2009 Volume 22 Issue 4 Pages 485-490
Magnesium alloy sheets were coated with diamond-like carbon (DLC) using low-temperature plasma for the improvement of formability. For the better adhesion between Mg and DLC, Si-containing intermediate layer was necessary. In SEM observation, Si-containing layer formed by tetraethoxysilane (TEOS) plasma exhibited very tight and regular waving pattern, which was inherited to DLC layer deposited successively, and showed good adhesion. From the X-ray photoelectron spectroscopy (XPS) measurement, Si-C bond was found at the interface after DLC coating. Concerning the surface chemical structure, both sp3 fraction and hydrogen content measured by XPS and glow discharge spectroscopy, respectively, decreased with increasing CH4 concentration in the mixed gas with H2 in DLC coating. The friction coefficient was reduced by the TEOS and DLC coating to a compatible level with MoS2 lubricated one, but its clear dependence on CH4 concentration was not found. The formability by deep drawing of DLC coated Mg alloy sheet was as good as that of MoS2 lubricated one.
