Abstract:

         We employed the new technology of chromium free chemical conversion surface treatment and plasma  enhanced  chemical vapor deposition (PECVD) to prepare diamond like carbon (DLC) films by two steps. We initially formed a porous structure on Mg alloy substrate and took a high adhesion film as the transitional layer. We further employed PECVD technology to prepare DLC films with Si-DLC. Scanning electron microscope and Raman spectroscopy demonstrate that the films are uniform, smooth and compact, and composed of layered compounds of C, Si and H. The films also have the same characteristics as DLC. Observation through an atomic force microscope (AFM) shows that  Si-DLC films are more compact than un-doping Si-DLC films. Si-DLC films are the most compact and completely cover the chemical conversion coating. Performance test shows that the intermediate layer between chemical conversion coating and Si-DLC film significantly improves the bond strength between Mg alloy substrate and DLC film. The intermediate layer also dramatically improves wear resistance, high temperature resistance and corrosion resistance capabilities of Mg alloy.

Key words: chemical conversion coating, plasma enhanced chemical vapor deposition, diamond like carbon film, magnesium alloy