Super Alloy

What Is Super Alloy?

Super Alloys is one of the important end products of molybdenum. Usually include: titanium-based alloys, nickel-based alloys, cobalt-based alloys and iron-based alloys containing refractory metals such as molybdenum. Some people also classify molybdenum-based alloys as super alloys. Super alloys have high strength, high hardness, high corrosion resistance, high thermal stability and good workability, and are widely used in aviation, aerospace, automotive, medicine, chemistry, petrochemical, coal chemical and high temperature industries.

Application of Super Alloys

Super alloys have high strength, high hardness, high corrosion resistance, high thermal stability and good workability, and are widely used in aviation, aerospace, automotive, medicine, chemistry, petrochemical, coal chemical and high temperature industries.

More and more studies have shown that superalloys can meet the requirements for high-performance materials in various industries, medicine, and sports that are developing day by day, and thus become a hot spot for molybdenum metallurgists and researchers.

According to the World Metal Statistics report, the demand for super alloys in the world’s industrialized countries is increasing. In 2000, US superalloys consumed 1,880t of molybdenum, 2229t of molybdenum in 2001, 1880t of molybdenum in 2002, and 1870t of molybdenum in 2003. The average annual consumption of molybdenum accounts for about 8% to 12% of total molybdenum consumption.

Molybdenum-based superalloys are mainly used in high-temperature fields, and the consumption of various molybdenum-rhenium alloys accounts for about 0.7% to 1.0% of the total consumption of molybdenum.

Gas Turbine Blades

Kansai Electric Power Corporation, Nagoya University and Hitachi have developed a new type of nickel-based single-crystal superalloy for gas turbine blades. The high temperature resistance value of this material has set a global record of 1400°C. It is mostly used for power generation at around 1300°C. If the new alloy is used, it can withstand high temperatures above 1500°C, so the temperature at the entrance of the turbine can be increased and the thermal efficiency can be improved. In order to produce alloys with high temperature resistance, high strength and corrosion resistance, Nagoya University applied the “Molecular Orbital Method” for analyzing the molecular structure of substances to the design of alloys for the first time in the world, designing the combination of various metal elements. By modifying the composition ratios of alloying elements such as cobalt, chromium, tungsten, aluminum, titanium, tantalum, clamp, and hafnium based on nickel, the optimal alloy material was developed. If this superalloy is used in gas turbine blades, it can achieve 1500°C combustion at a combustion temperature that greatly exceeds 1300°C. As a result, the power generation efficiency (the highest calorific value standard) can be increased from the highest 49% to 55%, and the cost of power generation based on fuel costs can be reduced by about 11%. If the utilization rate is set to 50%, it is estimated that 600,000 KW-class thermal power plants generate electricity per unit, which can save about 1 billion yen per year, reduce CO2 emissions by about 11%, and reduce about 100,000 tons per year.

The Classification Of Super Alloy

Titanium-based alloy

James A. Davidson and others have developed a series of new titanium-molybdenum-hafnium-based alloys. The alloy contains 5% to 11% of molybdenum (mass fraction, the same below), 6% to 15% of hafnium, at least one of titanium, chromium and silicon, and the content is 2% to 3%. Oxygen, nitrogen, hydrogen and carbon are trace amounts. The rest is titanium. The above-mentioned titanium-based alloys exhibit high strength, high hardness, low modulus of elasticity, high corrosion resistance and hardened surfaces, which can be hot-worked or cold-worked.

The reason why molybdenum is added to titanium-based alloys is that adding molybdenum can effectively reduce the modulus of elasticity of the alloy. Adding 6% molybdenum is equivalent to adding 16% niobium. In addition, adding molybdenum can significantly improve the corrosion resistance of titanium-based alloys, especially in reducing acid environments and low pH environments. Because it can produce passive molybdenum oxide film. Zirconium can also improve the corrosion resistance of the alloy, but it is not as good as hafnium, and the matching of hafnium and molybdenum is better.

This new type of titanium molybdenum hafnium alloy is particularly used in medical implants and medical equipment. Such as dental implants, intraosseous implants, intraperiosteal implants, endometrial implants, permanent implants, jaw periosteal plants, vascular implants, arterial clips, vascular filters, valve rings , Heart valve, artificial heart, ventricular muscle device, coil and bone splint, etc. In non-medical fields, it is widely used as oil drilling equipment, golf clubs, various fasteners, etc.

