Molybdenum metal is usually produced by powder metallurgy techniques in which Mo powder is hydrostratically compacted and sintered at about 2100°C. Hot working is done in the 870-1260°C range. Moly forms a volatile oxide when heated in air above about 600°C and therefore high temperature applications are limited to non-oxidizing or vacuum environments.
Molybdenum Alloys have excellent strength and mechanical stability at high temperatures (up to 1900°C). Their high ductility and toughness provide a greater tolerance for imperfections and brittle fracture than ceramics.
The unique properties of molybdenum alloys are utilised in many applications:
High temperature heating elements, radiation shields, extrusions, forging dies, etc;
Rotating X-ray anodes used in clinical diagnostics;
Glass melting furnace electrodes and components that are resistant to molten glass;
Sprayed coatings on automotive piston rings and machine components to reduce friction and improve wear.
For specialised applications, Mo is alloyed with many other metals like Lanthanated Molybdenum Alloy:
Mo-tungsten alloys are noted for exceptional resistance to molten zinc;
Mo is clad with copper to provide low expansion and high conductivity electronic circuit boards;
Mo-25% rhenium alloys are used for rocket engine components and liquid metal heat exchangers which must be ductile at room temperature.
Except for Molybdenum, Tungsten is also a popular metal. Tungsten is an invaluable element in the alloying process, where elements are blended to form new and improved metals known as alloys. Tungsten provides a unique contribution, as it imbues exceptional strength, corrosion resistance, and other useful properties to base metals. Besides being a great alloying element, tungsten can also be the base for its own alloys.
Tungsten alloys, sometimes referred to as heavy alloys, are usually 90-97% tungsten with the rest of its composition being a matrix of metals which improve the ductility and machinability of the resulting alloy. There is no true naming standard for these alloys, as they are set individually by the manufacturer and are not superimposable onto a general scheme such as with the alloys of steel or aluminum.
Tungsten nickel iron alloys
The most common of the tungsten alloys, tungsten nickel iron alloys are top of the list in terms of ductility, strength, and density. They are a silvery-grey color, have a range of densities from 16.85-19.3 g/cm3, and are also known as Densalloy?, Mallory, WNiFe, and/or Densimet?. These metals have tensile strengths ranging from 600-1000 MPa, which surpasses most if not all other alloys. These alloys have good machining qualities and plasticity and can withstand intense temperatures, while still having a thermal conductivity that is 5 times that of die & punch steels. They have 1.7 times the radiation shielding capabilities of lead and are non-toxic to biological systems (which cannot be said for lead). Iron makes these alloys magnetic, which is important to know if they are planned to be used in any magnetism-sensitive operations such as medical imaging equipment. Tungsten nickel iron alloys have a low expansion coefficient useful for glass-to-metal seals and possess high moduli of elasticity, which makes them resistant to elastic deformation. These alloys are perfect for radiation shielding, as its high density matched with its radiation resistance are ideal for protective components. Some notable applications include balance weights, security and defense applications, ballasts, bearing assemblies, and more.
Tungsten nickel copper alloys
The non-magnetic cousin to tungsten nickel iron alloys is the tungsten nickel copper alloys. They are about as popular as nickel-iron alloys, but generally, have lower tensile strength (500-700 MPa) and ductility. They are great electrical conductors and are easy to machine despite their high mechanical strength. They possess excellent thermal stability and can shield from radiation about as well as other tungsten alloys. The greatest advantage to tungsten nickel copper alloys is their non-magnetic nature; this feature allows them to be used in applications where tungsten nickel iron alloys would be magnetically disruptive. They are widely specified in oncology tools, electrical sensor shields, guidance system components, and military technology.
In addition, there are other kinds of Tungsten alloys like Tungsten Heavy Alloy and Copper Tungsten Alloy are more and more popular. And in the industrial production, other metals like Tantalum, Titanium, Niobium and Chromium are all applied more and more often.
- Létrehozva: 17-02-22
- Utolsó belépés: 17-02-22