Characterization of Spatter and Sublimation in Alloy 718 during Electron Beam Melting

Due to elevated temperatures and high vacuum levels in electron beam melting (EBM), spatter formation and accumulation in the feedstock powder, and sublimation of alloying elements from the base feedstock powder can affect the feedstock powder’s reusability and change the alloy composition of fabricated parts. This study focused on the experimental and thermodynamic analysis of spatter particles generated in EBM, and analyzed sublimating alloying elements from Alloy 718 during EBM. Heat shields obtained after processing Alloy 718 in an Arcam A2X plus machine were analyzed to evaluate the spatters and metal condensate. Comprehensive morphological, microstructural, and chemical analyses were performed using scanning electron microscopy (SEM), focused ion beam (FIB), and energy dispersive spectroscopy (EDS). The morphological analysis showed that the area coverage of heat shields by spatter increased from top (<1%) to bottom (>25%), indicating that the spatter particles had projectile trajectories. Similarly, the metal condensate had a higher thickness of ~50 μm toward the bottom of the heat shield, indicating more significant condensation of metal vapors at the bottom. Microstructural analysis of spatters highlighted that the surfaces of spatter particles sampled from the heat shields were also covered with condensate, and the thickness of the deposited condensate depended on the time of landing of spatter particles on the heat shield during the build. The chemical analysis showed that the spatter particles had 17-fold higher oxygen content than virgin powder used in the build. Analysis of the metalized layer indicated that it was formed by oxidized metal condensate and was significantly enriched with Cr due to its higher vapor pressure under EBM conditions.

CREATION OF MATHEMATICAL MODELS FOR PARAMETRIC IDENTIFICATION DURING TESTS TO DETERMINE THE FUEL CONSUMPTION OF THE HELICOPTER WITH EXHAUST- HEAT SHIELDS

With the increasing effectiveness of guided missile weapons, the problem of protecting helicopters from these means of destruction is becoming increasingly important. To date, the issue of assessing the protection of helicopters in tests of helicopter equipment are insufficiently developed and require more careful consideration. Therefore, the research of the protection of helicopters equipped with an integrated protection system against guided missiles with infra-red target seeker devices and the impact of exhaust-heat shields on the values of flight characteristics of the helicopter is quite relevant. The article researches the influence of exhaust-heat shields on the flight technical characteristics of helicopters, their change during the installation of exhaust-heat shields. The estimation of the change in geometric, mass and center characteristics of helicopters by the calculation method is given and the method determining the characteristics of fuel consumption by the calculation and experimental method is given. The methodology and results of experimental researches of flight technical characteristics of the helicopter with the established exhaust-heat shield are described. The basic result of the research is the study of existing methods for determining the impact of exhaust-heat shields on the flight characteristics of helicopters. Methods of parametric identification for determination of fuel consumption are worked out and the analysis of flight technical characteristics of the helicopter is developed. The fuel consumption of the helicopter with exhaust-heat shield is defined. Integrated assessment of the effectiveness of protection of helicopters from guided missiles with infra-red targeting device can be directly used in practice in test systems for the protection of upgraded and the latest models of helicopters. According to the results of research, mathematical models for determining the fuel consumption of a helicopter with exhaust-heat shields have been developed.

Space Debris Removal and Exploitation of Lunar Resources - Profitability Perspectives

Removing at least half of space debris, consisting of large metal objects, could be a cost-effective activity if, first, it becomes raw material, along with other extraterrestrial resources such as regolith, for the production of heat shields which is aimed to return the upper stages of medium and heavy rockets and, secondly, as a working medium for low-thrust electric rocket engines of interorbital tugs. Heat shields from external resources provide a means of increasing the payload of reusable launch vehicles.