Tungsten carbide

Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into shapes through a process called sintering for use in industrial machinery, cutting tools, abrasives, armor-piercing rounds, other tools and instruments, and jewelry.

Tungsten carbide is approximately twice as stiff as steel, with a Young's modulus of approximately 530–700 GPa (77,000 to 102,000 ksi),[4][7][8][9] and is double the density of steel—nearly midway between that of lead and gold. It is comparable with corundum (α-Al
2
O
3
) in hardness and can only be polished and finished with abrasives of superior hardness such as cubic boron nitride and diamond powder, wheels, and compounds.

Tungsten carbide
α-Tungsten carbide in the unit cell
Names
IUPAC name
Tungsten carbide
Other names
Tungsten(IV) carbide
Tungsten tetracarbide
Identifiers
3D model (JSmol)
ECHA InfoCard 100.031.918
EC Number 235-123-0
Properties
WC
Molar mass 195.85 g·mol−1
Appearance Grey-black lustrous solid
Density 15.63 g/cm3[1]
Melting point 2,785–2,830 °C (5,045–5,126 °F; 3,058–3,103 K)[3][2]
Boiling point 6,000 °C (10,830 °F; 6,270 K)
at 760 mmHg[2]
Insoluble
Solubility Soluble in HNO
3
, HF[3]
1·10−5 cm3/mol[3]
Thermal conductivity 110 W/(m·K)[4]
Structure
Hexagonal, hP2[5]
P6m2, No. 187[5]
6m2[5]
a = 2.906 Å, c = 2.837 Å[5]
α = 90°, β = 90°, γ = 120°
Trigonal prismatic (center at C)[6]
Thermochemistry
39.8 J/(mol·K)[4]
32.1 J/mol·K
Related compounds
Other anions
Tungsten boride
Tungsten nitride
Other cations
Molybdenum carbide
Titanium carbide
Silicon carbide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Naming

Historically referred to as Wolfram, Wolf Rahm, wolframite ore discovered by Peter Woulfe was then later carburized and cemented with a binder creating a composite now called "cemented tungsten carbide".[10] Tungsten is Swedish for "heavy stone".

Colloquially among workers in various industries (such as machining and carpentry), tungsten carbide is often simply called carbide, despite the imprecision of the usage. Among the lay public, the growing popularity of tungsten carbide rings has also led to consumers calling the material tungsten.

Synthesis

Tungsten carbide is prepared by reaction of tungsten metal and carbon at 1400–2000 °C.[11] Other methods include a patented lower temperature fluid bed process that reacts either tungsten metal or blue WO
3
with CO/CO
2
mixture and H
2
between 900 and 1200 °C.[12]

WC can also be produced by heating WO
3
with graphite: directly at 900 °C or in hydrogen at 670 °C following by carburization in argon at 1000 °C.[13] Chemical vapor deposition methods that have been investigated include:[11]

WCl
6
+ H
2
+ CH
4
→ WC + 6 HCl
WF
6
+ 2 H
2
+ CH
3
OH
→ WC + 6 HF + H
2
O

Chemical properties

There are two well-characterized compounds of tungsten and carbon, WC and tungsten semicarbide, W
2
C
. Both compounds may be present in coatings and the proportions can depend on the coating method.[14]

At high temperatures WC decomposes to tungsten and carbon and this can occur during high-temperature thermal spray, e.g., in high velocity oxygen fuel (HVOF) and high energy plasma (HEP) methods.[15]

Oxidation of WC starts at 500–600 °C (932–1,112 °F).[11] It is resistant to acids and is only attacked by hydrofluoric acid/nitric acid (HF/HNO
3
) mixtures above room temperature.[11] It reacts with fluorine gas at room temperature and chlorine above 400 °C (752 °F) and is unreactive to dry H
2
up to its melting point.[11] Finely powdered WC oxidizes readily in hydrogen peroxide aqueous solutions.[16] At high temperatures and pressures it reacts with aqueous sodium carbonate forming sodium tungstate, a procedure used for recovery of scrap cemented carbide.

