Mechanische und tribologische Eigenschaften von hochstickstoffhaltigen Austeniten

Mechanical and tribological Properties of High‐Nitrogen Austenitic Steels Austenitic stainless steels provide a fair combination of strength, toughness and corrosion resistance. Undergoing tribological stresses – in particular under self‐mating contact situations ‐ their performance is not sufficient. Thus the more wear resistant austenitic Co‐base alloys with different carbon contents are applied under these circumstances, which may prevail in medical applications. Austenitic high‐Nitrogen Steels might be an alternative under these circumstances. Strength, corrosion resistance and tribologcial properties are similar to those of CoCrMo‐alloys, while their toughness is higher. This contribution presents the metallurgical mechanisms, which bring about this combination of properties.     

Mechanische Eigenschaften und Verformungsverhalten einer metallischen Matrix mit nichtmetallischen anorganischen Zusätzen

Mechanical properties and deformation behavior of metallic composites with anorganic admixtures . Composite Materials with Al and Fe as Matrix containing α-Corundum (Al₂O₃) and BN as second phase were produced powdermetallurgically. All specimens show a smaller grain size than the pure materials because of the inhibition of the secondary recrystallization during the deformation at high temperatures. The heterogeneous materials show on the one hand better values of the strength, on the other hand better fracture behaviours under dynamical strain, which is caused by terncating and turning around the crack by the fibers and particles. The formation of the extrusion textures is not inhibited by the addition of the deformable BN-particles, but by that of the undeformable Corundum-particles. The quantitative measurements of the texture exspecially the calculation of the three dimensional orientation distribution function (ODF) shows decrease of the texture index with the logarithm of the particle distances. The maximum cold-workability falls with decreasing interparticle distance and is connected with the increase of the strength. It could be reached in all cases until 80%-reduction of crossection by drawing.     

Optimierung warmgepreßter Sinterstähle–Mechanische Eigenschaften,Bruchverhalten und Wirtschaftlichkeit

Optimization of Hot Forged Sintered Steels – Mechanical Properties, Fracture Mechanism and Economy . The hot forging technique of powder metal preforms is a new technology for manufacturing structural parts with close tolerances and better surface roughness than conventional forging. A particular significance is gained by the development of high strength materials, whereby the alloying systems and alloying content have to be adjusted in an optimum way. The present work deals with a systematic investigation of static and dynamic properties of H/F steels. By using a new developed alloying technique, the processing of the high oxygen affinity elements, manganese, chromium and vanadium results in H/F steels with minimum oxygen content. It was established that these materials fulfil certain correlations between the individual mechanical properties and the reduction of area. These relations allow to optimize the materials as well as compare them with normal wrought steels. The investigation of fracture mechanism with the help of scanning-electron-microscope gave valuable information of the material behaviour.     

Mechanische Eigenschaften von kaltgezogenem und gegossenem Titan Grad 2

Mechanical properties of cold-drawn and cast Grade 2 Titanium The static and dynamic properties of Grade 2 Titanium for dental applications are investigated. The typical casting procedures used in dental laboratories lead to a drastic deterioration of the mechanical properties compared to wrought material. This deterioration is caused by changes in microstructure and surface roughness. The experimental results are used to determine opportunities for improvements and their limits.     

Mechanische,chemo-mechanische und optische Oberflächenprüfung

Every surface will experience some kind of wear which is caused by abrasion. Depending on the use of the surface this damage can affect only the optical appearance or even affect the function. It depends on the use of product whether abrasion of the surface is relevant or not. In any case there are many different methods and instruments for measuring and evaluating the mechanic, chemo-mechanic and optic degree of abrasion.     

Mechanische Eigenschaften der Legierung Hastelloy alloy C 22®

Mechanical Properties of Hastelloy alloy C-22 Hastelloy alloy C-22 is an advanced alloy of the Hastelloy alloy C-series with outstanding corrosion resistance. The alloy is used in the construction of pressure vessels which are used in the temperature range of ?196°C to 400°C. For this application, mechanical properties and fabrication data were documented. The testing program included as mill annealed material as well as material in conditions typically experienced during vessel fabrication. The mechanical behavior of alloy C-22 was found to be comparable to the other C-type alloys. The alloy possesses high toughness at low temperatures even in a cold worked condition and it has good weldability.     

Aufbau und Eigenschaften glasfaserverstärkter Eisenverbundwerkstoffe

Properties and Microstructure of Iron-Glassfiber Composites It is possible to produce powdermetallurgically glasfibre reinforced iron composites after high deformation by extrusion. These materials represent some interesting technological aspects because an anomalous increasing in tensile strength and other mechanical properties can be found, although the Young's-Modulus of the additive is lower than of the matrix. On the other hand electrical conductivity and Young's Modulus of the composites show a linear decreasing with the volume fraction of the second phase. This behaviour is reasoned in the fibre structure of the composites. Other physical properties such as thermal conductivity or the internal friction show an anomalous behaviour because of an excursive phononscattering at the interphases, which the curled microstructure possess in multiple forms.     

