Cemented carbide
Encyclopedia
Cemented carbide, also called tungsten carbide
, hardmetal, or widia, is a hard material used in machining tough materials such as carbon steel or stainless steel
, as well as in situations where other tools would wear away, such as high-quantity production runs. Most of the time, carbide will leave a better finish on the part, and allow faster machining. Carbide tools can also withstand higher temperatures than standard high speed steel
tools.
where tungsten carbide
particles are the aggregate and metallic cobalt
serves as the matrix. The process of combining tungsten carbide with cobalt is referred to as sintering
or Hot Isostatic Pressing
(HIP). During this process cobalt eventually will be entering the liquid stage and WC grains (much higher melting point) remain in the solid stage. As a result of this process cobalt is embedding/cementing the WC grains and thereby creates the metal matrix composite with its distinct material properties. The naturally ductile cobalt metal serves to offset the characteristic brittle behavior of the tungsten carbide ceramic, thus raising its toughness and durability. Such parameters of tungsten carbide can be changed significantly within the carbide manufacturer's sphere of influence, primarily determined by grain size, cobalt content, dotation (e.g. alloy carbides) and carbon content.
than other typical tool materials, and it is more brittle, making it susceptible to chipping and breaking. To offset these problems, the carbide cutting tip itself is often in the form of a small insert for a larger tipped tool
whose shank is made of another material, usually carbon tool steel
. This gives the benefit of using carbide at the cutting interface without the high cost and brittleness of making the entire tool out of carbide. Most modern face mills use carbide inserts, as well as many lathe tools and endmill
s. In recent decades, though, solid-carbide endmills have also become more commonly used, wherever the application's characteristics make the pros (such as shorter cycle times) outweigh the cons (mentioned above).
), TiC (titanium carbide
), Ti(C)N (titanium carbide-nitride), and TiAlN (titanium aluminum nitride). (Newer coatings, known as DLC (Diamond-like carbon
) are beginning to surface, enabling the cutting power of diamond without the unwanted chemical reaction between real diamond and iron.) Most coatings generally increase a tool's hardness and/or lubricity. A coating allows the cutting edge of a tool to cleanly pass through the material without having the material gall
(stick) to it. The coating also helps to decrease the temperature associated with the cutting process and increase the life of the tool. The coating is usually deposited via thermal CVD
and, for certain applications, with the mechanical PVD
method. However if the deposition is performed at too high temperature, an eta phase of a Co6W6C tertiary carbide forms at the interface between the carbide and the cobalt phase, facilitating adhesion failure of the coating.
Some key areas where cemented carbide components are used:
(Cemented Carbide) has become a popular metal in the bridal jewelry industry, due to its extreme hardness and high resistance to scratching. However, tungsten carbide is not a solid metal – it is a ceramic
containing ground tungsten
and ground carbon
that is bound together by an alloy
, formerly cobalt
and presently more often nickel
, through high pressure. This results in a very hard material that is also brittle
, thus prone to chip, crack or shatter from impact to a hard surface. Once fractured, it cannot be repaired.
What was considered ‘fine’ in one decade was considered not so fine in the next. Thus a grain size in the range 0.5–3.0 μm was considered fine in the early years, but by the 1990s, the era of the nano-crystalline material had arrived, with a grain size of 20–50 nm.
The name "tungsten" comes from Norwegian
; the metal was first discovered in Norway. "Tungsten", i.e., "tung sten", means "heavy stone" in Norwegian, referring to the high density
of the material.
The initial development of cemented carbides occurred in Germany in the early 20th century. Their commercial use began in 1927 in Germany with a brand called Widia [VEE-dee-uh], a name coined from the German phrase "wie Diamant" ("like diamond"), alluding to the material's hardness (somewhat hyperbolically). Subsequent development occurred in various countries.
The Widia name became a genericized trademark
in various countries and languages, including English (widia, [WID-ee-uh]), although the genericized sense was never especially widespread in English ("carbide" is the normal generic term). Since 2009, the name has been revived as a brand name by Kennametal, and the brand subsumes
numerous popular brands of cutting tools. For the sake of clear communication, the reviving of the Widia brand may naturally further discourage use of the genericized sense (which was not very common in English anyway).
Uncoated tips brazed to their shanks were the first form. Clamped indexable inserts and today's wide variety of coatings are advances made in the decades since. With every passing decade, the use of carbide has become less "special" and more ubiquitous.
