INFLUENCE OF THE INITIAL MICROSTRUCTURE ON THE STRESS-STRAIN STATE IN SAMPLES FROM DIFFERENT DEFORMED NICKEL-BASED ALLOYS AT THEIR WELDING BY PRESSURE-SHEAR WELDING
A finite-element modeling of the stress-strain state of disc-shaft type part from heterophase deformable high-temperature nickel-based superalloys subjected of pressure shear welding process is carried out. Computer modeling is carried out in a two-dimensional setting (axisymmetric problem) using the DEFORM-2D software package. The following alloys were used for the disk: 1) EP741NP, coarse-grained (CG) microstructure (60 μm); 2) EP741NP, ultrafine-grained (UFG) microstructure (≤1 μm); 3) EP975, fine-grained (FG) microstructure (8 μm). VKNA-25 alloy in the single-crystal state was chosen as the material for the shaft in all three cases. The initial strain rate was 10<sup>-4</sup> s<sup>-1</sup>, while the welding temperature was 1125 °C. Pressure welding was carried out by introducing the shaft into the disk on 2.5 mm disk. The simulation results showed that the effective stress values of materials in the pressure shear welding process for all three combinations do not exceed the yield strength. Stresses and strains when welding a disk from EP741NP (UFG) are lower than when welding discs from EP741NP (CG) and EP975 (FG) under identical conditions. But their maximum value is less than under identical conditions for welding disks from EP741NP (CG) and EP975 (FG). Based on the obtained results, it is shown that to create a solid-phase joint of the disk and shaft, it is preferable to use a combination of VKNA-25 alloys (shaft) and EP975 (FG) alloys (disk), since in this case an effective total effect of normal compressive stresses and shear deformations is provided.