Hüftgelenkersatz – eine tribologische und konstruktive Herausforderung

Artificial hip joints - a challange for ideasconcerning tribology and designing Artificial hip joints are successfully used since two decades. The artificial joint is set up out of a femoral ball head made of a cobalt chromium alloy or alumina ceramic. The ball head is mostly articulating against an acetabular cup made of polyethylene (UHMWPE). The polyethylene wear debris causes osteolysis. Because of the osteolysis the implants will loosen and a revision of the artificial hip joint has to be performed. The objective of all R & D projects is to minimize the polyethylene wear. The state-of-the-art is discussed. There are new materials and methods that offer oppertunities for new combinations. Possibilities, limitations and the successes are discussed. The clinical experience during the last two decades proved that femoral ball heads made of alumina ceramic could reduce the problems of osteolysis.     

Herstellung und Eigenschaften von glasfaserverstärkten Kunststoff-Stahl-Schichtwerkstoffen

Preparation and Properties of Layered Composites of GFK-Steel The development of insulating joints of GFK and steel is described. The strength of the GFK and steel is described. The strength of the GFK and the adhesion between the GFK and steel is in this context of special interest. Results for the Young's Modulus, the ultimate and adhesion strength measured in bursting and bending tests are compared to those measured in tensile- and adhesion tests; the data agree well with each other. The correspondence between literature data of mechanical properties of the GFK and the measured values is satisfying.     

Mechanische Bearbeitung sprödharter Körper und Grenzflächenwechselwirkungen

The effect of surface adsorption on the machining of brittle materials In the present paper is shown the importance of interfacial phenomena in the machining (grinding, cutting) of brittle materials. Especially influenced are the rate of the abrasion, the cutting forces and the roughness of the surface.     

Eigenschaften und Verwendungsgebiete von niedriglegierten warmfesten Stählen

Properties and applications of low-alloy steels for elevated temperatures. Demands on steels for elevated temperatures. Tensile and toughness data on Manganese Nickel Molybdenum Vanadium steels with ferritic-bainitic structures in dependence of the chemical composition and the temperature. Influence of pulsating stresses. Examples of application.     

Mechanische Eigenschaften der durch thermisches Spritzen hergestellten unidirektionalen Faserverbundwerkstoffe

Mechanical properties of unidirectional fibre-reinforced composites made by thermal spraying Basic mechanical and technological properties of continuous fibre-reinforced metal-matrix composites made by thermal spraying are presented. The simple model of continuum theory has been used for the calculation of composite properties parallel to the fibre direction [1]. Taking into account the results obtained the theoretical analysis of composite failure modes and difference between praxis and theory is carried out. Problems concerning the properties measurements of thermally sprayed composites are discussed and their influence on the results is analysed as well. The comparison between the theoretically estimated composite strength and the experimental results is presented. The directions of future research work to improve the composite mechanical properties are also given.     

Entwicklung verbesserter Bleiwerkstoffe für den Chemie-Apparatebau,III: Mechanische Eigenschaften

Improvements in lead alloys for chemical plants, III: Mechanical properties The hardness of copper-alloyed rolled lead for chemical plants is increased by further alloying additions. The hardness of the finegrained lead alloy PbCu0.04Sn0.05Pd0.03Se0.02, which is optimum as regards processability, fine-grained structure, structural stability, and corrosion resistance, lies between that of copper lead DIN 1719 and antimonial lead containing 4% Sb. The yield point (0.2% yield strength) and tensile strength of the tested rolled lead materials increase within a certain range in a linear proportion to the hardness. This also applies to the fatigue strength. The creep strength (1% time yield limit and long-time rupture strength) likewise increases with growing hardness; this dependency diminishes, however, with rising temperature and becomes insignificant at 110°C. The improvements in mechanical properties of copper-alloyed lead to be achieved by small additions of silver (up to 0.01%) are thoroughly discussed.     

Oberflächenbehandlung von Kohlenstoffasern und mechanische Eigenschaften von Laminaten

Surface Treatment of Carbon Fibres and Resulting Composite Properties In composites carbon fibres are used as reinforcing fibres with thermosetting and thermoplastic resins as martices. These carbon fibres differ strong in their micro-structure and therefrom in fibre properties. To achieve sufficiant composite properties special carbon fibre surface treatment methods are necessary. This paper describes a systematic study on oxidative surface treatment of carbon fibres by wet-, dry- and anodic oxidation. Further investigations by matrix variation show us the influence of matrix strength on the mechanical composite properties. Finally it is shown that in case of impact load composite fracture behaviour is controlled only by the fibre itself.