Tungsten carbide
Tungsten carbide is an inorganic chemical compound containing equal parts of tungsten and carbon atoms. Colloquially, tungsten carbide is often simply called carbide. In its most basic form, it is a fine gray powder, but it can be pressed and formed into shapes for use in industrial machinery,...
, hardmetal, or widia, is a hard material used in machining tough materials such as carbon steel or stainless steel
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....
, as well as in situations where other tools would wear away, such as high-quantity production runs. Most of the time, carbide will leave a better finish on the part, and allow faster machining. Carbide tools can also withstand higher temperatures than standard high speed steel
High speed steel
High speed steelMost copyeditors today would tend to choose to style the unit adjective high-speed with a hyphen, rendering the full term as high-speed steel, and this styling is not uncommon . However, it is true that in the metalworking industries the styling high speed steel is long-established...
tools.
Composition
Cemented carbide is a metal matrix compositeMetal matrix composite
A metal matrix composite is composite material with at least two constituent parts, one being a metal. The other material may be a different metal or another material, such as a ceramic or organic compound. When at least three materials are present, it is called a hybrid composite...
where tungsten carbide
Tungsten carbide
Tungsten carbide is an inorganic chemical compound containing equal parts of tungsten and carbon atoms. Colloquially, tungsten carbide is often simply called carbide. In its most basic form, it is a fine gray powder, but it can be pressed and formed into shapes for use in industrial machinery,...
particles are the aggregate and metallic cobalt
Cobalt
Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....
serves as the matrix. The process of combining tungsten carbide with cobalt is referred to as sintering
Sintering
Sintering is a method used to create objects from powders. It is based on atomic diffusion. Diffusion occurs in any material above absolute zero, but it occurs much faster at higher temperatures. In most sintering processes, the powdered material is held in a mold and then heated to a temperature...
or Hot Isostatic Pressing
Hot isostatic pressing
Hot isostatic pressing is a manufacturing process used to reduce the porosity of metals and influence the density of many ceramic materials. This improves the material's mechanical properties and workability....
(HIP). During this process cobalt eventually will be entering the liquid stage and WC grains (much higher melting point) remain in the solid stage. As a result of this process cobalt is embedding/cementing the WC grains and thereby creates the metal matrix composite with its distinct material properties. The naturally ductile cobalt metal serves to offset the characteristic brittle behavior of the tungsten carbide ceramic, thus raising its toughness and durability. Such parameters of tungsten carbide can be changed significantly within the carbide manufacturer's sphere of influence, primarily determined by grain size, cobalt content, dotation (e.g. alloy carbides) and carbon content.
Inserts for metal cutting
Carbide is more expensive per unitUnit cost
The unit cost of a product is the cost per standard unit supplied, which may be a single sample or a container of a given number. When purchasing more than a single unit, the total cost will increase with the number of units, but it is common for the unit cost to decrease as quantity is increased...
than other typical tool materials, and it is more brittle, making it susceptible to chipping and breaking. To offset these problems, the carbide cutting tip itself is often in the form of a small insert for a larger tipped tool
Tipped tool
A tipped tool generally refers to any cutting tool where the cutting edge consists of a separate piece of material, either brazed, welded or clamped on to a separate body. Common materials for tips include tungsten carbide, polycrystalline diamond, and cubic boron nitride...
whose shank is made of another material, usually carbon tool steel
Tool steel
Tool steel refers to a variety of carbon and alloy steels that are particularly well-suited to be made into tools. Their suitability comes from their distinctive hardness, resistance to abrasion, their ability to hold a cutting edge, and/or their resistance to deformation at elevated temperatures...
. This gives the benefit of using carbide at the cutting interface without the high cost and brittleness of making the entire tool out of carbide. Most modern face mills use carbide inserts, as well as many lathe tools and endmill
Endmill
An endmill is a type of milling cutter, a cutting tool used in industrial milling applications. It is distinguished from the drill bit, in its application, geometry, and manufacture...
s. In recent decades, though, solid-carbide endmills have also become more commonly used, wherever the application's characteristics make the pros (such as shorter cycle times) outweigh the cons (mentioned above).
Insert coatings
To increase the life of carbide tools, they are sometimes coated. Four such coatings are TiN (titanium nitrideTitanium nitride
Titanium nitride is an extremely hard ceramic material, often used as a coating on titanium alloys, steel, carbide, and aluminium components to improve the substrate's surface properties....
