TY - GEN A1 - Jokisch, Torsten A1 - Doynov, Nikolay A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin T1 - Heat source model for electron beam welding of nickel-based superalloys T2 - Materials testing : Materialprüfung Y1 - 2021 U6 - https://doi.org/10.1515/mt-2020-0002 SN - 2195-8572 SN - 0025-5300 VL - 63 IS - 1 SP - 17 EP - 28 ER - TY - GEN A1 - Jokisch, Torsten A1 - Doynov, Nikolay A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin A1 - Böttger, Bernd A1 - Senger, Aleksej T1 - Analysis of temperature field during electron beam welding of hot crack sensitive nickel base alloy T2 - IEBW International Electron Beam Welding Conference: lectures of the 6th International Conference taking place online on 9 to 10 March 2021 N2 - The use of temperature-resistant nickel-based superalloys in the field of industrial gas turbines is increasing due to constantly rising operating temperatures. Among different joining methods the electron beam welding is commonly used for manufacturing of turbine components because it provides a reduced heat input. However, the highly localized beam impact causes high temperature gradients and leads to the formation of hot cracks. Welding of such material with a high brittle temperature range is challenging and needs an increasing effort of process adaption. Experiments indicate a significant improvement of hot crack susceptibility when welding outside the common welding parameter range. To understand these observations a study of the temperature field in the specimens using numerical simulations was carried out. For this purpose, a validated simulation model was used. Special attention was paid to the domain in close vicinity of the weld pool. The results illustrate the velocity of solidification isotherm as well as the temperature rates when crossing the melting point. Finally, the relations between thermal fields, crack types and distributions in the different specimens are discussed. Y1 - 2021 UR - https://www.dvs-media.eu/media/pdf/DVS_Bericht_368_Inhalt.pdf SN - 978-3-96144-133-4 SP - 81 EP - 87 PB - DVS Media GmbH CY - Düsseldorf ER - TY - GEN A1 - Jokisch, Torsten A1 - Doynov, Nikolay A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin T1 - Analysis of Local Strain Evolution during Electron Beam Welding of Hot Crack Sensitive Nickel Base Conventionally Cast Alloy 247 LC CC T2 - Journal of Materials Engineering and Performance N2 - Among different joining methods, the electron beam welding is recently applied for manufacturing of turbine components from temperature-resistant nickel-based conventionally cast Alloy 247 LC CC. However, the high tendency to hot cracking, in particular the formation of solidification cracks, remains a major challenge. Experiments indicate a significant reduction in hot cracks if the welding is performed outside the common welding parameter range. To understand these observations, a study of local thermo-mechanical conditions during electron beam welding of Alloy 247 samples was carried out using numerical simulations. The results were subsequently compared with reference test welds. For this purpose, a finite element model for coupled transient thermal and mechanical analysis was created and used. The work presents a comparative analysis of the evolution of strain components in brittle temperature range during cooling, considering the distribution and orientation of the cracks. Various relations between local strain kinetics and crack appearance, with notable influence of the plastic strain vector, were observed. Finally, the aspects of assessment of hot crack susceptibility with aid of thermo-mechanical welding simulation are discussed. KW - computational welding mechanics KW - electron beam welding KW - hot crack susceptibility KW - modeling of welding and joining KW - nickel-based alloys Y1 - 2022 U6 - https://doi.org/10.1007/s11665-022-06660-4 SN - 1544-1024 VL - 31 IS - 9 SP - 7009 EP - 7017 ER -