Verschleißschutz für Titanbauteile

Wear Protection for Titanium Components The use of titanium and its alloys in the last decades keeps on increasing due to its material‐specific characteristics like high firmness, good corrosion characteristics and very high thermal maximum stress. However nowadays, the use of titanium components in systems where wear resistance is important is limited by titanium’s relatively low wear resistance. Surface wear is in principle a characteristic, conditioned by chemical and physical effects of the elements involved as well as collective stress. The necessity for new systems where good wear resistance and excellent mechanical properties are combined keeps on showing up. Due to titanium’s tendency to react with surrounding media, titanium alloys are difficult to be welded. Embrittlement by admission of hydrogen and oxygen can occur at high temperature processes or even changes on titanium’s microstructure may appear. Brazing techniques, which are actually applied to steel, have been modified and adapted for using them to titanium materials. Here, commercially available braze pastes and hard materials where combined and applied on titanium.     

Materialeinsparung durch aktiven Verschleißschutz

Active Protection against Wear saves Material In almost all industrial branches, wear processes cause considerable loss of material mainly in the field of metal:metal and metal:mineral contact. The so accrueing significant loss of material grows owing to an increase of specific throughput in machinery, processing in combined systems, more efficient utilization of raw material and introduction of modern technology for the extraction of raw material and the recycling processes. Finally the progressing desires exists to reduce the consequential expenses arising from such losses. In the future, however, the decisive factor will not be the actual shortage of raw material but moreover the politically caused shortage and the ratio of increasing expenditure between raw material and wages. Material savings are possible by making use of the presently known fundamentals of wear. In details the following precautions are available: – Saving of material in new parts – Utilization of higher class materials – Application of parts produced out of different materials – Reclamation of worn-out parts The problems of metal:mineral wear are illustrated by numerous examples. The here described precautions enable the engineer to save raw materials.     

Verschleißschutz für hochbelastete Umformwerkzeuge

Wear protection for heavy duty forming tools — PVD‐, CVD‐ and laser treatment The PVD‐ or CVD‐ coating of heavy duty tools for cold forging and metal sheet forming is a today's standard for a wide variety of applications in mass production. This article leads into this matter and demonstrates by means of some typical examples the state of the art.     

Verschleißschutz und Korrosionsbeständigkeit von austenitischem Stahl durch Plasmadiffusions behandlung

In this paper, we report on a series of experiments designed to study the influence of plasma nitriding on the mechanical properties and the corrosion resistance of austenitic stainless steel. Plasma nitriding experiments were conducted on AISI 304L steel in a temperature range of 375‐475°C using pulsed‐DC plasma with different N ₂‐H ₂ gas mixtures and treatment times. First of all, the formation and the microstructure of the modified layer will be highlighted followed by the results of hardness measurement, adhesion testing, wear resistance and fatigue life tests. In addition the corrosion resistance of the modified layer is described. The microhardness after plasma nitriding is increased by a factor of five compared to the untreated material. The adhesion is examined by Rockwell indentation and scratch test. No delamination of the treated layer could be observed. The wear rate after plasma nitriding is significantly reduced compared to the untreated material. Plasma nitriding produces compressive stress within the modified layer. This treatment improves the fatigue life which can be raised by a factor of ten at a low stress level. The results show that plasma nitriding of austenitic stainless steel is a suitable process for improving the mechanical and the technological properties without significantly effecting the excellent corrosion resistance of this material.     

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.     

Spritzgießen keramischer Bauteile

Powder injection moulding of ceramic parts Powder injection moulding is a parts production technology that combines the advantages of plastics injection moulding with the materials properties of ceramics. It makes possible the production of complex shaped parts for high production numbers. Almost all possibilities of parts design used in plastics injection moulding can transfered to ceramics. Paying attention to the special properties of highly filled thermoplastics and the well known rules for parts and tools construction, new parts can be realized in short development times. This article will have a closer look at the parameters for injection moulding, at rules for design of ceramic parts and the corresponding tools as well at a never debinding technology.     

Neue Sol-Gel-Beschichtungen als Korrosions-und Verschleißschutz für NE-Metalle

New Sol-Gel Based Coatings as Corrosion- and Wear-Protection On Non-Ferrous Metals A new composite coating material has been developed for the protection of non-ferrous alloys (e.g. aluminum, magnesium, zinc and brass). The coating materials were prepared by the solgel process from epoxyalkoxysilanes and aromatic diols to act as crosslinking agents. As solvent, alcohols and glycol ethers have been used. The viscosity of the system (7–55 mPas) was established in a way to be used in spray, dip or flow coating processes. The transparent coatings were cured at T = 100–220°C. In corrosion tests, 3000 hours salt-spray climate and 240 hours CASS-test = Copper chloride and Acetic acid added Salt Spray, no infiltration of the metal-coating interface and no ?filiform-corrosion”? on A199.5, AlMg₃ and AlMgSil was observed. Brass samples showed less than 4 mm extension of a scribe after 500 hours salt-spray-test. The coatings showed no visible traces of abrasion after 1000 cycles taber abrader test and an excellent adhesion (cross cut and tape-test: grade 0). The transparent basic systems were pigmented by 5 – 10 wt.% of colored organic pigments to obtain all kind of colored coatings.     

