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Description / Table of Contents: Preparation and Testing of Solid-State Bonded Ceramic-to-Metal-JointsCeramic-to-metal joints were manufactured by solid-state bonding in a R. F.-high-vacuum apparatus. The influence of welding temperature, welding time and welding pressure on the bond strength was investigated for an alumina/niobium-combination consisting of a layered composite ceramic-metal foil-ceramic. As a measure of bond quality the fracture resistance KICV was chosen. KICV date were obtained by the use of 4-point bend tests and tensile tests. For comparison, data are presented concerning the fracture resistance KIC of the bulk alumina and the conventional bond strength of the joints. In addition to the Nb/Al2O3-data, KICV factors are determined for other metal/alumina combinations and for a Zr/Si3N4 joint. The present solid-state bonding apparatus was used for the preparation of the specimens. A device for high-temperature bend testing in a high vacuum was constructed. Some data for the high-temperature bond strength of solid-state bonded joints are given.

Description / Table of Contents: Structural changes and corrosion behaviour of a ferritic-austenitic chromium-nickel-molybdenum steel after short time heat treatments with special consideration of weldingSusceptibility of the ferritic-austenitic steel X 2 CrNiMoN 225 in the solution treated and quenched state to intergranular corrosion and to stress corrosion cracking and pitting corrosion in solutions with chloride ions. Comparison with two austenitic steels (X 5 CrNi 189 and X 3 CrNiMoN 17135). Investigations of the influence of structural changes due to short time isothermal heat treatments and to welding on the mentioned three corrosion types.

Description / Table of Contents: Einige metallurgische Beobachtungen zur Herstellung von diffusionsgeschweißten Übergängen zwischen Zircaloy 2 und EdelstahlEs wird ein Verfahren zur Verschweißung von Zircaloy 2 mit Edelstahl durch Ko-Extrusion vorgeschlagen. So hergestellte Schweißverbindungen wurden an der Nahtstelle zwischen Zircaloy 2 und Edelstahl metallographisch und im Rasterelektronenmikroskop untersucht. Außerdem wurden eine chemische Analyse sowie mit der Elektronen-Mikrosonde durchgeführt.Die Ergebnisse dieser Untersuchungen zeigt, daß mit diesem Verfahren eine perfekte Verbindung der beiden Materialien durch mechanische und metallurgische Vorgänge erzielt wird, die besser sein sollte als durch Diffusion bei hohen Temperaturen hergestellte Übergänge.

Description / Table of Contents: The material selection for tribologically stressed specimen and tools has to be done not only from the view point of economics but also of the consumption of scarce materials and energy.Empirical methods are used for this selection to get a reasonable compromise between surface and bulk functions to satisfy stability and rigidity.By applying system- and stress analysis for the estimation of surface and bulk properties some examples of metallurgical, manufacturing, operational and lubricating aspects to improve the tribological behaviour of components are shown.Using the friction energy for a wear prediction model the calculation of lifetime for dry lubricated roller bearings is possible.

Description / Table of Contents: Results of Creep Tests With Smooth and Notched Specimens of the Steels 20 CrMoV 13 5 and X20 CrMoWV 121Two hydrogen resistant steels, viz. 20 CrMoV 13 5 W.-Nr. 1.7779) and X20 CrMoWV 12 1 (W.-Nr. 1.4935) used for bolts and nuts as well as for pressurized components were tested with respect to their creep resistance. Using smooth and notched specimens creep data for 450°C 500°C and 550°C were established. Steel 20CrMoV 13 5 was investigated in two quenched and tempered states (225…250 HB, 285…310 HB. The tempering treatments of X20 CrMoWV 12 1 (W.-Nr. 1.4935) lead to hardness levels of 215…226 HB resp. 275… 310 HB.Creep tests at 450°C and 500°C resp. at 500°C and 550°C were undertaken with smooth and notched specimens of 20 CrMoV 13 5-resp. X20 CrMoWV 12 1 -steels. At each temperature two resp. three different hardness levels were investigated which were produced by changing the quenching and tempering procedure. The results prove the X20 CrMoWV 12 1-steel to show high ductility in all three Q + T conditions even after long creep tests. This holds true for the 20 CrMoV 13 5-steel in the soft condition and at a test temperature of 450°C only. The creep strength of both steels is about proportional to the ultimate strength of both steels is about proportional to the ultimate strength at room temperature. With regard to the allowable stresses it could be shown that in each case the creep strength for 100.000 hours divided by a safety factor of 1.5 is smaller than the 1% creep limit for the same time.

