Nickel base gamma prime strengthened superalloy

Abstract

A nickel base gamma prime strengthened superalloy with a unique blend of high hot corrosion resistance, high oxidation resistance, high coating compatibility, good weldability, high phase stability and at least moderate creep resistance is disclosed. The composite includes: Up to 20 wt % Co, between 17 and 21 wt % Cr, between 2 and 5 wt % of Mo+W+Re, at most 2 wt % Mo, between 4 and 4.7 wt % AL, between 3 and 7 wt % Ta, 0.01 and 0.2 wt % Ta, between 0.01 and 0.3 wt % of C+Zr+B between 0.05 and 1 wt % Hf, between 0.05 and 1 wt % Si, and between 0.01 and 0.2 wt % of the sum of rare earths such as SC, Y, the actinides and the lanthanides. The composition is intended for use as base alloy for moderately stressed hot components and as filler alloy for cladding and weld repair in moderately stressed parts of hot components.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is the US National Stage of International Application No. PCT / EP2009 / 052341, filed Feb. 27, 2009 and claims the benefit thereof. The International Application claims the benefits of European Patent Office application No. 08003904.3 EP filed Mar. 3, 2008. All of the applications are incorporated by reference herein in their entirety.FIELD OF INVENTION[0002]The present invention relates to a nickel-base gamma prime strengthened superalloy. It further relates to its use in hot components such as, but not restricted to, vanes, heat shields, sealings and combustor parts in gas turbines. It further relates to its use as filler alloy for cladding and repair of hot components such as, but not restricted to, blades, vanes, heat shields and combustor parts in gas turbines. It further relates to its use in equiaxed, directionally solidified or monocrystalline form.BACKGROUND OF INVENTION[0003]Gamma prime strengthened nickel-base sup...

AI Technical Summary

Benefits of technology

[0040]None of the alloys above provide a blend of high hot corrosion resistance, high oxidation resistance, high coating compatibility, good weldability, high phase stability and at least moderate creep resistance, and it is an objective of this invention to provide such a blend.

[0042]Consider a component and a hot spot on said component. A base alloy with this blend of properties would provide a higher cyclic life for an applied thermal barrier coating than an Ti rich alloy such as IN939, and, would provide a longer residual life if spallation occurs.

[0043]Consider further a component cast in a Ti rich alloy such as IN939 and protected by a thermal barrier coating, and that said component has suffered local spallation of this thermal barrier coating at a hot spot, leading to oxidation damage. Weld-repair with a filler alloy having the said blend of properties would result in locally improved resistance to spallation of the thermal barrier coating when re-applied after weld-repair, and, increased residual life if spallation occurs.

[0044]Base and filler alloys with this blend of properties will also provide better robustness in corrosive environments than high Mo content alloys such as U-700, or low Cr content alloys such as Mar M-247. Further, they will provide better dimensional stability than a weak alloy such as Haynes-214.

[0046]In the present invention, the requirements on high hot corrosion resistance, high oxidation resistance, high coating compatibility, good weldability, high phase stability and at least moderate creep resistance are met through the use of moderate levels of Al and Ta, high levels of Cr, multiple reactive elements, moderate levels of matrix strengthening elements like Mo, W and Re, a particular restriction on the level of Mo, and by avoiding detrimental gamma prime strengthening elements like Ti and Nb.

[0047]The idea is that moderate levels of Al and Ta are sufficient to enable formation of an adherent continuous AL2O3 scale thanks to support from high levels of Cr, multiple RE effects and that we avoid detrimental elements like Ti and Nb. Therefore, the gamma prime content is kept sufficiently low to allow for good weldability. Further, moderate levels of matrix and gamma prime strengthening elements enable moderate creep strength. Further, high levels of Cr and a strict limit on Mo enable high hot corrosion resistance. Further, high levels of Cr can be tolerated from a phase stability point of view because the gamma prime content and the amount of matrix strengthening elements are moderate. Further, high coating compatibility is enabled by avoiding detrimental elements like Ti and Nb, and, by a combination of clean casting and the use of RE to neutralize any remaining S.

Problems solved by technology

Consider further a component cast in a Ti rich alloy such as IN939 and protected by a thermal barrier coating, and that said component has suffered local spallation of this thermal barrier coating at a hot spot, leading to oxidation damage.

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