Review of possibilities of increasing the thickness of an anti-wear coating on piston rings by using specifically designed physical vapour deposition process

The super-hard, anti-wear amorphic coatings based on carbon-like diamond (called DLC) show a promising direction in automotive industry, mainly in terms of decreasing friction coefficient in parts of internal combustion engine. However, the technology of producing DLC-coated parts, which is most often chemical vapour deposition (CVD) or physical vapour deposition (PVD) is proven to be still not perfect for achieving desired characteristics of the coating. The thickness of a coating is the main issue one should strive to improve, as the PVD methods produce films as thin as few micrometres. In such case, the coating is not only exposed to cracking, but also pitting is possible to happen. This is proven to be highly undesirable and unacceptable for this process. In addition, in case of thin films, the adhesion to the base is often too weak, despite the coating itself being extremely durable and hard. In this article, a theoretical ways to improve the process of coating are presented. The process itself is described, the achievable parameters are defined and the possible improvements are stated. The research made for the purpose of this article will be further exploited to design a process allowing creating the coating for testing of the best possible characteristics.