Chemical Vapor Deposition of Titanium Oxycarbide
Abstract: Ti(C,O) coatings have been generated in a hot wall CVD system on WC/Co, fine and coarse grained Ti(C,N), TiN, Cr and c-BN substrates. The research in this thesis has focused on deposition, characterization, and analysis in the perspective of the bonding layer of a coated insert. The precursors, H2, TiCl4, CO, temperature and pressure have been coupled to the texture using a Design of Experiment software. Samples have been characterized by XRD, SEM and TEM prepared by FIB. Analysis of crystal growth is based on a literature study of Ti(C,N), TiN, TiC and CO adsorption on transition metals. Rare up to 10μm long ”five-ling” multiple twinned crystals have been obtained at a pressure of 0.5 atm and 1000◦C. Favorable crystal growth on the Ti(C,N) substrate in the perspective of a bonding layer in a cutting tool insert was found for 1000◦C, TiCl4/CO≥1 in a H2 rich environment. The lattice parameter at different deposition conditions varied from 4.270 to 4.295 ̊A. Ti(C,O) coatings demonstrate thin, high index grains centered around the (111) twinning boundary, the literature analysis of CO adsorption indicates these are made possible due to the adsorption properties of CO.
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