γ-TiAl intermetallics are attractive materials for high-temperature structural applications in the aerospace and automobile industries. However, they show environmental embrittlement at elevated temperatures that is mainly related to their low high-temperature corrosion resistance. One way how to improve the high-temperature corrosion resistance is the deposition of protective coatings on the surface of the base material. In this study, samples of a Ti-Al alloy with the chemical composition Ti-48Al-2Cr-2Nb (at.%) were covered by physically vapour deposited (PVD), by metalorganic chemically vapour deposited (MOCVD) and by high-velocity oxy-fuel (HVOF) sprayed coatings. All coatings were based on the Ti-Al alloys and contained different amounts of alloying elements. The corrosion experiments were performed in molten salts containing 75 wt.% Na2SO4 and 25 wt.% NaCl at 850°C up to 336 h. Both, PVD and CVD protected coatings reduced the changes in the mass of the samples over the corrosion time. Still, the formation of TiO2 could not be avoided, as it was confirmed by glancing-angle X-ray diffraction experiments.

Alternative methods for hot dip- or electrogalvanic deposition of zinc coatings on steel are gas phase depositions (PVD). They posess high flexibility with respect to alloy composition, and are environmentally harmless. However, a PVD-coated steel must have at least the same corrosion resistance than steels with "classical" surface finishing.Therefore, the corrosion behaviour of Zn-coatings and Zn/Mn/system-coatings deposited by electron beam evaporation without and with ion beam assistance (IBAD) on low alloy steel, was determined by means of salt spray test and electrochemical potential/time measurements. At first the influence of chemical and irradiation pre-treatment and ion bombardment during deposition on the corrosion resistance of the coatings was investigated. Than the effect of the Zn-layer thickness was determined in comparison with an 8 mu m thick electrogalvanized reference coating.Finally Zn/Mn-alloys, Zn/Mn-multilayers and Zn-coatings with Mn- or Zn/Mn-surface layers (top layers) were investigated. By means of optimised pre-treatment and ion bombardment conditions one obtains, considering the layer thickness, PVD-Zn coatings with corrosion resistance comparable with the reference layer. The best Mn-containing coatings are Zn-coatings with Mn-toplayer. They surpass the corrosion resistance of the reference layer considerably. Additionally it could be shown that in tendency the potential/time measurements agree very well with the results of the salt spray test.

For the purpose of providing corrosion protection, multilayered Al/Al2O3 coatings were deposited on CK45 steel by an Ion Beam Assisted Deposition (IBAD) facility. Five kinds of multilayered coatings with overall thickness of 3 μm were made in the experiment, and 0.1 μm graded Al2Ox (x<3) layers were formed between the Al and Al2O3 layers instead of sharp Al/Al2O3 interface. The coating structure and composition were examined with RBS and AES measurement; and the corrosion behavior was determined by potentiodynamically controlled current–potential measurements under conditions of uniform corrosion and pitting corrosion attack. The results show that these multilayered coatings can give good protection to the steel substrate, the corrosion current density decreases three to four orders. Also, the protection ability depends on the coating structure and composition when the overall thickness was fixed.

Zn alloys are able to surpass the performance of electrogalvanised or hot-dip Zn (at same thickness) for corrosion protection of car bodies. In particular, vacuum deposited Zn alloy layers have higher protection power on non-painted steel surfaces as compared with pure Zn layers. In the present work the Zn–Mn system was investigated: Zn/Mn alloys of different compositions as well as Zn/Mn multilayers of 5–6 μm total thickness were prepared on low alloy steel by ion beam assisted deposition (IBAD). The equipment contained two electron beam evaporators and a slit extraction ion source, delivering ions of 100–1500 eV energy. The corrosion behaviour of the samples was evaluated by standard salt spray tests (SST). The composition and microstructure of the coatings was studied by scanning electron microscopy (SEM) and EDX-depth profiling. The behaviour of the coating/substrate system is discussed in comparison with ‘state of the art’ Zn-coatings (EZ) produced by electrogalvanizing. Generally speaking, the performance of the optimised coatings is as good or better than the reference standard.

This paper describes the progress made during a 4-year BRITE/EURAM Collaborative Programme(1) to develop thinner zinc coatings applied by PVD processing to steel strip, for use in automotive body structures. Alloy and multilayer coating deposition techniques were assessed in the laboratory, the technology later being transferred to a pilot line for the production of wide strip which was used for automotive evaluation. This included processing aspects such as pressing (including wear and friction), welding, adhesive bonding, painting and corrosion tests using cyclic laboratory tests and on-vehicle proving using production models. Results show that a reduction in thickness can be achieved (compared with the 7.5 mum electrogalvanised standard) by using an alloy coating, e.g. Zn-Ti, whilst meeting all usual automotive criteria. The work is regarded as a significant stepping stone in the development of thinner, more environmentally friendly zinc coatings. The adoption of this type of coating will depend on cost and an adequate supply base, but with process modification the indications are that this type of product could be a viable alternative to both hot-dip and electrogalvanised alternatives in the future. (C) 2003 Elsevier Science B.V All rights reserved.

