SEDL / STP / STP1263-EB / STP16444S

Thermo-Mechanical Fatigue of the Monocrystalline Nickel-Base Superalloy CMSX-6

Kraft, SA
Research Associate and Professor, Institut für Werkstoffwissenschaften, Lehrstuhl I, UniversitÄt Erlangen-Nürnberg, Erlangen,

Mughrabi, H
Research Associate and Professor, Institut für Werkstoffwissenschaften, Lehrstuhl I, UniversitÄt Erlangen-Nürnberg, Erlangen,

Pages: 14    Published: Jan 1996

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Abstract

Total strain-controlled thermo-mechanical fatigue (TMF) tests were performed between 600 and 1100‡C on as-grown near to [001]-orientated specimens of the γ′ precipitate-strengthened monocrystalline nickel-base superalloy CMSX-6. The strain-temperature cycle (in-phase, out-of-phase, diamond) has a strong influence on the mechanical and microstructural events occurring during TMF. For given temperature intervals, the fatigue lives were shortest for out-of-phase tests and longest for in-phase tests, respectively. For all cycle shapes applied, the maximum tensile stress level was concluded to be the lifetime-limiting factor. The failure mode of the investigated alloy depends also on the conducted strain-temperature history. While strongly localized crystallographic shearing along {111} planes was dominant for in- and out-of-phase cycling, creep-induced damage occurred in diamond cycle tests. The evolution and coarsening of the microstructure were also studied. The latter is compared with the formation of stress-, strain- and diffusion-induced coarsened raft-like structures found in creep testing of similar materials.