Diamond-like carbon coatings for moulding

• Main Author: Toh, Wei Quan
• Other Authors: Liu Erjia
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/61358
• Institution: Nanyang Technological University

Diamond-Like Carbon (DLC) thin film coatings are a novel type of Carbon materials. Their unique properties such as low coefficient of friction combined with high wear resistance have allowed them to find applications in modern industries. One application is in the field of molding process. The sp3 bonds in DLC are responsible for the mechanical properties and wear resistance of the DLC coatings. The present work is aimed at looking how sp3 affects the coefficient of friction of the coating and how this subsequently affects their wear characteristics like wear rate. A Ti layer was first coated on silicon substrates before DLC was coated with respect to various DC powers applied using DC Magnetron Sputtering system. The effects of doping various elements such as Nitrogen, Platinum and Ruthenium in DLC (PtRuN-DLC) on coefficient of friction and wear resistance were also investigated. The DLC and PtRuN-DLC coatings were characterized by using Raman Spectroscopy and X-Ray Photoelectron Spectroscopy (XPS). The coefficient of friction and wear resistance of the coatings were done through the use of ball-on-disc Tribometer while, further study was done through the use of Confocal Image Profiler and Scanning Electron Microscope (SEM). In Ti interlayer DLC, it was found that the coefficient of friction increased with decreased sp3 content. However, the wear rate decreased accordingly. This may be due to the involvement of the formation of a transfer layer whereby this process of removal requires more time that results in a higher wear resistance [7]. Conversely, in the case of PtRuN-DLC coating, the sp3 content decreased with the usage of N, while the sp2 content increased with increased addition of Pt and Ru. This increase in sp2 content led to the increased coefficient of friction and subsequently, investigation revealed that a higher coefficient of friction led to a higher wear rate.