Predicting the Thickness of the Hardening Coating during Diffusion Metallization of Cast Iron

The article presents the calculations of diffusion indices of saturation of high-strength cast iron VCh 60 from powder filling. Carbide-forming elements were used as diffusers: vanadium, chromium and manganese. As a result of the research, empirical equations have been established for predicting the thickness of strengthening diffusion coatings depending on the temperature and saturation time.

RESEARCH OF LOW TEMPERATURE NITROCARBURIZING TECHNOLOGY FOR COMPLEX HARDENING OF MACHINE PARTS

The study of changes in the microstructure, thickness of the ε-phase and the hardness of diffusion coatings obtained by varying the temperature in the process of low-temperature nitrocarburizing was carried out. Studies have shown the possibility, through the use of low-temperature nitrocarburizing technology, to reduce the labor intensity of technological operations, shorten the processing time and reduce energy consumption.

Sulfidation-Oxidation Resistance of Thermal Diffusion Multi-Layered Coatings on Steels

The high-temperature sulfidation-oxidation corrosion resistance of protective coatings deposited on carbon and 316L steels was studied. The coatings obtained via the thermal diffusion process had multi-layered architectures and consisted of aluminides, iron borides, or iron boride–TiO2 layers. The protective coatings experienced a minimal rate of mass changes, insignificant scale formation, and no delamination and surface micro-cracking after 504 h of exposure in 1% (Vol.) H2S-air atmosphere at 500 °C. Furthermore, the coatings demonstrated a high degree of integrity compared to bare 316L stainless steel. Aluminized steels demonstrated the highest performance among the studied materials. The developed thermal diffusion coatings are promising candidates due to their enhanced stability in H2S–air atmosphere; they may be employed for protection of inner and outer surfaces of long tubing and complex shape components.

Analytical solution of diffusion equations in multicomponent systems when applying diffusion coatings

For multicomponent coatings, analytical equations are obtained that take into account the diffusion coefficients in the concentration equations. It is shown, that to solve the problem of multicomponent diffusion in a solid solution containing substitutional elements and interstitial elements, it is advisable to use the equations for the concentrations of chemical elements. Keywords: multicomponent coating, solid solution, concentration, diffusion coefficient, analytical solution [email protected]

Formation of Diffusion Coatings Based on Nickel and Chromium in the Medium of Fusible Liquid Metal Solutions on Austenitic Steels

The technology of diffusion saturation of austenitic steels by chromium and nickel in the medium of low-melting liquid metal melts is shown. The saturation temperature was up to 1050°C, and the duration was up to 8 hours. It was found that it is the most effective to apply coatings according to the technological scheme: pre-carburization-diffusion metallization – final carburization. It was found that the coating consists of 4 layers. The surface layer has a thickness of up to 5 mkm and a microtuberance of up to 19500 MPa. The second layer, up to 12 mkm thick, has a microhardness of up to 7500 MPa. The third, up to 50 mkm thick, has a microhardness of 2300 MPa. In the fourth layer, up to 150 mkm thick, the microhardness gradually decreases from 2300 MPa to the microhardness of the base. At the same time, the total thickness of the coatings is up to 200 mkm.

INCREASING THE PERFORMANCE OF STEEL PARTS BY COMPLEX SATURATION OF THE SURFACE WITH ALLOYING ELEMENTS

The change in the microstructure, hardness and thickness of diffusion coatings with varying content of boron carbide salts in the melt is studied. For samples made of U10 steel, the highest saturation capacity with the formation of a carbide layer is characteristic of a composition containing 2% BC, 5-6% alloying elements (Cr, V, Ti), 10% NaCl, the rest is borax NaBO. The addition of 3-5% aluminum oxide significantly increases the stability of the melt and contributes to the preservation of the saturating capacity. The technology of complex saturation of steel with alloying elements can be used to harden parts of stamping equipment and a wide range of tractor parts.