TY - JOUR A1 - Epishin, A. A1 - Bokstein, B. A1 - Svetlov, I. A1 - Fedelich, Bernard A1 - Feldmann, Titus A1 - Le Bouar, Y. A1 - Ruffini, A. A1 - Finel, A. A1 - Viguier, B. A1 - Poquillon, D. T1 - A vacancy model for pore annihilation during hot isostatic pressing of single-crystal nickel-base superalloys JF - Inorganic Materials: Applied Research N2 - An improved diffusion model is proposed for pore annihilation during HIP of single-crystal nickel-base superalloys. The model assumes the pore dissolution by emission of vacancies and their sink to the low angle boundaries. Calculation, considering distribution of the pore sizes, predicts the kinetics of pore annihilation similar to the experimental one. KW - Single crystal superalloys KW - Hot isostatic pressing (HIP) KW - Porosity KW - Diffusion KW - Vacancies PY - 2018 DO - https://doi.org/10.1134/S2075113318010100 SN - 2075-1133 VL - 9 IS - 1 SP - 57 EP - 65 PB - Pleiades Publishing, Ltd. AN - OPUS4-43990 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Höhne, Patrick A1 - Rabe, Torsten T1 - Limits of computer tomography aided characterization of different types of porous ceramic materials N2 - Ceramics with open porosity are attractive materials in many fields of applications covering medicine, catalysis, and filtration. Manifold technologies to produce porous ceramics are available, e.g. foaming and replica processes, resulting in various microstructures. Development and manufacturing of new materials is accelerating, while crucial characterization is becoming increasingly difficult and conventional measurements lack the desired speed. Computed tomography (CT) offers the possibility to three-dimensionally characterize entire samples with minimal sample preparation, while its main advantage is that it is non-destructive. Still, the assessment of quantitative results from CT measurements is not trivial. The poster presents CT characterizations of newly developed as well as commercially available openly porous ceramic samples. Properties such as porosity, permeability or pore characteristics were measured conventionally and compared to results calculated from CT-measurements using the commercial software VG StudioMax. The determined differences between measured and calculated values are presented and application areas as well as limits of the CT characterization are evaluated. T2 - Jahrestagung der Deutschen keramischen Gesellschaft 2021 CY - Online Meeting DA - 19.04.2021 KW - Ceramic KW - Porosity PY - 2021 AN - OPUS4-52724 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Epishin, A.I. A1 - Nolze, Gert A1 - Alymov, M.I. T1 - Pore Morphology in Single Crystals of a Nickel-Based Superalloy After Hot Isostatic Pressing JF - Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science N2 - The morphology of pores partially shrunk during a half-hour HIP at temperature of 1288 °C and pressure of 103 MPa has been investigated in nickel-based superalloy CMSX-4. The investigation resulted in the following findings: surrounding the shrinking pores by a c¢-shell (Ni3Al), faceting of the pores surface by {023} and {011} planes, and formation the submicroscopic satellite pores connected by channels with the neighboring larger pores. It is assumed that the formation of the c¢-shell around the pores and the faceting of the pore surface is due to diffusion processes occurring during pore shrinkage, and therefore these findings can be considered as arguments supporting the vacancy model of pore annihilation. The submicroscopic satellite pores are expected to be the result of dividing the casting pores of a complex initial shape during their shrinking. The connecting channels are probably required for the gas to escape from the rapidly shrinking small satellite pores into the slowly shrinking large pore. Thus, it is reasonable to assume that the casting pores may contain some amount of gas. KW - HIP KW - Superalloy KW - Porosity KW - Faceting KW - negative crystal growth PY - 2022 DO - https://doi.org/10.1007/s11661-022-06893-x SN - 1073-5623 SP - 1 EP - 9 PB - Springer Nature AN - OPUS4-56409 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -