The oxidation resistance of tungsten-nickel-iron alloy refers to its ability to resist oxidation reactions in an oxygen-containing environment and avoid performance degradation due to oxidation, which is crucial for the application of the alloy in high-temperature environments or long-term exposure to air. Its oxidation resistance is mainly determined by component characteristics, the formation and stability of oxide films, and environmental factors.
In terms of composition, tungsten has strong oxidation resistance at room temperature, and a dense tungsten trioxide (WO₃) film is easily formed on its surface. This oxide film can effectively prevent oxygen from further diffusing into the interior, thereby inhibiting the continuous oxidation of tungsten. However, in high-temperature environments (above 500℃), WO₃ will gradually volatilize, causing the oxide film to lose its protective effect, and the oxidation rate of tungsten will accelerate. Nickel has excellent oxidation resistance. In the environment from room temperature to medium and high temperatures, a stable nickel oxide (NiO) film will form on the surface, which can effectively block oxygen. Moreover, the NiO film has a high melting point and stable structure, and is not easy to crack or volatilize even at higher temperatures. Iron is easy to oxidize at room temperature to form iron oxide (Fe₂O₃ or Fe₃O₄), but the formed oxide film is relatively loose and cannot effectively prevent oxygen from invading, so the oxidation resistance of pure iron is poor. In tungsten-nickel-iron alloy, the existence of nickel not only forms a stable oxide film itself, but also forms a solid solution with iron, improving the oxidation behavior of iron. At the same time, the high content of tungsten also provides a basic oxidation-resistant framework for the alloy. The synergistic effect of the three makes the overall oxidation resistance of the alloy better than that of single iron or tungsten.
Ambient temperature has a significant impact on the oxidation resistance of the alloy. In dry air at room temperature, the oxidation of tungsten-nickel-iron alloy is very slow, and it can maintain a stable surface state for a long time; when the temperature rises to 300 – 500℃, the oxidation rate of iron begins to accelerate, but due to the protective effect of nickel, the overall oxidation degree of the alloy is still low; when the temperature exceeds 600℃, the oxide film of tungsten begins to volatilize, and although the oxide film of nickel can still play a certain role, the overall oxidation resistance of the alloy will decrease significantly, and oxidation spalling may occur on the surface; at higher temperatures (such as above 800℃), the oxidation reaction intensifies, and the alloy will become loose in structure and reduce in strength due to severe oxidation.
In addition, other factors in the environment can also affect oxidation resistance. For example, in humid air or air containing corrosive gases (such as sulfur dioxide, chlorine), the oxidation rate of the alloy will accelerate because these substances will damage the integrity of the surface oxide film; in inert gas or vacuum environment, oxidation reaction hardly occurs, and the alloy can maintain good stability.
In practical applications, the oxidation resistance of tungsten-nickel-iron alloy makes it suitable for various environments. In the fields of mechanical manufacturing and electronic equipment at room temperature, its oxidation resistance can ensure that components do not rust after long-term use; in industrial environments with medium and low temperatures (below 500℃), such as some non-high-temperature components of aerospace equipment, the alloy can resist oxidation erosion; but in high-temperature oxygen-containing environments, the alloy needs to be surface treated (such as coating anti-oxidation coating) to enhance its oxidation resistance and expand the application range. By optimizing the composition ratio (such as appropriately increasing nickel content) and improving the preparation process (such as increasing density), the oxidation resistance of the alloy can be improved to a certain extent to meet the needs of different scenarios.
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