bluuebunny/crossref_metadata_2025 huggingface dataset:
Entwicklung eines Mikrostrukturatlanten für die neuesten hitzebeständigen Schleudergusswerkstoffe
Authors: Berghof-Hasselbächer E. , Schütze M. , Schorr M. , Gawenda P. , Hoffman John J.
Published: December 2013

Kurzfassung

Die vorliegende Arbeit skizziert die Entwicklung eines umfassenden Gefügeatlanten, der die mikrostrukturellen Veränderungen der hitzebeständigen Schleudergusswerkstoffe HP-modifiziert, HP-mikrolegiert und 35Cr/45Ni nach Langzeit-Kriechversuchen und Einsatz unter Betriebsbedingungen als Funktion der Auslagerungstemperatur und -dauer detailliert durch die Betrachtung mit verschiedenen Verfahren dokumentiert. Zur Gefügecharakterisierung kamen die folgenden Untersuchungsmethoden zum Einsatz: Lichtmikroskopie im Auflicht-Hellfeld am ungeätzten und geätzten Schliff, Differential-Interferenz-Kontrast, Interferenzschichten-Metallographie, Bildanalyse, Rasterelektronenmikroskopie, Elektronenstrahlmikroanalyse. Die Zusammensetzungen der Ausscheidungen wurden analysiert und die entsprechenden Karbide und intermetallischen Phasen identifiziert. Die Phasenanteile wurden bildanalytisch am mit Zinkselenid bedampften Schliff mit Echtfarbensegmentierung quantifiziert. So konnten Diagramme entwickelt werden, die die Kinetik der Phasenumwandlung als Funktion der Auslagerungsdauer für bestimmte Temperaturintervalle aufzeigen. Der Gefügeatlas stellt somit eine ausführliche Informationsquelle zur Beurteilung des Alterungszustandes und zur Einschätzung der Restlebensdauer von hitzebeständigen Schleudergusswerkstoffen dar, die in dieser Form bisher noch nicht erhältlich war.
Digital Light Microscopy of Macroporous Ceramics Processed by Consolidation Casting with Mixtures of Native Starches
Authors: Cruz Tessie G. , de O. Hein Luis Rogerio , de Siqueira Rafael Humberto M. , de Carvalho Kelly Cristina C.
Published: December 2013

Porosity in starch consolidation casting technique is rightly related to original size and morphology of starch granules, leaving a pore structure after burning out. This work reports the results for the addition of different native potato and corn starch proportions in suspensions with TiO2 (rutile) powder. Gelling temperature have been defined after observation under light microscopy using a heating stage. Analysis of porous network and isolated pores have been done from images of samples surfaces obtained by depth from focus reconstruction, revealing a qualitative correlation of pores characteristics and starches additions in suspensions, suggesting that the presence of isolated or interconnected pores can be handled by starches selection to control the amylopectin and amylose contents in slurries. Also, the analysis of porous fraction distribution shows no consistent pattern through specimens’ volume according to starches in mixtures.
Investigation on Manganese Sulfide Inclusion Sizes in 50CrMo4 Steels by means of Fractography, Micrograph Analysis and Immersion Ultrasound
Authors: Temmel Cornelius , Karlsson Birger , Torresvoll Ketil , Fallqvist Christopher
Published: December 2013

Increasing loads in powertrain components have put manganese sulfide inclusions in the spotlight of engineers. The indigenous sulfides are accounted responsible for the poor fatigue performance of highly loaded steel parts. In order to relate fatigue performance to manganese sulfide inclusion size, an accurate geometrical description of the sulfides is necessary. Fatigue testing generally reveals maximum inclusion sizes, since the largest inclusions will initiate fatigue failure. Micrograph analysis and immersion ultrasonic testing have been carried out in order to compare those methods with the referenced values of fatigue testing. It showed that immersion ultrasound is not capable of detecting manganese sulfide inclusions of the present sizes. Micrograph analysis, however, is applicable, if analysis data is modified subjectively.
Effects of Heat Treatment on the Machinability of Cr-Ni Stainless Steels with Si and Mn Additives
Authors: Yaz Mehmet , Kök Metin , Turhan Hüseyin
Published: December 2013

In this work, the machinability of Cr-Ni austenitic stainless steels with Si and Mn additives was investigated based on tool life and tool wear by turning process without coolant on twelve different specimens in as-cast and heat-treated states. Metal removing process was carried out for four different cutting speeds using HSS cutting tools, while a cutting depth of 1.5 mm and a feed rate of 0.1 mm/min were kept constant. The effects of changes in microstructure with respect to addition elements and heat treatments on the tool wear and the hardness were examined. It was seen that the machinability for all of the specimens was not so good with the tools used. Although the hardness of the materials, which were as-casting, increased slightly with increasing the content of Cr and Ni addition elements, the machinability of these materials was not affected positively or negatively with respect to these elements. As heat treatments increased the hardness of the materials, the optimum tool lives were obtained in the machining of water quenched specimens. It was found that cutting speed was the most influential parameter on tool life.
Implementation of the Infrared Thermography for Thermo-Mechanical Analysis of the AlSi Cast Piston
Authors: Manasijevic S. , Radisa R. , Markovic S. , Raic K. , Acimovic-Pavlovic Z.
Published: December 2013