Description / Table of Contents: Model Investigation of the Fibre Reinforcement of Ceramic MaterialsA mechanism for fibre reinforcement of high-modulus brittle materials, in particular ceramics, is investigated both experimentally and theoretically. A simple mathematical formalism representing crack extension in a brittle matrix reinforced by ductile fibres is derived, and characteristic property values, adapted to composite structures, are introduced.Alumina with unidirectional reinforcement by thin 80Ni20Cr wires is used as a model material.The mechanism presented allows to reduce the high sensivity of ceramic materials to cracks. It is necessary for the fibres to bridge matrix cracks under load. For this purpose, the fibres must not be bound too tightly to the matrix, and while a high ductility is certainly of value, it is not a necessity. The efficiency of the mechanism depends on -interface energy and friction at the matrix-fibre interface,-deformation and fracture behavior of the fibre material,-radius of the fibres,-volume fraction of the fibres,-critical stress intensity factor of the matrix,-size of the largest crack.Among these, the fibre radius appears to be the most suitable one for variation with the goal of optimizing material quality.

Description / Table of Contents: Untersuchung der Spannungsrißkorrosionsanfälligkeit einer Legierung MgAlZn61 in wäßriger Lösung von 3,5% NaCl + 2% K2CrO4 bei Raumtemperatur.

Description / Table of Contents: Explosive Welding as a Technique for Cladding of Precious MetalsThe method of explosive welding and the importance of the cladding parameters are described. The “Explosive Weldability Window” is experimentally determined for the material combination AgCu 10/Fe. The behaviour of explosive claddings produced under different conditions during rolling is investigated.Best results are obtained with samples with a wavy interphase, produced under the following cladding parameters: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {10^ \circ \le \beta \le 18^ \circ} \\ {1400 \le {\rm v}_{\rm K} \le 2600{{\rm m} \mathord{\left/ {\vphantom {{\rm m} {\rm s}}} \right. \kern-\nulldelimiterspace} {\rm s}}} \\ \end{array} $$\end{document}It is shown, that in comparison with conventional methods explosive cladding has advantages both in processing and quality.

Description / Table of Contents: Silizium-TechnologieZuerst wird in Kap. 1 eine kurze historische Übersicht gegeben. Im Folgenden wird gezeigt, daß die „Silizium-Technologie“ vom Schwermaschinenbau bis zu mikroskopischen Arbeitsgängen reicht. In Kap. 2…5 wird dies an der Herstellung des Werkstoffs „Silizium“ demonstriert, in Kap. 6 an der Herstellung von diskreten Bauelementen und integrierten Schaltkreisen. In Kap. 7 werden einige Anwendungen in der Leistungs-Elektronik und in der Nachrichten- und Informations-Technik dargestellt. Abschließende Bemerkungen in Kapitel 8 weisen darauf hin, daß trotz aller Wichtigkeit für die Leistungs-Elektronik die wirklich umwälzenden Folgen der Silizium-Technologie auf ihrer Bedeutung für die Computer-Technik beruhen.

Description / Table of Contents: The Influence of Chemical Composition, Structure, and Mechanical Strain on the Hydrogen Embrittlement of Fine-Grained Low-Alloy SteelsOn specimens from fine-grained low-alloy steels StE 51 and StE 36 strain induced hydrogen embrittlement has been studied under increasing, pulsating, and static load conditions in hydrogen sulphide at various strain rates, gas pressures, gas compositions, and surface qualities. Both steels displayed equal sensitivity compared to mild constructional steels, Hydrogen pick-up occurred only during plastic-deformation of the specimens and led mainly to a decrease of the reduction of area and to the formation of side cracks in the necking zone. This type of embrittlement is important for constructions subjected to pulsating load conditions causing plastic deformation in areas with constructional notches.As part of the research and development project “Corrosion and Corrosion Prevention” this investigation was supported by the Federal Ministry of Research and Technology.

