An analysis of common reinforcement methods of machine parts and theoretical bases for the selection of their chemical composition were carried out. Prospects for using flux-cored arc welding (FCAW) to restore and increase the wear resistance of machine parts in industries such as metallurgy, agricultural, wood processing, and oil industry were presented. It is noted that conventional series electrodes made of tungsten carbide are expensive, which limits their widespread use in some industries. The scope of this work includes the development of the chemical composition of tungsten-free hardfacing alloys based on the Fe-Mo-B-C system and hardfacing technology and the investigation of the microstructure and the mechanical properties of the developed hardfacing alloys. The composition of the hardfacing alloys was developed by extending the Fe-Mo-B-C system with Ti and Mn. The determination of wear resistance under abrasion and impact-abrasion wear test conditions and the hardness measurement by means of indentation and SEM analysis of the microstructures was completed. The results obtained show that the use of pure metal powders as starting components for electrodes based on the Fe-Mo-B-C system leads to the formation of a wear-resistant phase Fe(Mo,B)₂ during FCAW. The addition of Ti and Mn results in a significant increase in abrasion and impact-abrasion wear resistance by 1.2 and 1.3 times, respectively.

Substitutional solid solutions of the Mo ₂ FeB ₂ –Mo ₂ MnB ₂ system exhibit high stability and a sufficient level of mechanical properties to be used as a reinforcement phase in high-manganese alloys (steels), providing both impact- and wear-resistance.

In this work was established that serial traditional hardfacing materials based on the Fe-Cr-C system are not effective for improvement of abrasion resistance of elements of equipment for production of bricks, solid fuel briquettes and for restoration of augers, due to the fact that this equipment works at significant specific and cyclic loads. Features of the coarse-grained structure of Fe-Cr-C based coatings leads to intensive abrasive wear. The aim of this study was to increase a durability of that equipment by using of flux cored electrodes with reaction components of Ti, Cr, Mo, B4C and their combinations to provide synthesis, which leads to fine-grained structure of refractory borides and carbides and their solid solutions with increased hardness. Structure of the hardfacing coatings were investigated by method of metallography, scanning electron microscopy (SEM), electron backscatter diffraction (BSD) mode and energy dispersive X-ray spectroscopy (EDS). Temperature dependences of equilibrium phase amount of the hardfacing materials were calculated by the CALPHAD technique, using JMatPro software. It was investigated that the offered materials are characterized by higher wear resistance at high specific and cyclic loads in comparison with serial production high-chromium hardfacing materials (Lastek, ESAB, Paton IEW). It was established that the abrasion wear resistance at high specific and cyclic loads depends mostly of formation of the structure of hardfacing material, and not the hardness. Also, using of powders of pure metals and their combination as reaction mixture for FCAW leads to fine structure which contains of refractory borides and carbides and their solid solutions.

The overall study objection is selection and optimization all available thermodynamic data required for using calculation of phase diagram (CALPHAD) technique within the Fe-C-Cr-Mn-Si-Ti system. Such data collected in the thermodynamic database can be used for predicting the phase constitution states of a given composition for Fe-based hardfacing materials, which often use in energy industry in order to increase the abrasion and impact wear resistance of equipment parts. In order to compare theroretical calculation results with experimental data, four different types of hardfacing were deposited using flux-cored arc welding. Microstructure and chemical composition of deposited layers was investigated using optical and scanning electron microscopy together with energy dispersive X-ray spectroscopy. Comparison of experimental and computed results shows that they are in good agreement in meaning of presence of all-important phase equilibrium regions. The developed database can be used for rational selection of hardfacing materials for energy industry equipment and reasonable choice of new alloying systems.

Forming the structure and the properties of electric arc coatings based on high manganese steel alloyed with titanium and niobium carbides