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.

Formation of Cemented Tungsten Carbide Layer with Compositional Gradient Processed by Directed Energy Deposition

In order to partially improve the wear resistance for dies and jigs, layer-forming technologies for adding cemented tungsten carbide is effective way as an additive manufacturing technique. As one of the layer-forming technologies, directed energy deposition (DED) has attracted much attention from industry. However, many cracks are usually observed inside a formed layer processed by the DED due to the difference of material properties between an iron-based substrate and a cladded cemented tungsten carbide layer. In terms of durability of the formed layer, the crack formation is not preferable as well. In this study, as an attempt to suppress the crack initiation and propagation in cladded layers processed by the DED, formation of compositionally graded cemented tungsten carbide layer was performed by inserting a layer with low to medium tungsten carbide content between the substrate and cemented tungsten carbide layer. At first, single layers of cemented tungsten carbide having various tungsten carbide content were formed on iron-based substrates by the DED processing to understand the relationships between the tungsten carbide content and the number of formed cracks. By considering these experimental results, the compositionally graded cemented tungsten carbide layers were optimized. It was revealed that the crack initiation and propagation could be suppressed by compositionally graded cemented tungsten carbide layers.

RESEARCH OF WEAR RESISTANCE OF IRON GEAR WHEELS WITH DIFFUSE CARBIDE LAYER

The article is concerned with wear resistance increase of saw-tooth enclosed drives applying instead of iron gear wheels, made from cement steel quality, gear wheels from high-duty cast iron of HF 60 with thermodiffusion carbide layer. Elements- diffusants were chosen according to level of carbide forming and hardness of formed layersvanadium- for forming very hard, chrome-medium according to coating and manganese- for low layers according to coating hardness. Layers are formed on spur gears, which are reverse gear of light vehicle. Setting for research included draw gear- asynchronous electric drive, placed on lathe-bed with the help of which rotation of gear shift transmission with powered reverse gear was done. Transmission output shaft was pressed into chunk. Kinematick of disconnected machine provided necessary moment resistance. Through given number of cycles the box was taken down, gear set was removed and metal graphic research was carried out. Residual layer thickness and linear wear were diagnosed, on the basis of obtained experimental data we built characteristic curves of linear wear from number of stress cycles. For comparative evaluation in this type of research we carried out experiments on measurement of linear wear of case – hardening steel 20 ChGn after cementation and further quenching and research of hardened cast iron HF mark 60. It was found out that the highest quality wearing in this type of research vanadium layers have, slightly lower quality wear chromium plate have and on the 3rd place manganese layers. The worst quality wear we observed in steel 20 ChGN. On the basis of obtained –experimental data empirical regularities of wear rate of layers from their Brinnel hardness and diameter of obtained copy were determined.