Dedicated to Prof. Wolfgang Bunk on the occasion of his 70th birthdayThe efficiency and performance of advanced aircraft turbines can be markedly increased if higher gas temperatures are used. Although the highly loaded blades and vanes in the high pressure turbine are heavily cooled, today's substrate materials are unable to provide sufficient strength in the temperature range up to 1500 "C and above. If thermal barrier coatings (TBCs) are applied on superalloy turbine blades a substantial temperature drop of the parts can be achieved. The resulting increase in efficiency comes from reduced cooling andlor increased gas turbine inlet temperatures of up to 150°C. TBCs are either processed by plasma spraying (PS) or electron beam physical vapour deposition (EB-PVD). While PS is lower in cost EB-PVD leads to superior strain and thermoshock tolerant coatings. Furthermore, cooling hole closure of turbine blades and vanes is prevented and aerodynamic design maintained. Finally, future research and development needs in TBC technology are stressed.Die Verbesserung des Wirkungsgrades stationarer wie auch fliegender Gasturbinen erfordert eine Erhohung der ProzeRtemperaturen und damit auch der Werkstoffeinsatztemperaturen. Trotz aufwendiger Kuhlung und einkristalliner Bauweise stoRen die hochstbeanspruchten rotierenden Teile in der Turbinedie Turbinenschaufelnheute an Einsatzgrenzen, die durch den Schmelzpunkt der Ni-Superlegierungen vorgegeben sind. Hier haben Warmedammschichten eine zentrale Bedeutung erlangt. Aufgrund der im Vergleich zum Substrat aul3erst geringen Warmeleitfahigkeit dieser keramischen Schichten lassen sich bei innengekuhlten Turbinenschaufeln Gastemperaturerhohungen von bis zu 150 "C erzielen. Warmedammschichten werden primar durch thermisches Spritzen (PS) oder Elektronenstrahlverdampfung (EB -PVD) hergestellt. Wahrend PS kostengunstiger ist, weisen EB-PVD-Warmedammschichten ein uberlegenes Schadenstoleranzverhalten auf. Zudem werden durch das Aufdampfen die Kuhlluftbohrungen nicht verstopft, und aerodynamisch glatte Oberflachen bleiben erhalten. Zum SchluR wird ein Ausblick auf Forschungs-und Entwicklungstrends in der Warmedammschichttechnologie gegeben.

Butt welds of 1.6 mm thick 6013‐T6 sheet were produced using laser beam welding and friction stir welding processes. Employing the former joining technique, filler powders of the alloys Al‐5%Mg and Al‐12%Si were used. Microstructure, hardness profiles, tensile properties and the corrosion behaviour of the welds in the as‐welded condition were investigated. The hardness in the weld zone was lower compared to that of the base material in the peak‐aged temper. Hardness minima were measured in the fusion zone and in the thermomechanically affected zone for laser beam welded and friction stir welded joints, respectively. Metallographic and fractographic examinations revealed pores in the fusion zone of the laser beam welds. Porosity was higher in welds made using the filler alloy Al‐5%Mg than using the filler metal Al‐12%Si. Transmission electron microscopy indicated that the β″ (Mg2Si) hardening precipitates were dissolved in the weld zone due to the heat input of the joining processes. Joint efficiencies achieved for laser beam welds depended upon the filler powders, being about 60 and 80% using the alloys Al‐5%Mg and Al‐12%Si, respectively. Strength of the friction stir weld approached over 80% of the ultimate tensile strength of the 6013‐T6 base material. Fracture occurred in the region of hardness minima unless defects in the weld zone led to premature failure. The heat input during welding did not cause a degradation of the corrosion behaviour of the welds, as found in continuous immersion tests in an aqueous chloride‐peroxide solution. In contrast to the 6013‐T6 parent material, the weld zone was not sensitive to intergranular corrosion. Alternate immersion tests in 3.5% NaCl solution indicated high stress corrosion cracking resistance of the joints. For laser beam welded sheet, the weld zone of alternately immersed specimens suffered severe degradation by pitting and intergranular corrosion, which may be associated with galvanic coupling of filler metal and parent material.

Das Reihriihrachwcil~cn (friction \tir welding FSW) ist cin ncues Fiigeverfahren, init dcm such die achwer schiiielzscliweil~b~iren, hiiherfesten Aluminitimlegiertiiigeii ohnc grolk Festigkeitsverluste verschwci0t werden kiinncn. Erstc Ergebniw von Untcrsuchungen an sc I bs t hergea t el I ten FS W -S t um pfnii h ten der A I u mi n i um Icgierungen 2024-T3 und 60 I3-T4 werden vorgcstellt. Zuniichst wird das Gefiige der Naht und der Wiirmeeintlul~zone mikrostrukturell und durch Hiirtcvcrliiufe charakterisiert. Weitcrhin wird rnit Zug-, Schwingfestigkeits-und Ril.ifortscliritlsver~uclicn nachgewiesen, daB insbesondere die FSW-Niihte der Legicrung 2024-T3 aulierordentlich Iiohc mechanische Belaslungen crtragen. Ab-schlieRende Korrosionsuntersuchungcii dcr FSW-Niihte xigen c Anliilligkeit der ~ibschrcckciiipfiiiclliehen Legierung r interkristallinc Korrosion und Schiclitkorrosion.

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