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.     

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.     

Verschleiß und Verschleißschutz beim Spritzgießen

Wear and Wear Protection for Injection Moulding Increased power installations at injection moulding machines for higher polymer output rates require improved wear protection measures since the so called ?standard steels”? cannot cope with these demands. This publication describes the adhesive, abrasive and corrosive wear phenomena which are taking place in plasticating units of injection moulding machines as well as the causing factors and resulting effects by means of examples. The influence of different polymers and additives on the service life of the machinery components is also being considered. Finally the article presents solutions to achieve an effective reduction of wear by processing and design related measures, suitable metal surface treatment and adequate material selection for the plasticating unit.     

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.     

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.     

Schichten in der Kunststoffverarbeitung. Mittels MSPVD abgeschiedene CrxN-Schichten eröffnen neue Möglichkeiten für den Verschleißschutz von Plastifiziereinheiten

Coatings in polymer processing Cr_xN coatings produced by PVD-magnetron sputtering (MSPVD) open units For several years hard coatings have been used in plastic processing. The reduction of adhesion and contamination effects play a more and more important role besides the wear protection of injection moulds and extrusion tools. Applications of hard coatings in the field of highly stressed screws and barrels of plastification units are very seldom. In these cases the tribological effects are very intense so that the demanded wear resistance of hard coatings in the range 10μm is not sufficient. Different hard coatings based on titanium and chromium were tested according to their applicability for wear protection of screws in plastification units. Thickness, hardness, internal stresses and adhesion of the coatings were studied. Afterwards tribological tests in a model testing unit were investigated. Here the coatings were studied under tribological conditions, similar to those in a real plastification unit. The Cr_xN multilayer coatings showed extremely better wear resistance than the titanium based coatings. For this reason the Cr_xN coatings were optimized by help of the deposition parameters. These optimized coatings have been investigated according to their applicability for different polymers in comparison to other coating systems. First tests of CrCN/TiCN coated screw elements in practice showed very pleasing results. The test in practice with the optimized Cr_xN multilayer coating has yet to take place, but in the model tests the Cr_xN coatings showed excellent results.     

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.     

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.     

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.     

Mikrostrukturieren von thermisch gespritzten Mo‐Schichten für Anwendungen im Bereich hoher Reib‐ und Verschleißbeanspruchungen

The properties of thermally sprayed coatings are dependent on many parameters such as the spraying material, substrate properties, and the injection parameters. In this study, the influence of two variable spray parameters (spraying distance and current) were investigated on molybdenum‐containing thermal spray coatings. Particularly, materials and surface characterizing properties were analyzed, and the dependence on each other was examined. The important surface parameters studied in this case are the porosity and the pore depth of the coatings. Following the correlation between spray parameters and coating properties, the influence of surface properties on the tribological behavior will be discussed, in comparison to an uncoated steel surface.     

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.     

Ventilwerkstoffe für Verbrennungsmotoren

Valve Materials for Combustion Engines An overview is being given on production numbers, requirements and properties of valve materials. Their development from the beginning till today's state of the art is reviewed with a focus on Chromium-Manganese-Nitrogen-alloys. Valve materials are grouped by the criteria of density – heavy, lightweight – and alloying elements. The multiple stresses of the material in the valve are being met with a few standardised grades and specific ways of manufacture. The path of the material from bar stock to the finished valve is being followed. Engine development in the past decades increased the load on the valves which could be met by continuously developing their structural strength. Also the strength of all valve materials could be raised to nominal strength above 1100 Mpa by applying specific methods. Higher strength at the surface is being effectuated by work hardening effects. The technology to increase reliability of hollow valves and new aspects of valve seat facing including residual stress is explicitly discussed. General aspects of alloy utilisation is followed by a discussion of lightweight valve materials as Titanium alloys, intermetallic Titaniumaluminide alloys and ceramic materials, spec. Silicon Nitride, which all have a potential as forthcoming valve materials capable of reducing fuel consumption of the engines.