Gamma Prime Morphology and Creep Properties of Nickel Base Superalloys with Platinum Group Metal Additions

Abstract

The microstructure and creep properties of platinum group metal (PGM) modified nickel based superalloys have been investigated. Alloys containing Pt and/or Ir along with variations in Cr, Ta, Re, Ru, and W exhibited relatively high solidus and liquidus temperatures. Differential thermal analysis (DTA) showed a strong dependence of the γ´ solvus on the level of Ta. The morphology of the γ´ precipitates was influenced by the presence of Cr, Ta, Ru, and W and ranged from cuboidal to semi-spherical. Compression creep tests were conducted at 1000°C at stresses ranging from 40-90 MPa. Alloys containing approximately 8 wt% Pt combined with Cr and Ta displayed the best resistance to creep deformation at stresses around 80 MPa. Post-creep analysis of the rafted structures indicated that all PGM modified alloys without Ru and W possessed positive misfit with magnitudes ranging from ≈ 0.3 to 1.5%. The partitioning of PGMs between the γ and γ´ phases and their resultant influence on creep performance is discussed.

Archives of Metallurgy and Materials

“…Creation of islands occurs due to complex chemical composition and the resulting microsegregation during solidification of superalloy. Volume fraction of eutectic islands is substantially higher in comparison with other nickel based superalloys [16].…”

High-Temperature Mechanical Behavior of End-of-Life Cryomilled NiCrAlY Bond Coat Materials

“…Consequently, a superior strength of the cryomilled material compared to the conventional material is observed at temperatures of 1173 K (900°C) and higher, even stronger than the as-deposited Pt modified bond coat. [6] Samples from Reference 14 also demonstrate the supremacy of the cryomilled bond coat materials in comparison with the conventional bond coats at high temperatures. It should be noted, however, that the strength was not determined with microsamples.…”

“…These bond coats have superior mechanical properties at high temperatures and strong oxidation resistance compared to MCrAlY bond coats. [6] Unfortunately, the lifetime of TBCs containing Pt modified bond coats can be limited due to the high-temperature martensitic phase transformation developing during service or thermal cycling. [7] The large strain cycles can lead to the formation of interface undulations, and as a result, the TBC can undergo spallation.…”

Oxide‐Assisted Degradation of Ni‐Base Single Crystals During Cyclic Loading: the Role of Coatings

“…The high‐temperature properties of the Pt aluminide bond coat measured in samples removed directly from coatings have been incorporated into the model 30 . While the properties of the interdiffusion zone have not been directly measured, the properties of alloys with compositions similar to those observed in the interdiffusion zone indicate that the creep rates are likely to be intermediate to those of the weak β‐coating and the precipitation‐strengthened superalloy 31 . To capture the lateral straining in the TGO, in the model, is imposed during those stages of the strain cycle when the crack is open.…”