M. Ewering

Impact Behaviour of PtIr-Based Coatings with Different Interlayers for Glass Lens Moulding

Over the last decades demands for optical systems and complex optical products made of glass increased steadily. Precision glass moulding has a great potential for the bulk production of complex lenses with high precision and low costs. To prevent sticking or reactions between hot glass and moulding, and to reduce abrasive wear of the die a protective coating is deposited on the tool. In this research two coating systems suitable for this application are compared by analysing their behaviour under an impact load. The PVD (Physical Vapor Deposition) coating PtIr with two different bond coatings Ni or Cr is analysed. During impact test number of impacts and loads are varied. Compared to industrially used coating system PtIr with a Ni interlayer the adhesion can be improved by using a Cr interlayer. The PtIr-based coating with Cr as bond coating shows an excellent endurance even at very high loads causing Hertzian stresses in the range of 10 14 GPa. An impact load of 600 N which corresponds to a contact pressure of app. 13.2 GPa generates almost no damage after 200,000 impacts.

Metal flow and die wear in semi-solid forging of steel using coated dies

Thixoforging of steels is a potential forming technology, which aims at producing near-net-shaped components with good quality from high strength steels in one forging step. The thixoforging process parameters such as billet temperature, temperature distribution after reheating, argon gas pressure, transportation time and forging load were investigated on the thixoforging of non axis-symmetric parts of steel grade X210CrW12. The experimental and numerical study of the material flow and tool temperature load reveal the areas of intensive tool wear, thus being useful for further tool design. Hardened hot working steel X38CrMoV5-1 as a tool bulk material with protecting thin films of TiAlN/γ-Al2O3 shows good experimental results at 170 forging cycles.

Entwicklung neuer PVD-Beschichtungen

Der Leitgedanke des SFB 442 besteht in der Realisierung neuartiger umweltfreundlicher tribologischer Systeme. Bisherige tribologische Systeme werden hierbei derart modifiziert, dass die oberflachenaktiven Funktionen hochadditivierter mineralolbasierter und oftmals umweltbedenklicher Schmierstoffe auf die Werkzeug- und Bauteiloberflachen ubertragen werden. Hierzu war die Entwicklung innovativer Werkstoffverbunde erforderlich, die die Aufgaben wie Verschleisschutz, Reibungsminimierung und Korrosionsschutz ubernehmen konnen. Unter Werkstoffverbund sind in diesem Zusammenhang komplexe Systeme, bestehend aus Beschichtung und Grundwerkstoff zu verstehen, die entsprechend den auftretenden Beanspruchungen ausgelegt werden. Ein groses Potential bieten an dieser Stelle mittels PVD (Physical Vapour Deposition)-Technologien abgeschiedene Dunnschichtsysteme, da diese trotz geringer Schichtdicken (1–20 µm) beispielsweise einen hohen Verschleisschutz gewahrleisten. Das geringe Aufmas ermoglicht zudem die Beschichtung endkonturgetreuer Geometrien mit engen Form- und Mastoleranzen, sodass mechanische Nachbehandlungen nicht mehr erforderlich sind.