Friction properties of protective DLC films on magnesium alloy in aqueous NaCl solution

Friction properties of DLC films deposited on magnesium alloy, AZ31 (Mg-3%Al-1%Zn) were investigated using a ball-on-flat type reciprocal friction tester in aqueous 0.05 M NaCl solution. The DLC, DLC/interlayer and Si-DLC films were prepared on the sputter-deposited AZ31 films on glass substrates using a bi-polar type plasma based ion implantation and deposition (PBII&D). The DLC/interlayer/AZ31 sample shows good friction and wear properties in NaCl solution, but the large corrosion pits were developed on the surface during the friction test in NaCl solution. The low adhesion strength and high internal stress of the DLC coatings on the AZ31 are the reason for the poor corrosion properties in corrosive NaCl solution. The Si-DLC coating on the AZ31 has high adhesion strength and a low internal stress, and no large corrosion pits are observed on the surface after the friction test in NaCl solution. The Si-DLC coating also shows stable friction properties. (c) 2007 Elsevier B.V. All rights reserved.