In this paper, the possibility of implementation of the infrared thermography as a technical systems’ diagnostic method is investigated. The infrared thermography as a contemporary method was used for visualization of the working conditions in the piston of an automotive engine as well as for analyzing of the thermal changes the piston sustained under exploitation. The obtained results were used to define the properties of the alloy used for production of the piston for a highly loaded diesel engine. In such way, the problems caused by erroneous choice of the material could be avoided.
Einfluss des Schweißens auf die Hochglanzpolier- und Narbeignung eines kupferlegierten martensitaushärtbaren Kunststoffformenstahles
Authors: Ernst Claudia , Richert Svenja
Published: December 2013

Kurzfassung

In der vorliegenden Studie wird der Einfluss des Schweißens, insbesondere des Schweißzusatzwerkstoffes und der Wärmenachbehandlung, auf die Hochglanzpolier- und Narbeignung unter Berücksichtigung metallographischer Untersuchungsverfahren an dem von den Deutschen Edelstahlwerken vertriebenen kupferlegierten Kunststoffformenstahl Thyroplast PH × Supra gezeigt. Es wurde nachgewiesen, dass der Werkstoff im lösungsgeglühten und ausgelagerten Zustand grundsätzlich im Rahmen von Reparaturen und konstruktiven Änderungen des Werkzeuges schweißbar ist. Ein negativer Einfluss des Legierungselementes Kupfer auf die Schweißbarkeit wurde nicht festgestellt. Das Schweißen kann beispielsweise mit dem artähnlichen Werkstoff Cronitex 470 — 17Cr/4Ni/4Cu oder mit einem niedrig kohlenstoffhaltigen, korrosionsbeständigen Zusatzwerkstoff mit martensitischer Gefügeausbildung im vorgewärmten Zustand durchgeführt werden.

Im Folgenden wird anhand von drei Beispielen das fotochemische Ätzverhalten einer Struktur in der Schweißzone und dem Grundwerkstoff, unter Verwendung unterschiedlicher korrosionsbeständiger Schweißzusatzwerkstoffe und verschiedener Temperaturführung, gezeigt.
Mikrostrukturelle Charakterisierung von PH 13-8 Mo Maraging-Stählen
Authors: Schnitzer Ronald , Hochfellner Rainer , Nöhrer Matthias , Schober Michael , Clemens Helmut , Zinner Silvia , Leitner Harald
Published: December 2013

Kurzfassung

Maraging-Stähle zeichnen sich durch eine günstige Kombination von hoher Festigkeit bei gleichzeitig akzeptabler Zähigkeit aus. Ihre Mikrostruktur besteht aus einer martensitischen Matrix, in der intermetallische Ausscheidungen eingelagert sind und einem, je nach Wärmebehandlung und Legierungszusammensetzung variierenden, geringen Anteil an Austenit.

In dieser Arbeit werden Methoden und Verfahren angeführt, um die Mikrostruktur von Maraging-Stählen umfassend zu charakterisieren. Neben der ehemaligen Austenitkorngröße, dem Martensit und den intermetallischen Phasen umfasst dies auch den rückumgewandelten Austenit, der während der Wärmebehandlung entsteht. Neben der Beschreibung des Wachstums der Austenitkörner mithilfe des Gesetzes vom isothermen Kornwachstum werden hochauflösende Methoden wie Rückstreuelektronenbeugung (EBSD), Transmissionelektronenmikroskopie (TEM) und Atomsonde (AP) angewendet.
Untersuchungen zum Einfluss der Kornorientierung auf Nanoindentations-Messungen an Reineisen
Authors: Pfetzing Janine , Wagner Martin F.-X. , Zarnetta Robert , Tak Kwan-Gyu , Eggeler Gunther
Published: December 2013

Kurzfassung

Bei Lasten im mN-Bereich und Eindringtiefen im nm-Bereich erlauben Nanoindentations-Versuche die Untersuchung der lokalen mechanischen Eigenschaften einzelner Körner. Dabei ist ein Einfluss der Kornorientierung auf Elastizitäts-Moduli und Härte zu erwarten. In dieser Arbeit wird der Einfluss der Kornorientierung auf Nanoindentations-Messungen an reinem α-Eisen dokumentiert. Einzelne Körner mit <001>-, <101>- und <111>-Oberflächennormalen werden per Rückstreu-Elektronenbeugung identifiziert und anschließend indentiert. Die Kornorientierung hat einen deutlichen Einfluss auf die ermittelten Härtewerte, aber einen vernachlässigbaren Effekt auf richtungsabhängige E-Moduli. Diese Ergebnisse können durch die Art der Aktivierung der Gleitsysteme und durch den komplexen Spannungszustand unter der Indenterspitze erklärt werden und zeigen den Einfluss anisotroper elastischer und plastischer Eigenschaften auf Nanoindentations-Messungen.
Henry Clifton Sorby — ein Privatgelehrter begründete vor rund 145 Jahren die Metallographie
Authors: Piersig Wolfgang
Published: December 2013

