The effect of transition-metal seeding powder on deposition and growth of diamond synthesized by hot filament chemical vapor deposition processes on cemented carbide substrates and its characterization

Hot Filament Chemical Vapor Deposition is a well-established method to synthesize diamond thin films on a non-diamond substrate. Here, we have deposited microcrystalline diamond on tungsten carbide cutting tool insert by using conventional Hot Filament Chemical Vapor Deposition technique. The substrates were ultrasonically seeded with Carbon, Diamond, Iridium, Molybdenum, Palladium, Platinum, Tantalum, Tungsten and Chromium natural powders and thereafter were deposited with the same deposition parameters to observe the effects of different seeding powders on the diamond coating. The coated tools were characterized by X-ray Diffraction and the quality of diamond crystals was assessed by using micro Raman spectroscopy. The surface morphology was studied by utilizing Scanning Electron Microscope. The discrete spherical diamond crystals were formed with carbon powder seeding while very dense along with uniform coatings were deposited on the diamond powder seeded substrate. Larger diamond crystals with good density were observed on the palladium seeded substrate. The micro Raman spectroscopy showed mixed results of sp(3) and sp(2) bonding. But the palladium seeding showed clear sp(3) bonding due to the formation of crystals with bigger size. The Vickers microhardness value for the substrate with diamond seeding was found to be much higher than other coated tools.