Einsatz des Ritzpendels zur Quantifizierung des Verschleißverhaltens bei der Bearbeitung von Naturstein

Use of a Scratch Pendulum for Quantification of the Abrasive Behaviour in Machining Stones The machining of natural stones is one of the most demanding applications of today´s cutting technique. Modern stone processing is based on grinding and it is usually done with diamond based tools. The achievable material removal rate is process dependant and mainly determined by tool speed and infeed. The tool durability depends on the adjustment of the parameters to the wear resistance of the processed material. This resistance is a material characteristic value. Using a scratch pendulum, it is possible to determine the energy needed to create a defined scratch and relate it to the induced material loss and the chipped material volume. The analysis provides a value which, after verification by industrial production data, can be seen as characteristic for the material. It therefore enables the quantification of a material dependant scratch resistance.     

Herstellung und Untersuchung des Verschleißverhaltens von induktiv eingeschmolzenen Hardpaint‐Schutzschichten

Friction and wear processes generate significant economic damage annually in industrial production due to maintenance and repair costs as well as loss associated with production downtime. Wear‐resistant coatings are a measure for reducing wear. In this context, the novel hardpaint technology for coating of parts with a fusible metal powder composition is described. Components with complex geometries as well holes or undercuts can be coated easily and inexpensively. Two protective layers are discussed and characterized in terms of their microstructure. Density measurements, hardness tests and scanning electron microscopic investigations were carried out. Both powder layers were inductively melted after application and are based on a hard alloy (iron‐based) commonly used for plasma transferred arc powder surfacing. Abrasion wear resistance is evaluated based on the results of the wear tests and microstructural investigations. Furthermore the results are discussed in comparison to a martensitic fine‐grain steel (Hardox 450), which is commonly used in abrasively stressed areas. Compared to Hardox 450 both hardpaint coatings have a much more wear‐resistant behavior due to their hard phases. In addition, it was confirmed that the hardpaint technology is able to embed thermally sensitive fused tungsten carbides which are significantly increasing the wear resistance against abrasion.     

Potenziale von ausgewählten Randschichtbehandlungsverfahren sowie deren Kombinationen zur Verbesserung des Verschleiß‐ und Korrosionsverhaltens von Gusseisenwerkstoffen

Die typischen hohen C‐ und Si‐Gehalte von Gusseisenwerkstoffen und der weiche Graphit limitieren die Behandel‐ und Beanspruchbarkeit nach dem Nitrieren und der Hartstoffbeschichtung. Wenn die Gusseisenoberfläche vor den genannten Randschichtbehandlungen mittels Elektronstrahls umgeschmolzen wird (Kombinationsbehandlung) und eine harte, graphitfreie ledeburitische Randschicht gebildet wird, dient diese als Stützschicht für die harte und dünne Verbindungs‐ bzw. Hartstoffschicht. Vergleichende Verschleißtests (Stift‐Scheibe) zeigten, dass bei geringen Lasten die Verschleißrate aller Einzel‐ und Kombinationsbehandlungen auf einem vergleichbar niedrigen Niveau wie der unbehandelte und beschichtete Grundwerkstoff liegen. Bei höheren Lasten kommt das überragende Verschleißverhalten der Kombinationsbehandlungen gegenüber den Einzelbehandlungen voll zum Tragen. Die Bildung defektfreier Randschichten nach der Kombinationsbehandlung resultiert außerdem in einer deutlichen Verbesserung der Korrosionsbeständigkeit in chloridhaltiger Lösung. Im Vergleich zum Grundwerkstoff und den Einzelbehandlungen wurden die relevanten Potenziale zu deutlich positiveren Werten verschoben.     

Verarbeitung von feinen Spritzwerkstoffen zur Verbesserung von Korrosions‐ und Verschleißschutzeigenschaften von thermisch gespritzten Schichten

About the application of fine spray materials for improvements in terms of corrosion and wear protection of thermal spray coatings Within a research project the spray materials Cr₂O₃, Cr₃C₂ NiCr and WCCoCr were considered. Process parameters were determined, optimized and validated allowing the application of very fine spray material fractions (< 25 μm) with plasma and high velocity oxy‐fuel spray systems. In addition to improved coating properties like low porosity and improved corrosion resistance the application of near net shape coatings was enabled. The subsequent reduced effort for after‐treatment of the coatings can contribute to further rationalization of thermal spray processes.     

Verschleißprüfung und Verschleißverhalten von Hartmetallen

Wear testing and wear behaviour of cemented carbides Wear resistance is not a mater constant but a quantity of a system. For the judgement of a case of wear or for the choice of the suitable grade of cemented carbide it is necessary to investigate exactly the limiting conditions and the appearance of wear. The wear test can only be considered with exactly defined limiting conditions and only be compared with application of similar limiting conditions.     