Physical properties

Tungsten carbide has a high melting point at 2,870 °C (5,200 °F), a boiling point of 6,000 °C (10,830 °F) when under a pressure equivalent to 1 standard atmosphere (100 kPa),[2] a thermal conductivity of 110 W·m−1·K−1,[4] and a coefficient of thermal expansion of 5.5 µm·m−1·K−1.[7]

Tungsten carbide is extremely hard, ranking about 9 on Mohs scale, and with a Vickers number of around 2600.[8] It has a Young's modulus of approximately 530–700 GPa,[4][7][8][9] a bulk modulus of 630–655 GPa, and a shear modulus of 274 GPa.[17] It has an ultimate tensile strength of 344 MPa,[9] an ultimate compression strength of about 2.7 GPa and a Poisson's ratio of 0.31.[17]

The speed of a longitudinal wave (the speed of sound) through a thin rod of tungsten carbide is 6220 m/s.[18]

Tungsten carbide's low electrical resistivity of about 0.2 µΩ·m is comparable with that of some metals (e.g. vanadium 0.2 µΩ·m).[11][19]

WC is readily wetted by both molten nickel and cobalt.[20] Investigation of the phase diagram of the W-C-Co system shows that WC and Co form a pseudo binary eutectic. The phase diagram also shows that there are so-called η-carbides with composition (W,Co)
6
C
that can be formed and the brittleness of these phases makes control of the carbon content in WC-Co cemented carbides important.[20]

Structure

Alpha tungsten carbide crystal structure
α-WC structure, carbon atoms are gray.[5]

There are two forms of WC, a hexagonal form, α-WC (hP2, space group P6m2, No. 187),[5][6] and a cubic high-temperature form, β-WC, which has the rock salt structure.[21] The hexagonal form can be visualized as made up of a simple hexagonal lattice of metal atoms of layers lying directly over one another (i.e. not close packed), with carbon atoms filling half the interstices giving both tungsten and carbon a regular trigonal prismatic, 6 coordination.[6] From the unit cell dimensions[22] the following bond lengths can be determined: the distance between the tungsten atoms in a hexagonally packed layer is 291 pm, the shortest distance between tungsten atoms in adjoining layers is 284 pm, and the tungsten carbon bond length is 220 pm. The tungsten-carbon bond length is therefore comparable to the single bond in W(CH
3
)
6
(218 pm) in which there is strongly distorted trigonal prismatic coordination of tungsten.[23]

Molecular WC has been investigated and this gas phase species has a bond length of 171 pm for 184
W
12
C
.[24]

Applications

Cutting tools for machining

Tungsten carbide
Cemented carbide drill and end mills

Sintered tungsten carbide - cobalt cutting tools are very abrasion resistant and can also withstand higher temperatures than standard high-speed steel (HSS) tools. Carbide cutting surfaces are often used for machining through materials such as carbon steel or stainless steel, and in applications where steel tools would wear quickly, such as high-quantity and high-precision production. Because carbide tools maintain a sharp cutting edge better than steel tools, they generally produce a better finish on parts, and their temperature resistance allows faster machining. The material is usually called cemented carbide, solid carbide, hardmetal or tungsten-carbide cobalt. It is a metal matrix composite, where tungsten carbide particles are the aggregate, and metallic cobalt serves as the matrix.[25][26]

Ammunition

Tungsten carbide is often used in armor-piercing ammunition, especially where depleted uranium is not available or is politically unacceptable. However, it is also common to use powder metallurgic tungsten alloys (in which metallic tungsten powder has been cemented with a metallic binder). W
2
C
projectiles were first used by German Luftwaffe tank-hunter squadrons in World War II. Owing to the limited German reserves of tungsten, W
2
C
material was reserved for making machine tools and small numbers of projectiles. It is an effective penetrator due to its combination of great hardness and very high density.[27][28]

Tungsten carbide in its monolithic sintered form, or much more often in tungsten carbide cobalt composite (in which fine ceramic tungsten carbide particles are embedded in metallic cobalt binder forming a metal matrix composite or MMC) can be of the sabot type. SLAP, or saboted light armour penetrator where a plastic sabot discards at the barrel muzzle is one of the primary types of saboted small arms ammunition. Non-discarding jackets, regardless of the jacket material, are not perceived as sabots but bullets. Both of the designs are, however, common in designated light armor-piercing small arms ammunition.

