Abstract
In this thesis, the 90o-bend filtered cathodic vacuum arc (FCVA) technology was employed to deposit the chromium carbide films on the steel (AISI D2). This investigation was to compare various conditions which including the deposition temperature, the substrate bias voltage and the C2H2/Ar flow. The micro-structures, mechanical properties, corrosion behavior and optical properties of the chromium carbide film are thoroughly discussed. The uniform and dense of the chromium carbide films have been successfully synthesized using our FCVA system. The chromium carbide is transformed from amorphous to crystallized phase, as the negative substrate bias voltage increases from -50 to -550 V at 500 ℃.Moreover, the crystallized Cr23C6 phase appears as the negative substrate bias voltage further increases. A compact and dense Cr3C2 film with the fibrous structure of Cr23C6 was successfully prepared. The Cr3C2 coated steel has a relatively high nanohardness and excellent adhesion compare with the amorphous chromium carbide. The corrosion resistance of the Cr3C2 coated steel is owing to the establishment of a defects-free microstructure. No pitting corrosion was observed on the Cr3C2 coated steel. The corrosion behaviors of cryst-Cr3C2/steel and a-CrC/steel were investigated further. All samples was measured and the results obtained from electrochemical impedance spectroscopy (EIS) simulated by the equivalent circuit to interpret the corrosion mechanism of the cryst-Cr3C2/steel and a-CrC/steel were compared. The results indicated that the cryst-Cr3C2/steel more effectively isolates the defects than dose a-C:Cr/steel in saline environment. The cathodoluminescence spectra of the DLC:Cr films are evident in the visible region, thereby shifting the red emission to 1.99 eV. The orange emission at 2.03 eV also appears due to transitions between chromium-related electron levels and σ* states. Additionally, the peak at 2.10 eV likely results from the defective structures in the DLC:Cr films. The effect of Cr doping changed DLC band structure and its consequent cathodoluminescence property.