Description / Table of Contents: Evidence of the Instrumented Fatigue Test for Fatigue Strength of Structural SteelIn the instrumented fatigue test the measurement of the frequency of loading and the power absorption of the resonance endurancetesting machine with electromagnetic energization discovery the rate of damage of the specimen. The energy and the energy gradient per cycle are especially suitable for characterize the fatigue life of the specimen. Rapid methods for evaluation fatigue strength are developed constructive on the results of experiments of fatigue tests in one load stage. The rapid methods are tested with cylindrical specimen (St 52-3) and spot weldings (St 1203). The results of measurement indicate a certain possibility of evaluation fatigue strength.

Description / Table of Contents: Description of the time dependent stress-strain-behaviour of viscoelastic materials investigated in basic testsAssuming the existence of a mechanical equation of state calculation procedures are investigated in order to formulate the mechanical behaviour of viscoelastic materials in general and independent on the loading form. A case in point would be the derivation of creep behaviour from constant strain rate tensile tests or vice versa. Based on the ordinary log-log-plot for experimental data found in creep tests (constant stress conditions) and/or tensile tests a mechanical equation of state is developed. The results of the application of this equation to describe the mechanical behaviour under constant strain rate, creep and relaxation conditions in basic tests are compared with time-dependent behaviour of polycarbonat.

Description / Table of Contents: Keramische Werkstoffe für Fahrzeuggasturbinen

Description / Table of Contents: Dimensioning of Complicated Steel Machine Parts in the Whole Range of Load Cycle and EnduranceThere is given a concept for the early state of dimensioning machine parts, developed by multiple regression from an extensive collection of data. Starting with static strength, it is possible to evaluate fatigue strength of specimens, also notched or of real machine parts under each kind of stresses including preloads and  -  in a first rough approximation  -  also for mechanical- or heat-treated steel parts in the whole range of load cycle and endurance.

Description / Table of Contents: Cyclic Work Hardening Behavior of the α-copper tin alloy CuSn6.Polycrystalline specimens of the copper-tin alloy CuSn6 have been subjected to strain-controlled single step and two step fatigue tests. In a single step test the cyclic deformation curve at the beginning reveals strong work-hardening which is decreasing in the course of the test. A saturation of the stress amplitude is not observed. In two step tests, the material shows strong cyclic work hardening immediately after the change from low to high amplitudes, After the high amplitude is being changed into a low one, pronounced softening occurs. After changes of the strain amplitudes both these typical reactions of the material are observed up to fatigue crack initiation.

Description / Table of Contents: Fracture Mechanical Considerations on the Effect of Hot Cracks.There exists a lot of literature (1, 2) concerning the mechanisms of the origin of hot cracks. Something essential about the effects of hot cracks on the mechanical behaviour of components hardly can be found. These hot cracks can be valuated only by a quantification of the cracks and by an estimation of their behaviour under operational loadings.It is shown how by means of fracture mechanic material laws and calculation methods the growth of hot cracks under operational conditions can be evaluated. By a simple example of a fatigued vessel the systematic procedure is demonstrated and the results of calculation are explained. This procedure can be applied on the most technical problems as the operational stresses generally are below the yield point. For the region of the yield point and above it neither experimental nor theoretical results are available at the moment.The possibility of simplified calculations of burst stress of vessels is mentioned, which is derived from experiments. Experimental data (11) confirm the chosen hypothesis in so far as the burst stress can be realistically or rather conservatively evaluated by this method.It is concluded: With regard to the fact of unavoidable hot cracks for some certain austenitic steels the authors are convinced that basing on the examples and using the well known data of an austenitic steel as well as modified fracture mechanical rules the up to now empirically assumed stability of hot cracks is practically existent against intolerable crack growth. The given examples make it quite significant that the tolerable defect can be rather big without any critical consequences.If the operational conditions are at or above the level of the tolerable stresses, then safety precautions exist in so far as by means of non destructive - for instance during inservice inspections - volumetric examinations can be carried out. This will enable the detection of a critical defect or of one which becomes critical. Whilst the classic hot crack ranges in a micro dimension and therefore remains undetectable for the non destructive testing methods available at present the increased defect is detectable. Furtheron it should be pointed out that this detectable defect will surely be below the critical size and therefore will not be dangerous.

