Nickel-based superalloy welding filler

Abstract

A welding filler comprising the following components (in weight%) is proposed to significantly improve the weldability of some nickel-based superalloys: 14.6% to 15.6% chromium (Cr), 10.4% to 11.4% cobalt (Co), 4.6% to 5.0% molybdenum (Mo), 4.4% to 5.2% tungsten (W), 1.4% to 1.8% tantalum (Ta), 3.0% to 3.7% aluminum (Al), 0.7% to 1.3% titanium (Ti), 0.14% to 0.16% carbon (C), 0.0425% to 0.0575% zirconium, 0.7% to 1.2% hafnium (Hf), up to 0.15% iron, up to 0.1% manganese, up to 0.1% silicon, up to 0.1% vanadium, up to 0.015% boron, trace elements, and the remainder nickel.

Description

Technology Field Cross-references for related applications This application is a partial continuation of application No. 17 / 051,468 filed on October 29, 2020, which is the U.S. national phase of international application PCT / US2018 / 030385 filed on May 1, 2018, and claims the benefit of such application. All applications are incorporated herein by reference in their entirety. field

[0001] The present disclosure relates generally to the field of materials technology, and more specifically to nickel-based superalloy welding fillers. Background Technology Among all high-temperature materials, nickel-based superalloys possess the most favorable combination of mechanical properties, corrosion resistance, and machinability for gas turbine structures in aircraft and power plants. This is partly due to the fact that nickel-based superalloys can be strengthened by the precipitation of the γ phase. Nevertheless, cracks can still occur over time in nickel-based superalloy components operating in harsh environments, such as gas turbine engines. As the manufacturing of these components is complex and costly, efforts are being made to repair damaged sections of the components instead of discarding them as a whole. Therefore, welded nickel-based superalloy components are a desirable and cost-effective option for the refurbishment of nickel-based superalloy components.

[0002] However, welding nickel-based superalloy materials is known to be difficult. To avoid the difficult weldability of γ'-hardened nickel-based superalloys, welding is often performed using ductile welding fillers. Commonly used ductile welding fillers, such as IN-625, IN-617, Hast-W, and HA-282, were developed when gas turbine temperatures were relatively lower than those of current and future designs. When these ductile welding fillers are used in current gas turbine components that operate at increasingly higher operating temperatures than recent gas turbine components, they may not be able to withstand the oxidation that occurs at those higher operating temperatures.

[0003] For this reason, ductile weld fillers capable of withstanding higher temperatures than those used in the past are required.

[0004] Briefly, aspects of the present disclosure relate to a ductile weld filler and a method for welding nickel-based superalloy components. A first aspect provides a ductile weld filler having the following composition: 14.6 to 15.6 weight% of chromium; 10.4 to 11.4 weight% of cobalt; 4.6 to 5.0 weight% molybdenum; 4.4 to 5.2 weight% of tungsten; 1.4 to 1.8 weight percent tantalum; 3.0 to 3.7 weight percent aluminum; 0.7 to 1.3 weight% of titanium; 0.14 to 0.16 weight% carbon; 0.0425 to 0.0575 weight% of zirconium; 0.7 to 1.2 weight% of hafnium; Up to 0.15 wt% iron; Up to 0.1 wt% manganese; Up to 0.1 wt% silicon; Magnesium up to 70 ppm by weight; Up to 0.005 wt% sulfur; Up to 0.1 wt% vanadium; Up to 0.015 wt% of boron; and Remaining nickel. Brief explanation of the drawing

[0005] Figure 1 is a chart illustrating the relative weldability of various superalloys.

[0006] Figure 2 is a chart of the coefficients of thermal expansion of various welding fillers and superalloy base materials.

[0007] FIG. 3 illustrates a perspective view of a rotor blade or guide vane. Specific details for implementing the invention

[0008] To facilitate understanding of the embodiments, principles, and features of the present disclosure, they are described below with reference to implementations in exemplary embodiments. However, the embodiments of the present disclosure are not limited to use in the described systems or methods.

[0009] The components and materials described below as constituting various embodiments are intended to be exemplary rather than limiting. Many suitable components and materials that perform the same or similar functions as the materials described herein are intended to be included within the scope of the embodiments of this disclosure.