Kurzfassung

Dieser Text ist eine Würdigung H.C. Sorbys, des Begründers der klassischen Metallographie, der mikroskopischen Petrographie, der Mikrospektroskopie und der wissenschaftlichen Sedimentation. Nach der Darstellung der ersten visuellen Betrachtungen von Metalloberflächen und Metallbruchgefügen führt der Text über die erste mittels optischer Mittel wie Lesesteinen, Lupen, Vergrößerungsgläsern und einfachen Mikroskopen vorgenommenem Beschau bis hin zum makroskopischen und mikroskopischen Erschließen, Identifizieren, Festhalten und Photographieren der wahren Metallgefüge. Es folgen Angaben zu Sorbys Vita, namentlich zu seinem Lebenswerk für die Wissenschaft, und insbesondere zu seiner Maxime, “Ziel muß es sein, die Ursachen der Dinge zu entdecken” [18, 43]. Des Weiteren sind die bedeutendsten Veröffentlichungen von Henry Clifton Sorby und seine wichtigsten Vorträge auf den Tagungen wissenschaftlicher Institutionen und Gesellschaften mit eingebunden, wie auch die erhaltenen Anerkennungen.
An Investigation on Weldability of AISI 304 and AISI 1040 Steels on Friction Welding
Authors: Celik Sare , Dinc Dincer , Yaman Ramazan , Ay Irfan
Published: December 2013

In welding technology, joining processes of different materials, which have dissimilar crystal structures are difficult. Welding of different materials becomes very important to reduce costs. Furthermore, the friction welding method is processed in lower temperature than the melting temperature. Especially, this is a big advantage to overcome difficulties that occur in the heat affected zone during usage of conventional methods.

In this study, the weldability of AISI 304 stainless steel and AISI 1040 carbon steel by friction welding is studied. During the welding process, temperature variations in the welding zones were measured with an infrared temperature measurement device. After welding of the samples, tensile and hardness experiments were carried out. For metallographic investigations, optical microscope and scanning electron microscope (SEM) pictures were taken. Energy dispersive spectroscopy (EDS) analysis was carried out for composition investigations on welding and heat affected zones. As a result, these two steels could be joined by friction welding for industrial usage.
Crevice-Galvanic Corrosion in Aluminium Shower Curtain Poles
Authors: Birol Feriha , Birol Yucel
Published: December 2013

Light microscopy, scanning electron microscopy and energy dispersive X-ray analysis were employed to identify the key factors responsible for the crevice-galvanic corrosion of shower curtain poles produced from EN AW-6060 alloy. The corrosion process has started between the aluminium poles and the metallized plastic hooks used to hang the shower curtains on the poles. The highly alkaline bathroom cleaning agent has penetrated between the aluminium profile and the plastic hooks leading to the dissolution of the unusually thin anodic oxide layer. The aluminium profile which has been stripped of its anodic oxide locally via crevice corrosion is then allowed to contact the Ni-, Cr- and Cubearing coating of the plastic hooks. The corrosion process has accelerated due to a galvanic couple effect as evidenced by the analysis of the corroded regions where Cu and Ni were abundant.
Beitrag zum Verständnis von Solingenstahl des 19 Jahrhunderts
Authors: García Sánchez Laura , Azor Lafarga Alberto , Javier Criado Martín A. , Criado Portal Antonio J. , Dietz Christian
Published: December 2013

Kurzfassung

Zwei im späten 19. Jahrhundert in Solingen angefertigte Blankwaffen wurden einer eingehenden metallographischen und chemischen Untersuchung unterzogen, wobei die gemessenen mechanischen Eigenschaften einer Struktur von feinlamellaren Perlit zugeordent werden konnten. Der Produktionsprozess wurde daraufhin unter Verwendung einer modernen Stahlsorte mit einer der bei der Herstellung der Blankwaffen möglichst ähnlichen Zusammensetzung nachvollzogen, wobei ein Material mit fast identischen Eigenschaften erhalten werden konnte.
Zum Mechanismus des Ausscheidens von Ag auf der Oberfläche von Ag-Sn-In-Legierungen bei der Inneren Oxidation
Authors: Wiehl Gunther , Kempf Bernd , Rettenmayr Markus
Published: December 2013

Kurzfassung

Ag-Sn-In-Legierungen mit zwei unterschiedlichen Sn/In-Gehalten wurden zur Beobachtung von Ag- Ausscheidungen auf der Probenoberfläche innerlich oxidiert. Es wird gezeigt, welchen Einfluss die Probenpräparation (Verformungszustand der Oberfläche), die Oxidationstemperatur und die Ausgangskonzentration auf die Ausbildung der Ag-Ausscheidungen bezüglich kristallographischer Orientierung und Morphologie haben. Auf ionenstrahlpräparierten Probenoberflächen entstehen unter definierten Oxidationsbedingungen und Ausgangskonzentrationen facettierte Ag-Ausscheidungen mit derselben kristallographischen Orientierung wie die Substratkörner, auf mechanisch präparierten Probenoberflächen werden zufällig orientierte Ausscheidungen beobachtet. Der Einfluss von dünnen äußeren Oxidschichten auf die Morphologie und die kristallographische Orientierung der Ag-Ausscheidungen wird diskutiert.
A Mechanical Method for Preparing TEM Samples from Brittle Films on Compliant Substrates
Authors: Taylor A.A. , Cordill M.J. , Moser G. , Dehm G.
Published: December 2013

