Phase stability,oxidation, and interdiffusion of a novel Ni−Cr−Al−Ti−Si bond-coating alloy between 900 and 1100°C

A novel, low-expansion experimental Ni–Cr–Al–Ti–Si bond-coating alloy was investigated in the as-cast state concerning its phase stability, oxidation resistance in air, and interdiffusion with single-crystal IN-100 at 900, 1000, and 1100°C. Isothermal oxidative thermogravimetry was employed up to 500 hr. Interdiffusion was compared to a commercial Ni–Co–Cr–Al–Y alloy on IN-100. Oxidized Ni–Cr–Al–Ti–Si specimens and diffusion couples were characterized by metallography, SEM, EDX, XRD, and XRF. The Ni–Cr–Al–Ti–Si alloy provides good oxidation resistance in air at least up to 1000°C. The alloy is an alumina former. Due to its coarse microstructure, other oxides (e.g., rutile) may form and considerably dominate the oxidation behavior. The kinetics of oxidation were correlated with temperature, formation of phases, and morphology of oxides. Interdiffusion fluxes between Ni–Cr–Al–Ti–Si and IN-100 were mainly directed to the superalloy. They were faster than in Ni–Co–Cr–Al–Y/IN-100 diffusion couples.     

Simulationsuntersuchungen zur Evaluierung der Kapazität eines neuen Fertigungssystems

Zusammenfassung In dieser Arbeit wird die Verwendung der diskreten Simulation zur Bestimmung von Kapazitäten und maximalen Produktionsmengen einer neu errichtenden Fertigungsanlage beschrieben. Aufgrund fehlender Erfahrungswerte ist es dabei notwendig, die Kapazität jeder einzelnen Maschine im Produktionsprozeß bzw. jeder Produktionsstufe zu bestimmen. Davon ausgehend wird die maximale Produktionsmenge der gesamten Fertigungsanlage ermittelt. Die Analyse des Fertigungssystems zeigt, daß die Lage der Engpässe sehr stark vom tatsächlichen Produktionsprogramm abhängig ist. Aus diesem Grund wird das maximale Kapazitätsangebot der einzelnen Produktionsstufen getrennt bestimmt und als Restriktionen bei der Einlastung der einzelnen Aufträge verwendet. Ein heuristisches Verfahren zum Festlegen des Produktionsprogramms unter Beachtung aller durch verschiedene Simulationsläufe ermittelten Restriktionen bildet den Abschluß der Arbeit.     

Entwicklung einer Dekompositionsstrategie für die Strukturoptimierung komplexer Bauteile

Zusammenfassung Der Einsatz von Finite-Elemente-Optimierungsprogrammen für die konstruktive Auslegung von Bauteilen ist mit gro?em Rechenaufwand und Speicherplatzbedarf verbunden. Die Dekompositionsstrategie stellt ein effizientes Verfahren dar, das zu einer drastischen Reduzierung der Rechenzeiten bei der L?sung von Problemen der Gewichtsminimierung führt. Darüber hinaus verringert sich der immens hohe Bedarf an Plattenplatz und nicht zuletzt wird ein schnelleres Konvergenzverhalten bei der Optimierung erreicht. Die in diesem Beitrag vorgestellten Arbeiten sind Gegenstand des von der Deutschen Forschungsgemeinschaft (DFG) gef?rderten Forschungsprojektes “Entwicklung von Dekompositionsstrategien für die Strukturoptimierung unter Einsatz von Parallelrechnern?     

Effet ďun champ magnétique sur les modes TMnmo ďune cavité cylindrique circulaire partiellement remplie de ferrite

The resonant modes of a circular cylindrical cavity resonator containing a coaxial circular ferrite rod are investigated. The ferrite sample is partially magnetized by means of a constant external magnetic field applied along its axis. A computer program for deriving the resoant frequencies of this system as a function of the externally applied magnetic field and of the sample radius has been developed. Results for the special cases of the tm₀₁₀ and tm110 modes are presented. The possible application of such a cavity resonator for the remote sensing of magnetic fields is discussed.     

Bedeutung der Vakuumtechnik in der Metallpulver-Technologie

Powder-Technology has developed into a significant and still increasing market. There is a demand for high quality meaning highest purity and spherical particle shape of the powder. In order to reach this aim metal alloys are melted under vacuum and atomized with intertgas. To improve the chemical purity the produced powder is treated under vacuum for instance by the static or dynamic degassing process.     

An initial approach to establishing an experimentally proven ‘leak before rupture criterion’ for SNR-300 components

Examination of experimental results and fracture mechanics analysis has shown the sudden rupture of one of the SNR-300 main coolant pipes to be impossible. The analysis indicates that, excluding small leaks, the integrity of the sodium filled heat transfer system under normal operating conditions will also be maintained. With regard to small leaks it is considered that if these are smaller than those which would give a leak rate of less than about 1 kg/h, they can be detected.     

Stacking fault energy and mechanical properties

Several deformation mechanisms are discussed which may be influenced by the stacking fault energy: forest cutting at the beginning of plastic deformation in fcc and hex metals, cross slip in fee metals, prismatic slip in hexagonal metals, and slip in bee metals. Existing experimental data for the temperature and strain rate dependence of the shear stress at which the relevant deformation mechanism begins are analyzed. It is shown that the data for cross slip in fee metals, for prismatic slip, and for slip in bee metals can be described by an Arrhenius equation with an activation energy that is proportional to the logarithm of the stress. Stacking fault energies are determined from the strain rate sensitivity of the shear stress.     

Untersuchungen über den Einfluß des Gefügezustandes auf das Korrosionsverhalten hochlegierter,rost- und säurebeständiger Stähle in reiner sowie in chloridhaltiger Schwefelsäure

Corrosion Properties of High Alloyed Stainless Steels in Pure as well as in Chloride Containing Sulfuric Acid The corrosion behaviour of the high alloyed stainless steels material no. 1.4439 (X3CrNiMoN17135), 1.4539 (X2NiCrMoCu25205), 1.4503(X3NiCrMoCuTi2723) as well as the reference materials AlSI 316 L and alloy 825 was tested in diluted sulfuric acid (5, 10, 20 and 50%) at 50, 100 and 150°C. The test solutions additionally contained impurities as chlorides and cupric ions. On the material side the effect of various microstructures was checked as well: material as received (commercial production), solution annealed under laboratory conditions, cold deformed and for two selected steels electroslag remelted. Corrosion testing methods are: the immersion test will sheet coupons and the measurement of the weightloss; electrochemical testing, i.e. Current potential-and free corrosion potential-time-curves. No pitting corrosion is observed in the presence of chloride ions. In some cases the general corrosion rate is lowered if chloride ions are present. This beneficial effect of chloride ions, however, is observed only at low chloride concentrations (500 ppm). Annealing under laboratory conditions as well as electroslag remelting does not generally improve the corrosion resistance. A negative effect by cold deformation is only observed for standard stainless steel AlSI 316. Cupric ions added to the 20% sulfuric acid solution improve the corrosion resistance of all steels investigated to that extent, that they can be used in practice up to 100°C provided that the concentration of cupric ions in the solution is sufficiently high (2000 ppm). Electrochemical test results indicate that the positive effect of cupric ions is due to the shift of the free corrosion potential into the potential range of stable passivity. Copper alloyed stainless steels show the highest corrosion resistance.