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

TL;DR

This paper introduces a new Si-B-N ceramic film created through plasma treatment that significantly enhances oxidation and corrosion resistance of Mg-Li alloys, demonstrating long-term protection and stability in harsh environments.

Contribution

The study presents a novel plasma-enhanced chemical vapor deposition method for applying a compact Si-B-N ceramic coating on Mg-Li alloys, improving their corrosion resistance.

Findings

The Si-B-N coating provides protection against oxidation for over 500 days.

The coating prevents observable changes in saltwater immersion tests.

Optimal B2H6 proportion enhances coating stability and reduces bubble formation.

Abstract

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.