A Novel Compact Si-B-N Barrier on Mg-Li Alloys via Plasma Treatment.

Mg-Li alloys have attracted much attention due to their superior properties. However, it is a great challenge to improve their inferior oxidation and corrosion resistance. We report a novel Si-B-N ceramic film deposited on the Mg-9.6Li alloy surface as an effective barrier against oxidation and corrosion. The films were deposited by using plasma enhanced chemical vapor deposition from a N2-B2H6-SiH4 gas mixtures, showing compact structure and adhesive attachment to the alloy surface. The barrier revealed excellent protection against oxidation in humid air for 500 days, and no observable changes were found in immersion test of the 3.5 wt.% NaCl solution for 10 min. The superior oxidation and corrosion resistance are attributed to the excellent material property of Si-B-N coatings with compact structure via plasma treatment. Moreover, it is found that moderate proportion of B_2 H_6 in the source gas mixture is beneficial to the protection of alloys, where the hydrogen release reaction nearly disappeared and no bubbles were generated on the surface in the immersion test.