Existing titanium and titanium alloys are mostly used to make high-end watch parts, jewelry, eyeglass frames and other decorative products. In order to make the surface of pure titanium or titanium alloy has higher hardness and gloss, mostly in pure titanium or titanium alloy surface for hardening treatment. The existing surface hardening methods of pure titanium or titanium alloy are as follows:
1. Atmospheric thermal oxidation treatment: The pure titanium or titanium alloy parts are directly heated in the atmosphere to 750℃ to 1000℃, so that the surface of pure titanium or titanium alloy forms a layer of rutile crystal titanium dioxide (Rutile), the surface hardness can reach Hv1100, but the color of the oxide layer made by this method is gray, no metallic luster, and the surface is rough, when applied to general commercial products, Usually need to do post-processing;
2. atmospheric thermal oxidation + vacuum diffusion treatment: After dealing with the atmospheric thermal oxidation of pure titanium or titanium alloy parts further in vacuum heat treatment furnace, at a temperature between 750 ℃ to 850 ℃ for a period of time, the surface of titanium dioxide crystals decomposition, producing oxygen diffusion way into the crystalline structure of pure titanium or titanium alloy, to create solid solution hardening effect of metal base, oxygen content is higher, the higher the hardness, However, this method will cause the crystallization grain coarseness, resulting in a significant decrease in surface finish, and is not easy to polish;
3. vacuum thermal nitriding diffusion treatment: Nitrogen and a certain proportion of oxygen or water vapor are put into the vacuum furnace, and the temperature is held at 700℃ ~ 800℃ for a period of time under the fixed vacuum pressure, so that nitrogen and oxygen diffuse into the crystalline structure of pure titanium or titanium alloy, so that the surface of pure titanium or titanium alloy parts can produce a hardened layer of nitrogen oxygen solid solution of a certain thickness. This method can obviously improve the coarse grain surface roughness in method 2, but the ratio of nitrogen to oxygen or water vapor and the heat treatment temperature must be carefully controlled in the process, otherwise the surface discoloration and roughness of pure titanium or titanium alloy will occur.
4. ion nitriding method: To pure titanium or titanium alloy parts put in vacuum furnace, high voltage source, and ventilation with nitrogen, nitrogen ions to produce, nitrogen ions attracted to pure titanium or titanium alloy to form the electrodes, electrode surface at high speed bump, produce high temperature made nitrogen atoms into titanium substrate, and the surface produces chemical reaction, formed on the titanium surface diffusion of nitrogen and titanium nitride compound layer, In this method, in addition to the infiltration of nitrogen atoms into pure titanium or titanium alloy, titanium nitride crystal layer is also formed on the surface, so the hardness is much higher than that of oxidation method, but the surface roughness of pure titanium or titanium alloy will be greatly increased. 5, vacuum physical evaporation method: the use of vacuum physical evaporation method, on the surface of pure titanium or titanium alloy directly plated a layer of hard film, although this method does not damage the surface roughness of pure titanium or titanium alloy, but due to the limited thickness of the coating, for pure titanium or titanium alloy this soft substrate and can not provide effective hardening performance. The invention relates to pure titanium or titanium alloy and a surface hardening method thereof.
