Improving the efficiency of surface-thermal hardening of machine parts in conditions of combination of processing technologies, integrated on a single machine tool base

OBRABOTKAMETALLOV Vol. 23 No. 3 2021 technology Structural studies of the samples were carried out using a Carl Zeiss Axio Observer Z1m optical microscope and a Carl Zeiss EVO 50 XVP scanning electron microscope equipped with an INCA X-ACT energy dispersion analyzer (Oxford Instruments). The microstructure of the samples was detected by etching with a 5-% alcohol solution of nitric acid, as well as a saturated solution of picric acid in ethyl alcohol with the addition of surfactants [62]. The microhardness of the hardened surface layer of the parts was evaluated using the Wolpert Group 402MVD device. Studies of residual stresses were carried out using the X-ray method on a high-resolution diffractometer ARL X’TRA and a mechanical destructive method – layer-by-layer electrolytic etching of the sample [63, 64]. To identify defects in the surface layer at each transition, the following methods were used: optical method using a Carl Zeiss Axio Observer A1m microscope, capillary method, eddy current method using an eddy current flaw detector VD-70 . Statistical processing of the results of experimental studies was performed in the software products Statistica , Table Curve 2D and Table Curve 3D . Mathematical simulation of thermal fields and structural-phase transformations in the HEH HFC The finite element model was constructed in the software complexes ANSYS and SYSWELD , which use numerical methods for solving differential equations of non-stationary thermal conductivity (Fourier equation), carbon diffusion (Fick’s 2nd law) and elastic-plastic behavior of the material [27, 28, 33, 34, 38–40, 43–45]. The preparation of the finite element model was carried out in the ANSYS software package. The ANSYS Meshing generator formed a hexahedral finite element grid using the following types of finite elements: Solid bodies – solid bodies were modeled with 8-node SOLID 45 tetrahedra; Surface bodies – surface bodies were modeled with 4-node 4-angle shell elements – SHELL 63 ; Line bodies – line bodies were modeled with 2-node LINK 8 linear elements. The size of the finite elements was 0.01...1 mm. When creating a finite element model, the following components were created: “Volume” – a group of three-dimensional elements denoting the object being processed; “Trajectory” – a group of one-dimensional elements that determines the trajectory of a high-concentration energy source; “Reference” – a reference equidistant – a group of one-dimensional elements that helps orient the local coordinate system of the energy source; “StartElem” – starting elements of the beginning of the source action; “StartNodes” and “EndNodes” – the initial and final nodes on the trajectory of movement; “Skin” is a group of two-dimensional elements denoting the surfaces on which convective and radiative heat losses occur; “ClampedNodes” is a group of nodes on which the disk is fixed (Fig. 4). Simulation of the process of high-energy heating by high-frequency currents was carried out in the SYSWELD software package, which allows using a model of elastic-viscoplastic behavior of the material and modern mathematical apparatus to calculate temperature fields, the distribution of structural components, internal stresses and deformations. During the preparation of the finite element model, the specifics of the distribution of the specific power of the HFC heating source directly under the inductor and along the depth of the material were taken into account [27, 28, 33, 34, 38–40, 43–45]. Results and its discussion When developing integrated metalworking equipment, it is planned to implement a method of high- energy heating with high-frequency currents at one of the technological transitions of a hybrid machine. Taking into account the design features of inductors for HEH HFC, the formation of the production lines of the treated surface occurs by localized heating areas, the dimensions of which are determined by the width of the active inductor wire and the length of the ferrite magnetic core (Fig. 1). As a result, to ensure surface quenching, exactly the same coordinated relative movements of the workpiece and the tool are required as when forming through the processes of turning and diamond smoothing (Fig. 5). Structural and kinematic