High temperature hardness

The CVD of TaC has few industrial applications. It has been used as a coating on tantalum metal to improve chemical resistance, high-temperature hardness, and wear and oxidation resistance. 

Distillation of phenols with zinc dust [617] or with dry lithium aluminum hydride [618] also results in hydrogenolysis of phenolic hydroxyls but because the reaction requires very high temperatures hardly any other function in the molecule can survive, and the method has only limited use. 

With the possible exception of common line insulators, electrical porcelain is especially formulated and may contain varying percentages of zirconia and beryllia. These ingredients increase both strength (mechanical) and resistance to high temperatures. Hard porcelains are especially formulated to resist thermal shock as well. 

Properties Amorphous, black solid. D 2.15-2.18, sublimes at high temperature, hard and abrasive. Noncombustible. 

Fiq. 60,—High Temperature Hardness Tests (600 Kg.) on Duralumin quenched from 475°. 

Fig. 726.—High-temperature Hardness Tests (500 Kg.) on Aluminium Bronze, Type I —...

Model for polymer-induced F-S P-T High-temperature (hard spheres) 65... 

A. Krell and O. V. Bakun, High-temperature hardness of Al203-base ceramics, Acta Metall. 1986, 34, 1315-1319. 

A further example of production of boride-based fully-dense materials is recently reported by Olevsky et al. [99]. The product, a TiB2 TiN-Ni cermet, a material with a unique combination of high temperature hardness and stability and with a reasonable ductility/fracture toughness. 

Figure 106. Room-temperature hardness HViq and high-temperature hardness HV2 of TiB2-Fe cermets and conventional hard metals (after [340]).

Figure 126. High-temperature hardness of ceramic materials in comparison to diamond and cubic boron nitride.

If these grades are designed without any WC phase, they are named cermets which give a unique combination of high temperature hardness, chemical wear resistance, and low... 

K. Nakano, H. Matsubara, and T. Imura, High temperature hardness of titanium diboride single crystal, pn. J. Appl. Phys., 13(6) 1005-1006,1974. 

K Nakano, H Matsubara, T Imura. High-temperature hardness of IV a-diboride single crystals. J Less Common Met 47 259, 1976. 

K Nakano, K Nakamura, T Okubo, T Sugimura. High temperature hardness and slip system of NbB2 and TaB2 single crystals. J Less Common Met 84 79C, 1982. 

Reply bv the Authors We were not able to measure high temperature hardness (bulk or matrix) of the examined composite. Therefore we did not make any attempt to determine the K value. Abrasion tests were carried out at different temperatures under a constant test load on abrasive grains having a certain grain size. These testing conditions gave appropriate results to compare the effect of test temperature and composition on the abrasion resistance of the examined composites. 

Nis] Mechanical tests High-temperature hardness... 

The mechanical properties were investigated in some early studies. In these studies, the creep properties [111], tensile strengths [112], flow stress [113] and high temperature hardness [113,114] of various oxides were measured. The mechanical properties of wustite were also related to scale-steel interface adhesion [115] and marker movement [116] in the wustite scale layer. Based on these early studies, it was concluded that at temperatures above 800°C, wustite was deformable, and even in the range of 650-800°C, wustite still possessed certain plasticity [117], while magnetite and hematite were not deformable even at 1000°C. 

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