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Tantalum Performance Significantly Pulled High
Oct 12, 2017

China developed the high temperature alloy K438 contains 1.5% to 2.0% Ta, K409 contains 4.0% to 4.5% Ta, K4002 contains 2.25% to 2.75% Ta. US-made nickel-based superalloys IN738LC, IN939, IN792, M22, MM-002, MM-005, MM-006 and MM-011 contain 1% to 4% Ta, PWA1480 contains 12% Ta. Tantalum is a strategic element that is expensive and should be used as little as possible. Tantalum in the nickel-based superalloy in about 80% into the γ 'phase, Tantalum enhanced γ' phase of the strengthening effect, about 10% to 15% of the formation of Ta-rich MC carbide, only about 5% to 10% into the γ solid solution, solid Solubility. Like Nb, the atomic radius of Ta is also large, 15% to 18% larger than Ni, Co and Fe atoms. Therefore, the addition of nickel-based solid solution, Tantalum causing a greater increase in lattice constant. The resulting elastic stress field poses a greater resistance to the dislocation movement, and at the same time, Ta also reduces the stacking fault of the γ solid solution, so that the instantaneous tensile strength and creep performance of the γ solid solution are obviously increased.

The results show that with the increase of the tantalum content in the alloy from 1% to 6.4%, the tensile strength increases at 760 ℃, the plasticity improves, the creep resistance is improved, Tantalum and the creep rupture time is improved. The tantalum content on the mechanical properties and microstructure of the K409 alloy shows that extend. The tantalum in the alloy enters the γ 'phase, increases the γ' phase, the number and the dissolution temperature of the γ 'phase, changes the composition of the γ' phase, the size of the γ 'phase, Tantalum increases the γ' phase precipitation strengthening effect, In order to distinguish the effect of solid solution strengthening and precipitation strengthening, the components containing Ta and Ta-free γ-austenite were analyzed by phase analysis, respectively, and the contents of Ta and Ta-free The content of austenite matrix alloy in γ austenite is increased from 30% to 38.5% by the sum of Cr + Co + Mo. K409 alloy matrix containing 1% Ta, these large Ta atoms, Tantalum combined with increased content of Cr, Co and Mo atoms, is bound to cause a large elastic stress field, while the γ austenite matrix layer error The creep life of the Ta-containing austenitic matrix alloy is greatly prolonged, and the creep plasticity is improved obviously, that is, the solid solution strengthening of Ta and the increase of Cr, Co and Mo contents caused by Ta. At the same time, the instantaneous tensile strength and plasticity are also greatly improved. Ta also significantly improved the thermal corrosion resistance and hot and cold fatigue properties of the alloy. Tantalum In the range studied, the higher the Ta content, Tantalum the better the thermal corrosion resistance and the hot and cold fatigue resistance. In the cobalt-based sheet alloys MM-918 and S-57 used at high temperatures, W has been successfully substituted for W, and the oxidation resistance is remarkably improved.

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