Optimized pre-coating of equipment used for CVD

In the cutting tool industry, replaceable cutting edge (insert) is often used. As insert support,steel nets are used which are pre-coated before use, since the iron will affect the coatingquality of the inserts. Titanium carbide (TiC) is an ideal material for pre-coating purposes andthe deposition of TiC is performed by chemical vapor deposition (CVD) using a gaseousmixture of TiCl4, CH4 and H2. In order to optimize both the process time and to ensure goodquality, in this master thesis a series of experiments were designed to investigate the influenceof gas flow rates, the CH4/TiCl4 ratio, and the total pressure. The measured parameters werethe coating thickness and the coating quality. The experimental results showed that increasingthe TiCl4 flow rate resulted in an increased coating thickness, but generated HCl has aretarding effect by adsorption. Increasing the CH4/TiCl4 mole ratio led to higher depositionrates, but outgrowth was observed at high ratios. Increasing the total pressure resulted in anincreased deposition rate, but hazardous TiO2 white smoke was observed.The optimal receipt with higher gas flow, CH4/TiCl4 mole ratio, and depositiontemperatures gave a 3.4 μm thick TiC coating after 12.5 h. Compared with the originalprocess, the optimal process obtained in this thesis saved 47 % process time.Surface morphology and grain size were examined using an optical microscope and ascanning electron microscope, and deposited TiC had a grain size of 1-2 μm. Line profileanalysis using energy-dispersive X-ray spectroscopy showed that the coated TiC layerprevented the diffusion of iron and there was no iron on the surface of the coated steel nets