The treatment of stainless steel by pulsed energetic nitrogen ion irradiation in the millisecond regime may cause phase transformations close to the surface. The characterization of the phases was done by measurements of Mobetabauer and grazing incidence X-ray diffraction. The results indicate transformations of the austenitic phase into Cr2N, Fe2N and the gamma(N)-phase (paramagnetic and magnetic) in dependence on the bombardment conditions and the nitrogen depth profiles measured by nuclear reaction analysis. Some samples were studied by depth selective conversion electron Mobetabauer spectroscopy One of these samples contained three new phases: Fe2N, gamma(N2)-phase (paramagnetic) and gamma(N1)-phase (magnetic). The magnetic phase is found predominantly in the surface region, whereas the Fe2N and the gamma(N2)-phase (paramagnetic) reach their maximum concentration at a depth of approximately 100 nm. The other sample contained four new phases: the three phases mentioned above and additionally alpha-(Fe,Ni)-martensite, indicating the formation of Cr2N. This phase reaches its maximum concentration at a depth of approximately 40 nm. Thus, by interaction of different mechanisms, i.e. segregation of Cr and formation of Fe-Ni rich clusters by radiation enhanced diffusion, the alpha-(Fe,Ni)-phase is formed on the expense of the other phases. Hardness was measured as Vickers hardness and current-density/potential-curves in a 5 N H-2 SO4-solution were performed as corrosion tests. The influence of the different surface phases on mechanical and chemical properties are discussed. (C) 2002 Elsevier Science B.V All rights reserved.

The composition of Zr-based thin films on vulcanized synthetic rubber by means of self-ion-assisted deposition was investigated by utilizing the Rutherford backscattering technique and rump code simulation. Pin Pull Test method was applied both to measure the level of adhesion between the deposited metal (Me)-based layer and rubber and mechanical properties of modified rubber surface. Hardness measurements of the thin films on substrate were fulfilled by applying a conventional Knoop method, an ultra-low load indenter and a laser-acoustic test method. The deposited films may be soft or very hard in dependence of Me species. Deposition of Me-based coatings changes the wettability of the modified rubber to water. We observe 10% decrease and 30% increase in a contact angle of water when Mo-based and Zr-based coatings are deposited on the rubber.

Coil coating by using a continuous belt inside an IBAD chamber allows not only the coating of steel or polymer strips in the IBAD mode, but represents also a very flexible device for the preparation of multilayers on relatively large substrates (typically 20×30 cm2). The specific geometrical arrangement of two evaporators and a slit extraction source together with variation of the speed and direction of the moving belt provides the necessary parameters. The possible variations range from single metal layers, alloy layers over gradient layers with increasing or decreasing content of one or both phases to multilayers consisting of 2 or more sublayers. The advantages of this technique are demonstrated by the preparation of Zn/Cr-, Zn/Ti- and Zn/Mn-coatings on steel. Mainly the improvement of the corrosion behaviour was studied in comparison with conventional electrogalvanized steels and alloys prepared by normal ‘static’ alloy deposition. The samples were analyzed by SEM/EDX measurements and an industrial-like salt spray test. It could be shown that most of the multilayer coatings had much better corrosion behaviour than the electrogalvanized reference samples.

Silver doped titanium oxide coatings for biomedical application were prepared by ion beam assisted deposition in an oxygen atmosphere. X-Ray photoelectron spectroscopy (XPS) was used to examine the chemical states and composition. Critical surface tension, dispersive and polar components of the surface energy were investigated by contact angle analysis. The influence of experimental conditions on the chemical states, composition and surface energy were investigated. The chemical state of silver was not affected by the process parameters and silver existed always in metallic state. XPS analysis confirmed the presence of TiO, Ti2O3 and TiO2, and the concentrations of the different oxidation states were influenced by the deposition rate of Ti and Ag. The oxygen flow rate had only a minor influence. On the other hand, dispersive and polar components of the surface energy were significantly affected by the oxygen atmosphere. The results also showed that samples with a higher concentration of silver exhibited a somewhat larger critical surface tension.

