M. Pashechko

Evaluation of the Wear Resistance of Eutectic Coatings of the Fe–Mn–C–B System Alloyed by Si, Ni, and Cr Using Multi-Criteria Analysis

We have analyzed the structure and composition of eutectic composite dispersion-hardened materials of the Fe–Mn–C–B system alloyed by Si, Ni, and Cr. A multi-criteria evaluation of the choice of a material characterized by the highest wear resistance under different friction conditions and with different riders is presented. We have evaluated developed PMI-12, PMI-13, PMI-14, and PMI-15-type materials and quantity-produced PG–SR3, PG–10N–01 materials of the Ni–Cr–B–Si system, which are known for many years in the world market. For the analysis, we have used the compromise solution determination method and the undifferentiation interval method that enter the evolution system of multi-criteria analysis.

GRADIENT COMPOSITE COATINGS FOR WORKING SURFACES OF BRAKING DEVICES

In this paper a study to develop a composite wear-resistant coatings for application to the working surface of linings of brake devices, which is based on a rule of a positive gradient of mechanical properties was carried out. These devices and so coatings work in conditions of rapid rise of temperature. Thermal properties of matrix and inclusions should not differ a lot. Otherwise this will cause internal cracking and deterioration of coating. With this purpose we did the analyses of thermal properties of matrix and carbide particles of coating and concluded thet a material with balanced composition based on thermal properties will have the best wear resistance It was created and tested eutectic composites based on alloy steel 12X18H9T based on thermal characteristics of all components. Wear tests indicated the best wear resistance of coating with composition: steel 12X18H9T (matrix) – 75%; fillers TiB2 – 10%, VC – 15%.

Multicriterion Assessment of Wear Resistance of Fe–Mn–C–B Eutectic Coatings Alloyed with Si, Ni, and Cr

The results of tribological studies on Fe–Mn–C–B eutectic coatings alloyed with Si, Ni, and Cr are presented. The coatings are produced by gas metal arc welding with use of powder wires (2.4 mm in diameter). Multicriterion assessment is used to analyze the tribological properties of the coatings and determine the most wear-resistant one. This assessment involves first a search of Pareto optimum solutions and then compromise solutions with use of the Chebyshev norm. This approach allows choosing the coating that shows the highest abrasive wear resistance among the six eutectic materials under study at a specific load varying from 3 to 15 MPa.

Surface Hardening of HS6-5-2 Quick-Cutting Steel in the Course of Chemical Thermal Treatment

The physical and mechanical properties of HS6-5-2 steel after nitriding, carbonitriding, and carbonitriding with oxidation are studied with the help of a modern environmentally safe Zero-Flow method. The one-component atmosphere of ammonia (NH3) is used for the surface hardening. The temperature of the realized processes does not exceed 570°C. After various procedures of chemical and thermal treatment of steel, we performed its phase analysis and determined the surface hardness and the distribution of hardness over the depth of surface hardened layers. The thicknesses of hardened layers varied from 0.147 mm for carbonitriding with oxidation to 0.325 mm for nitriding. The results of investigation reveal a significant increase in the hardness of the surface layer.

Structure and Construction Assessment of the Surface Layer of Hardfaced Coating after Friction

The paper presents an analysis of the surface layer of Fe-Mn-C-B-Si-Ni-Cr alloy coating after friction with C45 steel. The coatings were obtained by arc welding (GMA). Flux-cored wires were used as a welding material. The flux-cored wires had a diameter of 2.4 mm. The tribological assessment was performed with the Amsler tribotester under dry friction conditions at unit pressures 10 MPa. The use of XPS spectroscopy allowed deep profile analysis of the surface layer. Based on the obtained results developed model of the surface layer for friction couple, hardfaced coating obtained from Fe-Mn-C-B-Si-Ni-Cr alloy – C45 steel. It was observed that the operational surface layer (OSL) of hardfaced coatings contained oxides (B2O3, SiO2, NiO, Cr2O3, FeO, Fe3O4, Fe2O3), carbides (Fe3C, Cr7C3) and borides (FeB, Fe2B).

Beam–to-column connection calculations using robot software

A beam–to-column connection design and results of engineer calculations using Autodesk’s Robot Structural analysis are shown in the article. Two types of connections, bolted and welded, were calculated. The tensile resistance amounted to 912.74 kN, bending resistance to 100.87 kN·m and effective design capacity of the bolt amounted to 27.69 kN. Normal stress in the weld amounted to σ⊥max = τ⊥max = 72.72 MPa, in the vertical weld to σ⊥= τ⊥= 63.34 MPa and tangent stress amounted to τ|| = 4.37 MPa. The results allowed us to implement minor changes such as increasing the distance between the bolt and the edge and decreasing the size of the fillet welds. The design is fully compliant with the EN 1993-1-8 norm. Using Robot Structural Analysis substantially increased the pace of calculations giving precise and clear outcomes.

THE MECHANISM OF FRICTION BETWEEN SURFACES WITH REGULAR MICRO GROOVES UNDER BOUNDARY LUBRICATION

The results of researches related to the influence of partially regular microrelief parameters on the adhesion component of the friction factor under boundary lubrication have been given. A special ring-on tape test rig is proposed in order to avoid errors during running-in process. Special technique is used to form sinusoidal microgrooves what helped to create a partially regular microrelief on the surface with controlled contour and nominal contact areas. Fatigue and deformation components of wear process are considered. We proved that microtexturing with proposed parameters decreases the adhesion component of friction and reduces the probability of microwelding. It has been shown that under boundary friction micro grooves are effective on precision surfaces with low roughness when lack of film and probability of seizure appear.