Description / Table of Contents: Study on the Application of the Fracture Mechanics Concept to Ductile Materials-Fracture Behavior of Rigid PVCThe fracture behavior of ductile materials cannot be treated by the methods of linear elastic fracture mechanics concept. For these materials the application of extended theories, which consider the non-linear stress-strain-relationship, is necessary.The test results being reported here have been obtained from rigid blue colored PVC. CT-specimens of different sizes were tested in tension at different loading rates. Above a certain strain level, the material shows crazing. This makes it possible to determine the plastic zone size. The relatively low Young's modulus originates in great deformations of the specimen. The deformation can therefore be measured with great accuracy.During the tests, a great number of quantities were registered. From these quantities the stress intensity factor, crack opening displacement, I-Integral and so on were calculated. The applicability of the results, in order to describe the fracture behavior of ductile materials, is being discussed.

Description / Table of Contents: Pilot Tests with a Directionally Solidified Eutectic SuperalloySeveral vanes of a directionally solidified eutectic superalloy Co—Cr7C3 (40.7 mass% Cr, 2.4% C, rest Co) have been tested for 18 000 hrs in a stationary gas turbine plant. The average material temperature was 700 °C with maximal values at 780 °C. The vanes were demounted after 900 operation cycles and were given a thorough metallographic investigation. Due to non-constant eutecticity over the length of the blade the following effect was observed: The purely eutectic microstructure stably survived the 18 000 hrs test (lower part of the blade). That part of the blade exhibiting off-eutectic (matrix-rich) micro-structure showed carbide transitions (Cr7C3 → Cr23C6) which, in turn, induced coagulation of the carbide fibers. It is concluded that microstructural stability in Co—Cr7C3 alloys is being favored by homogeneous eutectic compositions deviating from the pseudoeutectic point towards the direction of C-rich alloys only on the eutectic trough.

Description / Table of Contents: Einfluß der Modifizierung von Belastungsprogrammen bei Umlaufbiegeversuchen auf das Ermüdungsverhalten von Luftfahrtwerkstoffen

Description / Table of Contents: Fatigue Tests on Threaded FastenersBy conducting fatigue tests on threaded fasteners the size of the transition range in the Wöhler-diagramme and the kind of distribution of failure and non-failure in this transition range was determined as a function of the stress-amplitude.On this basis it was attempted to find a suitable statistical evaluation method for the procedure and evaluation of fatigue tests on threaded fasteners regarding to the following criterions: Number of screws to be tested,reliability and precision of the achieved values,wasting of time at the testing machine,capability of extrapolation to load-levels which had not been considered during the test procedure andexpenditure in evaluation of the test results.The results show that the function of distribution within the transition range can be sufficiently described with the Gaussian-Normal-distribution.They show furthermore that the Boundary Technique is superior to the other two tested evaluation methods (stair-case-method and arc sin method) as far as the above mentioned criterions are concerned.