Discarding sabots like used with M1A1 Abrams main gun are more commonplace in precision high-velocity gun amunition.[29][30]

Mining

Drill bit 2-italy
A Tricone roller cone assembly from a raiseboring reamer, showing the protruding tungsten carbide buttons inset into the rollers

Tungsten carbide is used extensively in mining in top hammer rock drill bits, downhole hammers, roller-cutters, long wall plough chisels, long wall shearer picks, raiseboring reamers, and tunnel boring machines. It is generally utilised as a button insert, mounted in a surrounding matrix of steel that forms the substance of the bit. As the tungsten carbide button is worn away the softer steel matrix containing it is also worn away, exposing yet more button insert.

Nuclear

Tungsten carbide is also an effective neutron reflector and as such was used during early investigations into nuclear chain reactions, particularly for weapons. A criticality accident occurred at Los Alamos National Laboratory on 21 August 1945 when Harry Daghlian accidentally dropped a tungsten carbide brick onto a plutonium sphere, known as the demon core, causing the subcritical mass to go supercritical with the reflected neutrons.

Sports usage

Nokian Gazza Extreme 294 29er
A Nokian bicycle tire with tungsten carbide spikes. The spikes are surrounded by aluminum.

Trekking poles, used by many hikers for balance and to reduce pressure on leg joints, generally use carbide tips in order to gain traction when placed on hard surfaces (like rock); carbide tips last much longer than other types of tip.[31]

While ski pole tips are generally not made of carbide, since they do not need to be especially hard even to break through layers of ice, rollerski tips usually are. Roller skiing emulates cross country skiing and is used by many skiers to train during warm weather months.

Sharpened carbide tipped spikes (known as studs) can be inserted into the drive tracks of snowmobiles. These studs enhance traction on icy surfaces. Longer v-shaped segments fit into grooved rods called wear rods under each snowmobile ski. The relatively sharp carbide edges enhance steering on harder icy surfaces. The carbide tips and segments reduce wear encountered when the snowmobile must cross roads and other abrasive surfaces.[32]

Car, motorcycle and bicycle tires with tungsten carbide studs provide better traction on ice. The tungsten carbide insert protruding from inside of a zinc or aluminium seating is commonly called a "soul" in the tire manufacturing business. These are generally preferred to steel studs because of their superior resistance to wear.[33]

Tungsten carbide may be used in farriery, the shoeing of horses, to improve traction on slippery surfaces such as roads or ice. Carbide-tipped hoof nails may be used to attach the shoes;[34] in the United States, borium – chips of tungsten carbide in a matrix of softer metal such as bronze or mild steel – may be welded to small areas of the underside of the shoe before fitting.[35]:73

Surgical instruments

Tungsten carbide is also used for making surgical instruments meant for open surgery (scissors, forceps, hemostats, blade-handles, etc.) and laparoscopic surgery (graspers, scissors/cutter, needle holder, cautery, etc.). They are much costlier than their stainless-steel counterparts and require delicate handling, but give better performance.[36]

Jewelry

Tungsten Carbide
Tungsten carbide ring

Tungsten carbide, typically in the form of a cemented carbide (carbide particles brazed together by metal), has become a popular material in the bridal jewelry industry due to its extreme hardness and high resistance to scratching.[37][38] Even with high-impact resistance, this extreme hardness also means that it can occasionally be shattered under certain circumstances.[39] Some consider this useful, since an impact would shatter a tungsten ring, quickly removing it, where precious metals would bend flat and require cutting. Tungsten carbide is roughly 10 times harder than 18k gold. In addition to its design and high polish, part of its attraction to consumers is its technical nature.[37] Special tools, such as locking pliers, may be required if such a ring must be removed quickly (e.g. due to medical emergency following a hand injury accompanied by swelling).[40]

Other

Tungsten carbide is widely used to make the rotating ball in the tips of ballpoint pens that disperse ink during writing.[41]

Tungsten carbide is a common material used in the manufacture of gauge blocks, used as a system for producing precision lengths in dimensional metrology.

English guitarist Martin Simpson is known to use a custom-made tungsten carbide guitar slide.[42] The hardness, weight, and density of the slide give it superior sustain and volume compared to standard glass, steel, ceramic, or brass slides.

