Metallic hard materials

Hard materials are divided into metallic and nonmetallic hard materials 

The industrially important hard materials can be divided into two groups, metallic and nonmetallic  

As the metallic hard materials, particularly the carbides, alloy easily with iron group metals, they are important in the production of cemented carbides (see Section 5.6.5.4). Apart from their great hardness, which is in the range 9 to 10 on the Mohs scale, they exhibit comparable electrical and thermal conductivities to metals, very high melting points and high chemical resistance. 

In crystal structure the metallic carbides and nitrides are almost all interstitial compounds in which the carbon or nitrogen atoms are found in the octahedral interstices of the metal lattice. The borides and silicides as well as a few carbides (e.g. Cr3C2) possess more complex structures. 

The most important metallic hard materials, as regards quantity, are tungsten carbide, WC, and titanium carbide, TiC with a production worldwide in 1995 of 20 10- t/a and 3.5 10 t/a respectively. Also worthy of mention is the 1.5 10 t/a of titanium carbonitride, Ti(C,N), produced in 1995, which is used as the hardening component in the cermet sector. Other metallic hard materials are produced in quantities below that of titanium carbide. In individual cases they can be very important as components of alloys in the realization of particular material properties. 

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Metal silicides Manufacture and applications in the metallic hard materials sector, see Section 5,6.9. 

The hardne.ss of metallic hard material.s i.s almost without exception between those of corundum and diamond... 

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 ... 

The silicides exhibit the lowest melting points and hardness values of the metallic hard materials (see Table 5.6-5). Their brittleness makes them unsuitable for utilization in hard metal alloys. Silicides have only been utilized industrially in metallurgical fields in which their scaling resistance and chemical resistance are important. They are also deposited using the CVD process e.g. as protective layers on high melting metallic surfaces. 

J. K. Park, S. T. Park, Densification of TiN-Ni cermets by improving wettability of liquid nickel on TiN grain surface with addition of MojC. Internatiorral Jourttal of Refractory Metals Hard Materials. 

D. Mari, S. Bolognini, G. Feusier, et al, TiMoCN based cermets Part 1. Morphology and phase composition. International Journal of Refractory Metals Hard Materials. 21,37(2003). 

Methods Appl. Mech. Engrg., Vol. 195, pp. 6737-6749 Mukhopadhyay, A. Basu, B. Das Bakshi, S. (2007). Pressureless sintering of ZrC>2-ZrB2 composites Microstructure and properties. International Journal of Refractory Metals Hard Materials, Vol. 25, pp. 179-188... 

Basu SN, Ye G, Gevelber M, Wroblewski D. Microcrack formation in plasma sprayed thermal barrier coatings. International Journal of Refractory Metals Hard Materials. 2005 23 335-343. 

Effect of CrB2 addition on densification, properties and oxidation resistance of TiB2, Inc. Journal of Refractory Metals Hard Materials, 27, 976-984 (2009)... 

Song, G. M., Wang, Y. J., Zhou, Y. (2003). Thermal-mechanical properties of TiC particle-reinforced tungsten composites for high temperature apphcations. International Journal of Refractory Metals Hard Materials, 27(1), 1—12. doi 10.1016/ S0263-4368(02)00105-l. 

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