), TiC (titanium carbide
Titanium carbide
Titanium carbide, TiC, is an extremely hard refractory ceramic material, similar to tungsten carbide.It is commercially used in tool bits. It has the appearance of black powder with NaCl-type face centered cubic crystal structure...
), Ti(C)N (titanium carbide-nitride), and TiAlN (titanium aluminum nitride). (Newer coatings, known as DLC (Diamond-like carbon
Diamond-like carbon
Diamond-like carbon exists in seven different forms of amorphous carbon materials that display some of the typical properties of diamond. They are usually applied as coatings to other materials that could benefit from some of those properties. All seven contain significant amounts of sp3...
) are beginning to surface, enabling the cutting power of diamond without the unwanted chemical reaction between real diamond and iron.) Most coatings generally increase a tool's hardness and/or lubricity. A coating allows the cutting edge of a tool to cleanly pass through the material without having the material gall
Galling
Galling usually refers to the adhesive wear and transfer of material between metallic surfaces in relative converging contact during sheet metal forming and other industrial operations....
(stick) to it. The coating also helps to decrease the temperature associated with the cutting process and increase the life of the tool. The coating is usually deposited via thermal CVD
Chemical vapor deposition
Chemical vapor deposition is a chemical process used to produce high-purity, high-performance solid materials. The process is often used in the semiconductor industry to produce thin films. In a typical CVD process, the wafer is exposed to one or more volatile precursors, which react and/or...
and, for certain applications, with the mechanical PVD
Physical vapor deposition
Physical vapor deposition is a variety of vacuum deposition and is a general term used to describe any of a variety of methods to deposit thin films by the condensation of a vaporized form of the desired film material onto various workpiece surfaces...
method. However if the deposition is performed at too high temperature, an eta phase of a Co6W6C tertiary carbide forms at the interface between the carbide and the cobalt phase, facilitating adhesion failure of the coating.
Inserts for mining tools
Mining and tunneling cutting tools are most often fitted with Cemented Carbide tips the so called "Button Bits". Only man made diamond may replace the Cemented Carbide buttons when conditions are ideal, but as rock drilling is a tough job the Cemented Carbide button bits remain the most used type throughout the world.Rolls for hot-roll and cold-roll applications
Since the mid-1960s, steel mills around the world have applied cemented carbide to the rolls of their rolling mills for both hot and cold rolling of tubes, bars, and flats.Other industrial applications
This category contains a countless number of applications, but can be split into three main areas:- Engineered components
- Wear parts
- Tools and tool blanks
Some key areas where cemented carbide components are used:
- Automotive components
- Canning tools for deep drawingDeep drawingDeep drawing is a sheet metal forming process in which a sheet metal blank is radially drawn into a forming die by the mechanical action of a punch. It is thus a shape transformation process with material retention. The process is considered "deep" drawing when the depth of the drawn part exceeds...
of two-piece cansTin canA tin can, tin , steel can, or a can, is a sealed container for the distribution or storage of goods, composed of thin metal. Many cans require opening by cutting the "end" open; others have removable covers. Cans hold diverse contents: foods, beverages, oil, chemicals, etc."Tin" cans are made... - Rotary cutters for high-speed cutting of artificial fibres
- Metal forming tools for wire drawingWire drawingWire drawing is a metalworking process used to reduce the cross-section of a wire by pulling the wire through a single, or series of, drawing die. There are many applications for wire drawing, including electrical wiring, cables, tension-loaded structural components, springs, paper clips, spokes...
and stampingDie (manufacturing)A die is a specialized tool used in manufacturing industries to cut or shape material using a press. Like molds, dies are generally customized to the item they are used to create...
applications - Rings and bushings typically for bump and seal applications
- Woodworking, e.g., for sawSawA saw is a tool that uses a hard blade or wire with an abrasive edge to cut through softer materials. The cutting edge of a saw is either a serrated blade or an abrasive...
ing and planingPlanerThe term planer may refer to several types of carpentry tools, woodworking machines or metalworking machine tools.*Plane : a hand tool used to produce flat surfaces by shaving the surface of the wood...
applications - Pump pistons for high-performance pumpPumpA pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...
s (e.g., in nuclearNuclear powerNuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...
