Present work focuses on the in-situ 316L/Cu alloy development by using laser beam powder bed fusion (PBF-LB) additive manufacturing. Influence of the most influential processing parameters i.e., the laser power, and the number of scans i.e., single melting (SM), double melting (DM) and triple melting (TM), on the in-situ alloying ability was studied. At the lowest laser power, 175 W, some 316L powder particles were unmelted and the Cu was not mixed properly into the matrix of 316L. Increasing the laser power from 175 W to 235 W, improves the complete melting of all the components in 316L/Cu powder mix and effective alloying of Cu into 316L with improved homogeneity in its distribution after solidification. However, there is minor copper rich banding at the track overlaps in SM sample prepared at 235 W. Employing of rescanning strategy further improves the homogeneity in distribution of copper owing to the clean and high-quality molten pool with better intermixing by strong molten pool convection.

Duplex stainless steels (DSS) are characterized by a two-phased microstructure (δ-ferrite and γ-austenite) with equal phase fractions, providing an exceptional combination of high strength, toughness, and corrosion resistance. This duplex microstructure is conventionally achieved by a precise thermo-mechanical process (e.g., hot rolling) followed by multiple post-processing steps (coating, joining, assembly) to meet the requirements in high-performance applications (e.g., advanced wear and corrosion resistance). Laser directed energy deposition of metals (DED-LB/M) enables simultaneous processing of multiple materials in a single component, allowing for the customization of the functionality while reducing the number of process steps required. In this study, a 1.4462 DSS was manufactured by DED-LB/M and compositionally modified (in-situ alloyed) with increasing proportions of elemental Cr and/or Mo powder to control both the phase formation and material hardness. Subsequent solution annealing (1050 °C; 2 h) and quenching homogenized the as-built microstructure within each grading increment. Microstructure analysis (phase fraction, morphology, and grain size using electron backscattered diffraction) was correlated with the local chemical composition by energy dispersive X-ray spectroscopy. Hardness profiles along the grading direction indicated a gradual increase in material hardness due to the stabilization of δ-ferrite (+ 69 HV10) or σ-phase (+ 683 HV10) with the addition of Cr and/or Mo. This approach demonstrates that in-situ alloying in DED-LB/M facilitates the spatial control of phase structures and the customization of functional properties. Components can now be manufactured in a single process with smooth compositional transitions and locally enhanced material properties, e.g. ductile core with wear and corrosion resistant shell.

A high-alloy (Cr-Mo-V) cold-work tool steel was manufactured by laser powder-bed fusion (PBF-LB) without preheating and by electron-beam powder-bed fusion (PBF-EB) with the build temperature set at 850 degrees C. The solidification rates, cooling, and thermal cycles that the material was subjected to during manufacturing were different in the laser powder-bed fusion than electron-beam powder-bed fusion, which resulted in very different microstructures and properties. During the solidification of the PBF-LB steel, a cellular-dendritic structure was formed. The primary cell size was 0.28-0.32 mu m, corresponding to a solidification rate of 2.0-2.5 x 106 degrees C/s. No coarse primary carbides were observed in the microstructure. Further rapid cooling resulted in the formation of a martensitic microstructure with high amounts of retained austenite. The high-retained austenite explained the low hardness of 597 +/- 38 HV. Upon solidification of the PBF-EB tool steel, dendrites with well-developed secondary arms and a carbide network in the interdendritic space were formed. Secondary dendrite arm spacing was in the range of 1.49-3.10 mu m, which corresponds to solidification rates of 0.5-3.8 x 104 degrees C/s. Cooling after manufacturing resulted in the formation of a bainite needle-like microstructure within the dendrites with a final hardness of 701 +/- 17 HV. These findings provide a background for the selection of a manufacturing method and the development of the post-treatment of a steel to obtain a desirable final microstructure, which ensures that the final tool's performance is up to specification.

This study addresses the critical need for a constitutive model to analyze the cyclic plasticity of additively manufactured 316L stainless steel. The anisotropic behavior at both room temperature and 300 degrees C is investigated experimentally based on cyclic hysteresis loops performed in different orientations with respect to the build direction. A comprehensive constitutive model is proposed, that integrates the Armstrong-Frederick nonlinear kinematic hardening, Voce nonlinear isotropic hardening and Hill's anisotropic yield criterion within a 3D return mapping algorithm. The model was calibrated to specimens in the 0 degrees and 90 degrees orientations and validated with specimens in the 45 degrees orientation. A single set of hardening parameters successfully represented the elastoplastic response for all orientations at room temperature. The algorithm effectively captured the full cyclic hysteresis loops, including historical effects observed in experimental tests. A consistent trend of reduced hardening was observed at elevated temperature, while the 45 degrees specimen orientation consistently exhibited the highest degree of strain hardening. The applicability of the model was demonstrated by computing energy dissipation for stabilized hysteresis loops, which was combined with fatigue tests to propose an energy-based fatigue life prediction model.