Versuche zur Verbesserung des Wirkungsgrades von Dampfturbinenschaufeln

Zusammenfassung Es wird der absolute Wert der Dampfreibung an der Hohlfl?che eines Zylinders entsprechend der Hohlfl?che einer Dampfturbinenschaufel mittlerer Verh?ltnisse gemessen, wobei festgestellt wird, da? dieser Wert bei 1 at abs sehr klein ist. Daraus wird geschlossen, das andre Ursachen für die Verschlechterung des Wirkungsgrades vorliegen müssen. Der Verfasser erblickt diese Ursachen in der üblichen hohen Verdichtung des Dampfes auf der Schaufel-Hohlseite und folgert, da? wesentlich breitere Laufschaufeln als bisher bessere Wirkungsgrade ergeben müssen. Es wird eine Formel für den mittleren Verdichtungsdruck aufgestellt, ferner werden Hinweise für den Bau wirtschaftlicher Dampfturbinen gegeben.     

Reibung und Verschleiß von Polymer-Verbundwerkstoffen

Friction and Wear of Polymer Composites Polymer composites are more and more used as structural components which are very often subjected to friction and wear loadings under use. This paper describes the principle microstructure in polymer composites and their friction and wear properties as a function of microstructural composition. Special attention is focussed on the behavior of these materials under sliding situations against steel and under severe abrasive loading (wear by rough abrasive paper). Models to describe the tribological properties of composites by modified rules of mixtures and/or by terms combining mechanical and microstructural parameters of the partners in contact are introduced.     

Wechselwirkungen beim abrasiven Verschleiß von Grobblech

Experimental Design of the emery-paper-method The abrasive wear of heavy plates is mainly influenced by size and hardness of the penetrating abrasive particle (abrasive material). Formerly abrasion-tests are dealing with the one-factor-at-a-time-method. This method allows to investigate the influence either of the hardness or the size of abrasive material upon the wearing surface. Mutual dependence (interactions) between this factors could not be discovered. So the one-factor-at-a-time-method allows to find only suboptimum conditions. In this publication the Statistical Design of Experiments is used for the first time in the field of abrasion-test, because this method allows to analyze interactions between hardness and size of the abrasive particle.     

Untersuchung des Fließverhaltens der Magnesiumknetlegie‐rung AZ31 mit Hilfe von Schichtstauch‐ und Zugversuchen

Today design of metal forming processes is often supported by numerical simulation. To obtain realistic simulation results, the used material models need accurate material parameters from the material characterization. Magnesium alloys in particular are not yet sufficiently investigated. Therefore, their material parameters are scarce in literature. Especially determination of flow curves at higher degrees of deformation represents a challenge, but is necessary in order to describe the characteristic hardening and softening, as they occur in magnesium materials at elevated temperature of forming process. In this paper, an approach for the determination of a combined hardening curve from a tensile test and a layer compression test is presented. For this purpose, the corresponding values are recorded experimentally and evaluated based on the principle of the plastic work equivalence.     

Lasererwärmung zur Verbesserung des Umformergebnisses beim Kragenziehen von Aluminium‐ und Magnesiumknetlegierungen

Laser heating for improvement of forming results in hole flanging of magnesium and aluminium wrought alloys Warm sheet metal forming has proven itself for the production of parts made of magnesium and aluminium wrought alloys. In many cases, e.g. in deep drawing, the heating of large surfaces makes sense. If only small areas of a larger part have to be formed, as with hole flanging, a local heating by means of laser irradiation is more advantageous. So the heat quantity can be brought in well metered temporally and locally. The expanding ratio could be increased, depending on material, with a local temperature of about 200 °C by more than double in comparison to cold conditions. It was shown that a narrow process window is to be kept, since material failure arises not only from too low, but also from to high forming temperatures.     

Verschleiß und Verschleißprüfung

Wear and wear Testing. The following six different wear mechanisms are briefly discussed: adhesive wear, abrasive wear, fatique wear, mechano-chemical wear and thermal wear. As to wear testing it is concluded that for obtaining a priori information on materials, laboratory testing can be quite useful, provided that the environmental conditions that prevail in practice are successfully reproduced in the laboratory. Further, it is always advisable to include in a test programme some reference materials on which practical information is available.     

Auftraglöten zum Verschleißschutz von Titanwerkstoffen

Wear Protection of Titanium using Surface Brazing Titanium and titanium alloys possess high specific strengths up to a temperature of about 600 °C in addition to an extraordinary corrosion resistance [1]. The low wear resistance constitutes a crucial impediment for a much broader use. Titanium materials are especially susceptible to friction fatigue and erosion. Coating techniques have to be developed in order to counteract this technical constraint. Surface brazing presents a promising approach. Hard metals mixed with brazing filler metals on a silver and titanium basis were brazed in a vacuum furnace and subsequently characterized. Wear resistance was quantified and optimized using ball on disc measurements.     

Verschleißverhalten von Innenbüchsenwerkstoffen für das Strangpressen von Nichteisenmetallegierungen

Wear Resistance of Liner Material for Extruding Non-ferrous Alloys Extruding Al and its alloys Cu, brass, Cu-Ni alloys and Ni on account of variable working conditions (as temperature) different liner materials are used. Processing Al martensitic hot work steels are successful in application. Working up copper high temperature resistant and austenitic steels are additional in use. The high-temperature strength of these materials is well-known. Based on the investigation of the high-temperature wear this paper presents several new considerations.