Obtaining multicomponent chromium coatings using functionally active mixtures

Abstract

The purpose of our research is to obtain wear-resistant chrome coatings on carbon steels under non-stationary temperature conditions using functionally active powder mixtures, which allows reducing the chemical-thermal treatment time from 6-8 hours to 1 hour. The scientific novelty of the work lies in the original use of thermodynamic analysis to determine the composition of the gas phase formed during chemical-thermal treatment with functionally active charges, which made it possible to optimize the concentration of ammonium compounds for boron-alloyed chrome surface and predict its physical and mechanical characteristics. The practical significance of the developed technology is to increase the wear resistance of chrome coatings on steels with a ferrite-pearlite structure, which ensures their effective use under dynamic and impact loads. The proposed method opens up new opportunities for the creation of highly effective protective coatings for industrial applications. Optical microscopy (Neophot-32) and scanning electron microscopy (REM-106i) were used to study the microstructure and phase composition of the coatings. Tribotechnical tests were carried out on friction installations SMT-1 and MT-5. The composition of the gas medium formed during the chemical heat treatment was determined by thermodynamic modeling, and the optimization of the component composition of the charge materials was carried out using the methods of mathematical planning of experiments with the optimization criterion in the form of wear resistance of the boron-alloyed chrome surface. As a result, it was found that the addition of boron-containing components and ammonium gas transport reagents to the powder charge composition contributes to the generation of gaseous compounds and condensed phases. The proposed functionally active mixtures ensure the formation of protective chromium layers up to 150 μm thick within 15-60 minutes.