Foundations of the Fabrication Technology of Wear-Resistant Coatings Made of Mixtures of Chromium Carbide Powders with a Metallic Binder by Explosive Pressing

Abstract

Experimental data on the explosive compaction of powder mixtures of chromium carbide (Cr3C2) with metals (Ti, Ni, Cu) are presented, their theoretical explanations are given, and scientifically substantiated principles of the composition selection and development of the explosive fabrication of wear-resistant antifriction chromium carbide hard alloys and coatings are formed on this basis. The explosive pressing of powder mixtures was performed according to the scheme with the use of a plane normally incident detonation wave in a broad range of loading parameters (the powder heating temperature in shock waves was varied in experiments from 200 to 1000°C, while the maximal pressure of the shock-wave compression varied from 4 to 16 GPa). To analyze the phase transformations, the numerical thermodynamic simulation of the phase equilibrium was performed applying the Thermo-Calc software complex. The microstructure and the chemical and phase compositions were investigated using an Axiovert 40 MAT optical microscope (Carl Zeiss, Germany), Versa 3d and Quanta 3D FEG scanning electron microscopes (FEI, United States), BS 540 (Tesla, Czech Republic) and Titan 80–300 and Techai G2 20F (FEI, United States) transmission electron microscopes, and a Solver Pro atomic force microscope (OOO NT-MDT, Zelenograd). The temperature stability and oxidation resistance at elevated temperatures of materials formed by the explosion were investigated by thermogravimetric analysis using an STA 449 F3 Jupiter device (NETZSCH, Germany) in synthetic air upon heating to 1500°C. Tribotechnical tests were performed using an MI-1M friction machine (MEZIMiV, Moscow) according to the pin–ring scheme with digging in distilled water. Mechanisms of compaction and formation of strong boundaries between the particles of powder materials during the explosive pressing are described. It is shown that chromium carbide hard alloys with a titanium binder formed by explosion retain their phase composition invariable, do not oxidize to 600°C, and have considerably better antifriction properties and wear resistance when compared with SGP-0.5 and KKhN-20 materials lubricated with water, which have been applied in friction pairs until now.