In this contribution we are reporting about experimental results on the surface treatment of aluminium and stainless steel by pulsed energetic nitrogen and neon ion beam irradiation in the millisecond pulse range. The characterization of the modified near surface layers of stainless steel by CEMS and aluminium by XPS showed that phase transformations, iron nitride and aluminium nitride formation took place. Results of nitrogen depth-profiling by NRA and RBS indicate that for stainless steel the diffusion process is depending on the pulse duration and the time between two pulses, and for aluminium on the energy density, respectively. Microscopic investigations of the pulse treated surfaces showed crater formation and in some cases surface melting for both materials. Cross-sectional investigations of irradiated aluminium and stainless steel show the modification of the substructure by subsurface melting and grain refining down to 50μm and 200μm below the surface, respectively. Microhardness measurements indicate a hardness increase for most of the treated samples in dependence on the irradiation parameters.

In the last years many studies on IBAD coatings on metals and insulators for wear reduction and corrosion protection have been published. However the IBAD deposition of larger areas (>10×10 cm) is still a major problem. Therefore we have developed a coil coater running inside the IBAD deposition chamber and allowing very flexible deposition modes. Single layers, multilayers and alloys can be deposited under ion bombardment on substrates up to 30 by 40 cm or on metal and polymer strips 30 cm wide. A number of examples dealing with Zn-alloy coatings on low alloy steel are reported: pure Zn-coatings were compared with Zn/Ti-alloys Zn/Cr-alloys and Zn/Mn-alloys. In some cases also multilayers of the different metals were studied in the static and dynamic operation mode. The coatings had a thickness of 2–8 μm and their corrosion behaviour was investigated by salt spray tests. The microstructure of the coatings was studied by electron microscopy and EDX-depth profiling. The behaviour of the coating/substrate system is discussed in comparison with “state-of-the-art” Zn-coatings produced by electrogalvanizing. Generally speaking the performance of the optimized coatings was as good as or better than the electrogalvanized standard.

Besides the commonly used procedures of UV-, X-ray and electron beam lithography, surface structuring by ion beam processes represents an alternative route to receive patterns in the nanometre–micrometre scale. In this work we focused on changes of surface properties of the polymer materials induced by ion irradiation and on reproducing hexagonal and square patterns in the micrometre scale. To achieve a better understanding of modification and structuring of insulating and conducting polymers by ion beam treatment we investigated effects of 14 keV Ar+ bombardment on thin films of doped conducting polyethoxithiophene (PEOT) and polyethylenedioxithiophene (PEDT) on polyethersulfone (PES) as insulating substrate within the fluence range from 1014 to 1017 ions/cm2. Changes of surface properties like wettability, solubility, topology and electrochemical behaviour have been studied by contact angle technique, AFM/LFM, cyclovoltammetry and electrochemical microelectrode. By irradiation through copper masks structured patterns were achieved. These patterns can be converted by galvanic or electroless copper deposition in structured metal layers.

Various high-temperature polymeric materials were preconditioned and metallized by using ion-assisted processes for adhesion improvement. The surface of the polymers was investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and stylus profilometry. The adhesion of the coatings was controlled by pull-off and peel tests. The measurement of the specific electrical conductivity, the helium gas tightness and soldering experiments give valuable information concerning possible applications. In comparison to the pure copper evaporation onto polyphenylensulfid (PPS) the ion beam assisted deposition (IBAD) of copper films results in a distinct increase of the pull-off force. At ion energies around 2.5 keV and at low ion-to-deposited-atom ratio of 0.01 the film adhesion was enhanced from a pull-off strength of 10 N mm(-2) up to 25 N mm(-2).Plasma processes at a low pressure provide a high polymer etching rate by a plasmachemical attack and ion sputtering effects in a synergistic manner. The plasma etching process attack the polymer material preferentially. Therefore, mineral particles must still adhere strongly to the polymer to provide mechanical adhesion sites for the metal layers. An peel strength of about 1 N mm(-1) was obtained on different substrate materials. (C) 2000 Elsevier Science B.V. All rights reserved.

