Cermet

Last updated

A cermet is a composite material composed of ceramic and metal materials.

Contents

A cermet can combine attractive 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, [1] have potential applications in automotive and aerospace applications. [2] [1]

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.

History [3]

After World War II, the need to develop high temperature and high stress-resistant materials became clear. During the war, German scientists developed oxide base cermets as substitutes for alloys. They saw a use for this for the high-temperature sections of new jet engines as well as high temperature turbine blades. Today ceramics are routinely implemented in the combuster part of jet engines because it provides a heat-resistant chamber. Ceramic turbine blades have also been developed. These blades are lighter (less massive) than steel and allow for greater rotational acceleration (“spool-up time”) of the blade assemblies.

The United States Air Force saw potential in the material technology and became one of the principal sponsors for various research programs in the US. Some of the first universities to research were Ohio State University, University of Illinois, and Rutgers University.

The word cermet was actually coined by the United States Air Force, the idea being that they are a combination of two materials, a metal and a ceramic. Basic physical properties of metals include ductility, high strength, and high thermal conductivity. Ceramics possess basic physical properties such as a high melting point, chemical stability, and especially oxidation resistance.

The first ceramic metal material developed used magnesium oxide (MgO), beryllium oxide (BeO), and aluminum oxide (Al2O3) for the ceramic part. Emphasis on high stress rupture strengths was around 980 °C. [4] Ohio State University was the first to develop Al2O3 based cermets with high stress rupture strengths around 1200 °C. Kennametal, a metal-working and tool company based in Latrobe, PA, USA, developed the first titanium carbide cermet with a 19 megapascals (2,800 psi) and 100-hour stress-to-rupture strength at 980 °C. Jet engines operate at this temperature and further research was invested on using these materials for components.

Quality control in manufacturing these ceramic metal composites was hard to standardize. Production had to be kept to small batches and within these batches, the properties varied greatly. Failure of the material was usually a result of undetected flaws usually nucleated during processing.

The existing technology in the 1950s reached a limit for jet engines where little more could be improved. Subsequently, engine manufactures were reluctant to develop ceramic metal engines. Interest was renewed in the 1960s when silicon nitride and silicon carbide were looked at more closely. Both materials possessed better thermal shock resistance, high strength, and moderate thermal conductivity.

Cermet production, Helipot Division of Beckman Instruments, 1966 [5]

Applications

Ceramic-to-metal joints and seals

Cermets were first used extensively in ceramic-to-metal joint applications. Construction of vacuum tubes was one of the first critical systems, with the electronics industry employing and developing such seals. German scientists recognized that vacuum tubes with improved performance and reliability could be produced by substituting ceramics for glass. Ceramic tubes can be outgassed at higher temperatures. Because of the high-temperature seal, ceramic tubes withstand higher temperatures than glass tubes. Ceramic tubes are also mechanically stronger and less sensitive to thermal shock than glass tubes. [6] Today, cermet vacuum tube coatings have proved to be key to solar hot water systems.

Ceramic-to-metal mechanical seals have also been used. Traditionally they have been used in fuel cells and other devices that convert chemical, nuclear, or thermionic energy to electricity. The ceramic-to-metal seal is required to isolate the electrical sections of turbine-driven generators designed to operate in corrosive liquid-metal vapors. [6]

Bioceramics

Hip prosthesis.jpg

Bioceramics play an extensive role in biomedical materials. The development of these materials and diversity of manufacturing techniques has broadened the applications that can be used in the human body. They can be in the form of thin layers on metallic implants, composites with a polymer component, or even just porous networks. These materials work well within the human body for several reasons. They are inert, and because they are resorbable and active, the materials can remain in the body unchanged. They can also dissolve and actively take part in physiological processes, for example, when hydroxylapatite, a material chemically similar to bone structure, can integrate and help bone grow into it. Common materials used for bioceramics include alumina, zirconia, calcium phosphate, glass ceramics, and pyrolytic carbons.