Tungsten carbide has been investigated for its potential use as a catalyst and it has been found to resemble platinum in its catalysis of the production of water from hydrogen and oxygen at room temperature, the reduction of tungsten trioxide by hydrogen in the presence of water, and the isomerisation of 2,2-dimethylpropane to 2-methylbutane.[43] It has been proposed as a replacement for the iridium catalyst in hydrazine-powered satellite thrusters.[44]

A tungsten carbide coating has been utilized on brake discs in high performance automotive applications to improve performance, increase service intervals and reduce brake dust.[45]

Toxicity

The primary health risks associated with tungsten carbide relate to inhalation of dust, leading to fibrosis.[46] Cobalt-cemented tungsten carbide is also anticipated to be a human carcinogen by the American National Toxicology Program.[47]

References

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Cited sources

External links

American National Carbide

American National Carbide is a privately held company that manufactures tungsten carbide products and is headquartered in Tomball, Texas, which is just northwest of Houston. Also known as "ANC," the company specializes in the production of finished carbide tools for metalworking, rock drilling, and wear applications and is one of a few companies worldwide that is able to recycle tungsten carbide scrap into raw material. ANC, a member of the United States Cutting Tool Institute, was founded in 1970 and sells its products worldwide.

In June 2012, American National Carbide announced a $2.5 million expansion of its raw material production operation.

Annular cutter

An annular cutter (also called as core drill, core cutter, broach cutter, trepanning drill, hole saw, or cup-type cutter) is form of core drill used to create holes in metal. An annular cutter cuts only a groove at the periphery of the hole and leaves a solid core or slug at the center.An annular cutter is a more expensive and more efficient alternative to spiral drill bits and standard hole saws. An annular cutter is similar to a hole saw but differs in geometry and material. The two most common types are high-speed steel (HSS) and tungsten carbide tipped (TCT).

Like a hole saw, but unlike a spiral drill bit, an annular cutter cuts only the periphery of a hole, leaving a circular "slug" at the center.Annular cutters are available from 12 mm (1/2’’) diameter to 200 mm (7 7/8’’) and larger. Depths of 30 mm, 55 mm, 75 and 110 mm are commonly available.

Annular cutters are best used with a drill press or magnetic drilling machine, both for their stability against high torque forces created by such a drill bit and lower RPMs compared to other types of drills.

Ballpoint pen

A ballpoint pen, also known as a biro or ball pen, is a pen that dispenses ink (usually in paste form) over a metal ball at its point, i.e. over a "ball point". The metal commonly used is steel, brass, or tungsten carbide. It was conceived and developed as a cleaner and more reliable alternative to dip pens and fountain pens, and it is now the world's most-used writing instrument: millions are manufactured and sold daily. As a result, it has influenced art and graphic design and spawned an artwork genre.

Pen manufacturers produce designer ballpoint pens for the high-end and collectors' markets.

The Bic Cristal is a popular disposable type of ballpoint pen whose design is recognised by its place in the permanent collection of the Museum of Modern Art, New York.

Brinell scale

The Brinell scale /brəˈnɛl/ characterizes the indentation hardness of materials through the scale of penetration of an indenter, loaded on a material test-piece. It is one of several definitions of hardness in materials science.

Proposed by Swedish engineer Johan August Brinell in 1900, it was the first widely used and standardised hardness test in engineering and metallurgy. The large size of indentation and possible damage to test-piece limits its usefulness. However it also had the useful feature that the hardness value divided by two gave the approximate UTS in ksi for steels. This feature contributed to its early adoption over competing hardness tests.

The typical test uses a 10 mm (0.39 in) diameter steel ball as an indenter with a 3,000 kgf (29.42 kN; 6,614 lbf) force. For softer materials, a smaller force is used; for harder materials, a tungsten carbide ball is substituted for the steel ball. The indentation is measured and hardness calculated as:

where:

BHN = Brinell Hardness Number (kgf/mm2)
P = applied load in kilogram-force (kgf)
D = diameter of indenter (mm)
d = diameter of indentation (mm)

Brinell hardness is sometimes quoted in megapascals; the Brinell hardness number is multiplied by the acceleration due to gravity, 9.80665 m/s2, to convert it to megapascals. The BHN can be converted into the ultimate tensile strength (UTS), although the relationship is dependent on the material, and therefore determined empirically. The relationship is based on Meyer's index (n) from Meyer's law. If Meyer's index is less than 2.2 then the ratio of UTS to BHN is 0.36. If Meyer's index is greater than 2.2, then the ratio increases.

BHN is designated by the most commonly used test standards (ASTM E10-14 and ISO 6506–1:2005) as HBW (H from hardness, B from brinell and W from the material of the indenter, tungsten (wolfram) carbide). In former standards HB or HBS were used to refer to measurements made with steel indenters.

