The Influence of Process Parameters on Structure and Phase Composition of Boride Coatings Obtained on X39CrMo17-1 Stainless Steel

The boride coatings are characterized by attractive set of properties: high wear resistance and good high-temperature corrosion. In present research the diffusion boride coatings were obtained on X39CrMo17-1 stainless steel. The pack-boriding process was conducted using commercial Ekabor 2 powder. The influence of time of process on thickness and chemical composition was analysed. The boriding process was conducted in 2, 4, 6 hours at 1000 °C using retort furnace. The obtained coating was characterized by double layer structure and contained the FeB in outer layer and Fe2B in inner layer. The thickness of boride coatings increased with process time. The analysis of obtained results showed that the optimal thickness of coating was obtained during 4-h pack boriding.

MICROHARDNESS OF BORIDE COATINGS OBTAINED ON 65G STEEL FROM DIFFERENT COMPOSITIONS OF BORATING MIXTURES

The surface of the working organs of tillage equipment is subject to wear during operation. To obtain a surface layer of a part with high hardness and strength, corrosion resistance and abrasive resistance, there are used methods of chemical-thermal treatment, which consist in simultaneously exposing the surface to temperature and substances that can react chemically with the organ material. In this article, we consider the method of diffusion boronizing in coatings using the method of non-contact heating by high-frequency currents to study the microhardness of various boride coatings. (Research purpose) The research purpose is in studying the mechanical properties of boride coatings obtained by boronizing by heating 65G steel with high-frequency currents using various borating mixtures. (Materials and methods) An HDTV-40AV furnace was used to study the processes of boronizing using high-frequency surface heating. The temperature of the boronizing process was 950-1250 degrees Celsius, and the saturation process time was 40-180 seconds. Boron-carbide-based compositions were used. (Results and discussion) As a result of the studies, the microhardness of samples with different compositions of boronizing mixtures was studied. 65G steel was boronized. (Conclusions) According to the results of the study, the greatest microhardness was obtained using composition 6, containing manganese boride crystals (HV100 of 27570 megapascals, coating thickness of 250 micrometers) for a time of 120 seconds. However, the most suitable and less expensive to use in the agricultural industry were compositions based on boron carbide.

Preparation of di-boride coatings by electrophoretic deposition in nanoparticle-containing molten inorganic salts

Molten inorganic salts containing solid nanoparticles with a stable and uniform dispersion have attracted great attention as efficient heat transfer and storage materials1,2 and for catalysis for chemical reactions3-5. Electrophoretic deposition in molten inorganic salts containing nanoparticles, have not been reported in the literature, compared with the related wide investigations in aqueous and organic suspensions6,7. Here we report the possibility of electrophoretic deposition of nanoparticles in high-temperature molten salts. In molten fluorides and chlorides, cell voltages of 1.2-1.5 V below the decomposition voltage of the electrolytes, were applied to perform the electrophoretic deposition of nanoparticles (e.g., TiB2 and ZrB2) on different cathode substrates, resulting in compact and adhesive coatings with high hardness. These findings should present opportunities to synthesize additional coatings and films via the proposed process.

Influence of the Composition of Boriding Mixture on the Saturation of the Surface of Various Steels with Boron during High-Speed HFC-Boriding

The use of borate fluxes is an important component of the part hardening process by HFC-heating. The article discusses the possibility of using various coatings to saturate the surface of steel parts, as well as the features of using various boriding agents. Microstructures of the obtained boride coatings at various fractions of the boriding agent have been considered, and the areas of carbide inclusions and average thickness of the resulting coatings have been analyzed. The expediency of P-0.66 fused flux using and changes in the resulting coatings due to the changes in the mass fraction of this flux in various boriding mixtures have been investigated. Based on the obtained data on the microstructures of boride coatings, conclusions were made concerning the most appropriate compositions of boriding mixtures and the mass fraction of fused flux in their composition.

Research of high-speed HFC-boriding kinetics

The paper presents studies boride coatings, which were created using high-frequency treatment with currents. Chemical reactions characterized the boriding procedure at various temperatures are show. The choice of the main element, of the reaction-boriding scheme is characterize, their role is revealed, and the probable processes leading to the realization of topochemical boriding initiated by HFC-heating are established. The kinetic curves received during the test at different temperatures are showed. Anamorphoses of the kinetic curves are showed, and the values of activation energy and parameters of the boriding process using HFC-heating are calculated on the basis of linearization of the Arrhenius equation.

Analysis of Wear Resistance of Borided Steel C45

The wear resistance of diffusion coatings in conditions of specific pressures of 3, 7 and 10 MPa was studied. The boride coatings were prepared by means of diffusion methods using C45 steel as the substrate material. Research on the microstructure and redistribution of chemical elements on wear surface of a borided layer was carried out. It was found that the boride coatings should be used under a specific pressure of 7 MPa. It was found that the wear of friction couple coating of steel C45 under specific pressure of 3 MPa proceeds according to the oxidation wear mechanism, while under specific pressures of 7 and 10 MPa the abrasive wear prevails. The wear-induced segregation of atoms in coatings was studied using secondary mass-spectroscopy method (SIMS). Increased C, O, and B concentrations were noticed at the wear surface on depth from 50 to 2000 Å. The secondary wear-induced structure formation on the wear surface resulted in high wear resistance of diffusion borided coatings.