The application of PVD coatings for wear protection of tools is well known. Since many years, TiN coated cutting and forming tools are state of the art. In contrast, the application of PVD coatings on machine parts is not standard today. This is caused by the problems of coating deposition on components as well as the fact that wear protection and corrosion protection is demanded for many parts with longer lifetime. TiN produced by means of PVD technique is good for wear protection, but with respect to corrosion there are problems. On the other hand electropolated chromium is a reliable coating to resist corrosion, but wear resistance is limited. PVD CrxN coatings promise to combine the advantages of hard coatings and electropolated chromium. The present study focuses on the corrosion properties of magnetron sputtered CrxN coatings. Different types of coatings on steel substrates with various amounts of nitrogen were investigated in order to take into account aspects of coating deposition resp. coating material, coating structure and coating morphology. Additionally several graded and multilayer coatings were studied to show influences of coating system design. Electroplated hard chromium was used as reference material for corrosion resistance. To explain the corrosion behaviour, crystallographic phases and structure of coatings were analysed by X-ray diffraction and morphology by SEM. It could be shown that the corrosion behaviour depends on all these parameters and that 8 μm chromium nitride provides the same corrosion protection as 48 μm electroplated chromium. Korrosionsverhalten von CrxN beschichtetem Stahl Anwendungen von PVD-Beschichtungen im Bereich des Verschleißschutzes, z. B. TiN-Schichten auf Zerspanungs- und Umformwerkzeugen sind Stand der Technik. Im Gegensatz dazu sind Anwendungen von PVD-Schichten auf Bauteilen kaum im Einsatz. Gründe hierfür sind unter anderem Probleme bei der Schichtabscheidung, aber auch die für Bauteile im Gegensatz zu Werkzeugen typischen kombinierten Anforderungen bzgl. Verschleiß- und Korrosionsschutz. TiN (PVD) zeichnet sich durch gute Verschleißeigenschaften, nicht aber durch die Verbesserung von Korrosionseigenschaften aus. Bei galvanisch abgeschiedenen Chromschichten kann man hingegen von gutem bzw. verlässlichem Korrosionsschutz bei hinlänglich ausreichendem Verschleißwiderstand sprechen. PVD CrxN Schichtsysteme scheinen die Vorteile von Hartstoffschichten und galvanisch abgeschiedenen Chromschichten zu vereinen. Inhalt dieser Arbeit sind die Korrosionseigenschaften von mittels HF-Magnetronsputtern abgeschiedenen CrxN Schichten. Die dazu untersuchten auf Stahlsubstraten abgeschiedenen Schichtsysteme unterscheiden sich in ihrem Schichtaufbau (Gardientenschicht, Mehrlagenschicht) und in ihrer stofflichen Zusammensetzung (Stickstoffgehalt). Es konnte gezeigt werden, daß das Korrosionsverhalten von allen Aufbauparametern abhängt und daß 8 μm Chromnitrid denselben Korrosionsschutz liefern kann, wie 48 μm galvanisch abgeschiedenes Chrom.

The main problem in growing c-BN rich films in the past has been their very high intrinsic stress, leading to partial or complete detachment from the substrate after reaching a critical thickness of 200 nm. The process we are using is closely related to IBAD or IAE. However. in addition to the evaporation of boron atoms and simultaneous nitrogen ion bombardment by an ion gun, the films were grown in a highly reactive gas (SF6, BF3) atmosphere, provided by a nozzle close to the Si substrate [chemically modified ion assisted evaporation (CMIAE)]. Reactive gases were used to verify preferential etching of impurities and different phases of boron nitride. SF6 represents a pure etchant. BF3, in addition, is a boron source.With this modification it was possible to grow films at 450 degrees C with a c-BN content of 85% up to a thickness of 800 nm. The films showed very good adhesion and could be deposited over a wide range of ion/neutral (I/N) ratios (0.4-1.2), depending on gas flux and geometrical condition. Furthermore, c-BN films could also be grown at much lower temperatures down to 120 degrees C.The analysis of the films was performed by IR and AES spectroscopy. The film thickness was measured independently by Talystep and Dektak. Although the details of the mechanism are not yet understood, the reactive gas assistance is very promising for obtaining rather thick films with high c-BN content and good adhesion. Further experiments on CMIAE deposition on iron and steel substrates are in preparation. (C) 2000 Elsevier Science S.A. All rights reserved.

Coil coating is state of the art for the production of electroplated or hot-dip-plated steel sheets for automobile bodies. Vapour deposition techniques in the coil coating mode are up to now only used industrially for metallizing polymers and deposition of very thin and barrier coatings on various substrates. For physical vapour deposition (PVD) of steel sheets only experimental coil coaters are placed in different institutions. A short survey on the state of the art is given followed by considerations for the application of ion sources and ion beam-assisted deposition (IBAD) arrangements for coil coating purposes. A mini-coil-coater integrated in the Heidelberg IBAD plant is described. Results on the generation and performance of Zn layers with a thickness of 3–8 μm and of Zn/Ti-, Zn/Al- and Zn/Cr-alloys on steel sheets of 10×10 cm and 20×30 cm are presented, especially on the corrosion performance in the salt-spray test and microstructural characterization. The transfer of the batch procedures to continuous coil coating processes is discussed and the future perspectives are considered.

