Rejuvenation of creep resistance of a Ni-base single-crystal superalloy by hot isostatic pressing. (15th November 2017)

• Record Type: Journal Article
• Authors: Ruttert, Benjamin; Bürger, David; Roncery, Lais Mujica; Parsa, Alireza Basir; Wollgramm, Philip; Eggeler, Gunther; Theisen, Werner
• Is Part Of: Materials & design. Volume 134(2017)
• Page Start: 418
• Page End: 425
• Publication Date: 2017-11-15
• Subjects: Creep -- Creep life -- γ/γ′-microstructure -- Hot isostatic pressing -- HIP -- Pores -- Rafting -- Rejuvenation -- Recrystallization -- Single crystal superalloy; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2017.08.059
• Languages: English
• ISSNs: 0264-1275

Abstract

Highlights: A single specimen is exposed to a creep-rejuvenation-creep test cycle. A hot isostatic press providing fast quenching rates is used for rejuvenation. Microstructural evolution before and after creep as well as, rejuvenation are studied. Focus is on the γ/γ′-microstructure, pores, dislocations, and recrystallization. The impact of rejuvenation on additional creep life is evaluated. Graphical abstract: Abstract: Ni-base single-crystal turbine blades are exposed to a combination of high temperatures and high stresses during their service life in high-pressure turbines of aero engines or stationary gas turbines. This unavoidably leads to various internal microstructural changes such as rafting and the formation of cavities. This study introduces a creep-rejuvenation-creep test cycle using one miniature Ni-base single-crystal creep specimen. A novel hot isostatic press providing high quenching rates was applied to rejuvenate the damaged microstructure of the specimen after the first high-temperature creep degradation before the same specimen was repeatedly creep-tested under the same initial creep conditions. After rejuvenating, microstructural results obtained from high-resolution microscopy prove that the creep cavities were closed, dislocation densities were re-set, and the original but now slightly finer γ/γ′-microstructure was restored without any recrystallization. The subsequent creep test of the rejuvenated specimen demonstrated that the proposed rejuvenation procedure in this work is a suitable method to reproduce the initial creep behavior and to thus prolong the lifetime of an already crept Ni-base single-crystal specimen.