Huh? That was a response to your original assertion that "Tungsten carbide is not an alloy."
Here's the contextual bit from the Encarta excerpt you seem to keep missing: "Compounds that contain both a metal or metals and certain nonmetals, particularly those containing carbon, are also called alloys. The most important of these is steel."
Besides, is a substance composed of two or more metal an alloy, or not? Bottom line is that you took something out of context to make it appear that something was said that wasn't. Now you're trying to defend that action by continuing to ignore the context? LOL
Quit wasting my time with your silly trolling word games.
Just got done with a metallurgy class and WC is not an alloy it's a compound. When looking at binary Phase Diagrams the straight verticle lines are compounds.
Right. :)
The tool-material, "Tungsten Carbide" is like a composite material. The manufacturing of WC tools resembles a ceramic material.
Newsgroups: sci.engr.metallurgy From: snipped-for-privacy@ucd.ie (Dr Alun J. Carr) Subject: Re: Can someone tell me what WC is?
Richard Larker wrote:
Again, 'hardmetal' comes from the German. The hard phase was known by the Germans as 'hartstoffe' and the sintered material, with metallic binder, as 'hartmetalle'. According to Scwarzkopf & Kieffer (Schwarzkopf, P. & Kieffer, R. (1953) Refractory Hard Metals, New York: Macmillan):
In English -- at least in a number of American and English publications, including this book -- the term "hard metals" is used for the binder-free substances as well as for the cemented materials. In view of the physical properties, particularly the electrical conductivity which clearly indicates metallic bonding, the use of the term for binder-free substances also appears justified.
In English, we would also refer to the hard phase as an 'Interstitial Alloy' (Goldschmidt, H. J. (1967) Interstitial Alloys, London: Butterworth), because it is _not_ a ceramic. WC, TiC, ZrC, TiN, etc. are all brittle solids, with hardnesses similar to ceramics, but unlike ceramics, the interatomic bonding is predominantly _metallic_ (evidenced by, amongst other things, the high electrical conductivity (see above), and the metallic lustre). To quote Schwarzkopf & Kieffer again (ibid):
The term "hard metals" is used to specify a group of high-melting hard substances which have metallic character although, on the basis of chemical composition, they would be considered inorganic compounds. Typical representatives of these materials are the refractory carbides of the transition metals of the fourth to sixth groups of the periodic system, such as, particularly, the carbides of tungsten, titanium, and tantalum.
It is therefore incorrect to refer to cemented carbides as 'cermets', as they contain no ceramic. To do so is a sign of intellectual laziness (unfortunately common in the hard materials community today -- I do not intend to attack Dr Larker personally: I feel he has been misinformed), merely classifying all hard substances as 'ceramics', merely because they are 'hard', when one should instead consider the nature of the interatomic bond as the basis for a system of classification.
========================================================== ...Max-Planck Society, Berlin, and their colleagues investigated the electronic structure of a quasicrystalline alloy of aluminum-nickel-cobalt (AlNiCo) by means of angle-resolved photoemission. ==========================================================
Interesting, but exactly what do these aluminum-nickel-cobalt quasicrystals have to do with the properties of tungsten carbide tooling? Are you trying to make a parallel that both quasicrystals and tungsten-carbon-cobalt are alloys?
Actually I believe it was "Carbide Tooling" made up of Tungsten carbide & a Cobalt binder that I was referring to, which is as yet, unresolved to my satisfaction since they retain the free electrons of metals, and therefore share the properties of metals. Here's a tid-bit on Carbides, note the last section on WC:
Although carbon is essentially inert at room temperature, it reacts with less electronegative negative elements at high temperatures to form compounds known as carbides. When carbon reacts with an element of similar size and electronegativity, a covalent carbide is produced. Silicon carbide, for example, is made by treating silicon dioxide from quartz with an excess of carbon in an electric furnace at 2300 K. SiO2(s) + 3 C(s) SiC(s) + 2 CO(g)
Covalent carbides have properties similar to those of diamond. Both SiC and diamond are inert to chemical reactions, except at very high temperatures; both have very high melting points; and both are among the hardest substances known. SiC was first synthesized by Edward Acheson in
1891. Shortly thereafter, Acheson founded the Carborundum Company to market this material. Then, as now, materials in this class are most commonly used as abrasives.
Compounds that contain carbon and one of the more active metals are called ionic carbides. CaO(s) + 3 C(s) CaC2(s) + CO(g)
It is useful to think about these compounds as if they contained negatively charged carbon ions: [Ca2+][C22-] or [Al3+]4[C4-]3. This model is useful because it explains why these carbides burst into flame when added to water. The ionic carbides that formally contain the C4- ion react with water to form methane, which is ignited by the heat given off in this reaction. C4- + 4 H2O CH4 + 4 OH-
The ionic carbides that formally contain the C22- ion react with water to form acetylene, which is ignited by the heat of reaction. C22- + 2 H2O C2H2 + 2 OH-
At one time, miners' lamps were fueled by the combustion of acetylene prepared from the reaction of calcium carbide with water.
Interstitial carbides, such as tungsten carbide (WC), form when carbon combines with a metal that has an intermediate electronegativity and a relatively large atomic radius. In these compounds, the carbon atoms pack in the holes (interstices) between planes of metal atoms. The interstitial carbides, which include TiC, ZrC, and MoC retain the properties of metals. They act as alloys, rather than as either salts or covalent compounds. ==============================================================
See the above section on Interstitial carbides which retain the properties of metals as opposed to ionic and covalently bonded carbides that are generally non conductive.
The term "alloy" is not always defined in a consistent manner. Some definitions would include the intimate mixing of powders in powder metallurgy, some don't.
Ceramic is another term that seems to be limited in consistently addressing all the structural varieties & combinations of materials considered "ceramic", IMO.
The two most common chemical bonds for ceramic materials are covalent and ionic. The bonding of atoms together is much stronger in covalent and ionic bonding than in metallic. This is why ceramics generally have the following properties: high hardness, high compressive strength, and chemical inertness. This strong bonding also accounts for the less attractive properties of ceramics, such as low ductility and low tensile strength. The absence of free electrons is responsible for making most ceramics poor conductors of electricity and heat.
However, it should be noted that the crystal structures of ceramics are many and varied and this results in a very wide range of properties. For example, while ceramics are perceived as electrical and thermal insulators, ceramic oxide (initially based on Y-Ba-Cu-O) is the basis for high temperature superconductivity. Diamond and silicon carbide have a higher thermal conductivity than aluminum or copper. =============================================================
I posted an Encarta definition of alloy that included the process of powder metallurgy. You responded with a reference to the "CRC Materials Science and Engineering Handbook", but didn't list what they said OR an address to check exactly what they said, just that they think WC is a ceramic. I responded with the observation that you seem to think that the term ceramic and alloy are mutually exclusive. Do you?
Silly nonsense remarks neither adds support to your position nor makes you appear particularly objective. Either you have something intelligent to contribute related to the subject matter at hand, or you don't.
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