Aone Titanium Metal Materials
Research Status and Progress Analysis of Titanium Alloy Surface Strengthening Technology1-3
1, nitriding treatment
Vacuum nitriding is to increase the wear resistance by heating the titanium alloy to a certain temperature and introducing high-purity nitrogen under vacuum conditions. After a period of heat preservation on the surface of the titanium alloy, Ti2 N and TiN nitriding layer, thereby improving the wear resistance. After nitriding, the microhardness can reach above HV1000. Vacuum nitriding is easy to realize, but due to vacuum nitriding, the whole workpiece is heated for a long time at a high temperature, and the volume is low, which easily causes cracking or spalling of the nitride layer, and has the disadvantages of slow nitriding speed, thin layer, and brittle layer. Plasma nitriding is carried out by glow discharge. In the plasma osmotic state, nitrogen ions are accelerated by the electric field and collide with the workpiece. During the process of nitrogen removal, the kinetic energy is converted into heat energy, which increases the temperature of the workpiece and passes through the ion impact. Splashing and diffusion, so that nitrogen diffuses into the surface of the workpiece, up to 1) the purpose of pure nitrogen, to nitriding. In the literature [nitrogen-hydrogen mixed gas, nitrogen-argon mixed gas as the nitriding source, TC4 titanium alloy was treated with ionic nitrogen to TC, and nitrided at 940 °C for 2 h, the surface hardness of the alloy was increased by 4 times. The plasma nitriding surface has good hardness and uniform hardness, but the cost is high and the efficiency is low, which limits the application of this technology in actual production.
2. Vapor deposition
The CVD method deposits the desired compound on a solid titanium substrate by a gas phase reaction. A compact composite coating with a thickness of 15 μm to 25 μm is available for a wide range of applications. Depositing TiC, Ti (C, N) coatings on titanium alloy substrates can greatly improve the surface properties of titanium alloys, and obtain hardness  2 wear resistance, high temperature and corrosion resistant surfaces, but conventional CVD is high. 〔〕 8 〔〕 7 Generally carried out at a higher temperature (100 °C ~ 1 100 °C), it is easy to cause the crystallization of the matrix structure, and then grow up, etc., reduce the strength of the workpiece and affect the shape and size of the workpiece. Therefore, lowering the deposition temperature has become an important issue to be solved.
The PVD method is a physical method of depositing a desired coating on the surface of a substrate, and magnetron sputtering is widely used. At present, TiN, SiC, (C, etc.) can be obtained on the surface of  3 TiC, Ti N) titanium substrate by PVD method. However, PVD method has obvious interface due to the obvious interface between the film layer and the matrix. The thin coating results in many performance indicators that are not ideal.
3, plasma spraying
Plasma spraying heats the spray powder to a molten or molten state, and a high velocity, layer is obtained by spraying onto the surface of the substrate to form a coated plasma jet. The plasma spraying temperature is high and the speed is fast. The coating is not easily oxidized, and the coating with high density can be formed, which can greatly improve the corrosion resistance, wear resistance and oxidation resistance of the material. Zhao et al. treated Ti - 6Al - 4V alloy by plasma spraying to form TiN in situ, which significantly improved the wear resistance of titanium alloy. Plasma spraying has been widely used in the processing of aerospace and civil components, and has broad application prospects in the industry. However, the surface of the coating is rough after spraying, because the spraying speed is high, the spraying is difficult to control, and it is difficult to spray complex parts, which is easy to produce strong ultraviolet pollution.
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