Neuentwicklungen für den Verschleiß‐ und Korrosionsschutz beim Plasma‐Pulver‐Auftragschweißen

New developments for wear an corrosion protection by weld surfacing with plasma transmitted arc process Highly wear‐resistant claddings which contain carbides can be applied by weld surfacing with the PTA process. The use of vanadium carbide prevents undesirable reactions with the matrix material. Thus, highly corrosion‐resistant Fe‐based claddings can be produced for applications in the food and marine industries, and Ni‐based claddings can be applied to components exposed to inorganic acid attack. A combined test is applied for determining the relative effect of corrosion under combined exposure to abrasive wear and corrosion and indicates the primacy of abrasive wear for behaviour in operation.     

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.     

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.     

Verschleiß von Maschinen und Werkzeugen beim Verarbeiten von verstärkten und gefüllten Kunststoffen

Wear of Processing Equipment and Moulds by Filled and Reinforced Plastics The introduction of filled and reinforced plastics into the market increased the problem of wear during processing. It is estimated that in Germany wear based losses are up to 500 Millions DM per annum. Special test methods have been developed for systematic analysis of wear phaenomena. A considerable progress has been achieved in solving these problems in close contact to the concerning industry.     

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.     

Verfestigung und Verschleißverhalten von weißen Gußeisen bei abrasiver Beanspruchung

Work Hardening and Abrasion Resistance of White Cast Irons White cast irons are frequently used against abrasive wear under extreme loading conditions. The microsructure and the mechanical properties of these alloys play an important role to control their wear rates. Regarding the mechanical properties, it has been reported that the bulk hardness alone is not enough to describe the wear behaviour. Generally, it has been shown that the work hardening induced by the wear process has an essential effect on the abrasion resistance. In this investigation, using a pin abrasion test, the wear behaviour of Ni-Hard 4 and high chromium white cast irons has been studied. The results of this study contribute to discuss the correlation mechanisms between work hardening and abrasive wear behaviour.     

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.     

Fortschritte beim Rührreibschweißen von Aluminium,Magnesium und Stahl

Progresses on the friction stir welding of aluminium, magnesium and steel Friction Stir Welding (FSW) represents an innovative welding process for joining light metal, especially, aluminium and its alloys. Friction Stir Welding offers an attractive alternative to conventional fusion welding processes because of the excellent properties (particularly ductility), reproducibility, robustness, and surface finish obtained with the process. Within the scope of this work the Friction Stir Welding‐Process with its possible joint configurations is explained. The focus of this work concentrates on weldability studies concerning cladded aluminium alloys, aluminium cast alloys, aluminium tailored welded blanks both from similar and dissimilar joints produced in aluminium, magnesium and steel. The mechanical properties of the welded samples will be discussed.     

Kathodenverschleiß beim Elektronenstrahlschweißen

Cathode Deterioration During Electron Beam Welding In industrial practice, the integration of electron beam welding units into production lines requires the monitoring of a great number of main process parameters in order to provide for constant seam quality and undisturbed process behaviour. However, in these monitoring systems the condition of the cathode is generally not taken into consideration. Due to ion bombardement and partial evaporation of the cathode material, the emitting surface will be damaged resulting in a changed emission behaviour. In a further step, the cathode will break down, causing an unpredictable interruption of the weld process. The knowledge of the effective damage mechanisms is a basic assumption to forecast the life time of tungstencathodes resulting in an increase of process security. The level of the cathode damage is determined by means of SEM analyses after a defined operating time. The investigations show that the life time of tungstencathodes mainly depends on the welding material. For example, the life time of cathodes used for welding aluminium will be 4 hours only, while 9 hours can be achieved in welding steel.     

Verschleiß von TaC- und TiC-Laserdispersionsschichten durch weiche und harte Abrasivstoffe

Wear of TaC and TiC steel composite hardfacings by soft and hard abrasives TiC and TaC steel composite layers were produced on a die steel 90MnCrV8 (0.9% C) by using a CO₂-laser. The hard particles of it median size of 3 μm and 30 μm, respectively, and a volume fraction of about 50% were homogeneously distributed in the steel matrix. Hardness of the martensitie matrix was variied by heat treatments. Wear resistance of the hardfacings against flint and SiC with varying mesh sizes were measured using an abrasive wear tester at laboratory atmosphere. Abrasive wear resistance was increased by more than one magnitude of order by embedding the hard phases in the steel surface. The results showed the effects of type and size of the hard phase, hardness of the steel matrix and also of the type and mesh size of abrasive grits on wear resistance. Experimental results arc discussed as a function of those parameters and theoretical models arc developed.