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Streszczenie:
Anisotropic yield criteria and kinematic hardening laws have been independently validated for additively manufactured alloys. However, their specific combination has not been implemented in a finite element user subroutine and validated against 360° sequential biaxial probing data for LENS-deposited nickel-base alloys. Present work delivers the first validated implementation of this coupling for LENS-deposited Inconel 625, combining the Szczepiński quadratic yield criterion with Armstrong–Frederick kinematic hardening. The implemented return-mapping algorithm accumulates the plastic multiplier across Newton–Raphson iterations before updating the plastic and equivalent plastic strain state variables. This distinction is significant for the non-radially-symmetric Szczepiński surface where the flow direction rotates at each iteration unlike the fixed radial direction of isotropic return mapping. A two-step iterative boundary-condition correction scheme ensures each probing direction converges within ±1.5° of the experimental stress angle, achieved for 16 of 17 sequential paths. Path P1, the virgin specimen opening probe retains a residual angular deviation of −2.97° due to absent accumulated back-stress at the start of the sequential cycle. The validated UMAT reproduces all 17 directional yield points with a mean absolute angular error of 0.86°, mean absolute axial and shear stress deviations of 11.4 MPa and 12.5 MPa, respectively. Path-level deviations reach a maximum of 32 MPa in axial stress at P10 and 41.4 MPa in shear stress at P5, attributed to angular misalignment between back-stress and probing direction in the compressive–shear and near-pure-torsion sectors, respectively. This establishes the framework as a computational tool for characterising multiaxial yield surface under complex loading.

Słowa kluczowe:
Inconel 625, Anisotropic yield Surface, Szczepiński yield criterion, User subroutine, Kinematic hardening, Sequential multiaxial loading

Streszczenie:
In this study, tubular specimens of Inconel 625 and Inconel 718 were additively manufactured using the Laser Engineered Net Shaping (LENS) technique. Their initial yield surfaces were experimentally determined under biaxial stress loading at 0.005% and 0.01% plastic offset strain. Uniaxial tensile tests showed yield strengths of 509 MPa and 461 MPa, with Young’s moduli of 180 GPa and 171 GPa for Inconel 625 and Inconel 718, respectively. Yield surfaces, fitted using the Szczepiński anisotropic criterion, revealed elliptical shapes with axis ratios below 1.73, confirming moderate anisotropy. Inconel 625 exhibited nearly symmetric yield strengths in tension and compression, with a higher tensile-direction elongation of the surface, whereas Inconel 718 showed stronger directional dependence, reflecting a higher degree of mechanical anisotropy.

Słowa kluczowe:
Inconel, Yield surface, Additive manufacturing, Laser Engineered Net Shaping

Streszczenie:
In this paper, fatigue performance of Ti-5553 alloy fabricated using Laser Engineered Net Shaping (LENS) was investigated. Mechanical testing revealed high tensile strength (UTS: 1377 MPa) and good ductility (16 %). Fatigue tests under fully reversed loading expose superior endurance, with crack initiation mechanisms transitioning from surface-induced at high stresses to internal defect-assisted at lower amplitudes. Fractography exposed unmelted particles as initiation sites under moderate cyclic loads. The results establish LENS as a reliable method for manufacturing high-strength Ti-5553 components for high-performance applications.

Słowa kluczowe:
b-Ti alloys , Direct Energy Deposition (DED)

Streszczenie:
In this paper, the LENS technique with optimized parameters was applied to investigate the feasibility of Inconel 625 repair process. The process was performed on the substrate material heated to 300 ◦C at laser power of 550 W. Subsequently, the specimens were subjected to microhardness and three-point bending tests to assess the effectiveness of the repair system. The results showed that the mechanical properties of the Inconel 625 specimens repaired by using the LENS system were similar or even better than those of the substrate material.

Słowa kluczowe:
LENS technology, Inconel alloys, repair process, additive manufacturing

Streszczenie:
In this paper, the Inconel 625 laser clads characterized by microstructural homogeneity due to the application of the Laser Engineered Net Shaping (LENS, Optomec, Albuquerque, NM, USA) technology were studied in detail. The optimized LENS process parameters (laser power of 550 W, powder flow rate of 19.9 g/min, and heating of the substrate to 300 °C) enabled to deposit defect-free laser cladding. Additionally, the laser clad was applied in at least three layers on the repairing place. The deposited laser clads were characterized by slightly higher mechanical properties in comparison to the Inconel 625 substrate material. Microscopic observations and X-ray Tomography (XRT, Nikon Corporation, Tokyo, Japan) confirmed, that the substrate and cladding interface zone exhibited a defect-free structure. Mechanical properties and flexural strength of the laser cladding were examined using microhardness and three-point bending tests. It was concluded, that the LENS technology could be successfully applied for the repair since a similar strain distribution was found after Digital Image Correlation measurements during three-point bending tests.

Słowa kluczowe:
LENS technology, Inconel alloys, repair process, additive manufacturing

Streszczenie:
W niniejszej pracy zaproponowano wykorzystanie metody LENS do regeneracji modelowych elementów wykonanych ze stopu Inconel 625. Podczas badań wstępnych użyto sferycznego proszku ze stopu Inconel 625 o wielkości cząstek z przedziału 50-100 um oraz materiału podłoża wykonanego z tego samego materiału. Próby regeneracji przeprowadzono z użyciem lasera o mocy 550 W przy szybkości podawania proszku równej 12 RPM. Zastosowano trzy różne metody wypełniania modelowych ubytków, tj.: wypełnienie bez konturu (tylko w objętości modelowego ubytku), wypełnienie z konturem i w objętości ubytku oraz wypełnieniem tylko w postaci konturu. Po przeprowadzonych badaniach stwierdzono, że regeneracja powinna przebiegać na podgrzewanym podłożu, a proces napawania należy realizować w więcej niż dwóch przejściach, co do grubości napoiny.

Słowa kluczowe:
technologie laserowe 3D, regeneracja, LENS (Laser Engineered Net Shaping), techniki przyrostowe

Słowa kluczowe:
additive manufacturing, LENS, yield surface, deformation, superalloy, inconel, multiaxial, EBSD, pre-deformation, anisotropy

Słowa kluczowe:
plastic deformation, Inconel 718, LENS, EBSD

Słowa kluczowe:
LENS, wytwarzanie przyrostowe, stopy niklu, stopy tytanu, regeneracja

Słowa kluczowe:
inconel alloys, repair process, additive manufacturing

Słowa kluczowe:
inconel alloys, repair process, additive manufacturing

Słowa kluczowe:
LENS, additive manufacturing, Inconel 625, repair process