In this study, the DED-LB/M process of AISI H11 tool steel powder blends modified by adding WC nanoparticles (WC-np) in concentrations of 1, 2.5 and 5 wt.-% was the object of scientific investigations. For this, 30-layer cuboid specimens were manufactured. The overall scientific aim was to examine how the WC-np interact with the steel melt and in the end, influence the processability, microstructure and mechanical properties of produced specimens. The examinations were carried out on both as-built and thermally post-processed specimens. An advanced microstructural analysis (SEM, EDS, EBSD and XRD) revealed that due to the high solubility of WC-np in the molten steel, most of the WC-np appear to have dissolved during the ongoing laser process. Furthermore, the WC-np favor a stronger distortion and finer grain size of martensite in the manufactured specimens. An increase in hardness from about 650 HV1 for the H11 specimen to 780 HV1 for the one manufactured using the powder blend containing 5 wt.-% of WC-np was observed in as-built conditions. In the same way, the compression yield strength enhanced from 1839 MPA to 2188 MPA. The hardness and strength increasing effect of WC-np remained unchanged even after heat treatments similar to those used in industry.

This work investigates the influence of a single tensile preload, applied prior to fatigue testing, on the fatigue strength of 316L stainless steel parts manufactured using laser-based powder bed fusion (PBF-LB) with a porosity of up to 4 %. The specimens were produced in both the horizontal and vertical build directions and were optionally preloaded to 85 % and 110 % of the yield strength before conducting the fatigue tests. The results indicate a clear tendency of improved fatigue life and fatigue limit with increasing overload in both cases. The fatigue limits increased by 25.8 % and 24.6 % for the horizontally and vertically built specimens, respectively. Extensive modelling and experiments confirmed that there was no significant alteration in the shape and size of the porosity before and after preloading. Therefore, the observed enhancement in fatigue performance was primarily attributed to the imposed local compressive residual stresses around the defects. 

This study is focused on how the application of pulsed substrate bias during cathodic arc deposition affects the microstructure, texture, grain size and phase composition of (Ti,Al)N coatings. A series of Tix-1AlxN, 0.25≤x≤0.55 coatings were deposited on WC-Co cemented carbide substrates with -30 V, -60 V and -300 V pulsing bias (duty cycle 10 % and a frequence of 1 kHz) under controlled chamber conditions at 4.5 Pa N2-gas and a substrate temperature about 400 °C. The pulsing parameters for the bias (voltage, duty cycle and frequency) were deliberately selected to influence structure, microstructure and composition of the deposited coatings. All Tix-1AlxN coatings had a consistent columnar cubic B1 structure regardless of their chemical composition. Coatings grown at -30 V and -60 V pulsed bias exhibited a pronounced <111> texture attributed to a kinetically driven mechanism influenced by the relative flux of ion species, affecting the surface migration of adatoms during growth. In contrast, the coatings grown with a pulsed bias of -300 V exhibited a reduced <111> texture and the onset of grains with <100> preferred orientation. The transition to the <100> orientation with increased ion energy agrees with the fact that the <111> directions expose the densest array of atoms to the ion beam during growth while the <100> are the most open channeling directions in a B1 structure. The correlation to the preferred with respect to pulsing conditions during growth, correlated to microstructure, grain size and phase composition be further discussed. Surface roughness was highest (Sa≈0.17-0.22 µm) for coating deposited at pulsed bias -30 V. 

Hot isostatic pressing (HIP) is a near-net shape powder metallurgy (PM) technique, which has emerged as an efficient technique, offering precise control over the microstructure and properties of materials, particularly in high-performance alloys. This technology finds applications across a wide range of industries, such as aerospace, automotive, marine, oil and gas, medical, and tooling. This paper provides an overview of powder metallurgy and hot isostatic pressing, covering their principles, process parameters, and applications. Additionally, it conducts an analysis of PM-HIPed alloys, focusing on their microstructure and fatigue behavior to illustrate their potential in diverse engineering applications. Specifically, this paper focuses on nickel-based superalloys and martensitic tool steels. The diverse microstructural characteristics of these alloys provide valuable insights into the PM-HIP-induced fatigue defects and properties.

Digital twins (DT) of industrial processes have become increasingly important. They aim to digitally represent the physical world to help evaluate, optimize, and predict physical processes and behaviors. Therefore, DT is a vital tool to improve production automation through digitalization and becomes more sophisticated due to rapidly evolving simulation and modeling capabilities, integration of IoT sensors with DT, and high-capacity cloud/edge computing infrastructure. However, the fidelity and reliability of DT software are essential to represent the physical world. This paper shows an automated and systematic test architecture for DT that correlates DT states with real-time sensor data from a production line in the forging industry. Our evaluation shows that the architecture can significantly accelerate the automatic DT testing process and improve its reliability. A systematic online DT testing method can significantly detect the performance shift and continuously improve the DT’s fidelity. The snapshot creation methodology and testing agent architecture can be an inspiration and can be generally applicable to other industrial processes that use DT to generalize their automated testing. 

Prealloyed Fe3Al was successfully manufactured by laser powder bed fusion. The best set of process parameters led to parts with a relative density of 99.5 %, a surface roughness, Sa, of 31.5 ± 5.6 μm and a hardness of 319 ± 14 HV0.1. Its microstructure as well as its mechanical properties at room and high temperatures were analyzed. The results of the chemical composition showed minor variations in aluminum content oscillating between 21 and 28 at.% along the melt pool. Additionally, elongated grains were observed to grow parallel to the building direction, as well as the development of a weak 001 texture along the building direction. The mechanical properties were influenced by the temperature. Compression tests showed a loss in strength with the increase in temperature, from a yield strength of 621 ± 40 MPa at room temperature to 89 ± 20 MPa at 650 °C. Reciprocating sliding wear tests showed that fragmentation of the intermetallic at room temperature occurs, whereas plastic deformation dominated at higher temperatures. For all temperatures, tribochemical wear was also present due to the oxidation of wear debris.