Titanium wire forms a stable carbide with carbon with high hardness. The growth of the carbide layer between the titanium and carbon is determined by the rate of diffusion of titanium in the carbide layer.
The solubility of carbon in titanium is small, totalling 0.3% at 850X: and falling to approximately 0.1% at 600C. B Because of the small solubility of carbon in titanium, surface hardening is essentially only achieved by the deposition of a layer of titanium carbide and its underlying forsaken domains. Carburising must be carried out under the condition of removing oxygen, because the surface hardness of the surface layer formed by the powder commonly used for steel carburising against carbon monoxide or carbon monoxide containing oxygen reaches 2,700MPa and 8,500MPa, and the surface hardness of the surface layer reaches 2,700MPa and 8,500MPa, and the surface hardness of the surface layer reaches 2,700MPa and 8,500MPa. It flakes off easily.
In contrast, a thin layer of titanium carbide may be formed when carburising charcoal under deoxygenated or decarburised conditions. The hardness of this layer is 32 OUOMPa, which corresponds to the hardness of titanium carbide. The depth of the carburised layer is roughly greater than the depth of the nitrided layer when nitriding with nitrogen under the same conditions. Under oxygen-enriched conditions it must be taken into account that oxygen absorption affects the depth of hardening. Only at very thin layer thicknesses, in a vacuum or in an argon-methane atmosphere, can sufficient adhesion strength be formed by carburising powder. In contrast, the use of gaseous carburising agents may result in a particularly hard and well-bonded hardened layer of titanium carbide. At the same time, hardened layers formed at temperatures between 950 T: and 10201: were between 50 fim and 50 fim. As the layer thickness increases, the titanium carbide layer becomes brittle and tends to flake off.t In order to avoid the intrusion of carbon inclusions into the titanium carbide layer due to the decomposition of raffinose, gas carburisation should be carried out in an inert gas using a prescribed dose of additive with a volume fraction of approximately 2% raffinose. When methane carburising is used with propane additives, a lower surface hardness develops. When gas-carburised propane is used at bonding forces of up to 100 kPa, the hardened layer thickness measured is very thin, but it has the best wear resistance. Hydrogen is absorbed in the case of gaseous carburising agents, but has to be removed again during vacuum annealing.
