Improvement of Surface Properties of Aluminum Alloy-Based Composites by Multi-Layer DLC Coating

In recent years, it has been a challenge for the transportation sector to reduce the weight of vehicles for higher fuel efficiency. This expands the use of light metals such as Al alloys. However, these materials have low hardness and surface strength. In this study, Al-alloy (AC8A; Al-Si-Cu-Ni-Mg) composites reinforced with Al2O3 fibers were used as base materials and were coated with multilayer diamond-like carbon (DLC) films to improve their properties. The multilayer DLC films were deposited on the Al alloy composites by radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) using methane and acetylene gases as the raw materials. As the number of DLC film layers increased, the Young's modulus of the samples decreased and the following ratios of hardness (H) to elastic modulus (E) also increased: H/E, H-3/E-2, H-2/E. In addition, the critical number of peeling slides increased as the composite volume fraction and the number of layers increased.