Certain features of the structure and properties of titanium carbide coatings on steels and cemented carbides

Abstract

In recent years interest has increased in metal carbide and n#ride coatings, particularly of titanium carbide. Such coatings are used in industry for increasing the wear resistance of nonregrindable cutting tips of tungstencontaining cemented carbides and tool steel forming and measuring tools. At present in our country and abroad three methods of production of titanium carbide coatings are used: 1) the Sandvik Corromant (Sweden) method, CVD, for increasing the life of cutting tips and steel tools: 2) a method developed by Moscow Institute of Railroad Transportation Engineers in collaboration with Moscow Cemented Carbide Combine for increasing the life of cutting tips; 3) a domestic method, the basis of which was proposed in 1975 by N. A. Kulybaya and A. T. Reva, for increasing the life of steel tools. Despite the introduction into production of new and modern methods of plasma, ion-plasma, vacuum, and other methods of chemical deposition at high temperatures the CVD process continues to be successfully used in production. An analysis of the literature data shows that the properties of a titanium carbide coating may vary within very broad limits depending upon the method of application of it [1-3]. In this work titanium carbide coatings were applied using domestic methods 2 and 3 in a vacuum of 1.3.10-3-1.3" 10 -2 Pa in the presence of titanium sponge and titanium tetrachloride supplied to the working volume at 1000-1100°C. Specimens of carbon steels (0.2-1.2% C) and tungsten carbide-base cemented carbides (TT10K8B, TT7K12, VKS) were used as the base. The lattice parameter and orientation of the growth of titanium carbide were determined on a DRON-0.5 x-ray diffractometer in cobalt K s radiation. The lattice parameter was calculated from the centers of gravity of the diffraction peaks and the orientation of the titanium carbide growth from the results of comparison of the relative intensity of the diffractogram lines with theoretical data. The chemical composition of coatings on TT10K8B cemented carbide applied using methods 1 and 2 were also investigated. Formation of titanium carbide using the CVD-method occurs under conditions of continuous delivery through the muffle of a large quantity of hydrogen in a mixture with methane and titanium tetrachloride. In this case hydrogen is the carrier gas and the reducing gas of titanium tetrachloride. The investigation was made by the x-ray photoelectron spectroscopy method on a Zeibold Heraus LHS 10 spectrometer with use of aluminum K s radiation (h~ = 1486.6 eV) in a 3" 10 -9 Pa vacuum in combination with argon ion etching. The charge condition of the atoms was judged from the amount of the chemical shift of the spectral lines indicating a change in the energy of the bond of the electrons on the basic or outer electron levels. Titanium carbide was obtained using method 2 as the result of occurrence in the reaction volume of the following basic reaction: