APOLICATION TECHNOLOGY

As one of the representatives of high-temperature alloys, molybdenum-based alloys have been widely used in aerospace, nuclear industry, chemical industry, and other fields. However, there are still some limitations in the mechanical properties and high-temperature stability of molybdenum-based alloys, which has prompted researchers to explore new alloy design strategies and methods of adding alloying elements. Rhenium, as a high-melting point and high-density transition metal, possesses excellent oxidation resistance and corrosion resistance, and thus has been extensively applied in high-temperature alloys. Studies have shown that the addition of rhenium to molybdenum-based alloys can significantly improve the strength, plasticity, and high-temperature stability of the alloys. Furthermore, molybdenum-rhenium alloy materials have broad prospects in aerospace, nuclear industry, and other fields due to their high strength, high temperature durability, and good corrosion resistance. This article will introduce the strengthening effect of rhenium in molybdenum-based alloys and discuss the application prospects of molybdenum-rhenium alloy materials.

By adding rhenium to tungsten, the tungsten-rhenium alloy benefits from the "rhenium effect" and demonstrates a range of excellent properties including high melting point, high hardness, high strength, high ductility, high electrical resistivity, high thermoelectric potential, high recrystallization temperature, low vapor pressure, low electron emission work function, and low ductile-to-brittle transition temperature.

High-temperature alloy, also known as heat-resistant alloy or superalloy, refers to a type of metallic material that is composed primarily of iron, nickel, and cobalt. It is capable of long-term operation under high temperatures of 600℃ or above, as well as certain levels of stress. High-temperature alloys possess high strength at elevated temperatures, good oxidation and corrosion resistance, as well as excellent performance in fatigue and fracture toughness. Based on the matrix composition, they can be categorized into three types: iron-based, nickel-based, and cobalt-based alloys. Regarding the production methods, high-temperature alloys can be classified as cast high-temperature alloys, wrought high-temperature alloys, and powder metallurgy high-temperature alloys. Furthermore, they can be strengthened through mechanisms such as solid solution strengthening, dispersion strengthening, precipitation strengthening, and grain boundary strengthening.

Recently, a team of Central South University including Professor Huang Zaiwang and Professor Zhang Lijun published a paper in ACTAMATERIALIA, reporting the latest research trends: the creep resistance and phase stability of nickel-base single crystal superalloy are improved by replacing Re with OS. So, how likely is it that osmium (OS) will replace rhenium (Re) as the most important strengthening element in ni-base single crystal superalloys in practical production and application? Let's read through the core meaning of this paper.

as a rare and refractory metal, rhenium comes into being in nature in association with metallic minerals such as molybdenum and copper. Rhenium has high melting point, high strength, good plasticity and stable mechanical properties and is widely used in single crystal superalloys for aero-engine turbine blades due to the "rhenium effect" caused by the addition of rhenium. Besides, the scarcity of reserves and the difficulty of processing and obtaining result in its high price, so many countries regard it as a strategic element. Currently, the superalloy industry is the largest consumer of rhenium, accounting for about 80% of the total, and with the rapid development of human aerospace industry, the consumer market demand for rhenium resources at a growth rate of 5% annually, leading to more attention to the application of rhenium. In order to alleviate the growing tension in rhenium resources, diversified enrichment and separation methods, the use of alternative elements, low rhenium as well as rhenium recycling and other emerging technologies have been gradually developed to make rhenium metal more fully available.

Rhenium (Re) and its compounds have excellent catalytic activity (Re has a highly selective catalytic function for many chemical reactions), so it is often used as a catalyst in petrochemical and other fields. Catalytic reforming is one of the petroleum refining processes and an important means to improve the quality of gasoline and produce petrochemical raw materials. As a catalyst in catalytic reforming process, Re - Pt alloy can increase the depth of reforming reaction and increase the yield of gasoline, aromatic hydrocarbons and hydrogen. In addition, rhenium can also be used as a catalyst for automobile exhaust purification, and rhenium sulfide can be used as a hydrogenation catalyst for cresol, lignin, etc. The following lists the application of several rhenium metal catalysts.

Darpa and Elementum 3D Printing have signed a new contract to fund research into rhenium as a 3D printing material. The aim is to use rhenium as a material, rather than just as an alloy, which currently contains about 6 per cent rhenium.