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This paper deals with the results of combining Ti1 − xAlxN coatings with a subsequent electron beam surface-hardening process. The coatings - differing in their chemical composition (Al = 17EL30 at.%; Ti = 18EL30 at.%) and thickness (1-6 mm) - were deposited by reactive magnetron sputtering onto the heat-treatable steel 51CrV4. During electron beam hardening (EBH), a special energy transfer field causes an isothermal surface temperature distribution. By varying energy input and interaction time, the resulting hardening depth could be adjusted in the range of 0.1 to 0.4 mm. The results are characterised by means of optical and scanning electron microscopy, hardness measurements and the evaluation of the chemical composition of the coatings by glow discharge optical spectroscopy. The load supporting capacity and the adhesion of the hard coatings was determined using scratch tests with increasing load. The chemical composition and thickness of the coatings applied by physical vapour deposition (PVD) significantly affected the results of subsequent EBH. Hardening depth increased with the increasing thickness and increasing Al content of the PVD layer. Furthermore, the coatings exhibited increasing resistance against thermal stress during EBH for decreasing layer thickness and increasing Ti content. Load support of the base material was improved by a factor of 2 to 3. Therefore, the duplex treatment PVD + EBH has a high potential for industrial application with respect to locally highly loaded components.

Subsequent EBH improves the load-supporting capacity of PVD-coated steels. The influence of the chemical composition and layer thickness of Ti1−xAlxN coatings on the results of EBH was investigated. Increasing Al contents, along with increasing layer thicknesses improve the heat input during EBH. It is possible to harden the steel through the PVD layer without negative influences on the metastable coatings.

Ti-Al-N films with different compositions were prepared by varying the nitrogen flow rate using pulsed magnetron sputtering and subsequently annealed in air at 700 °C. The microstructure and microhardness of the films were investigated before and after heat treatment. The XRD results indicate that noTi2AlN MAX phase occurs in all the as-deposited films. Ti2AlN phases could be acquired only after annealing via solid state reaction. The formation condition of Ti2AlN phase is strongly dependent on the film composition. It has been found that the nitrogen concentration in the films plays a key role for the phase formation, and the critical value is in the range of 22.5-29.6 at.%. The fractured cross-section SEM images show that all the as-deposited films exhibit a fine columnar morphology. The annealed films with Ti2AlN phase components change the morphology from columnar to fine equiaxed polycrystalline. In addition, the microhardness of the films containing Ti2AlN phase is also explored, which is within the range of 18 - 24 GPa.

Current technologies for producing self-cleaning or low adhesion coatings have limitations,- PTFE is relatively soft, and while CrN is on the other hand very hard, but not stable in the long term. Diamond-like carbon coatings (DLC) have the advantage that their very hard basic structure can be modified by including other elements to give low surface energy, increased hardness or other desired properties. Multi-layer coatings can combine the properties of different modifications, while structured coatings imitate lotus-leaf properties. Practical applications include the reduction of material adhesion on stamps used in tablet production as well as the reduction of fouling on heating elements. In the case of heat exchangers, fouling still occurs on the DLC coated surfaces, but the poor adhesion allows it to be stripped off by the water flow or by thermal stresses. 'Sicon' (a-C:H:Si:O) has a rather low surface energy and is considerably harder than PTFE. With hard coatings such as Sicon (a-C:H:Si:O) or Sican (a-C:H:Si) mechanically and chemically stable coating materials with low surface energies are available. If the base material is soft and the abrasive particles are much larger than the thickness of the coating, the particles can penetrate the coating and destroy it. The ideal case would be to know the complete system hardness of the base material, particle size, the bonding links and the adhesion of the soiling. Modified DLC coatings are prepared by Plasma-Assisted Chemical Vapour Deposition (PACVD) processes. DLC coatings can be prepared as monolayers as well as multi-layers. Multi-layers can combine the properties of the individual layers and thus optimise the coating system. In order to investigate the fouling on surfaces, heat exchanger plates were covered with different types of DLC-based coatings.

