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Titanium nitride TiN, titanium boronitride Ti(B,N) and titanium carbonitride Ti(C,N) coatings were deposited by PA-CVD on tempering and stainless steel substrates. The deposition process can be supervised by OES. The coatings were characterized by XRD, SEM and WDS as well as hardness, adhesion and friction tests. Electrochemical impedance measurements and cyclic voltammetry in praxis relevant media were carried out. Mechanical and corrosion properties of the coatings can be controlled by the PA-CVD process parameters. The incorporation of chlorine in the coating can be varied by the process parameters with TiCl 4 or completely avoided using metallo-organic precursors. No influence of the chlorine content on the corrosion behavior was observed. Even coatings with extremely high chlorine content still exhibit an excellent corrosion resistance. Thus, the microstructure of the coating is the key to the corrosion properties of hard coatings on steel. A new micro electrochemical scanning droplet technique with a lateral resolution of 150 μm allows the investigation of TiN-coated substrates of complex geometry. The PA-CVD technique permits the deposition of dense and pinhole free coatings. On structures with simulated aspect ratios less than 3, a dense protective coating is proved. However, if the formation of micro pores is not suppressed by the optimal choice of deposition parameters, low-alloyed steel substrates corrode through pores, causing a detachment of the coating. On layers deposited on stainless steel, no sign of substrate corrosion could be detected. A model for the corrosion mechanism is given in Fig. 17.

Der heutige Stand der Technik in Aluminiumdruckgus erfordert den Einsatz von Formtrennmitteln. Zu deren Nebenwirkungen gehort aber eine Verschlechterung der Oberflachenqualitat des Gusteils. Formtrennmittel beeintrachtigen die Arbeitsplatzqualitat und sind unter okologischen Gesichtspunkten als bedenklich zu betrachten. Um den Einsatz von Trennmitteln zu vermeiden und gleichzeitig die Standzeit der Druckguswerkzeuge zu erhohen, wurden nitridische, karbidische und boridische Schichten auf Titanbasis mittels DC-Plus-PACVD abgeschieden und im Hinblick auf ihren Einsatz im Aluminiumdruckgus optimiert. Durch die Beschichtung konnte bei gleichzeitiger Steigerung der Qualitat der abgegossenen Teile die notwendige Trennmittelmenge um 97% reduziert werden. Die Standzeit der beschichteten Druckguskerne im Vergleich zu unbeschichteten erhohte sich durch die Beschichtung um uber das 300-fache. Application of Wear Resistant PACVD-Coatings in Aluminium Diecasting under Economical and Ecological Aspects Aluminium pressure diecasting is a frequently applied manufacturing process for the near netshape production of precision parts. State of the art production techniques still demand considerable amounts of die lubricants. But the side effects of these lubricants include a decrease in surface quality of the cast part as well as a prolongation of the casting cycle time. The job quality decreases and the waste and exhaust disposal during production and application of lubricants is ecologically risky. In this study different wear resistant coating systems have been developed in order to minimize the use of die lubricants in the casting process while at the same time increasing the service life of the diecasting tools. Nitrides, carbides and borides of titanium were synthesized by means of DC-pulse-PACVD. The influence of the process parameters gas composition, pressure, voltage and pulse/pulse repetition ratio was investigated. Compositional analysis was performed by analytical methods such as XRD, EDS, WDS and SIMS. Hardness, adhesion and friction behaviour of the layers were determined in order to describe their mechanical properties. The wetting angle was determined and the corrosion resistance was evaluated in dip tests in aluminium melt. A selection of the best coatings was then compared in diecasting praxis tests under tightened-up conditions reducing the amount of lubricants. TiN, Ti(B,N), TiC and multilayers of the system Ti-C-N were deposited exhibiting a wide range of stoichiometry. The coatings reached hardness values of up to 4400 HK0.005 and the friction coefficient μ was in the range of 0.3. In the diecasting praxis test the amount of die lubricant could be reduced by 97%. Under most severe conditions all layer types led to a minimum increase in the lifetime of the tool of factor 60 compared to an untreated dummy. A strong dependence on the layer type and on its stoichiometry could be observed. Ti(B,N) as the most successful coating in this study has not yet shown any sign of failure and already achieved an increase in lifetime of 300 times.

In dieser Arbeit werden zwei Verfahren zur Realisierung verschleis-und korrosionsbestandiger Oberflachensysteme beschrieben: Plasmadiffusionsbehandlung (PDT) und Plasmagestutztes CVD (PACVD). Neben den Plasmanitrierverfahren werden auch Plasmanitrocarburieren und Plasmanborieren von unterschiedlichen Substratwerkstoffen behandelt. Die Fortschirtte beim PACVD und die Entwicklung zu den Niedertemperaturbeschichtungsverfahren werden erlautert und Anwendungen dieser Techniken in der Industrie beispielhaft erwahnt. Develpoment of wear and corrosion resistant surface systems In this study two methods are described to realize wear and corrosion resistant surface systems: Plasma diffusion treatment (PDT) and Plasma assited CVD (PACVD). Plasma nitriding, Plasma nitrocarburizing and plasma boriding are used to treat different kinds of substrates. The advances of PACVD and the development of low temperature PACVD and industrial applications of these techniques are explained.