[0010] Now, referring to the drawings, where the showings are merely for the purpose of illustrating embodiments of the claimed subject matter of the present invention and for limitation purposes, FIG. 1 is a chart (100) illustrating the superalloy weldability of various base metals and weld filler materials as a function of their aluminum and titanium content. Generally speaking, the higher the aluminum content of the material, the more difficult it is to weld. Line (110) illustrates the recognized upper boundary of the weldability zone. Alloys above this line are recognized as difficult to weld. For example, as illustrated by the chart, Alloy-247LC is a very difficult alloy to weld, whereas IN-617 is easily weldable by the conventional TIG (tungsten inert gas) welding process. Regarding weld fillers, the chart also illustrates that HA-282 is easily weldable. To those with ordinary knowledge in the field of welding technology, HA-282 is a very good ductile weld filler, but this means it will not be able to withstand oxidation occurring at the relatively higher operating temperatures of current and future designs of gas turbine engines.

[0011] Alloy Rene-80 is a nickel-based superalloy that is a very popular aircraft engine base metal, but it has been proven to have limited oxidation in current gas turbine applications. IN-617 is a very ductile nickel-based superalloy weld filler. IN-617 is particularly useful because it exhibits increased ductility in the temperature range of 700 to 900 °C, which is the operating range for gas turbines, whereas most other superalloys exhibit decreased ductility in this temperature range.

[0012] The inventors recognized that the chemical composition of HA-282 is essentially a 50 / 50 (weight percentage) mixture of Rene-80 and IN-617 with some minor differences (e.g., W and Fe content). This is illustrated in Table 1 shown below, which lists the chemical compositions of base metal Rene-80 in line 1, weld filler IN-617 in line 2, a 50 / 50 (weight percentage) mixture of Rene-80 and IN-617 in line 3, and weld filler HA-282 in line 4. Table 1 thus, (1)

[0013] In current gas turbine castings, Alloy-247LC is the base metal selected because it can withstand continuously increasing gas turbine operating temperatures, which allow the gas turbine to operate more efficiently. Accordingly, the inventors propose replacing the base metal Rene-80 with Alloy-247LC in Equation (1) to arrive at a new ductile weld filler that is essentially a mixture of the base metal (Alloy-247LC) and the ductile weld filler (IN-617). Thus, the ductile weld filler of the present invention is described by Equation (2). (2) Ductile welding filler

[0014] The proposed weld filler is more oxidation-resistant than previously used weld fillers and is therefore much more compatible with currently used base metal alloys, such as Alloy-247LC and IN-738. For example, the properties of the ductile weld filler closely match those of Alloy-247LC and IN-738.

[0015] The proposed ductile weld filler comprises the following composition: 11.0 wt% to 15.5 wt% of chromium; 9.5 wt% to 11.0 wt% of cobalt; 2.0 wt% to 5.0 wt% molybdenum; 4.5 weight% to 7.5 weight% of tungsten; 1.5 wt% to 2.6 wt% tantalum; 3.0 wt% to 5.0 wt% aluminum; 0.4 wt% to 1.0 wt% titanium; Up to 0.8 wt% iron; Up to 0.3 wt% manganese; Up to 0.3 wt% silicone; Up to 0.1 wt% carbon; Up to 0.015 wt% of boron; Up to 0.02 wt% of zirconium; Up to 1.2 wt% of hafnium; Up to 0.1 wt% vanadium; Magnesium up to 0.1%; and Remaining nickel.

[0016] Table 2 below summarizes Ductilloy, SieWeld-A-247LC, SieWeld-B-247LC B, and SieWeld-C-247, which include three exemplary embodiments of ductile weld fillers (details in weight%), beneficial effects of each element on the alloy, and elemental ranges. Ductilloy and SieWeld-C-247 are essentially 50 / 50 (weight%) mixtures of Alloy 247 and IN-617. SieWeld-A-247LC essentially comprises a 75 / 25 (weight%) mixture of base metal Alloy 247 and weld filler IN-617, and SieWeld-B-247LC essentially comprises a 66.6 / 33.3 (weight%) mixture of base metal Alloy 247 and weld filler IN-617. Table 2 (All values ​​are in weight %)

[0017] It may be desirable for the weld filler to match the base metal to be welded as closely as possible in its composition and properties. For example, by matching the coefficient of thermal expansion of the weld filler to that of the base material as closely as possible, high stress levels resulting from differential thermal expansion can be avoided. Therefore, an example of the weld filler (SieWeld-A-247LC) will match the base metal Alloy-247 most closely. Currently, welding attempts made using conventional welding processes at room temperature with nickel-based superalloy base metals and weld fillers are not possible due to the formation of cracks in the heat-affected zone and weld metal.

