The present study was focused on assessing the molten salt-induced hot corrosion resistance of selective laser melting (SLM) manufactured Inconel 625 at 900 °C for 96 h and investigating the possibility of improving the superalloy’s corrosion resistance by applying a pre-oxidation heat treatment. The material’s hot corrosion properties were assessed in a heat-treated state (heat treatments performed at 1000 °C/1 h and 1150 °C/1 h, respectively) with and without pre-oxidation. The heat treatment at 1000 °C promoted the columnar dendrite morphology evolution, while the heat treatment at 1150 °C promoted the equiaxed dendrite morphology evolution. At 1150 °C, microstructural features specific to conventional manufactured material developed (annealing twin boundaries). They are considered a sign of anisotropy reduction due to equiaxed grains forming and it is believed that the internal stress in the material is reduced. High-temperature pre-oxidation heat treatment at 900 °C for 96 h ensured the formation of protective oxide scales with a reduced thickness (1.74 μm in the case of samples’ heat-treated at 1000 °C, and 2.22 μm in the case of samples’ heat-treated at 1150 °C, respectively). Experimentally, based on weight gain and oxide scale analysis, it was proven that pre-oxidation can improve the hot corrosion resistance of SLM manufactured Inconel 625 by forming a stable and protective oxide scale on the surface of the alloy before exposure to molten salts. The preformed oxide layer acts as a barrier for the corrosive species, reducing the formation of detrimental compounds, especially Mo-rich sulfides. Based on the tests, an improvement in corrosion resistance of up to 33.94% was observed in samples heat-treated at 1150 °C with pre-oxidation compared to samples heat-treated at 1000 °C without pre-oxidation.
In this study, a conceptual turbine blade model with internal cooling channels was designed and fabricated using the selective laser melting (SLM) process. The optimal manufacturing orientation was evaluated through simulations, and the results indicated that vertical orientation yielded the best outcomes, minimizing support material usage and distortion despite increased manufacturing time. Two configurations were produced, namely, an entire-turbine blade model and a cross-sectional model. Non-destructive analyses, including 3D laser scanning for dimensional accuracy, surface roughness measurements, and liquid penetrant testing, were conducted. Visual inspection revealed manufacturing limitations, particularly in the cooling channels at the leading and trailing edges. The trailing edge was too thin to accommodate the 0.5 mm channel diameter, and the channels in the leading edge were undersized and potentially clogged with unmelted powder. The dimensional deviations were within the acceptable limits for the SLM-fabricated metal parts. The surface roughness measurements were aligned with the literature values for metal additive manufacturing. Liquid penetrant testing confirmed the absence of cracks, pores, and lack-of-fusion defects. The SLM is a viable manufacturing process for turbine blades with internal cooling channels; however, significant attention should be paid to the design of additive manufacturing conditions to obtain the best results after manufacturing.
The small satellite market is set for rapid growth, driven by the need for independent space access. While current options involve ridesharing, dedicated small satellite launchers offer customized access, with nanosatellites taking as little as 8 months from concept to launch. Europe invests significantly in space transportation R&D through programs like HORIZON SPACE, aiming to boost competitiveness and reduce reliance on external providers. ESA initiatives like FLPP and BOOST! focus on technological advancements and commercial services. Despite efforts, the USA dominates the space launch market. Europe aims to double its space transportation market share by 2030 by developing low-cost propulsion and launch routes for SMEs. Over 100 projects worldwide are developing light-lift and micro-lift rockets, with consideration for geographically closer spaceports. Challenges like space debris are addressed through innovative solutions. Recommendations emphasize reusable technologies and greener propulsion systems. The COVID-19 pandemic highlighted vulnerabilities but also spurred innovation and resilience. This paper discusses the multifaceted aspects influencing the space launching market evolution, including market dynamics, European initiatives, external factors, innovation, and future potential.
The paper focuses on simulating the optimal resistive load for a piezoelectric harvester's power output maximization. The piezoelectric cantilever is simulated with a 4 g tip mass, according to the laboratory experiment, in order to obtain a valid comparison. The article shows how the power output increases by more than one order of magnitude with the optimal impedance of 21 k ohm + 50 pF, compared to the simulations with the input impedance of the spectrum analyser used in the laboratory, of 1 M ohm + 50 pF. The capacitance was left unchanged, with only the electrical resistance being modified. Under these conditions, the power output increases from 0.797 mW to 9.973 mW. The numerical simulations employ a fully coupled digital twin. Frequency-domain studies were conducted using systematic auxiliary sweeps of the load resistance, progressively narrowing the search range from coarse to fine steps until the optimal resistance value was computed with the desired precision.
Propulsion groups based on gas turbines are subassemblies that must be replaced in the case of the revitalization of a ship of a certain age. Due to the consumption of the vital resource of the ship's old gas turbines, they must be replaced with new turbines that have the same power, but greater efficiency due to the new manufacturing concept. The paper presents the case of replacing an old generation turbine with a modern turbine used in aviation but adapted for marine use. The new turbine together with the related automation was first tested on the stand and then was integrated on the ship instead of the old one. The tests carried out confirmed the fairness of the chosen solution, the power parameters being those expected. In tests the power and consumption of the new propulsion line were compared with the old propulsion line, the results showing a power developed equal to lower fuel consumption.
