Technical Analysis Of Titanium Plate Surface Alloying Modification Process

Surface alloying is an effective means to improve the corrosion resistance, hydrogen embrittlement resistance and wear resistance of titanium plates. This paper systematically introduces the two technical routes of aluminizing process by infiltration method and palladium-plated-laser diffusion alloying, analyzes its process conditions, coating structure and performance advantages, and provides a reference for the application of titanium surface engineering.

Although titanium and its alloys have excellent corrosion resistance and specific strength, in high temperature or hydrogen-containing environments, the surface is prone to oxidation or hydrogen penetration, resulting in performance degradation. By forming an alloying modified layer on the surface of the titanium plate, its interface characteristics can be significantly improved. Compared with the oxide coating coated with palladium, the surface alloying layer and the matrix belong to a metallurgical combination, which has outstanding advantages such as strong binding force, wear resistance, and corrosion resistance. It is an important development direction of titanium surface treatment.

1. Aluminizing Process By Infiltration Method

Aluminizing on the surface of the product can effectively reduce the hydrogen absorption tendency of titanium and form a dense hydrogen penetration barrier layer.

1) Aluminized Formula And Temperature Conditions

After process verification, the better aluminizing conditions are: After mixing 88% alumina (Al₂O₃), 4% aluminum fluoride (AlF₃) and 8% aluminum powder (Al) evenly, it is coated on the surface of the titanium work piece, and the heating temperature is controlled at 810℃.At this temperature, aluminum fluoride acts as an activator, promoting the diffusion of aluminum atoms into the titanium matrix.

2) Coating Thickness And Structure

The thickness and phase composition of the aluminized layer mainly depend on the insulation time. Using the encapsulation method for short-term diffusion treatment, a thin coating of about 2 mm thick can be obtained. The coating is well combined with the substrate and will not adversely affect the mechanical properties of the titanium substrate. The coating is mainly composed of titanium oxide (TiO₂) phase, which forms an effective hydrogen permeability barrier layer, which significantly reduces the risk of hydrogen absorption of titanium in acidic or high temperature and humidity environments.

2. Diffusion Alloying Process Of Palladium-Plated Layer

After the palladium is plated on the titanium plate, the palladium coating can be diffused to the surface area of the titanium matrix by heating to form a titanium-palladium alloying layer, thereby enhancing the corrosion resistance of the material in the reducing acid medium.

1) Heating Diffusion Method

The palladium-plated titanium plate is heated in an appropriate atmosphere, the temperature and time are controlled to diffuse the palladium atoms inward, and the titanium-palladium solid solution or intermetallic compound is formed on the surface, which can significantly increase the surface electrode potential and reduce the tendency to corrosion.

2) Laser Surface Remelting Method

Both heating diffusion and laser surface remelting methods are feasible in principle. Among them, laser remelting technology has more process flexibility: the use of high-energy laser beams to illuminate the titanium surface, so that the pre-vacuum deposited 150 micron thick palladium-plated film quickly melts, and mixes and diffuses with the titanium matrix below, forming a uniform composition of the modified layer of the palladium alloy in the subsequent rapid condensation process. The heat-affected zone of the process is narrow and the deformation is small, and the alloying depth and tissue morphology can be accurately controlled.

3. Conclusion

Aluminization by infiltration method and palladium-plated-laser diffusion alloying are two effective titanium plate surface modification techniques. The former focuses on hydrogen embrittlement resistance, simple process and low cost; the latter focuses on improving corrosion resistance, especially for environments with strong corrosive media. In practical applications, the appropriate scheme can be selected according to the service conditions of the workpiece, or the two processes can be used in combination to obtain composite performance. With the continuous maturity of laser processing and powder embedding technology, the surface alloying process of titanium plate is gradually evolving in the direction of precision and high efficiency, providing a reliable guarantee for the in-depth application of titanium materials in the chemical, marine, nuclear industry and other fields.