Carbides titanium

Titanium carbide is one of the most important coating materials and its deposition reactions are similar to those of other interstitial carbides. 1 1 A 

This reaction is usually carried out in die temperature range of 8S0-1050 C in a hydrogen atmosphere with pressure varying from less than 100 Pa to 1 atm. A common pressure is 4 kPa. l 

To deposit TiC, titanium tetrachloride (which is a liquid at room temperature) is vaporized and transported by flowing hydrogen into the reaction vessel where it reacts with a gaseous carbon source such as methane (CH4), toluene (C5H5CH3), or propane (CjHg).  

The high-temperature requirement places restrictions on the type of substrate that can be used. For instance some steels will lose their mechanical properties at these temperature and will require a heat treatment after coating. They may also change dimensions sufficiently to require post-deposition machining. 

Metallo-Organic CVD (MOCVD)I l It is possible to lower the deposition temperature of titanium carbide (i.e., 700°C) by using metallo-organic precursors such as  

After tungsten carbide, titanium carbide, TiC, is the most important metallic hard material. It is manufactured from pure Ti02 and carbon black in induction furnaces at 2000 to 2200°C  

TiC is also produced in small quantities from titanium scrap in nickel and iron baths using the men,struum process (see Section 5.6.2). 

Titanium carbide has the highest hardness of all metal carbides (see Table 5.6-1), but is rarely used on its own in cemented carbide technology, since the high oxygen content of the titanium carbide makes the hard metal too brittle. It is thus mainly utilized in the manufacture of 

Titanium carbide has the highest hardness of all metal monocarbides 

Thin layers of TiC on cemented carbides increase the abrasion resistance (application as a cutting material) 

Many CVD reactions are being investigated for the deposition of carbides and nitrides, particularly for titanium nitride for semiconductor applications, such as diffusion barrier. The following is a summary of the metallo-organic precursors and deposition condition presently used in development or production of these materials. 

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Figure C2.17.6. Transmission electron micrograph and its Fourier transfonn for a TiC nanocrystal. High-resolution images of nanocrystals can be used to identify crystal stmctures. In tliis case, tire image of a nanocrystal of titanium carbide (right) was Fourier transfonned to produce tire pattern on tire left. From an analysis of tire spot geometry and spacing, one can detennine that tire nanocrystal is oriented witli its 11001 zone axis parallel to tire viewing direction [217].

Figure C2.17.7. Selected area electron diffraction pattern from TiC nanocrystals. Electron diffraction from fields of nanocrystals is used to detennine tire crystal stmcture of an ensemble of nanocrystals [119]. In tliis case, tliis infonnation was used to evaluate the phase of titanium carbide nanocrystals [217].

Processing. Tungsten carbide is made by heating a mixture of lampblack with tungsten powder in such proportions that a compound with a combined carbon of 6.25 wt % is obtained. The ratio of free-to-combined carbon is of extreme importance. Tantalum and titanium carbides are made by heating a mixture of carbon with the metal oxide. Multicarbide powders, such as M02C—WC, TaC—NbC, and TiC—TaC—WC, are made by a variety of methods, the most important of which is carburization of powder mixtures. 

The cermet class of materials contains a large number of compositions (57). Most cermets are carbide-based, eg, WC and titanium carbide [12070-08-5] TiC. Cemented tungsten carbides are widely used for cutting tools and car parts. 

Fig. 14. Titanium carbide coating on graphite showing the nodular growth with a columnar morphology and the fracturing resulting from a coefficient of...

Titanium carbide is resistant to aqueous alkaU except in the presence of oxidising agents. It is resistant to acids except nitric acid, aqua regia, and mixtures of nitric acid with sulfuric or hydrofluoric acid. In oxygen at 450°C, a nonprotecting anatase coating forms. The reaction... 

Annual world production of titanium carbide is thousands of metric tons. It is manufactured mainly in-house by cutting-tool manufacturers by the reduction of titanium dioxide with carbon ... 

