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This work concerns the laser wire directed energy deposition (LW-DED) additive manufacturing process. The objectives were two-fold: (1) process mapping – demarcating the process states as a function of the processing parameters; and (2) process monitoring – detecting process anomalies (instabilities) using data acquired from an in-situ meltpool imaging sensor. The LW-DED process enables high-throughput, near-net shape manufacturing. Without rigorous parameter control, however, LW-DED often introduces defects due to stochastic process drifts. To enhance scalability and reliability, it is essential to understand how LW-DED parameters affect processing regimes, and detect deleterious process drifts. In this work, single-track experiments were conducted over 128 combinations of laser power, scanning velocity, and linear mass density. Four process states were observed via high-speed imaging and delineated as stable, dripping, stubbing, and incomplete melting regimes. Physically intuitive meltpool features were used to train simple machine learning models for classifying the process state into one of the four regimes. The approach was benchmarked against computationally intense, black-box deep machine learning models that directly use as-received meltpool images. Using only six intuitive meltpool morphology and intensity signatures, the approach classified the LW-DED process state with statistical fidelity approaching 90 % (F1-score) compared to F1-score 87 % for deep learning models.

Steels with high carbon content can hardly or not at all be welded, but are of great interest for cladding applications due to their high hardness. In this study, the influence of process parameters on weld seam geometry and process stability is investigated when welding AISI 52100 bearing steel using the laser hot-wire cladding process. Process stability is evaluated using actual and set values for the wire feed rate and current parameters to determine a process window for a stable welding process. Weld seams are measured and analyzed in terms of width, height, contact angle, and shape. The effect of the process parameters on the weld seam geometry is investigated and appropriate mathematical functions to describe the geometry are determined. Process parameter sets in the range of 1-2 m/min wire feed rate and 45-75 A hot wire current were investigated. Unstable parameter sets occur clustered at high wire feed rate of 2 m/min for all hot wire currents. In addition, the process is unstable at high hot wire current of 75 A and low wire feed speed of 1 m/min. The remaining parameter sets resulted in a stable process. The investigated functions parabolic, cosinusoidal and circular arc for the mathematical description of the weld seam geometry, no clearly significant result could be determined. Only a trend towards the circular arc function and the parabolic function is apparent.

Cross-feeding based on amino acids metabolism is an important strategy by which anammox bacteria and the co-existing heterotrophs facilitate their own growth and survival. Arginine is one of the necessary amino acids required for bacterial protein biosynthesis but whether adding arginine could benefit growth of anammox bacteria remains unknown. In this study, arginine was supplemented at dose of 5 mg·L -1 to promote the nitrogen removal performance of anammox bioreactors under varied loading rates. The results showed that nitrogen removal efficiency increased by 10.2 % under higher loading rates. Arginine addition substantially simulated the secretion of extracellular proteins and polysaccharides within anammox consortia as a strategy against unfavorable conditions. Canditatus Kuenenia dominated the anammox consortia and their 16S rRNA abundance and anammox-related functional genes were significantly increased by up to 0.42 times and 5.81 times, respectively. The findings of this study provided a feasible strategy to improve the performance of anammox reactors with arginine supplementation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Wire + arc additive manufacturing (WAAM) with cold metal transfer (CMT) process can reduce cost and lead time during the production of large-scale Ni-based components used in the transportation and energy sector. This paper investigates the effects of processing parameters and heat treatments employed on CMT-WAAM of a precipitation hardenable Ni-based alloy – Inconel 718. The process stability was analysed by electrical transients and melt pool imaging, showing an opposite trend to the measured heat inputs. A 1.2 mm diameter wire permitted deposition widths of 5.92–13.15 mm, but widths larger than ~10 mm decreased the arc stability considerably. Laves length and carbide diameter decreased with travel speed, while the as-deposited hardness increased. These observations permitted a linear wall to be fabricated with a minimal heat input per layer of 181–185 J/mm. An increase in the solution treatment temperature from 980 to 1040 °C reduced microsegregation, Laves and δ phase precipitation. Localised regions with high microhardness were found near interlayer regions due to a local dissolution of Nb-rich eutectic phases. Compared to powder-based additive manufacturing, CMT-WAAM IN718 exhibits a larger melt pool size and lower as-deposited hardness, but has been found to show satisfactory ageing response and similar Laves phase area fraction.

Both typical beam welding processes laser beam welding LBW and electron beam welding EBW feature the deep penetration welding process. Theses processes rely on a vapor capillary with a delicate, highly dynamic equilibrium of various opposing forces. The direct observation of the vapor capillary's inner surface is hindered with growing capillary depth by the thermal optical emissions with high intensities due to the high temperatures inside the capillary. Even with the use of high intensity laser based illumination and band pass filters adjusted for the laser wavelength, it is merely possible to observe only the upper most part of the capillaries opening. The lack of observability, especially with high temporal resolution to assess the highly dynamic effects contributes to the state of the capillary models that actually are describing quasi-static modes or implement the less dynamic effects that can be observed with state of the art methods.The topographical measurement system, developed by the Institut für Strahlwerkzeuge Universität Stuttgart IFSW, uses the process inherent thermal emission of the capillary governed by the complex refractive index of the base material to reconstruct the inner geometry of the visible capillary surface. This is achieved by using the dependence of the emissivity between emission angle and polarization that is described by the Fresnel equations (Sawannia et al., 2018). The measurement system uses the fact that the quotient of two or more polarization components of the emission from a surface increment is depending on the angle of surface inclination but are almost independent of the surface temperature (Weberpals et al., 2011). Based on the results of the application of the measurement principle with laser beam welding, an adaption to electron beam welding is developed to assess the observability of capillaries with large depth and to contribute in the improvement of capillary models in the wake of the development. To allow the use of the improved measurement system to capture the EBW process capillary with unmatched spatial and temporal resolution, a complete new optical observation beam path was developed and fitted insight a custom-made pressurized chamber inside an electron beam welding machine.