The improvement of the oxidation resistance of tungsten tubes needs to start from the material nature modification, surface protection construction, structural optimization design and other aspects, and through the synergistic effect of different technical paths, systematically enhance its ability to resist high-temperature oxidation. First of all, material alloying is the basic means to improve the intrinsic oxidation resistance of tungsten tubes. The introduction of rare earth elements or refractory metals into the tungsten matrix can change the crystal structure through solid solution strengthening and second phase strengthening mechanisms. For example, rare earth elements such as lanthanum and cerium can form a stable oxide film on the surface of tungsten, which is like a dense barrier to prevent oxygen atoms from diffusing inward, while refining the grains to increase the number of grain boundaries and complicate the oxidation path. The addition of refractory metals such as molybdenum and niobium can improve the high-temperature strength of the matrix and delay the grain boundary oxidation process. This modification method strengthens the "foundation" of oxidation resistance from the inside without significantly reducing the mechanical properties of tungsten tubes.
Surface coating technology is an intuitive and efficient means of oxidation resistance, which isolates the oxidizing medium by constructing a protective layer on the surface of tungsten tubes. Physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma spraying and other processes can realize the preparation of coatings with different characteristics. The PVD process is carried out in a low temperature environment, which can avoid affecting the performance of the tungsten tube substrate and prepare ultra-thin coatings with uniform thickness and strong bonding, but the equipment cost is high and the deposition rate is slow. CVD technology generates coatings through gas phase reactions, which are more firmly bonded to the substrate and are especially suitable for all-round coating of complex structures. However, high-temperature processes may change the substrate structure and have strict environmental protection requirements. Plasma spraying is better in terms of wide material adaptability and can quickly deposit thick coatings, but the coating has a high porosity and requires subsequent treatment to improve its density. These coating materials, such as oxides, carbides, borides, etc., each form a "protective armor" with characteristics such as high melting point and low oxygen permeability.
Micro-nano structure design has opened up a new dimension for improving the antioxidant performance of tungsten tubes, and micron or nano-scale rough structures are constructed on the surface through laser processing, electrochemical corrosion and other methods. This structure can increase the surface specific area, promote the more uniform attachment of the oxides generated during the oxidation process, and form a denser natural oxide film. At the same time, the pores and grooves of the micro-nano structure can store a small amount of antioxidants or lubricants, which are released and participate in the reaction at the beginning of oxidation, slowing down the oxidation rate. The introduction of the concept of bionics further optimizes the structural design. For example, by imitating the surface texture of high-temperature resistant organisms, the micro-nano structure has better stability and self-repair ability at high temperatures, and the passive defense ability of anti-oxidation is enhanced by optimizing the physical morphology.
The optimization of the heat treatment process is an important auxiliary means to improve the antioxidant performance of the tungsten tube. The internal organization state is improved by vacuum annealing, hydrogen reduction and other methods. Vacuum annealing can eliminate the internal stress generated during the processing of the tungsten tube in a low temperature environment, reduce the formation of oxidation starting points at the grain boundaries, and make the grain size uniform, thereby improving the structural stability. Hydrogen reduction treatment can purify the surface of the tungsten tube, remove adsorbed oxygen atoms and impurities, reduce the surface active sites, and make the tungsten tube have a stronger antioxidant initiation ability in the initial state. Reasonable control of the temperature, time and atmosphere of heat treatment can densify the matrix structure, reduce defects such as pores and cracks, and improve the overall anti-oxidation consistency of the material from the inside.
Environmental adaptability design is a targeted optimization strategy based on the use scenario, which needs to comprehensively consider factors such as oxygen partial pressure, temperature fluctuations, and corrosive media. In a high oxygen partial pressure environment, tungsten tubes with a high degree of alloying or thicker coatings are preferred to enhance active anti-oxidation capabilities; in scenarios where the temperature changes frequently, the thermal expansion coefficients of the coating and the substrate need to be matched to avoid coating peeling due to thermal stress. In addition, the passive protection design of the external environment is equally important, such as setting up a gas protection device or creating an inert atmosphere environment to reduce the oxygen concentration around the tungsten tube and minimize the external driving force of the oxidation reaction. This "internal and external combination" approach can significantly improve the service life of the tungsten tube under harsh conditions.
Composite anti-oxidation technology achieves performance breakthroughs through the synergistic effect of multiple means, such as the dual protection system of "alloyed substrate + multi-layer composite coating". First, the tungsten tube is alloyed with rare earth or refractory metals to improve the antioxidant capacity of the substrate itself, and then a bonding layer, a transition layer and an outer protective layer are prepared on the surface in sequence. The inner metal molybdenum layer can enhance the interfacial bonding between the coating and the substrate, the intermediate transition layer such as tungsten-molybdenum alloy can relieve the stress caused by the difference in thermal expansion coefficient, and the outer ceramic layer (such as aluminum oxide) directly resists the erosion of the oxidizing medium. This multi-level structure complements the characteristics of different materials to form a three-dimensional protective network from the inside to the outside, so that the antioxidant performance can be improved by leaps and bounds, especially for extreme environments such as aerospace and high-temperature industries.
Process compatibility and reliability verification are key links to ensure the implementation of antioxidant technology. In practical applications, the mutual influence between the various processes must be fully considered. For example, the high temperature of coating preparation may disturb the organization of the alloyed tungsten tube, and the negative impact must be eliminated through intermediate annealing or parameter adjustment. At the same time, through verification methods such as high-temperature oxidation experiments and long-term service simulations, quantitative evaluation of indicators such as oxidation weight gain, surface morphology changes and mechanical property attenuation is carried out to provide data support for technology optimization. Only solutions that have undergone strict process adaptation and reliability verification can play a stable role in practical applications, ensure the safe and reliable operation of tungsten tubes in high-temperature oxidation environments, and achieve effective transformation from laboratory technology to engineering applications.