HBW is calculated in both standards using the SI units as

where:

F = applied load (Newtons)
D = diameter of indenter (mm)
d = diameter of indentation (mm)
Carbide

In chemistry, a carbide is a compound composed of carbon and a less electronegative element. Carbides can be generally classified by the chemical bonds type as follows: (i) salt-like, (ii) covalent compounds, (iii) interstitial compounds, and (iv) "intermediate" transition metal carbides. Examples include calcium carbide (CaC2), silicon carbide (SiC), tungsten carbide (WC; often called, simply, carbide when referring to machine tooling), and cementite (Fe3C), each used in key industrial applications. The naming of ionic carbides is not systematic.

Cemented carbide

Cemented carbide is a hard material used extensively as cutting tool material, as well as other industrial applications. It consists of fine particles of carbide cemented into a composite by a binder metal. Cemented carbides commonly use tungsten carbide (WC), titanium carbide (TiC), or tantalum carbide (TaC) as the aggregate. Mentions of "carbide" or "tungsten carbide" in industrial contexts usually refer to these cemented composites.Most of the time, carbide cutters will leave a better surface finish on the part, and allow faster machining than high-speed steel or other tool steels. Carbide tools can withstand higher temperatures at the cutter-workpiece interface than standard high-speed steel tools (which is a principal reason for the faster machining). Carbide is usually superior for the cutting of tough materials such as carbon steel or stainless steel, as well as in situations where other cutting tools would wear away faster, such as high-quantity production runs.

Cermet

A cermet is a composite material composed of ceramic (cer) and metal (met) materials.

A cermet is ideally designed to have the optimal properties of both a ceramic, such as high temperature resistance and hardness, and those of a metal, such as the ability to undergo plastic deformation. The metal is used as a binder for an oxide, boride, or carbide. Generally, the metallic elements used are nickel, molybdenum, and cobalt. Depending on the physical structure of the material, cermets can also be metal matrix composites, but cermets are usually less than 20% metal by volume.

Cermets are used in the manufacture of resistors (especially potentiometers), capacitors, and other electronic components which may experience high temperature.

Cermets are used instead of tungsten carbide in saws and other brazed tools due to their superior wear and corrosion properties. Titanium nitride (TiN), titanium carbonitride (TiCN), titanium carbide (TiC) and similar can be brazed like tungsten carbide if properly prepared however they require special handling during grinding.

Composites of MAX phases, an emerging class of ternary carbides or nitrides with aluminium or titanium alloys have been studied since 2006 as high-value materials exhibiting favourable properties of ceramics in terms of hardness and compressive strength alongside ductility and fracture toughness typically associated with metals. Such cermet materials, including aluminium-MAX phase composites, have potential applications in automotive and aerospace applications.Some types of cermets are also being considered for use as spacecraft shielding as they resist the high velocity impacts of micrometeoroids and orbital debris much more effectively than more traditional spacecraft materials such as aluminum and other metals.

Cobalt poisoning

Cobalt poisoning is intoxication caused by excessive levels of cobalt in the body. Cobalt is an essential element for health in animals in minute amounts as a component of Vitamin B12. A deficiency of cobalt, which is very rare, is also potentially lethal, leading to pernicious anemia.Exposure to cobalt metal dust is most common in the fabrication of tungsten carbide. Another potential source is wear and tear of metal-on-metal hip prostheses.

Cold saw

A cold saw is a circular saw designed to cut metal which uses a toothed blade to transfer the heat generated by cutting to the chips created by the saw blade, allowing both the blade and material being cut to remain cool. This is in contrast to an abrasive saw, which abrades the metal and generates a great deal of heat absorbed by the material being cut and saw blade.

As metals expand when heated, abrasive cutting causes both the material being cut and blade to expand, resulting in increased effort to produce a cut and potential binding. This produces more heat through friction, resulting in increased blade wear and greater energy consumption.

Cold saws use either a solid high speed steel (HSS) or tungsten carbide-tipped, resharpenable circular saw blade. They are equipped with an electric motor and a gear reduction unit to reduce the saw blade's rotational speed while maintaining constant torque. This allows the HSS saw blade to feed at a constant rate with a very high chip load per tooth.