Preparing transmission electron microscopy (TEM) samples from thin films is technically challenging and traditional preparation routes can sometimes introduce unacceptable artefacts or even prove impossible. A novel method of preparing plan view TEM samples from thin films by a purely mechanical method is assessed. Two examples of films prepared by this route are briefly presented, a Cr film on PET and an amorphous AlxOy film on Cu. The application of this method allows for TEM analysis of the Cr film without the problems associated with a polymer such as PET disintegrating under the electron beam. For the AlxOy films it is demonstrated that this purely mechanical preparation prevents crystallisation of the film resulting from conventional ion milling preparation routes. The technique also allows for an upper bound of thickness approximation for these films.
Metallografische Methoden in der Archäologie
Authors: Berger Daniel
Published: December 2013

This short article will show with three current examples how metallographic methods can be used to answer archaeological questions and which kind of information these methods provide. Besides the Nebra Sky Disk, the examination of metal specimens taken from an Iron Age torc as well as from medieval moulds is described. These artefacts are part of the collection of the State Museum for Prehistory in Halle (Saale) in Saxony-Anhalt.
Chances and Limits of Computer Tomography in Materialographic Investigations
Authors: Faust W. , Noack E. , Michel B.
Published: December 2013

The spectacular perceptions into the volume of structural parts which can be achieved by computer tomography (CT) readily give the impression that materialographic microsection examinations can be omitted. The display of the volume, which is three-dimensional, permits to detect pores and their distribution or measure inner structures in a non-destructive way at an accuracy which has been unknown up to date. A failure analysis makes it possible to locate and assess damage or defects without interfering with the material composite. The CT also enables to non-destructively investigate structural parts which contain liquid, rubber-like or hazardous substances and, hence, are accessible to a microsection analysis only under certain conditions.
Pitting Corrosion Induced Fatigue Fracture on a Gas Turbine Compressor Blade
Authors: Neidel Andreas , Riesenbeck Susanne
Published: December 2013

According to VDI Guideline 3822-3 “this type of corrosion is … caused by the formation of anodic regions of slight local expansion on the electrolyte-wetted surface. The presence of protective layers (passive layers) is a prerequisite for the occurrence of pitting corrosion.”

Both requirements are met on gas turbine compressor blades if water condensates on the turbine blades when the machine is at standstill and/or if the compressor temperature remains low enough in a running machine to allow aqueous media to persist, i.e. for the condensation not yet to have evaporated. This is the case with the front row of blades, generally up to stage 6.

Passive layers are present on the gas turbine compressor blades, since these parts are generally manufactured from martensitic 12–16% chrome steel, as also the case for steam turbine blades and discussed in detail in other case studies in the book. The failed compressor stator blade in this case study is made of X15Cr13, material no. 1.4024.

Pitting corrosion on the front row compressor blades was not uncommon before the introduction of high temperature corrosion protection coatings containing aluminium pigments on these blades. After the introduction of protective coatings, this corrosion mechanism was absent on the coated blades. The coating systems contain aluminium spherules which, given the correct coating method, are in contact with each other to form a continuous electrically conducting layer between the surface of the blade and the protective coating, creating a sacrificial anode resulting in the less noble aluminium – as compared to steel – preferentially corroding to protect the blade material.

The damaged part discussed in this case study originates from an older model gas turbine commissioned in 1955 already, having accumulated almost 163000 hours of operation when the damage was diagnosed. Depending on the type of operation, this represents a period of operation of 15 to 25 years. Such compressor blades were not coated back then.
The Preparation of Magnesium Specimens for EBSD Using Ion Polishing
Authors: Ullrich Ch. , Schwarz F. , Franke A. , Marr T. , Rafaja D. , Krüger L. , Freudenberger J.
Published: December 2013

EDSD measurements were made for various thermally treated or deformed states of the magnesium alloy AZ31, which were produced from twin-roll cast strips. The article shows that a preparation route via the ion polishing method produces the best condition of the sample surface for the examinations and, in particular, yields very good results even in case of samples which are deformed or those the chemical composition of which is inhomogeneous.
Investigation of Vapor Phase Deposited Columnar Plasma Spray Coatings
Authors: Hospach A. , Kappertz M. , Mauer G. , Vaßen R.
Published: December 2013

The relatively new PS-PVD method (Plasma Spray – Physical Vapor Deposition) allows for an almost complete evaporation of the spray powder by means of a high energy input and a low ambient pressure. On the substrate to be coated, the spraying material condenses to columnar, feather-like structured layers as are known from the EB-PVD process (Electron Beam – Physical Vapor Deposition). These layer structures are of interest in applications in which high strain tolerances are required, such as for thermal barrier coatings in gas turbines where cyclic heating and cooling of the coatings takes place. Courtesy of the high growth rate, PS-PVD can represent a more cost-effective alternative to EB-PVD.

The main difference compared to EB-PVD coatings is the higher porosity of the PS-PVD coatings. However, this higher porosity leads to difficulties during the preparation when coatings are characterized.