installations) - Nozzles, e.g., high-performance nozzles for oil drillingOil wellAn oil well is a general term for any boring through the earth's surface that is designed to find and acquire petroleum oil hydrocarbons. Usually some natural gas is produced along with the oil. A well that is designed to produce mainly or only gas may be termed a gas well.-History:The earliest...
applications - Roof and tail tools and components for high wear resistance
- Balls for ball bearingBall bearingA ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races.The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. It achieves this by using at least two races to contain the balls and transmit...
s and ballpoint penBallpoint penA ballpoint pen is a writing instrument with an internal ink reservoir and a sphere for a point. The internal chamber is filled with a viscous ink that is dispensed at its tip during use by the rolling action of a small sphere...
s
Jewelry
Tungsten CarbideTungsten carbide
Tungsten carbide is an inorganic chemical compound containing equal parts of tungsten and carbon atoms. Colloquially, tungsten carbide is often simply called carbide. In its most basic form, it is a fine gray powder, but it can be pressed and formed into shapes for use in industrial machinery,...
(Cemented Carbide) has become a popular metal in the bridal jewelry industry, due to its extreme hardness and high resistance to scratching. However, tungsten carbide is not a solid metal – it is a ceramic
Ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
containing ground tungsten
Tungsten
Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...
and ground carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
that is bound together by an alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
, formerly cobalt
Cobalt
Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....
and presently more often nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
, through high pressure. This results in a very hard material that is also brittle
Brittle
A material is brittle if, when subjected to stress, it breaks without significant deformation . Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Breaking is often accompanied by a snapping sound. Brittle materials include most ceramics and glasses ...
, thus prone to chip, crack or shatter from impact to a hard surface. Once fractured, it cannot be repaired.
History
An attempt has been made to follow the scientific and technological steps associated with the production of fine grained hardmetal. This task is not easy, though, because of the restrictions placed by commercial, and in some cases research, organisations, in not publicising relevant information until long after the date of the initial work. Thus, placing data in an historical, chronological order is somewhat difficult. However, it has been possible to establish that as far back as 1929, approximately 6 years after the first patent was granted, Krupp/Osram workers had identified the positive aspects of tungsten carbide grain refinement. By 1939 they had also discovered the beneficial effects of adding a small amount of vanadium and tantalum carbide. This effectively controlled discontinuous grain growth.What was considered ‘fine’ in one decade was considered not so fine in the next. Thus a grain size in the range 0.5–3.0 μm was considered fine in the early years, but by the 1990s, the era of the nano-crystalline material had arrived, with a grain size of 20–50 nm.
The name "tungsten" comes from Norwegian
Norwegian language
Norwegian is a North Germanic language spoken primarily in Norway, where it is the official language. Together with Swedish and Danish, Norwegian forms a continuum of more or less mutually intelligible local and regional variants .These Scandinavian languages together with the Faroese language...
; the metal was first discovered in Norway. "Tungsten", i.e., "tung sten", means "heavy stone" in Norwegian, referring to the high density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
of the material.
The initial development of cemented carbides occurred in Germany in the early 20th century. Their commercial use began in 1927 in Germany with a brand called Widia [VEE-dee-uh], a name coined from the German phrase "wie Diamant" ("like diamond"), alluding to the material's hardness (somewhat hyperbolically). Subsequent development occurred in various countries.
The Widia name became a genericized trademark
Genericized trademark
A genericized trademark is a trademark or brand name that has become the colloquial or generic description for, or synonymous with, a general class of product or service, rather than as an indicator of source or affiliation as intended by the trademark's holder...
in various countries and languages, including English (widia, [WID-ee-uh]), although the genericized sense was never especially widespread in English ("carbide" is the normal generic term). Since 2009, the name has been revived as a brand name by Kennametal, and the brand subsumes
Consolidation (business)
Consolidation or amalgamation is the act of merging many things into one. In business, it often refers to the mergers and acquisitions of many smaller companies into much larger ones. In the context of financial accounting, consolidation refers to the aggregation of financial statements of a group...
numerous popular brands of cutting tools. For the sake of clear communication, the reviving of the Widia brand may naturally further discourage use of the genericized sense (which was not very common in English anyway).
Uncoated tips brazed to their shanks were the first form. Clamped indexable inserts and today's wide variety of coatings are advances made in the decades since. With every passing decade, the use of carbide has become less "special" and more ubiquitous.