A number of high temperature processes for the production of titanium carbide from ores have been reported (28,29). The aim is to manufacture a titanium carbide that can subsequently be chlorinated to yield titanium tetrachloride. In one process, a titanium-bearing ore is mixed with an alkah-metal chloride and carbonaceous material and heated to 2000°C to yield, ultimately, a highly pure TiC (28). Production of titanium carbide from ores, eg, ilmenite [12168-52-4], EeTiO, and perovskite [12194-71 -7], CaTiO, has been described (30). A mixture of perovskite and carbon was heated in an arc furnace at ca 2100°C, ground, and then leached with water to decompose the calcium carbide to acetjdene. The TiC was then separated from the aqueous slurry by elutriation. Approximately 72% of the titanium was recovered as the purified product. In the case of ilmenite, it was necessary to reduce the ilmenite carbothermaHy in the presence of lime at ca 1260°C. Molten iron was separated and the remaining CaTiO was then processed as perovskite. 

Titanium carbide may also be made by the reaction at high temperature of titanium with carbon titanium tetrachloride with organic compounds such as methane, chloroform, or poly(vinyl chloride) titanium disulfide [12039-13-3] with carbon organotitanates with carbon precursor polymers (31) and titanium tetrachloride with hydrogen and carbon monoxide. Much of this work is directed toward the production of ultrafine (<1 jim) powders. The reaction of titanium tetrachloride with a hydrocarbon-hydrogen mixture at ca 1000°C is used for the chemical vapor deposition (CVD) of thin carbide films used in wear-resistant coatings. 

Alternatives to the fluidized-bed method process include the chlorination of titanium slags in chloride melts, chlorination with hydrogen chloride, and flash chlorination. The last is claimed to be particularly advantageous for minerals having a high impurity content (133—135,140). The option of chlorinating titanium carbide has also been considered (30). 

G. W. Eiger, Preparation and Chlorination of Titanium Carbide from Domestic Titaniferous Ores, Report of Investigation 8497, U.S. Department of Interior, Bureau of Mines, Washington, D.C., 1980. 

Table 10. Composition and Properties of Steel Grades of Cemented Titanium Carbide ...

S. J. Whalen, Vapor Deposition of Titanium Carbide, ASTME Technical Paper No. 690, American Society of Tool and Manufacturing Engineers (now Society of Manufacturing Engineers (SME)), Dearborn, Mich., 1965. 

Ceramics (qv) such as those in Table 12 find high temperature use to over 800°C (32). Advanced ceramics finding interest include alumina, partially stabilized zitconia, siUcon nitride, boron nitride, siUcon carbide, boron carbide, titanium diboride, titanium carbide, and sialon (Si—Al—O—N) (33) (see... 

The four most important carbides for the production of hard metals are tungsten carbide [12070-12-17, WC, titanium carbide [12070-08-5] TiC, tantalum carbide [12070-06-3J, TaC, and niobium carbide [12069-94-2] NbC. The binary and ternary soHd solutions of these carbides such as WC—TiC and WC—TiC—TaC (NbC) are also of great importance. Chromium carbide (3 2) [12012-39-0], molybdenum carbide [12011-97-1], MoC, and... 

Titanium carbide may be prepared by a thermochemical reaction between finely divided carbon and titanium metal powder. The reaction proceeds exothermically. 

Annual world production of titanium carbide is 1200—1500 metric tons. On an iadustrial scale, it is produced most often through the reaction of Ti02 with carbon black (see Titaniumand titanium alloys Titanium compounds). 

In iadustrial production of titanium carbide, pure (99.8%, with minor impurities of Si, Fe, S, P, and alkahes) titanium oxide [13463-67-7] Ti02, iu the dry or wet state is mixed iu 68.5 31.5 ratio with carbon black or finely milled low ash graphite. The dry mixture is pressed iato blocks that are heated iu a horizontal or vertical carbon-tube furnace at 1900—2300°C hydrogen that is free of oxygen and nitrogen serves as protective gas. In the vertical push-type furnaces, the Hberated CO itself provides protection. 

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