High-temperature oxidation of composite based on double titanium–chromium carbide

Abstract

The effect of a metallic binder and nickel coating on the high-temperature oxidation resistance of a composite material based on double titanium-chromium carbide is studied. It is shown that the introduction of a Fe-Cr binder decreases the rate of oxidation of the base material, but the maximum weight increment of the samples remains as it is in the initial TiCrC because of the oxidation of binder components. The nickel coating not only substantially decreases the oxidation rate of the composite components, but also shifts the thermal effects toward much higher temperatures. The oxidation occurs in two stages for compact samples, in three stages for the composite material, and in four stages for the composite material with nickel coating.Refractory titanium compounds are widely used as structural and tool materials in various industrial fields. Double and triple systems of carbides, nitrides, and carbonitrides of transition metals for coatings are of high interest [1]. At high temperatures, their stoichiometric composition changes, giving rise to various compounds. As a consequence, the service characteristics of these materials may vary over a wide range [2].To find out whether titanium chromium carbide and TiCrC-based materials can work at high temperatures (to 1000°C) and can be employed as gas-thermal (plasma, detonation) coatings, the resistance to high-temperature oxidation (HTO) of these materials was tested. We tested powders of initial material TiCrC, composite material TiCrC-30 wt.% (Fe-Cr) (TKhKF-30), nickel-and phosphorus-clad composite material TKhKF-30, and TKhKF-30 compacts. The TKhKF-30 powder was produced by grinding and screening of sinters, while the compacts were made by hot pressing. The nickel-phosphorus (Ni-10 wt.% P) coating was chemically deposited in water solution using sodium hypophosphite as a reducer. The particle size was -100+40 μm.The HTO resistance of the samples was tested by nonisothermal heating to 1000°C in air at a rate of 10 °C/min using a Q-1500 derivatograph. An aluminum oxide powder was used as a reference material. The charge had 200 mg in weight.The differential thermal (DT) curve of TiCrC initial powder (Fig. 1) displays two exothermic effects. One (peak at 660°C) represents the reaction between TiCrC and oxygen in air:TiCrC + 2O 2 = TiO 2 + CrO + CO↑.(1)