Cold saws are capable of machining most ferrous and non-ferrous alloys. Additional advantages include minimal burr production, fewer sparks, less discoloration and no dust. Saws designed to employ a flood coolant system to keep saw blade teeth cooled and lubricated may reduce sparks and discoloration completely. Saw blade type and number of teeth, cutting speed, and feed rate all must be appropriate to the type and size of material being cut, which must be mechanically clamped to prevent movement during the cutting process.

Glass cutter

A glass cutter is a tool used to make a shallow score in one surface of a piece of glass that is to be broken in two pieces. The scoring makes a split in the surface of the glass which encourages the glass to break along the score. Regular, annealed glass can be broken apart this way but not tempered glass as the latter tends to shatter rather than breaking cleanly into two pieces.A glass cutter may use a diamond to create the split, but more commonly a small cutting wheel made of hardened steel or tungsten carbide 4–6 mm in diameter with a V-shaped profile called a "hone angle" is used. The greater the hone angle of the wheel, the sharper the angle of the V and the thicker the piece of glass it is designed to cut. The hone angle on most hand-held glass cutters is 120°, though wheels are made as sharp as 154° for cutting glass as thick as 0.5 inches (13 mm). Their main drawback is that wheels with sharper hone angles will become dull more quickly than their more obtuse counterparts. The effective cutting of glass also requires a small amount of oil (kerosene is often used) and some glass cutters contain a reservoir of this oil which both lubricates the wheel and prevents it from becoming too hot: as the wheel scores, friction between it and the glass surface briefly generates intense heat, and oil dissipates this efficiently. When properly lubricated a steel wheel can give a long period of satisfactory service. However, tungsten carbide wheels have been proven to have a significantly longer life than steel wheels and offer greater and more reproducible penetration in scoring as well as easier opening of the scored glass.

In the Middle Ages, glass was cut with a heated and sharply pointed iron rod. The red hot point was drawn along the moistened surface of the glass causing it to snap apart. Fractures created in this way were not very accurate and the rough pieces had to be chipped or "grozed" down to more exact shapes with a hooked tool called a grozing iron. Between the 14th and 16th centuries, starting in Italy, a diamond-tipped cutter became prevalent which allowed for more precise cutting. Then in 1869 the wheel cutter was developed by Samuel Monce of Bristol, Connecticut, which remains the current standard tool for most glass cutting.Large sheets of glass are usually cut with a computer-assisted CNC semi-automatic glass cutting table. These sheets are then broken out by hand into the individual sheets of glass (also known as "lites" in the glass industry).

Harry Daghlian

Haroutune Krikor "Harry" Daghlian Jr. (May 4, 1921 – September 15, 1945) was a physicist with the Manhattan Project which designed and produced the atomic bombs that were used in World War II. He accidentally irradiated himself on August 21, 1945, during a critical mass experiment at the remote Omega Site of the Los Alamos Laboratory in New Mexico, resulting in his death 25 days later.

Daghlian was irradiated as a result of a criticality accident that occurred when he accidentally dropped a tungsten carbide brick onto a 6.2 kg plutonium–gallium alloy bomb core. This core, subsequently nicknamed the "demon core", was later involved in the death of another physicist, Louis Slotin.

Metzenbaum scissors

Metzenbaum scissors are surgical scissors designed for cutting delicate tissue and blunt dissection. The scissors come in variable lengths and have a relatively long shank-to-blade ratio. They are constructed of stainless steel and may have tungsten carbide cutting surface inserts. The blades can be curved or straight, and the tips are usually blunt. This is the most common type of scissors used in organ operations.

Needle holder

A needle holder, also called needle driver, is a surgical instrument, similar to a hemostat, used by doctors and surgeons to hold a suturing needle for closing wounds during suturing and surgical procedures.

Companies like Hayden Medical carry similar styles of needle holders called Olsen-Hegar Needle Holders that are a scissor and needle holder combo allowing for quick cutting of suture. These are made to the industry standard with German Stainless steel and can have Tungsten Carbide inserts in the jaws for stronger grasping power.

The parts of a simple needle holder are the jaws, the joint and the handles. Most needle holders also have a clamp mechanism that locks the needle in place, allowing the user to maneuver the needle through various tissues. To maintain a firm grip on the needle, the jaws are often textured and short compared to the shank (increasing the applied force following the principle of a lever).