This publication describes how YSZ-coatings (Yttrium-stabilized zirconia) produced by means of PS-PVD are characterized with regard to specific surface area, density, pore distribution, hardness, and sintering activity and compared with EB-PVD coatings.
Orientation and Phase Analysis of Nanoscale Grains Using Transmission Electron Microscopy
Authors: Seyring M. , Song X. , Rettenmayr M.
Published: December 2013

The nanostructuring of materials is a process which enables their properties to be drastically changed as compared to their coarse crystalline condition. For example, peculiar features were achieved, e.g. extremely high yield and ultimate strengths. The structure of such nanoscale materials has not been characterized yet in detail as compared to materials of a coarser crystalline structure because an appropriate analytical technique did not exist. Nano beam diffraction (NBD) by transmission electron microscopy (TEM) makes possible a local resolution up to 1 nm and, thus, a diffraction analysis of individual nanograins. A recently developed method based on NBD allows determining crystallographic orientation relationships and analyzing the phases of individual nanograins. This article below sets forth the analytical possibilities of this method by way of a complete evidence of twin and small-angle grain boundaries in nanocrystalline copper and a phase identification of precipitates in an AlMg5Si2 alloy.
TEM Sample Preparation of a Hard Metal by Semiautomatic Wedge Polishing
Authors: Neumayer S. M. , Fisslthaler E. , Feistritzer S. , Grogger W.
Published: December 2013

Sintered hard metals like tungsten carbide compounds are a challenge for TEM sample preparation due to the diverging properties of the individual components. Especially when both very thin as well as large areas are required, for example for nanoanalysis investigations, conventional preparation techniques like ion milling and FIB preparation are often incapable of delivering samples of necessary quality. In this study, the preparation of a hard metal consisting of a tungsten carbide/cobalt compound via a technique called “Wedge Polishing” is described, along with the results of concomitant TEM investigations. The impact of the preparation procedure on the crystallographic structure of the material is discussed, and a post-treatment process to dispose of these artefacts is presented.
Stress Corrosion Cracking (SCC) in Copper Piping for Domestic/HVAC Heating and Cooling Systems
Authors: Hineman M. A. , Schmidt F. E.
Published: December 2013

Copper piping systems for HVAC (Heating Ventilation Air Conditioning) are used to transport heating and cooling water in high rise buildings. Commercial and residential plumbing has a design life that must be specified with respect to the water quality parameters associated with the geographic location. Stress corrosion cracking has been identified as one of the failure mechanism normally occurring in the infancy of the life of the systems that is highly associated with contamination. A metallurgical analysis of the characteristics of typical cold worked tubing, used in copper piping, with insulation, contamination and crack morphology are presented.
Preparation and Microstructural Characterisation of Metal Injection Moulded Powder Metallurgical Components (MIM) in the Green and Sintered Conditions
Authors: Maier J. , Knoblauch V. , Bernthaler T.
Published: December 2013

The aim of this work was to develop a reproducible method of preparation for green and brown bodies which, after injection moulding and sintering, would permit an entire MIM component to be microscopically examined for internal inhomogeneities such as porosity and segregation. The particular challenge was to prepare the fragile MIM microstructure prior to the sintering process free of artefacts.

Three different methods of preparation (variations in the polishing substrates and suspensions used) were compared. To evaluate the quality of the resulting preparation, the microscopically determined volume fraction of metal particles was chosen. This was determined after set preparation times using quantitative microstructural analysis (QMA/QGA) and evaluated during the various stages and times of the preparation process. The feedstock composition which had a defined volume fraction of 68 % was used as the reference value. The preparation of the brown sintered body proved to be the most successful. The volume fraction determined microscopically measured 67 %. The duroplastic infiltration mounting resin penetrates into the open pore structure effectively stabilising and fixing the powder particles. In contrast the preparation of the green body proved to be much more difficult as the breaking out of the metal powder particles from the comparatively soft thermo-plastic binder was not able to be prevented completely. The volume fraction measured microscopically was 62 % which is about 6 % less than the actual value.

The chemical removal of the binder from the surface of the green body significantly improved the overall result of the preparation as it was then possible to effectively fix the powder particles by subsequent infiltration with the duroplastic mounting resin, as in the case of the brown body. In addition to the qualitative appraisal of the microstructural specimens, quantitative microstructural analysis proved to be a valuable instrument for systematically and objectively evaluating the results of the preparation and for developing the preparation processes. Using the methods of preparation developed it is now possible to carry out qualitative examinations on almost artefact free microstructural specimens prior to the lengthy and costly thermal processing.
Identification of Precipitates in an IN792 Gas Turbine Blade after Service Exposure
Authors: Dahl K. V. , Hald J.
Published: December 2013

Plate-like precipitates were found in an exposed IN792 gas turbine blade after service exposure for 40,000–60,000 service hours at a temperature of 680–760 °C. The blade was heavily oxidised and therefore removed. During subsequent metallurgical investigations extensive precipitation was found in the metallic region beneath the outer oxide layer.

Further investigations were undertaken in order to understand the failure mechanism, especially the precipitate type and formation mechanism. Cross sections prepared from the turbine blade were studied using LOM and SEM. Composition profiles across the interface between bulk material and oxide layer revealed significant depletion of chromium below the oxide.

Thermodynamic equilibrium calculations were used as a practical tool supporting the investigations.

