"Direkte Bewertung der Kriechfestigkeit einer gerichtet erstarrten Turbinenschaufel mittels Minikriechproben

Abstract

The present paper presents a novel approach which allows a direct assessment of the creep strength of thin walled DS turbine blades at temperatures up to 1100 °C using a grain morphology sensitive miniature creep specimen test technique. The work builds up on earlier investigations by DeMestral and co‐workers ([i] B. DeMestral et al., Met. and Mat. Transactions A, 27A (1996) pp. 879–890 and [ii] B. DeMestral and G. Eggeler, Prakt. Metallogr., 29 (1992) pp. 174–191) on the influence of grain morphology on creep deformation and damage accumulation in superalloys with elongated macrograins. The paper reports the important features of this new procedure which include (i) the creep test technique (specimen geometry and grip design) and (ii) the removal of creep specimens from a DS CM 247 LC cast blade with respect to the morphology of the macrograins. The paper also reports creep results obtained with this new technique at temperature of 1030 °C and a tensile stress of 180 MPa and discusses the results on the basis of the associated microstructural creep deformation and damage mechanisms.

Novel experimentation techniques to study damage accumulation and microstructural instability during creep of super alloy single crystals at high temperatures (>1000°C)

“…Our miniature creep samples 4,7,17,18 are dog bone type specimens with a gauge length of 9 mm and a crosssection of 263 mm. Grips were machined by spark erosion from the oxide dispersion strengthened (ODS) alloy PM3030 obtained from Plansee (Reutte, Austria).…”

“…This early strain range must be subtracted from the miniature tensile specimen creep data which for strains in excess of 0?2% yields reliable creep data. All other details are reported elsewhere 4,7,[17][18][19] and sets of creep data obtained with our miniature creep specimen for ,100., ,110. and ,111. tensile directions from the 1000uC regime for the Ni base super alloy LEK 97 have been published elsewhere. 4…”

“…We have described the potential of the two techniques considered here for engineering purposes (property assessment, benchmark information for multiaxial loading conditions) in previous publications. 7,18 In the following we present two examples for new microstructural results which can be obtained using miniature tensile creep and double shear creep specimens.…”