International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

in this study, the hard facing with Fe-Cr-C base welded wire and Fe-Cr-Nb-C cored welding wire by using submerged-arc welding method in single-pass, two-pass and three pass over the pieces of carbon steel (St37 )was done. Cored welding wire Fe-Cr-Nb-C by an approximate ratio of 5.41 Cr to C ratio, was containing 5.6 to 7% of the niobium element. scanning electron microscopy, optical microscopy, X-ray diffraction and point analysis, indicates the presence of carbides (Fe, Cr)₇C₃ and Nb₂C in hardened samples with Fe-Cr-Nb-C welding wire. The results showed that with increasing number of hardened passes, the percentage of carbon, chromium and niobium concentrations increased and as a result the dilution percent was decreased that cause to increasing hardness and better performance. test results indicate higher hardness of hardened samples with Fe-Cr-Nb-C welding wire compared to samples hardened with Fe-Cr-C welded base wire. With increasing number of of hard passes, hardness was increased, so that the highest and lowest hardness is related to three pass samples that was hardened with metal cored wire Fe-Cr-Nb-C.The reason of increased hardness in three-pass samples hardened with Fe-Cr-Nb-C metal cored wire was to with increasing in the number of hardened passes , dilution rate was reduced by the base metal and this cause to coarse and more uniform distribution of carbides .

The results of computer simulation and physical experiment on angular pressing AD1 alloy billets are presented. There were microstructure and dyurametrix researches to confirm the changes in the structure of the structure and its mechanical properties.

The impact of current shape during consolidation of Fe – Ti – C – B system materials on the physio-mechanical properties of obtained specimens is studied in present paper. It is experimentally found that the use of method of decrease of voltage surge on output Schottky diodes of SPS device and the decrease of operation time of overcurrent protection in power circuit of SPS generator allowed changing current harmonic composition which lead to an increase of properties of consolidated Fe – Ti – C – B specimens – porosity decreased from 15.8 to 2.8 %, hardness increased from 50 to 55 HRC, loss of mass during abrasive wear decreased from 2 to 0.5 mass. %, and bending strength increased from 750 to 1500 MPa. It is found out that increase of input power during consolidation from 1.3 to 7.5 kJ/s by changing current harmonic composition leads to an increase of physico-mechanical characteristics of Fe – Ti – C – B system metalmatrix composites. Density of consolidated specimens increased from 75 to 95 %, their hardness increased from 35 to 50 HRC, loss of mass during abrasive wear decreased from 10 to 1 mass. % and their bending strength increased from 400 to 1100 MPa.

Studying the fracture characteristics of porcelain coatings plays a main role in selection of materials for metal-ceramic restorations. The aim of this work is to study the effect of the substrate manufacturing process on the adherence of the porcelain. The coatings of porcelain IPS.Inline (Ivoclar Vivadent) are fused onto dental Co-Cr alloys fabricated via casting (Biosil F) and Selective Laser Melting (SLM) (Co212-f). The adhesion strength of the ceramic coatings is studied under tensile load of flat specimens. The interfacial shear strength is determined using experimental results. The shear stress distributions in the metal-ceramic interface at the critical load are evaluated by analytical approach. It is established that the interfacial shear strength values of ceramic coating are 67.5 MPa for cast Biosil F alloy and 83.8 MPa for SLM Co212-f alloy. The higher shear strength of the porcelain to the SLM samples is due to the nearly two times higher surface roughness, which is reason for increasing both the mechanical and the chemical adhesion. The nature of the fracture of the ceramic coating on the Co-Cr alloys, produced by casting and SLM, is similar and is mixed adhesive–cohesive mode. The higher adhesion strength of the porcelain coating to the SLM dental alloy is a good precondition for the SLM application in production of metal-ceramic fixed partial dentures for areas with heavy loads.

Regularities of the influence of spark plasma sintering heating rate on the structure and properties of dispersion-strengthened materials based on Fe – Ti – C – (B) system are studied. Increasing heating rate of the samples from 10 °C/s to 20 °C/s induced by increasing current rise rate leads to decrease the average grain size in the material matrix of the Fe – Ti – C – B system from 2.5 to 1.5 microns. This allows to increase hardness from 48 HRC up to 70 HRC and wear resistance 7 times compared to R6M5 (full analog of HSS M2) steel during SPS consolidation in the mode with a heating rate of 20 °C/s and isothermal exposure 1100 °C for 180 s.

The aim of the present paper is to investigate the mechanical properties (hardness and tensile strength) of dental Co-Cr alloys fabricated via casting and selective laser melting (SLM). Two groups of metallic specimens (four-part dental bridges and standard tensile test specimens) made of Co–Cr dental alloys were produced by lost-wax casting and SLM processes. Vickers hardness distribution along the depth of the dental bridges as well as the Rockwell hardness and tensile strength of the samples were studied out. The hardness of Co–Cr dental alloys are dependent on the manufacturing technique employed. It was established that the average Vickers hardness of the samples, produced by SLM, was higher than that of the cast samples 382 HV and 335 HV respectively. The nearly even hardness distribution in the bridges, produced by SLM, and fluctuations of the hardness values along the depth of the cast bridges were observed. The Rockwell measurements confirmed the higher hardness of the SLM samples – 39 HRC in comparison with that of the cast ones – 33 HRC. The tensile strength is in good agreement with the hardness values. Due to the unique microstructure, the yield strength and tensile strength for the SLM samples were higher than those of the as-cast alloy.

This work was carried out studies on the effect of different ways of modifying the microstructure and mechanical properties of cast ductile irons identical to the final chemical composition. For comparative studies have chosen three ways of modifying the molten iron, characterized the time interval between the introduction of additives into the melt and crystallization of iron – autoclave method, processing method in an open ladle ( "Sandwich process") and a method of in-mold melt processing ("Inmold-process").

It is found that the process mold inoculation molten iron a more effective compared to other methods studied, by reducing the time interval between entering modifier in liquid iron and the onset of crystallization. This in turn enables the production of castings of several grades of ductile iron in the total process stream without additional alloying and heat treatment.

Results of research testify in favor of the fluctuation hypothesis about straight line graphitization of cast iron during primary crystallization.