The titanium wire forms a stable carbide with higher hardness with carbon. The growth of the carbide layer between titanium and carbon is determined by the diffusion rate of titanium in the carbide layer.
The solubility of carbon in titanium is small, which is 0.3% at 850X, while it drops to 0.1% at 600C. Because the solubility of carbon in titanium is small, the purpose of surface hardening is basically achieved only through the titanium carbide layer and the deposition layer in the lower region. Carburizing must be carried out under the condition of deoxidation, because the hardness of the surface layer formed by the powder commonly used for steel carburizing against the carbon monoxide or oxygen containing carbon monoxide surface reaches 2700MPa and 8500MPa, and it is easy to peel off.
In contrast, under deoxidation or decarburization conditions, a thin layer of titanium carbide may be formed when carburizing in charcoal. The hardness of this layer is 32OUOMPa, which is consistent with the hardness of titanium carbide. The depth of carburized layer is generally greater than that of nitrided layer under the same conditions. Under the condition of oxygen enrichment, the influence of oxygen absorption on hardening depth must be considered. Only under the condition of very thin layer thickness can carbon powder be infiltrated into the air or argon methane atmosphere to form sufficient adhesion strength. In contrast, the use of gas carburizing agent may form a particularly hard and well cohesive titanium carbide hardened layer. At the same time, the hardening spread formed at the temperature between 950T: and 10201: is between 50fim and. With the increase of the layer thickness, the titanium carbide layer becomes more brittle and tends to peel off. In order to avoid the carbon inclusion invading the titanium carbide layer due to the decomposition of rimane, the specified amount of additives with a volume fraction of about 2% rimane should be used for gas carburizing in inert gas. When propane additive is used and methane is used for carburizing, lower surface hardness is formed. When the bonding force reaches 90 kPa and the propane carburized by gas is used, although the measured thickness of the hardened layer is very thin, it has the best wear resistance. Hydrogen is absorbed under the condition of using gas type carburizing agent, but it has to be removed again during vacuum annealing.