Dmitriy Nikolaevich Trushnikov

Inter-pass forging with different degrees of deformation during WAAM of Inconel 718 specimens (single-stage, three passes; two-stage, six passes) was investigated. Macrostructural analysis of the specimens showed that inter-pass forging led to a recrystallized structure. Alternation of layers with different grain shapes (columnar and equiaxed) is observed throughout the height of the specimens. Increasing the number of passes improves the mechanical properties of the material (tensile strength, yield strength, microhardness). A finite element model of inter-pass forging was developed to determine the effect of inter-pass surface deformation during WAAM on the residual stress–strain state. The non-stationary formulation was replaced with a quasi-static one. Johnson–Cook material constants were obtained for the deposited Inconel 718 material, including the effect of forging. Verification of the mathematical model was performed using a wall (specimen 2) deposited with single-stage forging. The deviation between the simulation results and the experiment did not exceed 15%. It was found that the sequence and number of passes significantly affect residual strain and displacements but have little effect on residual stress. Numerical modeling showed that the depth of plastic deformation exceeds the melting depth when depositing the subsequent layer, ensuring the preservation and accumulation of the inter-pass forging effect throughout the deposition process.

This study employs a multilevel modeling approach to describe the deformation of specimens made from austenitic Wire Arc Additive Manufactured (WAAM) steel 308LSi. Two WAAM processing modes were investigated: (1) the Cold Metal Transfer (CMT) method and (2) Cold Metal Transfer combined with interlayer deformation strengthening (hammer peening/forging). Test specimens were cut from the deposited walls at 0° and 90° relative to the deposition direction. The grain and dendritic structures of the specimens were analyzed using optical stereomicroscopy. A statistical multilevel model has been developed, accounting for the features of the grain-dendritic and defect structures under various technological deposition modes. Parameter identification and model verification were conducted based on experimental data from uniaxial tensile tests of 308LSi steel specimens. The maximum deviation of the numerical results from the experimental data during the identification stage under uniaxial tensile loading did not exceed 3%, and during the verification stage it did not exceed 10%; the overall mean deviation did not exceed 1% for the identification stage and 2% for the verification stage. The model effectively captured the anisotropic mechanical behavior of WAAM-processed samples. The maximum calculated yield strength 360 MPa was obtained for specimens cut at an angle of 45°, while the minimum value 331 MPa was observed for vertically oriented specimens. Specimens subjected to interlayer forging (hammer peening) exhibited isotropic material properties. Explicit multilevel modeling, incorporating the presence of MnO oxide inclusions located within the austenite matrix, was performed. The results showed good correlation with experimental data and confirmed the localization of fatigue cracks at the phase boundary-matrix-oxide interface.

The development of additive technologies for manufacturing safety‑critical components operating under vibration must be accompanied by a careful analysis of the material’s resistance to high‑cycle fatigue (HCF). This paper presents a technique for the rapid assessment of the fatigue limit of nickel alloys fabricated by wire‑and‑arc additive manufacturing (WAAM). The technique grounded in infrared thermography (IRT), utilizes the self‑heating effect during cyclic loading. The technique realisation involves choosing specimen design, test equipment, the number and parameters of loading blocks, self‑heating indicators, and result‑processing procedures that account for material specifics. It is shown that the rate of temperature rise at the specimen surface at the start of each loading block can serve as an indicator of self‑heating. Experimental data on the fatigue limit of specimens made from the heat‑resistant alloy Inconel 625 produced by WAAM are obtained. Validation of the developed method is performed by comparing the fatigue limit derived from IRT with the results of conventional fatigue testing and the corresponding S–N curve. For additive nickel alloys, the proposed accelerated fatigue‑limit assessment allows a substantial reduction in the number of specimens and the time required to select technological parameters and refine additive manufacturing processes compared with traditional fatigue testing.

A system for laser additive surfacing by means of a rotating beam is described. This system ensures stable quality of the applied metal layers in additive

A system for wire supply in electron beam additive surfacing is proposed. This system ensures high accuracy in wire supply to the electron beam and effecti

The technology for wire-based electron beam 3D printing is improved. A 3D printing method with adaptive wire supply improves the stability and reproducibil

The regularities of residual stress formation and distortion of the product shape occurring during wire-arc surfacing are studied. Therefore, the results of full-scale experiments carried out by Cranfield University are reproduced numerically. In the experiments, surfacing of wire material is carried out in 9, 10, and 18 layers on a fixed substrate along a reciprocating path at a speed of 10 mm/s, including interlayer roller burnishing with variable pressure. The numerical modelling includes several stages, during which the following uncoupled problems are sequentially solved: a) thermal – surfacing of 9 to 18 layers of wire material, b) thermal elastic-plastic – formation of eigenstrains and residual stresses due to air cooling of the deposited wall with non-uniform temperature distribution, c) thermal elastic-plastic – forging of a stressed workpiece with a pneumatic tool at elevated temperature (the stage may be omitted), and d) elastic-plastic – changes in the field of residual stresses and distortion of the structure after its release. The problem of thermal conductivity (a), as well as the problems of deformation (b), and (d) during surfacing of wire material are implemented in the Comsol Multiphisics software package, and the problem (c) is solved in the LS-DYNA software package. In addition, an “engineering” beam-rod structural model of the built-up wall is developed, which makes it possible to predict the wall distortions and the distribution of eigenstrains and residual stresses along its height, and verify the numerical calculation. This model represents the magnitude of longitudinal bending of the specimen during surfacing, but excessively takes into account the effect of roller burnishing. Even a single roller burnishing causes the bending of the structure in the opposite direction, while in the experiment it only straightens.