Description / Table of Contents: Untersuchungen über die Spannungsrißkorrosion sensibilisierter austenitischer nichtrostender Stähle und von Nickelbasislegierungen in siedenden wäßrigen Lösungen durch potentiostatisch kontrollierte Versuche unter konstanter BelastungDie Empfindlichkeit sensibilisierter hochlegierter Werkstoffe für interkristalline Spannungsrißkorrosion wird nicht nur durch Werkstoffzusammensetzung und Angriffsmittel, sondern auch durch das Potential als Einflußgröße bestimmt. In der vorliegenden Arbeit wird besonders der Einfluß des Potentials auf die Anfälligkeit solcher Werkstoffe für interkristalline Spannungsrißkorrosion in unter Normaldruck siedenden Lösungen durch potentiostatisch kontrollierte Halteversuche unter konstanter Belastung von Zugproben untersucht. Dabei wurden folgende Parameter berücksichtigt: IWerkstoff 1Chemische Zusammensetzung: unstabilisierter 18/10 Chrom-Nickel-Stahl; Incoloy 800; Inconel 600;2Sensibilisierungsstärke;3Vorschädigung durch in schwefelsaurer Kupfersulfatlösung erzeugte interkristalline Korrosion;4Höhe der mechanischen Belastung.IIAngriffsmittel 1Natriumchloridkonzentration2Natriumsulfatkonzentration3pH (Pufferlösungen mit pH 2,2 und 4,5).IIIPotentialDie Versuchsdauer betrug bis zu mehreren 1000 Stunden.Die Versuchsart - interkristalline Korrosion, interkristalline und/oder transkristalline Spannungsrißkorrosion - wurde durch metallographische Untersuchungen ermittelt. Die Versuchsergebnisse werden in Form von Standzeit-Potential-Kurven mit den oben angegebenen Parametern dargestellt. Aus den Versuchsergebnissen werden Folgerungen für das Verhalten der Werkstoffe bei betrieblicher Anwendung unter erhöhtem Temperatur und erhöhtem Druck gezogen.

Description / Table of Contents: Transition from Stainless Steel to Metals of the Groups IVa, Va and VIa Produced by Solid State BondingWhen using expensive metallic materials very often transitions to other metals are necessary. To receive connections fulfilling proposed standards welding and brazing techniques must be used. A particularly suited process for joining different metallic materials is the solid state bonding. Connections produced by this method between stainless steel and metals of the group IVa, Va and VIa and the necessary interlayers of suited materials are described.

Description / Table of Contents: Fatigue Behaviour of Bolted ConnectionsIn bolted connections the bolt must withstand under alternating forces the resulting fatigue loads at each local area. Therefore the endurance limit of the first stressed engaged thread in the nut or tapered hole is related to the thread diameter, the nut heigth and the strength ratio of the bolt and nut. It is shown which influence on the fatigue limit has the thread profile, the pitch-diameter-ratio, the prestress in relation to the strength grade of the bolt and the thread rolling process before or after heat treatment. Additional bending will cause a significant loss of fatigue strength, while high temperature application does not decrease the fatigue limit.

Description / Table of Contents: Einfluß von Alterungswärmebehandlungen auf das Gefüge der Ni-Basis Superlegierung IN-738Proben der Ni-Basis Superlegierungen IN-738 LC und IN-738 HC wurden untersucht, um den Effekt vorhergegangener thermischer Alterung auf das Gefüge dieser Proben zu finden. Zwischen den Alterungsbedingungen und dem Gefüge konnten folgende Zusammenhänge aufgezeigt werden: (i) Größe, Morphologie und Verteilung der γ′-Phase, (ii) Vorliegen und Menge von M23C6-Phase und (iii) Auftreten zusätzlicher Phasen oder Phasenumwandlungen. Aufgrund des oben erwähnten Zusammenhanges zwischen Alterungsbedingungen und Gefüge ist es möglich, aus dem Gefüge unbekannter Proben deren thermische Vorgeschichte zu ermitteln.

Description / Table of Contents: Quantitative Measurement of Delta Ferrite in Cr-Ni Weld Metal Cladded by the Plasma Arc Hot Wire ProcessAccording to the requirements for resistance to corrosion and also to reduce to the susceptibility to hot cracking in austenitic clad weld metal, the ferromagnetic phase “delta ferrite” must be limited to value between “four and ten” percent.To control and record the amount of delta ferrite in one- and two layer PHA clad weld metal, a semi-automatic measuring device with translatory motion has been developed. The recorded ferrite content gives an idea about the distribution of the delta ferrite which depends on the parameters like weld metal solidification and cooling rate. A continous of delta ferrite content gives a better information about the distribution than a point-to-point measurement.Further, this method has an advantage that the recorded ferrite lines have a one to one correspondence with the test specimen dimension.