Werkzeuge für die Zerspanung sind hohen mechanischen und thermischen Beanspruchungen ausgesetzt. Infolge höherer Bearbeitungsgeschwindigkeiten und neuartiger Werkstückmaterialien nehmen die Anforderungen an Leistungsfähigkeit und Verschleißbeständigkeit der Werkzeuge ständig zu. Um ein wirtschaftliches Bearbeitungsergebnis zu erlangen, muss der Schneidstoff daher ein breites Anforderungsprofil erfüllen. Ein sehr interessantes Material für Zerspanwerkzeuge ist das superharte kubische Bornitrid (cBN). Dieses nach Diamant zweithärteste aller bekannten Materialien ist aufgrund seiner besonderen Eigenschaftskombination, z. B. hohe Warmhärte, hoher Verschleißwiderstand und hohe Oxidationstemperatur besonders gut als Hochleistungsschneidstoff in der spanenden Metallbearbeitung geeignet.

By combining nano-scale surface roughening with a hydrophobic a-C:H:Si:O coating, we generated the super-hydrophobic surface with very low wetting angle hysteresis. We focused on the effect of the dual structure of the surface on the static and the dynamic wetting behaviours. It was observed that the dual rough surface is super-hydrophobic with a wetting angle around 160° and a wetting angle hysteresis (difference between forwarding and receding angle) less than 5°. On the other hand, mono rough surfaces in any scale appeared sticky and the wetting angle hysteresis ranged from 30° to 60° depending on the dimension of the surface roughness.

Hard carbon coatings (DLC) with a low friction coefficient are an effektiv way to reduce wear and the use of lubricants in many tribological applications. Despite of well known material and film properties the calculation of efficiency and lifetime of coated systems is today not possible. Therefore coatings are normally used as a less-than-ideal solution when products not longer work because of increasing demands.This means high costs and a long time for the optimization of coatings for every especial application. Using finite-element methods for the calculation of coated surfaces under stress DLC coatings can be used as a new design element for creating new products with new functions. This will be an effective way for engineers to optimize their tribological systems.

Thick c-BN films (up to 2.7 m) were deposited onto Si substrates by an r. f. diode apparatus using boron carbide (B4C) targets. The c-BN films were deposited on a compositionally graded interlayer, which consisted of B, C and N. A thin B4C layer (~200 nm) had been initially deposited onto Si substrate in a pure Ar gas discharge. The following formation of the graded interlayer was conducted by step-like or smoothly replacing Ar with N2 gas. Depending on the method implemented, the secondary ion mass spectroscopy (SIMS) depth profile showed relatively smooth or step-like changes in the elemental concentration of B, C and N. The primary analysis on the chemical bond of the graded interlayer was conducted by measuring the chemical shift of B1s, C1s and N1s spectra by X-ray photoelectron spectrometry (XPS). It is shown that the B-C bond, which was a major bonding component in the B4C layer, was gradually replaced by a mixture of B-N and C-C bond as the N2 fraction was increased. Transmission electron microscopy (TEM) images of the gradient layer showed that (0002) oriented turbostratic BN (t-BN) structure started to appear after the N2 concentration was increased by more than 2 %. It was also observed that the c-BN phase nucleated non-uniformly in the gradient layer at 1 % of N2 fraction.

Coatings of cubic boron nitride (cBN), the second hardest of all known materials, were prepared using a sputter process.A new coating design, based on a special B-C-N layer system, allows to deposit thick (> 2µm) cBN films, however so far only on silicon substrates. The properties of the coatings are quite similar to those of bulk cBN. Promising experiments wer performed with respect to a transfer of this application relevant layer system to cemented carbide and steel substrates. First measurements of the mechanical and tribological properties confirmed the outstanding properties and the high potential of such cBN based coating systems.

Deposition of cBN films was carried out in a R.F. diode sputtering apparatus with an auxiliary magnetic field using a boron carbide (B4C) target. Adhesion of the cBN films was vastly improved by a compositional gradient layer which contains B, C and N. By employing this interlayer, the deposition of thick (up to 2 µm) and stable cBN films were enabled. The SIMS depth profile measurements revealed that the gradient layer system started with a boron carbide layer, which is the first layer on the substrate, and had a composition approximately that of B4C. At the interface between the B4C and the cBN layer, a step-like or continuous increase of N was clearly visible while B and C decreased, respectively. From the IR spectra of each gradient layer step, the B-C bonding was observed for the B4C layer and was gradually replaced by sp² B-N as the N concentration was increased. The gradient layer system exhibited relatively high plastic hardnesses ranging from 24 to 30 GPa. The IR spectra of thick films showed that these films contain a high amount of cBN phase. The X-ray diffraction confirmed that the film was predominately cBN and was [110] textured. The hardness measurements carried out by nano-indentation showed that these cBN layers have a hardness of up to 60 GPa. The suface morphology was observed by AFM and the surface roughness increased with increasing coating thickness. Based on the results of structural and mechanical property analysis, a primary mechanism for adhesion improvement will be proposed.