Chemical mapping using energy filtered TEM and selected area diffraction were used to prove that the precipitates were carbides and not an intermetallic phase like σ. The extensive oxidation resulted in dissolution of carbides near the outer surface, while reactive elements, e. g. chromium, released from this process would then diffuse outwards towards the oxide, carbon diffused inwards resulting in extensive re-precipitation of carbides.
Numerical Simulation of Extrusion Coating
Authors: Devisme S. , Haudin J.-M. , Agassant J.-F. , Rauline D. , Chopinez F.
Published: December 2013

In packaging industry, many structures are produced by extrusion coating. In this process, a polymer film is extruded through a slit die, then stretched in air, coated on a substrate (paper, aluminium or steel foil) between a chill roll and a flexible pressure roll, and finally cooled on successive chill rolls. Due to their non-polar character, polypropylenes are not suitable for extrusion coating on metallic surfaces. Adhesive properties can be improved by grafting on the polymer chain a polar group like maleic anhydride which may react with the aluminium surface.

Our purpose was to develop a general model in order to predict the temperature field in the thickness of the multilayered structure along the stretching, laminating and cooling steps, and especially near the polymer/metal interface. This model includes crystallization kinetics and accounts carefully for the heat transfer coefficient with the successive rolls and surrounding air. Its predictions have been successfully compared to experimental temperature measurements along the coating line for various processing conditions (velocity, roll temperature, etc). Moreover, thermal history has a real impact on structure and morphology in the film. All these aspects are revealed by microscopic observations of thin microtomed sections of the film and X-ray diffraction experiments. Finally, adhesion properties of the laminate have been tested for the same process conditions. A good correlation has been established between adhesion properties and the thermal history experienced by the grafted polypropylene near the interface with aluminium before crystallization.
New Multicomponent Compatibilization System for Polyolefin/Polystyrene Blends
Authors: Starý Z. , Kruliš Z. , Hromádková J. , Šlouf M. , Kotek J. , Fortelný I.
Published: December 2013

An efficient compatibilization system based on a combination of styrene-butadiene block copolymer (SBS) with ethene-propene random copolymer (EPM) has been developed for polyolefin/polystyrene blends. Model blends of polypropylene and polystyrene have been taken for compatibilization studies. Concentration of combined compatibilizer in all studied blends was 5 or 10 wt. %. The ratio of EPM/SBS in the compatibilizers was varied from 4/1 to 1/4. Tensile impact strength was used as the main criterion of compatibilization efficiency. Besides mechanical properties, basic morphological investigation of the prepared blends was carried out. The compatibilization efficiency of the EPM/SBS system in PS/PP blends depends on the type of blend matrix. Generally, the use of EPM/SBS leads to better or comparable mechanical properties of final polystyrene/polypropylene blends compared with those using common SBS compatibilizers.
Asymmetric Surface Roughness Formationon Moving Non-isothermal Liquid Coatings
Authors: Yamamura M. , Uchinomiya T. , Mawatari Y. , Kage H.
Published: December 2013

We present a lubrication model of thermo-capillary flows in moving volatile liquid film coatings. The forced air impingement from a slit nozzle onto the moving coating imposes an axi-symmetric surface temperature distribution, and thus the local surface-tension gradients on the liquid surface. Despite the symmetric temperature profile, local thickness variations became asymmetric and exhibited a particular ridge in downstream and a depression in upstream. The competing feature between the surface-tension-driven and the pressure-driven flows gives a characteristic growth and decay in the surface roughness as the temperature profile travels in the opposite direction to the moving coating. The model prediction showed that the surface roughness was first enhanced and then suppressed with increasing the impinging air velocity, suggesting some directions for achieving more uniform coatings at higher speeds.
Investigation of the Heat Affected Zone of Hot-gas Welded PP Joints
Authors: Marczis B. , Czigány T.
Published: December 2013

A large series of experiments was performed using an automated hot-gas welding apparatus to investigate the effect of welding parameters (welding temperature, welding gas flow rate, welding speed, welding force) on the structure of the heat affected zone (HAZ) in polypropylene sheets. Based on optical micrographic studies the HAZ can be divided into three well distinguishable parts: the cool, plastic and flow zone of the raw material. A strong correlation was found among the width of the HAZ and the macroscopic size of the welded seam and its strength. It was demonstrated that (under the given boundary conditions) the strength of the welded joint can be estimated from the external geometrical size of the welded seam well.
Rheology and Processing of Molten Poly(methyl methacrylate) Resins
Authors: Stamboulides C. , Hatzikiriakos S. G.
Published: December 2013

The rheological and processing behavior in capillary extrusion of several poly(methyl methacrylate) (PMMA) resins was studied. The rheological characterization included: (i) frequency sweep experiments at various temperatures and application of the time-temperature superposition to obtain the master curves from which the activation energy of flow was found to be independent of molecular weight, (ii) extensional measurements using the Sentmanat Extensional Rheometer (SER) where it was found that poly(methyl methacrylate) resins exhibit strain hardening effects only at high strain rates. The capillary extrusion experiments were performed for three poly(methyl methacrylate) resins using additives in order to identify suitable processing aids for PMMA resins. First it was found that poly(methyl methacrylate) polymers exhibit spiral/helical type of distortions at a critical shear stress value of about 0.35 ± 0.03 MPa, independent of temperature and molecular weight. “Traditional” processing aids used mainly in the extrusion of polyolefins and some other commercial polymers were found ineffective in eliminating instabilities in the case of poly(methyl methacrylate) processing. On the other hand, mixing of poly(methyl methacrylate) with a proprietary blend of synthetic resins and fatty glycerides with modified organic fatty acids, MoldWiz INT-35UDH, was able to reduce the extrusion pressure and postpone the onset of gross melt fracture to higher shear rates. Finally and most importantly, the addition of different polyethylenes (LLDPE, LDPE and HDPE) resulted into a significant pressure reduction along with significant postponement of gross melt fracture to higher shear rates.
Moisture Sorption and Transport in Polylactide
Authors: Cairncross R. A. , Ramaswamy S. , O'Connor R.
Published: December 2013