One important use of bioceramics is in hip replacement surgery. The materials used for the replacement hip joints were usually metals such as titanium, with the hip socket usually lined with plastic. The multiaxial ball was tough metal ball but was eventually replaced with a longer-lasting ceramic ball. This reduced the roughening associated with the metal wall against the plastic lining of the artificial hip socket. The use of ceramic implants extended the life of the hip replacement parts. [7]

Dental cermets are also used in dentistry as a material for fillings and prostheses.

Transportation

Ceramic parts have been used in conjunction with metal parts as friction materials for brakes and clutches. [6]

Electrical heaters

Cermets are used as heating elements in electric resistance heaters. One construction technique starts with the cermet material formulated as an ink which is printed on a substrate then cured with heat. This technique allows manufacture of complex shapes of heating elements. Examples of applications for cermet heating elements include thermostat heaters, heat sources for bottle sterilization, coffee carafe warmers, heaters for oven control, and laser printer fuser heaters. [8]

Other applications

The United States Army and British Army have had extensive research in the development of cermets. These include the development of lightweight ceramic projectile-proof armor for soldiers and also Chobham armor.

Cermets are also used in machining on cutting tools.

Cermets are also used as the ring material in high-quality line guides for fishing rods.

A cermet of depleted fissiable material (e.g. uranium, plutonium) and sodalite has been researched for its benefits in the storage of nuclear waste. [9] Similar composites have also been researched for use as a fuel form for nuclear reactors [10] and nuclear thermal rockets.[ citation needed ]

As nanostructured cermet, this material is used in the optical field, such as solar absorbers/selective surface. Thanks to the size of the particles (~5 nm), surface plasmons on the metallic particles are generated and enable the heat transmission.

For reasons regarding luxury, cermet is sometimes found to be case materials for some watches, including Jaeger-LeCoultre's Deep Sea Chronograph Vintage Cermet watch. It was also used (November 2019) on the bezel of the flagship diver Seiko Prospex LX Line Limited Edition watch.

See also

Notes

  1. 1 2 Hanaor, D.A.H.; Hu, L.; Kan, W.H.; Proust, G.; Foley, M.; Karaman, I.; Radovic, M. (2016). "Compressive performance and crack propagation in Al alloy/Ti2AlC composites". Materials Science and Engineering A. 672: 247–256. arXiv: 1908.08757 . doi:10.1016/j.msea.2016.06.073. S2CID   201645244.
  2. Bingchu, M.; Ming, Y.; Jiaoqun, Z., & Weibing, Z. (2006). "Preparation of TiAl/Ti2AlC composites with Ti/Al/C powders by in-situ hot pressing". Journal of Wuhan University of Technology-Mater. Sci. 21 (2): 14–16. doi:10.1007/BF02840829. S2CID   135148379.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. Tinklepaugh, James R.: "Cermets.", Reinhold Publishing Corporation, 1960
  4. Metallurgical Concepts, "Creep and Stress Rupture". "Creep and Stress Rupture". Archived from the original on 2007-01-05. Retrieved 2006-12-12.
  5. "The making of a cermet trimmer". Helinews. Beckman Instruments (36 Spring): 4–5. 1966.
  6. 1 2 3 Pattee, H.E. "Joining Ceramics and Graphite to Other Materials, A Report." Office of Technology Utilization National Aeronautics and Space Administration, Washington D.C., 1968
  7. Design Fax Online, "Hybrid Hip Joint". "Medical Equipment Designer - Application Ideas: Hybrid Hip Joint and Polycarbonate Liver". Archived from the original on 2007-09-27. Retrieved 2006-12-07.
  8. Lemon, Todd J. (September 1995). "Printed thick film heaters". Appliance Manufacturer. Troy. 43 (9): 32. ISSN   0003-679X.
  9. http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=APCPCS000532000001000089000001&idtype=cvips&gifs=yes [ dead link ]
  10. "Silicon carbide and uranium oxide based composite fuel preparation using polumer infiltration and pyrolysis". Archived from the original on 2007-11-26. Retrieved 2007-10-11.

