Speaker：Prof. Uwe Glatzel

         University Bayreuth, Germany

Time: 9:00-10:30 am. Sept.30^th, 2013

Venue：Room 468, Lee Hsun Building

Abstract:

Depending on application, high temperature alloys have to fulfill various demands. The most important requirements are: 1) high temperature mechanical strength (often determined by creep experiments); 2) oxidation resistance; 3) a certain amount of ductility in the whole temperature range; 4) low density, especially for rotating parts, and last but not least: 5) avoiding alloying elements which are expensive and/or prone to stock market speculations.

Examples of different development strategies for alloys having an fcc matrix with a coherently embedded L1₂ ordered γ' phases for strengthening will be presented.

Extremely good oxidation and corrosion resistant alloys are based on platinum group metals, with the two big disadvantages of being exceedingly expensive and heavy. Pt-based superalloys have been developed in cooperation of research groups in Tsukuba (Japan), Johannesburg (South Africa) and Bayreuth (Germany). They show an extremely good creep resistance in a temperature window in-between 1250°C and 1350°C due to the increased solvus temperature of the Pt₃Al γ' phase.

In order to reduce density, a Re-reduced Ni-base superalloy has been developed and put into service: LEK 94 in cooperation with MTU Aero Engines, Munich, Germany. This alloy is currently "flying" in the GP7270 engine for the Airbus A380. Recently, research projects have started in order to further reduce or even set to zero the content of Re. Target is to find Re-free alloys with comparable creep strength as Re-containing 2^nd generation Ni-base superalloys.

A brief outlook will be given towards the development of alloys with temperature capabilities beyond nickel-base superalloys, such as Mo-Si-B and Co-Re alloys.