Management of moisture penetration and hydrolytic degradation of polylactide (PLA) is extremely important during manufacturing, shipping, storage, and end-use of PLA products. Crystallinity in PLA was measured with Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD). Moisture sorption isotherms in PLA films were measured with Quartz Crystal Microbalance (QCM) and Dynamic Vapor Sorption (DVS) experiments with samples of varying crystallinity. A surprising result is that crystalline and amorphous PLA films exhibit nearly identical sorption isotherms, within the accuracy of the experiments. The effect of hydrophobicity of PLA end groups on degradation was evaluated by synthesizing PLA with hydrophobic and hydrophilic end groups.
A Novel High Flow Rate Pin for Water-assisted Injection Molding of Plastic Parts with a More Uniform Residual Wall Thickness Distribution
Authors: Liu S.-J. , Wu Y.-C.
Published: December 2013

Three types of water pins are currently used in the water-assisted injection molding technologies to mold plastic parts, including orifice, ring and piercing type pins. Nevertheless, the former two types of pins have the disadvantages of a low flow rate and high pressure drop, while the drawbacks for the latter type are that timing the piercing pin into the cavity is a challenge and the cost of a mold is high. This report describes the development a novel high flow rate water pin for water-assisted injection molding of plastic parts. The pin, which consists of a sintered porous surface outlet, has been tested on parts with two different geometries: a plate with a channel across the center and a float-shaped tube part. The experimental results suggests that the proposed water injection pin can mold parts of a large size with a more uniform residual wall thickness distribution.
Rheological and Theoretical Estimation of the Spinnability of Polyolefines
Authors: Vogel R. , Brünig H. , Beyreuther R. , Tändler B. , Voigt D.
Published: December 2013

Melt spinning is a polymer processing technique that makes great demands on the extensibility of the polymer melt in the distance between die exit and solidification point [1]. The polymer material is exposed to a rapidly growing deformation rate over a large range of deformation within a short time of about 100 milliseconds. Simultaneously an extreme cooling occurs with cooling rates of about 1000 K/s. For this reason only a few polymer materials are usable for this kind of polymer processing with sufficient take-up speeds. Most polymers show a fiber break in the molten state either by brittle cohesive rupture or ductile failure when approaching critical conditions of deformation. The rheological behaviour of a polymer melt at the critical conditions of deformation in the fiber forming process can not be predicted by means of usual rheological material functions. This paper reports the attempt to find out material functions, which describe the critical deformation states of the melt spinning process. The established material functions are compared with the results of spinning experiments to estimate their practicality.
Bulk and Dispersed Phase Polymerization of Urethane in Twin Screw Extruders
Authors: Cassagnau P. , Nietsch T. , Michel A.
Published: December 2013

The bulk and dispersed phase polymerizations of urethane were investigated in a co-rotating twin screw extruder. The residence time has predominant influence on the bulk polymerization in twin screw extruders. Furthermore, the polyurethane polydispersity decreases going down the screws, as the result of the extent of the reaction and mixing in the extruder. As expected, the polyurethane polydispersity at the die exit of the extruder is close to the theoretical value (Ip = 2). In the case of urethane polymerization in molten polyethylene matrix, the residence time distributions showed that the two monomers (isocyanate and alcohols) have different behaviors in the extruder in presence of PE due to the solubility of isocyanate and non-solubility of alcohols in PE. Furthermore, this solubility phenomenon PE induces an imbalance stoichiometry which limits the degree of polymerization (molecular weight) and a broadening of the molecular weight distribution during the blending process in extruder. Slip phenomenon was also observed at the die because of the presence of polyurethane, with low molecular weights, at the sample surfaces. An in-situ pre-polymerizing step of isocyanate/alcohols tends to eliminate this phenomenon. Then, the aim of the present work was to study the formation of a polyethylene/polyurethane blend polymer via in situ polymerization of diols and diisocyanate monomers dispersed in a twin screw extruder.
Injection Velocity Control Using A Self-tuning Adaptive Controller
Authors: Yang Y. , Gao F.
Published: December 2013

The injection velocity dynamics are found to be both time-varying and non-linear and therefore difficult to control using a conventional fixed parameter controller. In this work, an adaptive injection velocity control system with some special features such as anti-estimation windup, adaptive feed-forward, profile shifting and cycle-to-cycle adaptation is designed, implemented, and experimentally tested. The developed system is demonstrated to have excellent control performance with very good robustness for a wide range of operating conditions.
Long Glass Fibre Reinforcement of Thermo Plastics
Authors: Bush S. F.
Published: December 2013

The paper summarises the main experimental and theoretical results from a long-term programme of research (SAFIRE) to produce and apply long glass fibre compounds to the extrusion of pipes, sheets and profiles and to injection, blow and roto moulding. The overall objective is to obtain the processing speeds associated with short fibre reinforced thermoplastics with the reinforcement efficiencies associated with prepositioned or prepreg thermoset composites. Extrusion and injection moulding are now in the commercial domain, with industrial scale trials underway in the other technologies.