Nickel-based alloys

Nickel-based alloys are the most important and commonly used super alloys. As early as the middle of the 20th century, it was widely used in the chemical industry and the chemical industry. Molybdenum can significantly improve the corrosion resistance and mechanical properties of nickel, especially in reducing acids, such as acetic acid, hydrochloric acid or phosphoric acid. However, in order to further improve the corrosion resistance of the nickel-based alloy and the thermal stability of the alloy, 20% to 25% of molybdenum (atomic fraction, the same below) should be added. For a long time, when adding molybdenum to nickel to increase to 19%, the operation is very difficult, and this nickel-molybdenum alloy can hardly be processed into commercially available profiles (thick plates, thin plates and pipes). After years of hard work, Haynes International’s R&D personnel have developed a new nickel-based alloy with high molybdenum and almost no copper.

The new nickel-based alloy is prepared by casting the above alloy elements into electrodes, then electroslag remelting the electrodes into ingots, hot forging the alloy ingots into sheet steel, hot rolling into medium and thick plates, and finally cold rolling into thin plates. The thermal stability, strength, hardness, and corrosion resistance of the new nickel-based alloy are significantly improved compared with the performance of the current nickel-based alloy. It is widely used in the manufacture of chemical equipment, pipes and valves. It is a high-quality, high-grade new alloy material.

Iron-based alloy

Iron-based alloys usually contain 6% to 10% (mass fraction) of molybdenum. It has high corrosion resistance, high strength at high temperatures, and high hardness. It is widely used in industrial fields, such as automobiles, ships, and military industries. As we all know, due to the increasing importance of ecological and environmental protection, the regulations on automobile exhaust emissions are becoming more and more stringent, which requires engines, especially large diesel engines, to operate at high temperatures and high combustion pressures. Future diesel engines must enforce exhaust gas circulation. Operation (ie, EGR operation is used). Therefore, certain parts of the engine, such as valve seat inserts, are resistant to high temperature, high pressure, and corrosion. L.E.Junes introduced a new type of iron-based alloy. The alloy contains 0.005% to 0.5% of boron (mass fraction, the same below), 1.2% to 1.8% of carbon, 0.7% to 1.5% of vanadium, 7% to 11% of chromium, 1.0% to 3.5% of niobium, and 6% to 11 of molybdenum. %, the rest is iron. Niobium can be replaced by titanium, zirconium, hafnium and tantalum.

Molybdenum-based alloy

Molybdenum-based alloys show high strength and very stable mechanical properties at high temperatures, and are widely used in high-temperature industrial fields. Such as high-temperature heating elements, radiation heating shields, induction furnaces for sensing rings, rotating X-ray cathodes, glass melting furnace electrodes, anti-creep boats for sintering, high-temperature springs, high-strength reinforced fibers, high-strength ballistic tubes, runner sputtering coatings Layers and builds into line coatings and high-end automobile piston ring coatings. Due to the excellent high-temperature thermal properties of molybdenum-based alloys, its price is much cheaper than other refractory metals such as tantalum, niobium and tungsten. Therefore, the development of molybdenum-based alloys with better performance is more concerned by the industry. In recent years, researchers from the US Department of Energy have developed several new types of molybdenum-rhenium alloy products.

Generally, in the copper-molybdenum separation process, the biggest problem is the relationship between copper minerals and molybdenum minerals. One is because copper minerals and molybdenum minerals are closely connected, and the other is the flotability of copper minerals and molybdenum minerals. The sex is closer. The consequence is that the amount of sodium sulfide is large, and the copper content in molybdenum concentrate is high. Because of this, in the national standard of molybdenum concentrate product quality, molybdenum concentrate from a single molybdenum mineral and molybdenum from copper-molybdenum ore are by-produced. The requirements for impurity elements such as copper in the concentrate are different. Molybdenum concentrates recovered from copper concentrates generally contain copper. Molybdenum concentrates produced by Dexing Copper Mine generally contain copper from 1% to, sometimes higher. For this ore sample, the reason for the low copper content of molybdenum concentrate is that molybdenum minerals are mainly connected with gangue minerals and are not closely related to metal minerals.