An example is the Castroviejo needle holder, which is commonly used in eye surgery and microsurgery.

Neutron reflector

A neutron reflector is any material that reflects neutrons. This refers to elastic scattering rather than to a specular reflection. The material may be graphite, beryllium, steel, tungsten carbide, or other materials. A neutron reflector can make an otherwise subcritical mass of fissile material critical, or increase the amount of nuclear fission that a critical or supercritical mass will undergo. Such an effect was exhibited twice in accidents involving the Demon Core, a subcritical plutonium pit that went critical in two separate fatal incidents when the pit's surface was momentarily surrounded by too much neutron reflective material.

Rockwell scale

The Rockwell scale is a hardness scale based on indentation hardness of a material. The Rockwell test determines the hardness by measuring the depth of penetration of an indenter under a large load compared to the penetration made by a preload. There are different scales, denoted by a single letter, that use different loads or indenters. The result is a dimensionless number noted as HRA, HRB, HRC, etc., where the last letter is the respective Rockwell scale (see below).

When testing metals, indentation hardness correlates linearly with tensile strength. This important relation permits economically important nondestructive testing of bulk metal deliveries with lightweight, even portable equipment, such as hand-held Rockwell hardness testers.

Surgical scissors

Surgical scissors are surgical instruments usually used for cutting. They include bandage scissors, dissecting scissors, iris scissors, operating scissors, stitch scissors, tenotomy scissors, Metzenbaum scissors, plastic surgery scissors, and Mayo scissors. Surgical scissors are usually made of very hard stainless steel for ongoing toughness. Some scissors have tungsten carbide reinforcements along their cutting edges. The hardness of this material allows the manufacturers to create sharper edges, which allows for easier and smoother cuts and keeps the scissors sharp for longer.

Syndite

Syndite is a composite material which combines the hardness, abrasion resistance and thermal conductivity of diamond with the toughness of tungsten carbide.

Titanium carbide

Titanium carbide, TiC, is an extremely hard (Mohs 9–9.5) refractory ceramic material, similar to tungsten carbide. It has the appearance of black powder with the sodium chloride (face-centered cubic) crystal structure. As found in nature its crystals range in size from 0.1 to 0.3mm.

It occurs in nature as a form of the very rare mineral khamrabaevite (Russian: Хамрабаевит) - (Ti,V,Fe)C. It was discovered in 1984 on Mount Arashan in the Chatkal District, USSR (modern Kyrgyzstan), near the Uzbek border. The mineral was named after Ibragim Khamrabaevich Khamrabaev, director of Geology and Geophysics of Tashkent, Uzbekistan.

Tungsten

Tungsten, or wolfram, is a chemical element with symbol W and atomic number 74. The name tungsten comes from the former Swedish name for the tungstate mineral scheelite, tung sten or "heavy stone". Tungsten is a rare metal found naturally on Earth almost exclusively combined with other elements in chemical compounds rather than alone. It was identified as a new element in 1781 and first isolated as a metal in 1783. Its important ores include wolframite and scheelite.

The free element is remarkable for its robustness, especially the fact that it has the highest melting point of all the elements discovered, melting at 3422 °C (6192 °F, 3695 K). It also has the highest boiling point, at 5930 °C (10706 °F, 6203 K). Its density is 19.3 times that of water, comparable to that of uranium and gold, and much higher (about 1.7 times) than that of lead. Polycrystalline tungsten is an intrinsically brittle and hard material (under standard conditions, when uncombined), making it difficult to work. However, pure single-crystalline tungsten is more ductile and can be cut with a hard-steel hacksaw.Tungsten's many alloys have numerous applications, including incandescent light bulb filaments, X-ray tubes (as both the filament and target), electrodes in gas tungsten arc welding, superalloys, and radiation shielding. Tungsten's hardness and high density give it military applications in penetrating projectiles. Tungsten compounds are also often used as industrial catalysts.

Tungsten is the only metal from the third transition series that is known to occur in biomolecules that are found in a few species of bacteria and archaea. It is the heaviest element known to be essential to any living organism. However, tungsten interferes with molybdenum and copper metabolism and is somewhat toxic to more familiar forms of animal life.

Tungsten compounds
Tungsten(0)
Tungsten(II)
Tungsten(III)
Tungsten(IV)
Tungsten(V)
Tungsten(VI)
Tungsten(_)

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