Long glass fibres are defined by their ability to form lace-like mat structures within the polymer melt which persist into the solid state. Such structures, which greatly increase both melt strength and solid state thermo mechanical properties, can be formed with fibre volume concentrations (c) as low as .01. The formation of mat structures depends on the number N of virtual touches per filament. A minimum of around five touches is generally needed. From earlier work N is given as A.c. l/d. A varies with mean fibre orientation in the mat: for the random in-plane case it is approximately 8/π2, so that in contrast with typical fibre suspensions (c < d/l) extremely strong particle-particle interactions are involved in the melt state.

In the solid state, tensile strength is measured and modelled in terms of number average fibre length (l) and diameter (d), polymer yield strength, fibre distribution efficiency, interfacial shear strength and a specially defined matrix stress magnification factor M. The role of patented fibre management devices in optimising these variables as they appear in the solid state is defined and described.
Mixing Homologous High Viscosity Ratio Polymer Blends in Converging Flow
Authors: Meller M. , Luciani A. , Månson J.-A. E.
Published: December 2013

Several studies have shown that deformation and breakup of dispersed droplets is easier in extensional than in shear flow field and this is particularly true for systems with high viscosity ratios. The simplest way to generate a significant extensional flow field in compounding equipment is to use converging flow conditions. In this work, the mixing efficiency of converging flow has been investigated as a function of the entry profile and the flow rate by using a capillary rheometer equipped with dies of different geometries. The material used for this study was a bimodal polyethylene presenting inhomo-geneities due to the high viscosity ratio between the low and high molecular weight fractions. The results indicated that the mixing performance depended strongly on the die geometry and flow rate. A critical flow rate was observed for each particular entry profile at which the highest efficiency was observed. This critical flow rate was found to correspond to the onset of melt flow instabilities.
Numerical Simulation of the Film Casting Process
Authors: Beaulne M. , Mitsoulis E.
Published: December 2013

Numerical simulations have been undertaken for the film-casting process with viscoelastic fluids. Viscoelasticity is described by an integral constitutive equation of the K-BKZ type with a spectrum of relaxation times, which fits well experimental data for shear and extensional viscosities and the normal stresses measured in shear flow. Non-isothermal conditions are considered by applying the Morland-Lee hypothesis, which incorporates the appropriate shift factor and pseudo-time into the constitutive equation. A one-dimensional model derived from the conservation of momentum is used to approximate the thickness, while the stress free-surface condition is used to approximate the width. The resulting system of differential equations is solved using the finite element method and the Newton-Raphson iterative scheme. The method of solution was first checked against the Newtonian and Maxwell results for different film geometries. The simulations are compared to available experimental data and previous simulations in terms of film thickness, film width, and film temperature. Agreement between the experiments and the current simulations is considered good with subtle differences. Agreement is also considered good between the current one-dimensional simulations and previous two-dimensional simulations for viscoelastic fluids, in terms of width and thickness. The one-dimensional model is advantageous since the algorithm is relatively simple, convergence is almost guaranteed, and the computing time is short.
Tensile Force Measurements in the PA 6 High Speed Fiber Spinning and their Utility
Authors: Beyreuther R. , Brünig H. , Hoftmann H.
Published: December 2013

The paper deals with practical and theoretical investigations of the PA 6 high speed fiber spinning process in the velocity range from 3000 until 5450m/min by means of tensile force measurements in the spinning line below the fiber solidification point. The measurements were evaluated under three different goals as follows:

Quantitative determination and interpretation of relations between the technological and textile-physical fiber parameters spinning speed, throughput, and fiber fineness (in the range of 4.1 to 14.8 dtex for a single filament spun from a 9-holes die).

Comparison between the experimentally measured and the theoretically calculated tensile forces by means of the own fiber formation model developed in the last years. On this occasion a satisfactory concordance could be noticed between the experimental and theoretical results. In addition to this a good model parameter estimation could be proved in the force balance part of the differential equation system for the fiber formation.

Spectral analytical evaluations of the measured tensile force time functions by means of their autocorrelation functions. It could be demonstrated, that higher frequency tensile force disturbances could be caused both by the spinningpump and by unevennesses in the cross quench air conditions below the spinning die.

All results from the investigations above are discussed in relation to different technological process goals and their realization possibilities.
Effect of Wall Slip on Rheotens Mastercurves for Linear PE Melts
Authors: Bernnat A. , Wagner M. H.
Published: December 2013

For two linear polyethylene melts, a HDPE and a LLDPE, Rheotens experiments at constant extrusion pressure and different extusion temperatures are reported. While at sufficiently small extrusion pressure Rheotens mastercurves were found, various deviations from the mastercurves were observed at higher extrusion pressures. By use of capillary rheometry and Mooney's method, these deviations could be attributed to a stick-slip transition in the extrusion die, and, in the case of LLDPE, to partial wall slip below the stick-slip transition.