The Ta-W-Hf-Re-C alloy is composed of the following elements in mass percentage: W 6%–8%, Hf 3%–5%, Re 0.8%–0.9%, C 0.3%–2%, with the balance being Ta and unavoidable impurities. This invention also discloses a method for preparing Ta-W-Hf-Re-C alloy rods, which includes: 1. Molding after homogenizing the raw material powder; 2. Vacuum high-temperature sintering; 3. Vacuum electron beam melting; 4. Die forging. This invention improves the alloy's corrosion resistance, high-temperature performance, and processing properties by adding Hf to form a stable oxide. The addition of Re and C improves the alloy's creep strength, making it suitable for operation in extreme environments such as ultra-high temperature and ultra-high pressure. The preparation method of this invention promotes alloy homogenization, avoids significant volatilization of Hf, and ensures the performance of the Ta-W-Hf-Re-C alloy rods.
High neutron flux radiation, and potential contact with liquid alkali metal coolants. This necessitates materials with high high-temperature creep resistance, good corrosion resistance, high high-temperature endurance strength, and fracture toughness. Traditional nickel-based and cobalt-based high-temperature alloys cannot meet these requirements. High-tungsten tantalum alloys are a crucial and widely used high-temperature, high-strength material among tantalum alloys. They are continuous solid solution single-phase binary alloys composed of high-density, high-melting-point tantalum and tungsten, and are typical solid solution-strengthened alloys. Due to their high density, high melting point, corrosion resistance, and good machinability and weldability, they have been increasingly applied in weaponry, aerospace, and other fields in recent years, operating in extremely harsh environments. Currently, the most mature high-tungsten tantalum alloys used in my country are Ta10W and Ta12W. These alloys have high room-temperature strength, good plasticity, and high-temperature strength, but they all suffer from poor oxidation resistance. Tantalum is a highly reactive metal that readily absorbs oxygen when exposed to air above 300°C. Tantalum-tungsten alloys themselves have poor oxidation resistance, beginning to oxidize at 600°C. Therefore, the strengthening mechanism of such alloys is easily compromised in extreme oxygen environments such as high-speed airflow erosion and extreme temperatures. Furthermore, the creep resistance of tantalum-tungsten alloys drops sharply when the operating temperature exceeds 1100°C. Therefore, to meet the power requirements of future deep space exploration, it is essential to develop new high-temperature structural materials.
This paper presents a Ta-W-Hf-Re-C alloy. By adding Hf to the tantalum-tungsten alloy matrix to form a stable oxide, this alloy improves its corrosion resistance, high-temperature performance, and processing properties. It maintains excellent ductility and strength over a wide temperature range from low to high. Simultaneously, the addition of Re and C effectively improves the creep strength, making the alloy suitable for operation in extreme environments such as ultra-high temperature, ultra-high pressure, high-speed airflow erosion, and rapid heating and cooling. To solve the above-mentioned technical problems, a Ta-W-Hf-Re-C alloy is provided, characterized by comprising the following elements in mass percentage: W 6%–8%, Hf 3%–5%, Re 0.8%–0.9%, C 0.3%–2%, with the balance being Ta and unavoidable impurities.
The addition of hydrogen sulfide (Hf) to the tantalum-tungsten alloy matrix forms a stable oxide that is virtually immune to alkali metal corrosion, significantly improving the alloy's corrosion resistance, especially its high-temperature corrosion resistance. This raises the alloy's resistance temperature to liquid metals K, Na, and Li to 1260℃. Simultaneously, due to Hf's strong affinity for oxygen, the addition not only strengthens the alloy through solid solution but also promotes the formation of oxides from Hf and oxygen, reducing the adverse effects of oxygen on the alloy's properties. This results in a significant improvement in the alloy's high-temperature and processing properties. Within a temperature range of -160℃ to 1370℃, the alloy maintains excellent ductility and strength, making it suitable for operation in extreme environments such as ultra-high temperatures, ultra-high pressures, high-speed airflow erosion, and rapid heating and cooling. Furthermore, this invention refines the grain size by adding refractive index (Re) and effectively improves the creep strength of the alloy by adding carbon (C) to form a second-phase Ta₂C phase that pins dislocations, hindering dislocation movement.
The raw material powders are mixed and pressed into strips, then sintered under vacuum at high temperature to obtain sintered billets. These billets are then subjected to three rounds of vacuum electron beam melting and die forging to obtain Ta-W-Hf-Re-C alloy rods. This invention, by employing a vacuum high-temperature sintering process, effectively removes carbon, oxygen, nitrogen, and hydrogen gaseous impurities, as well as low-melting-point and volatile elements, from the billets. Simultaneously, pre-alloying is completed. Combined with three rounds of vacuum electron beam melting, this promotes alloy homogenization, effectively preventing the excessive volatilization of Hf and the introduction of impurity elements, thus ensuring the composition and content of the Ta-W-Hf-Re-C alloy and guaranteeing the performance of the Ta-W-Hf-Re-C alloy rods.
The particle size of the tantalum powder, tungsten powder, hafnium powder, rhenium powder, and carbon powder all does not exceed 60 mesh, and the purity of each is not less than 99.5%. This invention improves the uniformity of the alloy by controlling the particle size of each raw material powder to ensure uniform mixing. Simultaneously, using high-purity raw material powders avoids introducing large amounts of impurities at the source, further guaranteeing the alloy's composition. A V-type mixer is used for mixing, with a mixing time of 24 hours. A pressure press is used for molding. The use of a V-type mixer and a limited mixing time promotes thorough and uniform mixing of the raw material powders; the use of a pressure press provides good pressing results and is easy to implement.