Further reading

Related Research Articles

<span class="mw-page-title-main">Ceramic</span> Inorganic, nonmetallic solid prepared by the action of heat

A ceramic is any of the various hard, brittle, heat-resistant, and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain, and brick.

In materials science, a metal matrix composite (MMC) is a composite material with fibers or particles dispersed in a metallic matrix, such as copper, aluminum, or steel. The secondary phase is typically a ceramic or another metal. They are typically classified according to the type of reinforcement: short discontinuous fibers (whiskers), continuous fibers, or particulates. There is some overlap between MMCs and cermets, with the latter typically consisting of less than 20% metal by volume. When at least three materials are present, it is called a hybrid composite. MMCs can have much higher strength-to-weight ratios, stiffness, and ductility than traditional materials, so they are often used in demanding applications. MMCs typically have lower thermal and electrical conductivity and poor resistance to radiation, limiting their use in the very harshest environments.

<span class="mw-page-title-main">Zirconium dioxide</span> Chemical compound

Zirconium dioxide is a white crystalline oxide of zirconium. Its most naturally occurring form, with a monoclinic crystalline structure, is the mineral baddeleyite. A dopant stabilized cubic structured zirconia, cubic zirconia, is synthesized in various colours for use as a gemstone and a diamond simulant.

<span class="mw-page-title-main">Tungsten carbide</span> Hard, dense and stiff chemical compound

Tungsten carbide is a chemical compound 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 sintering for use in industrial machinery, cutting tools, chisels, abrasives, armor-piercing shells and jewelry.

<span class="mw-page-title-main">Refractory</span> Materials resistant to decomposition under high temperatures and pressures

In materials science, a refractory is a material that is resistant to decomposition by heat, pressure, or chemical attack, and retains strength and form at high temperatures. Refractories are polycrystalline, polyphase, inorganic, non-metallic, porous, and heterogeneous. They are typically composed of oxides or carbides, nitrides etc. of the following elements: silicon, aluminium, magnesium, calcium, boron, chromium and zirconium.

<span class="mw-page-title-main">Titanium diboride</span> Chemical compound

Titanium diboride (TiB2) is an extremely hard ceramic which has excellent heat conductivity, oxidation stability and wear resistance. TiB2 is also a reasonable electrical conductor, so it can be used as a cathode material in aluminium smelting and can be shaped by electrical discharge machining.

<span class="mw-page-title-main">Tantalum carbide</span> Chemical compound

Tantalum carbides (TaC) form a family of binary chemical compounds of tantalum and carbon with the empirical formula TaCx, where x usually varies between 0.4 and 1. They are extremely hard, brittle, refractory ceramic materials with metallic electrical conductivity. They appear as brown-gray powders, which are usually processed by sintering.

<span class="mw-page-title-main">Heating element</span> Device that converts electricity into heat

A heating element converts electrical energy into heat through the process of Joule heating. Electric current through the element encounters resistance, resulting in heating of the element. Unlike the Peltier effect, this process is independent of the direction of current.

<span class="mw-page-title-main">Titanium nitride</span> Ceramic material

Titanium nitride is an extremely hard ceramic material, often used as a physical vapor deposition (PVD) coating on titanium alloys, steel, carbide, and aluminium components to improve the substrate's surface properties.

<span class="mw-page-title-main">Superalloy</span> Alloy with higher durability than normal metals

A superalloy, or high-performance alloy, is an alloy with the ability to operate at a high fraction of its melting point. Key characteristics of a superalloy include mechanical strength, thermal creep deformation resistance, surface stability, and corrosion and oxidation resistance.

