Development of the composite material and coatings based on niobium carbide

We investigated the structure of composites based on the system NbC with a copper bond, obtained by impregnating the porous carbide skeletons with a metallic melt in a vacuum. In order to receive a porous skeleton, the powder of NbC, the average size of ~1 μm, was mixed on a 5 % solution of rubber in gasoline. After drying, the mixture was ground at a sieve into granules, which were pressed into briquettes of dimensions 55×30×10 mm. To ensure the intensification of the process, as well as wetting, impregnation was carried out at a temperature of 1,400 °C. The result was the obtained material with a fine-grained two-phase structure. The microstructure was investigated using a method of scanning electron microscopy (SEM), the chemical composition ‒ applying a method for energy dispersion analysis (EDS). The hardness was measured by Rockwell (scale C), the fracture toughness ‒ by the indirect Evans-Charles method. The composite's structure consists of rounded grains of NbC, which form a continuous skeleton, and the layers of copper bonding. The average size of grains and the intragrain layers of bonding is 1.8 μm and 1.1 µm, respectively. An analysis of the interaction zone between NbC and Cu via EDS method revealed the presence of a 0.5 μm thick zone of diffusion, resulting from the redistribution of Nb and Cu by limited solubility. The presence of the diffusion zone makes it possible to provide a solid interphase bonding and, accordingly, the high level of mechanical properties. The hardness and fracture toughness of the obtained material are 40 HRC and 24 MPa×м 1/ 2, respectively. Given the phase composition and properties of the developed composite, it is recommended to apply it as an alternative for composites of the system WC‒Cu in the form of a monolithic material or coatings. A coating was applied using the method of electric-spark doping, using the manual installation MP-EL2. The coating's thickness is 30 μm, microhardness is ~500 MPa, and the friction coefficient against steel without lubrication is 0.04. The designed materials are recommended for use in friction pairs in the form of a monolithic material, or anti-friction coatings