Effect of Ruthenium on Microstructure and Stress Rupture Properties of a Single Crystal Nickel-Base Superalloy

Abstract

The effect of Ru on microstructure and stress rupture properties of an advanced Ni base single crystal alloy has been investigated. The experimental results showed that the addition of 4 wt.% Ru had hardly effect on the phase precipitation behavior of as-cast alloy, i. e., the microstructure is composed of γ and γ' phases for both Ru free and Ru containing alloys. However, under the heat treatments of 1305℃-1315 /16h ℃ solutioning and 1140℃/4h＋ 870 /20h ℃ aging, and the thermal exposure under 1100 /1000h, ℃ the addition of 4 wt.% Ru restrained the precipitation and growth of TCP phase evidently, and increased the rafting structure tendency of γ/γ' phases. The results of stress rupture tests showed that the addition of 4 wt.% Ru in the alloy improved the stress rupture lives significantly for as-cast, as-heat treated and thermal exposed samples. The improvement of the stress rupture properties may be attributed to the restraint of μ phase precipitation and growth by the proper addition of Ru.

Formation and effect of topologically close-packed phases in nickel-base superalloys

“…[31][32][33][34][35] Fig. 3 also illustrates that the interpretation of the significance of observed results varies in the literature; for example, Han et al 30 concluded that there was evidence for reverse partitioning on addition of 1.49 at.% Ru to their alloy, whereas Reed et al 31 concluded that there was no evidence on addition of 1.26 at.% Ru to a different alloy. This is reflected by the relative behaviour of the Al partitioning ratios but, when considering γ-partitioning elements, the relative change in the W and Re ratios suggests that the former are ascribing greater significance to a similar magnitude of change than the latter.…”

“…This is reflected by the relative behaviour of the Al partitioning ratios but, when considering γ-partitioning elements, the relative change in the W and Re ratios suggests that the former are ascribing greater significance to a similar magnitude of change than the latter. It is worth considering also the variation in techniques used to measure the compositions in each of these investigations, from inductively-coupled plasma spectroscopy after extraction of the γʹ 30 to atom probe tomography 31 . The different levels of accuracy inherent in these techniques may explain some of the variation displayed in Fig.…”

Room temperature deformation in the Fe7Mo6 μ-Phase

“…On the other hand, this can be inhibited due to good interfacial strength towards the matrix or a γ'-film enclosing µ-phase particles (Simonetti and Caron, 1998;Wang et al, 2010;Yang et al, 2006). During creep of γγ'-superalloys, μ and other TCP phase precipitates have been observed to accelerate rafting (Zhao and Dong, 2012) and to distort the unrafted (Pyczak et al, 2000;Yang et al, 2007) and, more severely, rafted microstructures (Han et al, 2008;le Graverend et al, 2011;Moverare et al, 2009;Simonetti and Caron, 1998;Sugui et al, 2010). However, while in most studies the µ-phase precipitates are assumed not to deform themselves, ductility of needle shaped precipitates has indeed been found (Qin et al, 2009;Yang et al, 2006) and no detrimental effect on the tensile strength was found during high temperature tensile testing (Chen et al, 1980;Tawancy, 1996).…”

“…Particularly the mechanisms by which µ-phase precipitates affect creep at high temperatures are still under discussion (Cheng et al, 2011;Epishin et al, 2010;Han et al, 2008;He et al, 2005;Moverare et al, 2009;Simonetti and Caron, 1998;Sugui et al, 2010;Volek and Singer, 2004;Wang et al, 2010;Yang et al, 2006). Le Graverend et al (le Graverend et al, 2011) have conducted FEM calculations of nickel-based superalloys considering plasticity of µ-phase precipitates at higher temperatures.…”

The promotion of Ru on topologically close-packed phase precipitation in the high Cr-containing (∼9wt.%) nickel-base single crystal superalloy

“…However, Walston et al supported the "reverse partitioning" theory by studying lowCr-containing (2wt.%) and Ru-containing (0~6wt.%) superalloys [14]. Ofori et al [15] and Han et al [16] proved the "reverse partitioning effect" of high level of Ru content in the non-Cr-containing and in the low-Cr-containing superalloys. Ru has a tendency to partition into g matrix and has a strong preference to occupy Al sites.…”