.