Description / Table of Contents: Elevated Temperature Tensile and Tensile Creep Tests of Reaction-Bonded Silicon NitrideDesign and construction of a tensile testing device is described for short tensile testing and creep tensile testing of ceramic materials in the temperature range for room temperature up to 1500 °C in open air. Super imposed bending and the avoidance of it is emphasized. Results are reported of tensile tests on isostatically pressed RB-SN of different densities in dependence of test temperature. Also creep behavior in tensile and flexural tests is compared at temperatures of 1200 °C, 1250 °C and 1400 °C in open air.

Description / Table of Contents: A Contribution to the Problem of the Determination of the Creep Damage for a CrMoV-Steel0The lifetime of materials subjected to creep is limited by the accumulated damage. The estimation of the creep damage is difficult, especially in cases where there is uncertainty about the thermal history of a specific component. Creep damage usually consists of a reversible and an irreversible part. The reversible part can be recovered by a heat treatment and is mainly due to changes in the microstructure (dislocation configuration, state of precipitation etc.). Irreversible damage is usually a consequence of necking or of cavitation.In the present investigation a CrMoV-steel (0.18 C/0.6 Mn/0.4 Cr/1.1 Mo/0.4 V) was creep tested at 550 °C and a stress of 245 N/mm2. After certain times or strains the specimens were removed and their microstructural state was determined. From the removed specimens new samples with smaller dimensions were machined and again tested under the same conditions. Between the first and the second creep test a new heat treatment was applied for some of the samples, in order to remove the reversible creep damage and to gain more information about the influence of the irreversible damage on creep.The creep behavior of the investigated CrMoV steel depends very strongly on the initial microstructure. For the same testing conditions the time to fracture can vary from 740 hours (40% upper bainite/60% ferrite) up to almost 10000 hours (100% coarse grained upper bainite). This result indicates that the type and the progress of the creep damage could also be influenced by the microstructure. In fact with the ferritic-bainitic structure cavities mainly develop on ferrite-bainite grain boundaries and are usually not linked together. Within the purely bainitic microstructures, the cavities are found on former austenite grain boundaries and have very often a crack-like appearance.The behavior of newly machined samples after the first creep test without a new heat treatment is dictated by the internal damage of the sample. After the removal of the scale and the macroscopic inhomogeneities the creep curves of the second test can be considered as a continuation of the first creep (curves figure 10 in German text). A new heat treatment ( 1000 °C/l h/air + 725 °C/4 h/air) between te two creep tests leads to a partial recovery of the original properties. For the mixed bainitic-ferritic microstructure, even for fractured samples, a considerale increase in time to fracture is observed, e.g. 1156 hrs for the first test, 6821 hrs for the second test after a new heat treatment.The new heat treatment produced a much more creep resistant microstructure and recovers therefore the influence of any creep damage, especially in the case of the originally ferritic-bainitic microstructure. In order to reveal the effect of creep damage on the second test, the creep properties of the microstructure produced by the intermediate heat treatment has to be considered as a reference (100% upper bainite). This fully bainitic steel exhibited in its new state mean values of time to fracture tf = 8554 hrs, and secondary creep rate \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon _{\rm S} $\end{document} = 2 × 10-10 sec-1. The experimentally measured creep data of the second creep test and the mean values form a specific ratio as a measure of the damage during the course of the first creep test. This behavior is shown schematically in Fig. 14. In this figure the creep strain is plotted as a function of the ratio between the mean time to fracture and the time to fracture in the second creep test (or secondary creep rate). The experimental results show that it needs of a minimum creep strain to initiate irreversible creep damage. The amount of strain depends also on the microstructure. In a relatively brittle steel containing e.g. coarse rained upper bainite, creep damage commences early in the secondary creep stage, whereas in more ductile steel the onset of tertiary creep coincides with the begin of irreversible damage.