<span class="mw-page-title-main">Zirconium carbide</span> Chemical compound

Zirconium carbide (ZrC) is an extremely hard refractory ceramic material, commercially used in tool bits for cutting tools. It is usually processed by sintering.

<span class="mw-page-title-main">Uranium dioxide</span> Chemical compound

Uranium dioxide or uranium(IV) oxide , also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite. It is used in nuclear fuel rods in nuclear reactors. A mixture of uranium and plutonium dioxides is used as MOX fuel. Prior to 1960, it was used as yellow and black color in ceramic glazes and glass.

<span class="mw-page-title-main">Ceramic engineering</span> Science and technology of creating objects from inorganic, non-metallic materials

Ceramic engineering is the science and technology of creating objects from inorganic, non-metallic materials. This is done either by the action of heat, or at lower temperatures using precipitation reactions from high-purity chemical solutions. The term includes the purification of raw materials, the study and production of the chemical compounds concerned, their formation into components and the study of their structure, composition and properties.

<span class="mw-page-title-main">Solid</span> State of matter

Solid is one of the four fundamental states of matter. The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structural rigidity and resistance to a force applied to the surface. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire available volume like a gas. The atoms in a solid are bound to each other, either in a regular geometric lattice, or irregularly. Solids cannot be compressed with little pressure whereas gases can be compressed with little pressure because the molecules in a gas are loosely packed.

<span class="mw-page-title-main">Cemented carbide</span> Type of composite material

Cemented carbides are a class of hard materials used extensively for cutting tools, as well as in 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.

<span class="mw-page-title-main">Bioceramic</span>

Bioceramics and bioglasses are ceramic materials that are biocompatible. Bioceramics are an important subset of biomaterials. Bioceramics range in biocompatibility from the ceramic oxides, which are inert in the body, to the other extreme of resorbable materials, which are eventually replaced by the body after they have assisted repair. Bioceramics are used in many types of medical procedures. Bioceramics are typically used as rigid materials in surgical implants, though some bioceramics are flexible. The ceramic materials used are not the same as porcelain type ceramic materials. Rather, bioceramics are closely related to either the body's own materials or are extremely durable metal oxides.

<span class="mw-page-title-main">Ceramic matrix composite</span> Composite material consisting of ceramic fibers in a ceramic matrix

In materials science, ceramic matrix composites (CMCs) are a subgroup of composite materials and a subgroup of ceramics. They consist of ceramic fibers embedded in a ceramic matrix. The fibers and the matrix both can consist of any ceramic material, whereby carbon and carbon fibers can also be regarded as a ceramic material.

<span class="mw-page-title-main">MAX phases</span>

The MAX phases are layered, hexagonal carbides and nitrides which have the general formula: Mn+1AXn, (MAX) where n = 1 to 4, and M is an early transition metal, A is an A-group (mostly IIIA and IVA, or groups 13 and 14) element and X is either carbon and/or nitrogen. The layered structure consists of edge-sharing, distorted XM6 octahedra interleaved by single planar layers of the A-group element.

Ultra-high-temperature ceramics (UHTCs) are a type of refractory ceramics that that can withstand extremely high temperatures without degrading, often above 2,000 °C. They also often have high thermal conductivities and are highly resistant to thermal shock, meaning they can withstand sudden and extreme changes in temperature without cracking or breaking. Chemically, they are usually borides, carbides, nitrides, and oxides of early transition metals.

Materials that are used for biomedical or clinical applications are known as biomaterials. The following article deals with fifth generation biomaterials that are used for bone structure replacement. For any material to be classified for biomedical applications, three requirements must be met. The first requirement is that the material must be biocompatible; it means that the organism should not treat it as a foreign object. Secondly, the material should be biodegradable ; the material should harmlessly degrade or dissolve in the body of the organism to allow it to resume natural functioning. Thirdly, the material should be mechanically sound; for the replacement of load-bearing structures, the material should possess equivalent or greater mechanical stability to ensure high reliability of the graft.