Multi-layered tetrahedral amorphous carbon (ta-C) thick coating deposited by FCVA to enhance wear resistance in sliding contact

摘要

In recent years, the driving environment of the engine has become very harsh due to the issue of miniaturization and lightweight of automobile component parts. Especially, the piston ring, which is the one of the greatest reduction factor of the engine efficiency as shown in Fig.1.It is necessary to increase the wear resistance in a severe environment. Unfortunately, the geometrical and kinematic element of the materials has already been determined. Therefore, Diamond-like carbon (DLC) coating may have potential for tribological applications due to its excellent mechanical and tribological properties. Among the DLC coatings, tetrahedral amorphous carbon (ta-C) films attract more attention recently as a good thermal resistance, wear protection due to the hydrogen-free carbon coating with 70～80% of sp~3 phase. Moreover, ta-C coating can be synthesized through a relatively convenient method, and the surface is much smoother, the tribological performances of ta-C coating are superior to that of DLC. However, ta-C has limited tribological applications. It is related to high compressive stress of ta-C coatings, which can lead to bucking induced poor adhesion. In past our research, we were able to grow thick ta-C coating up to 20 μm thickness of single layer coating using FCVA (Filtered Cathodic Vacuum Arc) as shown in Fig. 2. The key technologies to reach that thickness level were control of substrate temperature and residual stress through multiple coating cycles. However, it is still necessary for further and to enhanced the study on wear resistance for ta-C coating. In this study, to enhance the wear resistance of ta-C coating, multi-layer (soft-layer and hard-layer mixed) have been prepared by the FCVA. The concepts of the multi-layer deposition, the specific thickness ratio of the hard layer to the soft-layer were deposition achieve the hardness and elastic modulus.