Introduction

Tungsten has high electrical and thermal conductivity, and low vapor pressure at high temperature. It has high meting point compared to all other metallic materials. It is also considered as a good element for high vacuum technology, furnace construction, glass seals, and dimensional stability. It has an ability to absorb radioactive radiation because it has high density. The following datasheet gives an overview of tungsten.

Physical Properties

The physical properties of tungsten are displayed in the following table.
Properties                Metric                      Imperial
Density                   19.27 g/cm³              0.70 lb/in³
Melting point            3410°C                    6170°F

Mechanical Properties
The mechanical properties of tungsten are outlined in the following table.
Properties                     Metric             Imperial
Tensile strength            1725 MPa       250 ksi
Elastic modulus            400 GPa         58000 ksi
Hardness                     300                 300

Fabrication and Heat Treatment

Forming
Before forming, tungsten should be preheated at 675°C (1247°F).

Applications
Tungsten is used in different kinds of furnace and lighting applications due to its high melting temperature. The thermal expansion coefficient value of tungsten is almost same as that of silicon, thus using the tungsten in brazed mounts for silicon diode chips.

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Sometimes you have to watch between the lines to understand how much authority governmental agencies really have. The Bureau of Alcohol, Tobacco, Firearms and Explosives is a case in point. The issue is what ammunition the ATF considers to be "armor piercing ammunition" and not ammunition used for "sporting purposes."

In early December meetings, the ATF met with gun control activist groups, the NRA, firearms industry groups and others. The ATF expressed opinions that "warrant particular scrutiny," NRA representatives, who attended those meetings, noted on the group's website.

Under a law adopted in 1986, the definition of "armor piercing ammunition" is "a projectile or projectile core which may be used in a handgun and which is constructed entirely (excluding the presence of traces of other substances) from one or a combination of tungsten alloys, steel, iron, brass, beryllium copper or depleted uranium."

The intent of the law, which is good, is to protect law enforcement officers from ammunition that could penetrate soft body armor.

The challenge is that there are handguns designed to fire certain rifle calibers and that rifle ammunition wasn't designed for anything other than sporting purposes. That means you could have a rifle caliber ammunition type outlawed on the basis that it can be fired in a handgun and pierce armor. That covers a wide range of rifle ammunition that could be outlawed under a stricter interpretation of this law.

According to the NRA representatives who attended the meetings, the ATF "suggested that it believes that the armor piercing ammunition law was intended to affect all ammunition capable of penetrating soft body armor worn by law enforcement officers."

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Tis the season...for wedding engagements. More than a third of engagements take place between Thanksgiving and New Year's, according to WeddingWire -- so many, in fact, that it's come to be known as "engagement season."

Which means that wedding planning kicks off in earnest in the new year -- followed closely by sticker shock at the price of gold and platinum wedding bands. As the cost of precious metals continues to rise, it comes as no surprise that more and more grooms are forgoing those traditional choices and opting for more adventuresome -- and less costly -- materials, such as tungsten carbide and palladium.

Grooms spent an average of $491 for their wedding bands in 2011, almost a 23 percent drop from the $637 average in 2009, according to wedding-planning website The Knot. That's in part because fewer are buying gold: 39 percent of grooms purchased white gold bands in 2009, versus 34 percent in 2011.

Ruth Batson, CEO of the American Gem Society, chalks up the popularity of alternative materials to style as well as economics. "Alternative materials like titanium, ceramic, tungsten are top trends right now, because of the hardness factor and also for ease of care. While cost may be a factor for some, overall design and how the ring looks and holds up tend to be a priority."

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Introduction
Super alloys or high performance alloys include iron-based, cobalt-based and nickel-based alloys. These alloys have good oxidation and creep resistance and are available in different shapes.

Super alloys can be strengthened by precipitation hardening, solid-solution hardening and work hardening methods. These alloys can function under high mechanical stress and high temperatures and also in places that require high surface stability.

Udimet 520™ is a nickel-chromium-cobalt alloy. Addition of tungsten and molybdenum result in age-hardening and strengthening of this alloy.

The following datasheet provides an overview of Udimet 520™.

Chemical Composition
The chemical composition of Udimet 520™ is outlined in the following table.
Element                   Content (%)
Nickel, Ni                 52.18-59.976
Chromium, Cr          18.0-20.0
Cobalt, Co               11.0-14.0
Molybdenum, Mo     5.50-7.00
Titanium, Ti             2.90-3.25
Aluminum, Al          1.80-2.30
Tungsten, W          0.800-1.20
Carbon, C             0.0200-0.0600
Boron, B               0.00400-0.0100

Physical Properties
The following table shows the physical properties of Udimet 520™.
Properties                       Metric            Imperial
Density                          8.21 g/cm³      0.297 lb/in³
Melting point                  1371°C            2500°F
Mechanical Properties

The mechanical properties of Udimet 520™ are displayed in the following table.
Properties                                             Metric                 Imperial
Tensile strength (@950°C/1740°F)        350 MPa               50800 psi
Yield strength (@strain 0.200%, temperature 850°C/strain 0.200%, temperature 1560°F)                                                          500 MPa               72500 psi
Elongation at break (@50°C/122°F)      100%                    100%

Fabrication and Heat Treatment

Annealing
Udimet 520™ is annealed at 1107°C (2025°F) and then cooled in air rapidly.

Cold Working
Standard cooling methods are used for cold forming Udimet 520™. Minimization of galling is possible with the usage of heavy duty lubricants and soft die materials though the die life is limited. Tooling is recommended in the cold working process to allow liberal radii and clearances.

Welding
Welding processes recommended for Udimet 520™ include gas-tungsten arc welding, gas metal-arc welding and shielded metal-arc welding. This alloy can be welded by the commonly used welding procedures, and the welding surfaces should be free from paint, crayon markings or oil.

Forging
Udimet 520™ is capable of being forged as it is ductile.

Forming
Conventional methods can be used to form Udimet 520™ with ease as it has good ductility. To obtain good forming results, a powerful equipment is used along with heavy- prevent embrittlement of this alloy at high temperatures.

Machinability
Udimet 520™ can be machined by conventional machining methods. and tThis alloy contains higher strength, gumminess and work-hardening qualities. Usage of water-based coolants is preferred for milling, turning or grinding. Usage of heavy lubricants is preferred for boring, drilling, broaching or tapping operations. Work-hardening of the alloy before the cutting process and chatter can be minimized by tooling and a heavy duty machining equipment.

Aging
Udimet 520™ is treated at three different temperatures to be air-hardened.

    Heat for 4 h at 1107°C (2025°F) and cool in air.
    Heat for 24 h at 843°C (1550°F) and cool in air.
    Heat for 16 h at 760°C (1400°F) and cool in air.

Heat Treatment
Udimet 520™ can be hardened when heat treated.

Applications
Udimet 520™ is used in gas turbine hot section components and industrial applications that need hot high heat strength with good quality.

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