The influence of Tungsten (W) on steel properties
Tungsten (W) is a crucial alloying element in steel, primarily recognized for its ability to enhance hardness, wear resistance, and high-temperature strength. The presence of tungsten in steel leads to the formation of stable carbides, such as WC, which significantly strengthen the microstructure, thereby improving the hardness and wear resistance of the material. Tungsten also contributes to the high-temperature stability of steel, allowing it to maintain strength and hardness under elevated temperature conditions. Due to these properties, tungsten is commonly used in tool steels and high-speed steels, imparting excellent cutting performance and heat resistance to these materials.
Impact of Tungsten on Steel Microstructure and Heat Treatment
Tungsten is a refractory metal, and its behavior in steel is similar to that of molybdenum (Mo). It narrows the austenite phase region and acts as a strong carbide-forming element, partially dissolving in iron. Tungsten’s influence on the hardenability of steel is not as pronounced as that of molybdenum or chromium (Cr). When present as special carbides, tungsten reduces both hardenability and quenching capability. However, these carbides inhibit grain growth, reduce the thermal sensitivity of the steel, and significantly enhance its tempering resistance.

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Tungsten’s Effect on Mechanical Properties of Steel
The inclusion of tungsten in steel enhances tempering resistance, owing to the presence of its highly stable carbides, which also improve the wear resistance of the steel and impart a degree of hot hardness. Tungsten also increases the creep resistance of steel at high temperatures, although this effect is not as strong as that of molybdenum. This makes tungsten an essential component in applications where the steel must withstand prolonged exposure to high temperatures and mechanical stress.
Tungsten’s Influence on Physical, Chemical, and Processing Properties of Steel
Tungsten significantly increases the density of steel and strongly reduces its thermal conductivity. Additionally, tungsten enhances the coercive force and residual magnetic induction of steel. However, tungsten does not have a favorable impact on the corrosion resistance and high-temperature oxidation resistance of steel. Steels containing tungsten exhibit reduced heat resistance at elevated temperatures but improved stability against hydrogen embrittlement. Tungsten-containing high-speed steels tend to have low ductility, high resistance to deformation, and poor hot workability. In high-alloy tungsten steels, there may be segregation of low-melting phases in the as-cast state, necessitating lower forging temperatures and preventing graphite-related defects in high-carbon tungsten steels.
Negative Impacts of Tungsten in Steel
The addition of tungsten to steel can increase the risk of decarburization, as tungsten stabilizes carbides and inhibits the formation of graphite. As a strong carbide-forming element, tungsten can lead to non-uniform carbide distribution, potentially compromising steel performance and resulting in defective products. This issue can be mitigated by increasing the number of forging passes and applying normalization treatments. When the tungsten content exceeds 9%, there is a significant increase in hardness, while ductility and reduction of area (ψ) decrease. Tungsten also lowers the thermal conductivity of steel; when the content exceeds 10%, the thermal conductivity is only about 70% that of pure iron. Additionally, increasing tungsten content reduces the forgeable temperature range.
Tungsten is a powerful alloying element that enhances the hardness, wear resistance, and high-temperature strength of steel. However, its effects on microstructure, heat treatment, and mechanical properties must be carefully balanced to avoid adverse impacts, such as reduced ductility, lower thermal conductivity, and difficulties in hot working. When properly managed, the inclusion of tungsten in steel results in materials that excel in demanding applications, particularly in tool and high-speed steels where cutting performance and heat resistance are critical.