Adhesion of cBN films on silicon substrate was vastly improved by the introduction of a compositional gradient layer which contains B, C and N. The cBN films were prepared by reactive sputtering using a boron carbide (B4C) target. By employing this gradient layer, deposition of thick (up to similar to 1,6 mu m) and stable cBN films was realized. Infrared (IR) spectra of thick films showed that the films contain a large amount of cBN. Secondary ion mass spectrocopy (SIMS) measurements confirmed that the gradient layer system starts from a B4C layer on the substrate followed by a subsequent step-like increase in the amount of N, while the amount of B and C decreased. Measurement of hardness by nano-indentation showed that these films have hardness up to 60 GPa. Superior performance against abrasive wear compared to hard nitride coatings was clearly demonstrated by the abrasive wear tests.

Superharte Schichten aus Diamant und c-BN zeichnen sich durch hervorragende tribologische, aber auch elektronische und optische Eigenschaften aus. Nicht zuletzt durch eine intensive Förderung des BMBF konnten in den letzten Jahren erhebliche Fortschritte auf dem Gebiet der superharten Schichten erzielt werden. Die Abscheidung von Diamant auf Hartmetall- und Keramikwerkzeugen ist gelungen. Die große Leistungsfähigkeit CVD-diamantbeschichteter Werkzeuge wurde in einigen Bereichen erfolgreich demonstriert. Bei der Abscheidung auf Stahl konnten entscheidende Fortschritte erzielt werden. Das Potential von Diamantschichten für elektronische Bauteile wurde an Teststrukturen aufgezeigt. Prototypen für Wärmesenken, Lithographiemaskenträger und Röntgenröhrenfenster konnten realisiert werden. Die Abscheidung von c-BN-Schichten befindet sich noch am Beginn der Entwicklung, bisher ist es gelungen 0,5 nm dicke Schichten abzuscheiden. Zukünftige Aufgaben liegen in der Ertüchtigung der Werkstoffe für die vielfältigen Anwendungen, der Bereitstellung einer Fertigungstechnologie und in der Untersuchung neuer superharter Werkstoffe wie dem theoretisch vorhergesagten Beta-C3N4.

PVD sputter deposition of cubic boron nitride (cBN) on Si(001) has been carried out using electrically conducting B4C as target material. While the target was powered with a r.f. generator the substrate electrode was connected to a d.c. power supply or a d.c.-pulse generator, respectively. The d.c. substrate bias was varied between -150... -200 V. As reactive sputter gas we used an Ar-N2 mixture with a N2 content of 10 per cent. The cBN content has been determined using the intensity ratio of the infrared absorption bands of the cubic (near 1100 cm(exp -1) and the hexagonal phase (near 1400 cm(exp -1), respectively. The thickness of the deposited films was about 0.2 mu m. The delamination process of films thicker than that has been studied using scanning electron microscopy (SEM). It turned out, that the beginning of the growth of the cubic phase could be correlated with an increase of the measured current at the substrate electrode. The reproducibility of the cubic fraction has been i mproved controlling this current. Additionally some results are presented from investigations, where the substrate electrode has been powered by a d.c.-pulse generator.

Cubic boron nitride (c-BN) is a superhard material with a high potential for applications in different fields. At present c-BN films are being prepared mainly by VD or PVD techniques. These techniques as well as the different methods used characterize the films will be discussed. Theoretical considerations have shown that a superhard carbon nitride phase C3N4 with mechanical properties equivalent to or even better than those of diamond can exist. In recent years there were many attempts to prepare carbon nitride coatings by PVD or CVD techniques. An essential problem is the incorporation of sufficiently high concentrations of nitrogen in the films. A clear evidence of crystalline Beta-C3N4 phases in C-N films is outstanding so far.