Thermal Oxidation Promotes Growth of Nanocrystalline Diamond on Co-Cr-Mo Alloy

Abstract

Diamond coatings are employed to yield significant benefits in applications such as for cutting tools, optical lenses, biomedical components, microelectronics, engineering and thermal management systems. Although there are many research reporting the successful of diamond coating on titanium, tungsten carbide and steel alloys but there are still lacking of research on the cobalt based alloy as the substrate. In order to coat thin film diamond on these metals substrate, chemical vapor deposition (CVD) technique is commonly used. This paper reports on investigations of nano-crystalline diamond (NCD) coating on different carbon content (0.24% and 0.03%) of cobalt based alloys. Emphasis is given to achieve good adhesion of NCD coating on low and highcarbon content of biomedical grade cobalt-chromium-molybdenum (Co-Cr-Mo) alloys using two different processes of surface pretreatment such as mechanical roughening and thermal oxidation. The results revealed that most of the diamond coating was peel-off on the roughened samples. However, there were small portion of diamond coating that still intact on sample that treatedusing thermal oxidation. The thickness diamond coating obtained was approximately 5µm on oxidized samples. Since the adhesion strength of the diamond coatings were very poor and easily delaminated on all samples condition, scratch test could not be performed. Surface morphology and characterization of diamond coatings were investigated by Field Emission Scanning Electron Microscopy (FESEM) and X-ray diffraction respectively.