Hard TiN layer coatings are commonly used as a single layer or sometimes as multilayers in order to improve wear resistance due to their outstanding mechanical characteristics. Usually the corrosion protection by these films is only moderate. Pores and defects can easily be formed in the processing stage. The mechanical properties as well as the porosity can be influenced by ion bombardment during deposition. This contribution has the objective of studying the correlation between corrosion and mechanical properties of the TiN layers and TiO2/TiN multilayers on steel (Ck45) produced by ion beam assisted deposition (IBAD) as a function of deposition parameters. The examination of the electrochemical phenomena occurring on the surface of the layer was based on the current density/potential measurements and on the scanning electrochemical microelectrode (SEME). Furthermore friction and wear resistance of the layer was determined by pin-on-disk measurements, and structure and morphology studied by X-ray diffraction (XRD) and AFM. The most important result was the finding that the degree of crystallinity of the coatings affected directly the hardness and wear resistance. The corrosion protection power on the other hand, increased with low crystallinity and high content of amorphous TiO2 or TiN.

The treatment of surfaces and thin layers of material with pulsed high-energy ions is a novel technique developed in Russia, Poland and USA. The advantages of this method, which is comparable with pulsed laser treatment, is the well-defined modification depth because of partial melting with subsequent quenching, the possibility of simultaneous doping and the low treatment costs in comparison with conventional ion-beam treatment. Important results of other groups and our own results are described and discussed. Stainless steel as well as aluminium and aluminium alloys were bombarded with pulses of different ions ranging from 10 ms down to 50 ns width. The energy density was in the region of 0.01–2 J cm−2. Thus the region where the microstructure of the materials was modified in the solid state was covered up to the melting point. The longer pulses (≥1 ms) were generated with the Heidelberg ion source MUCIS, the short ones (≤1 μs) in collaboration with the Institute of Nuclear Physics in Tomsk, Russia. The resulting microstructure was studied by X-ray diffraction, conversion electrons Mössbauer spectroscopy and atomic force microscopy; the macroscopic properties by hardness measurements and corrosion tests. The most important result was the proof that aluminium and stainless steel can be nitrided at low temperatures by pulsed nitrogen beams with ms pulse width. In addition, it was shown that various phase transitions occurred in stainless steel after ms- and ns-pulsed ion bombardment. This has consequences for the hardness of the material. For aluminium-based materials the hardness and pitting resistance could be improved.

The metallization of polymers for decorative and functional purposes is usually made by vacuum evaporation or electroplating. However, there are problems regarding adhesion and environmental pollution. In this study the possibility to metallize high-temperature thermoplasts homogeneously, without roughening the surface, by means of ion-beam-assisted deposition (IBAD) was studied. The polymers investigated were poly(ether sulfone) (PES), poly(phenylene sulfide) (PPS) and liquid-crystal polymer (LCP). A thin (200–600 nm) copper layer was deposited under bombardment with different argon-ion intensities and energies, and its adhesion was measured by the pull-off test. The adhesion obtainable for copper depends strongly on the chemistry of the polymer and on the filling material, ranging from poor to excellent. A titanium interlayer provides considerable additional adhesion and, for systems without an interlayer, the best performence is obtained for bombardment with low ion intensities and energies. Thickening of the copper layers galvanically to 20 μm does not affect the adhesion of the primary IBAD layers.

Chromium nitride films are a promising alternative to both electroplated hard chromium and TiN coatings prepared by physical vapour deposition (PVD). Deposition of the former still mostly requires highly toxic Cr(VI) solutions, causing environmental problems. Titanium nitride is an excellent hard coating but cannot efficiently protect the substrate from corrosion. Recently, some groups have obtained interesting results about PVD CrxN deposited by magnetron sputtering. In this work CrxN deposition was realised by ion-beam-assisted deposition (IBAD), evaporating chromium under irradiation with nitrogen ions. The arrival ratio of nitrogen ions to chromium atoms (I/A) was kept constant at 0.5, as this was known to be the best region for chromium nitride synthesis. However, the IBAD process allows many other deposition parameters to be varied and detailed investigations of IBAD CrxN are rare. In this study, the influence of ion energy and ion angle of incidence on film formation and properties was investigated. CrxN-coated steel samples were analysed by atomic force microscopy to gather information about morphology changes. In addition, they were investigated with respect to mechanical and corrosion behaviour. The results are discussed in terms of the effect of the ion-induced microscopic changes on the macroscopic properties. It was found that higher ion energy as well as higher ion incidence angle resulted in distinct improvements in corrosion behaviour. Better corrosion behaviour is combined with lower hardness improvements. (C) 1999 Elsevier Science S.A. All rights reserved.