Microstructure,creep properties,and rejuvenation of service-exposed alloy 713C turbine blades |
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Authors: | T M Maccagno A K Koul J -P Immarigeon L Cutler R Allem G L’espérance |
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Affiliation: | (1) Structures and Materials Laboratory, Institute for Aerospace Research National Research Council of Canada, K1A 0R6 Ottawa, ON;(2) Department of Metallurgical Engineering, école Polytechnique de Montréal, PQ H3C 3A7 Montréal, Canada |
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Abstract: | A study was carried out on the microstructure and creep properties of aero engine first-stage turbine blades made from Alloy
713C nickel-base superalloy. Results are reported for new blades, blades in two service-exposed conditions, and service-exposed
blades subjected to one of three rejuvenation treatments: a recoating heat treatment, a hot isostatic pressing (HIP) + recoating
heat treatment, and a HIP + controlled cooling + recoating heat treatment. The blade microstructure undergoes significant
change during service, and this leads to a loss in creep properties exhibited by specimens machined from the blade airfoils.
Good correlations were observed between the rupture time and the amount of blade airfoil untwist and between the minimum creep
rate and the amount of untwist. The recoating heat treatment and the HIP + controlled cooling + recoating treatment were moderately
successful in restoring the microstructure and creep properties of the service-exposed blades. In comparison, the HIP + recoating
treatment was very successful in rejuvenating creep properties but only for blades having a chemical composition with a lower
propensity to form σ phase. For the blades with an unfavorable composition, σ phase was found to form preferentially near
the grain boundaries during creep testing, and this had a detrimental effect on the creep properties. Nonetheless, the degree
of rejuvenation for these blades was always at least as good as that obtained through the recoating heat treatment alone.
Formerly National Aeronautical Establishment |
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