The Preparation, Microstructure, Properties And Tribology Behavior Of VB₂ Coatings

Coating has been an effective process to improve component properties, and has been widely applied in engineering. Especially, the well wear and corrosion resistance has elongated the lifetime of the material.In this thesis, three key parameters have been varied – temperature, substrate bias and target frequency – during the magnetron sputter deposition, and about 1.4 μm VB2 coatings were deposited. Then, the microstructure of the coatings was characterized by X-ray diffraction(XRD), field-emission second electron microscope(FESEM), atomic force microscope(AFM). The mechanical properties of the VB2 coatings were tested by nano-indentation, Vickers indentation and scratcher. And the relationship among the parameters, the microstructure and the properties were tried to build. The results showed: The microstructure was varied as the deposition parameters changed. The deposition temperature has controlled the diffusion of the deposition atom, and the substrate bias and frequency have controlled the energy of the deposition atom bombardment. As temperature increased, the orientation of the coatings was complete(001) with the denser microstructure, and become a homogeneous and featureless structure in SEM view; the ratio of(001)/(101) was increased and the microstructure was denser with the increasing substrate bias; and the similar phenomena were observed in changing the frequency. As the microstructure changed, the properties of the VB2 coatings were enhanced, such as the hardness was increased from 19.7 GPa to 43.6 GPa.The tribological behavior of the coatings was tested by UMT-3 tribometer, and analyzed by surface profiler, FESEM and energy diffraction spectrum(EDS). The results showed: the friction of coefficients(CoF) of the VB2 coatings were about ~0.7, when the load was 2 N, the wear rates of the coatings were quite stable, at the range of 6.8-9.2×10-16 m3/N m. The microstructure was no influence on the tribological behavior. When the load was 5 N, the wear rates changed very much, only some sample could be still at the order of 10-16 m3/N m, while others failed quickly. To expand the application of the coatings, one sample has been tested the tribological behavior at 500 oC in ambient air. Then, SEM was used to characterize the worn surface morphology and the annealed surface morphology. The results showed: after 500 oC annealing, the surface morphology changed much. And the CoF was low at first then rise to about ~1.2, the self-lubricious phenomenon was not observed.