As a novel surface treatment technology, nano processing offers promising opportunities to enhance the surface properties of titanium and titanium alloy materials. By utilizing physical and chemical means, nano processing can refine the surface grains of the material to the nanoscale, effectively addressing issues such as surface fatigue resistance and improving corrosion and wear resistance. Techniques such as shot peening and supersonic particle bombardment are employed to break and refine the surface grains, creating a hardened layer that significantly enhances the material's fatigue resistance.
High-energy shot peening utilizing surface nanotechnology on TC4 titanium alloy achieves a grain size close to 20nm, resulting in improved fatigue resistance due to the hardened layer with higher surface hardness. Similarly, the treatment of TA2 titanium alloy yields a nanosurface with a grain size close to 30nm, forming deformation twins on the surface grains, further enhancing the material's hardening degree. Notably, China's titanium and titanium alloy treatment at 623K surpasses the relevant specifications in the United States, positioning the country at the forefront of this field. However, despite its potential, the widespread adoption of surface nano-processing has been limited due to its relatively recent introduction.
In contrast to surface nano-treatment, surface diffusion, and ion implantation methods involve doping metal or non-metal materials into the titanium alloy matrix to modify its surface composition. This modification, achieved through processes like nitrogen or carbon permeation or diffusion of metals such as aluminum and molybdenum, enhances the wear and corrosion resistance of the titanium alloy matrix. For instance, the corrosion resistance of the TC4 matrix can be effectively improved by incorporating tantalum using the netted cathode glow discharge method. Surface phase structure modification and molybdenum infiltration significantly alter the surface properties of TC6, increasing its surface hardness to 1400HV. The advancement of vacuum technology has led to the emergence of ion implantation technology, which can enhance the surface hardness of TA7 titanium alloy to 1200HV through ion nitriding, and Ti6Al4V alloy to 935HV using arc glow ion treatment without hydrocarburizing, exhibiting strong wear resistance. Furthermore, liquid phase plasma electrolytic carbonitriding technology can deposit a hard coating of Ti on the surface of Ti6Al4V alloy, with the thickness of the hard layer and wear resistance improving with increased treatment time.
Surface coating technology involves applying composite coatings to the surface of the base material, enhancing its performance in chemical and thermal aspects. Coatings deposited through techniques like vapor deposition and cladding effectively improve the wear and corrosion resistance of titanium alloys, reducing production costs and extending the product's service life. The organic integration of surface activation and hydrogenation treatment enhances the surface conductivity of titanium alloys and protects against corrosion when exposed to light rain, for example. Vapor deposition technology enables the creation of TiAIN film layers on TA2 and TC11 substrates, forming a metallurgical bond with the matrix and enhancing various properties of the substrate.
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