[0018] Based on its ductility or tensile elongation, the proposed ductile weld filler will have good weld properties at room temperature. Additionally, based on its coefficient of thermal expansion, the ductile weld filler will have acceptable performance during turbine operation at elevated temperatures. FIG. 2 illustrates the coefficients of thermal expansion of several base metals, Alloy-247LC, IN-738, and Rene 80; weld fillers, IN-617 and HA 282; and the proposed weld fillers, Ductilloy / SieWeld-c-247, SieWeld-A-247LC, and SieWeld-B-247LC. FIG. 2 shows that the coefficients of thermal expansion of the proposed embodiments of the weld filler are nearly identical to the coefficient of thermal expansion of Alloy-247LC. It is advantageous to have a weld filler with a coefficient of thermal expansion that is nearly identical to that of the base metal, because the materials will be heated similarly during the welding process when high temperatures are applied to the alloys. By reducing the temperature difference between the weld joint and the substrate and the resulting stress gradient, cracks in the weld joint can be avoided.

[0019] In one embodiment, harmful trace elements that may have a detrimental effect on the properties of the weld filler composition are maintained at strict tolerances. These harmful trace elements may include silicon, carbon, boron, and zirconium. For example, the percentages of these elements should not exceed the concentrations listed in Table 2. In an alternative embodiment, (SieWeld-C-247) trace elements may be relaxed, that is, the tolerances are looser. In this alternative embodiment, the trace elements may include silicon, titanium, zirconium, carbon, and sulfur.

[0020] In one embodiment, materials, Mar-M-247, CM-247LC, PWA-1483, Alloy-247, IN-738, Mar-M002, Rene-N5, Rene-N4, CMSG-4, CMSG-2, Rene-142, GTD-111, MGA-1400 and IN-939 can be welded using the proposed ductile weld filler.

[0021] Referring again to FIGS. 1 and 2, a method for welding nickel-based superalloy components is proposed. The ductile weld filler described above is utilized for welding nickel-based superalloy components onto a substrate. The method comprises the step of applying the ductile weld filler to the surface of the substrate. The proposed ductile weld filler has a coefficient of thermal expansion that is nearly identical to the coefficient of thermal expansion of the substrate. Heat may be applied to the weld filler to melt the weld filler and form a molten weld filler. At ambient temperature, the molten weld filler is utilized to weld the substrate. The welded substrate is allowed to cool and re-solidify, thereby creating a solidified joint on the substrate. For the purposes of this disclosure, "nearly identical" refers to having a coefficient of thermal expansion within 3% of Alloy-247LC in the range of 600°C to 1000°C, which is the range in which gas turbines currently operate.

[0022] FIG. 3 illustrates a perspective view of a rotor blade (120) or guide vane (130) of a turbo machine extending along a longitudinal axis (121). The turbo machine may be a power plant for generating electricity or a gas turbine, steam turbine, or compressor of an aircraft. The blade or vane (120, 130) has a fixed area (400), an adjacent blade or vane platform (403), and a main blade or vane portion (406) continuously along the longitudinal axis (121). As a guide vane (130), the vane (130) may have an additional platform (not shown) at its vane tip (415). A blade or vane root (183) used to secure the rotor blades (120, 130) to a shaft or disk (not a shaft) is formed in the fixed area (400). The blade vane root (183) is designed, for example, in a hammerhead form. Other configurations, such as a fir-tree or dovetail root, are possible. The blade or vane (120, 130) has a leading edge (409) and a trailing edge (412) for the medium flowing through the main blade or vane portion (406). For example, in the case of conventional blades or vanes (120, 130), solid metallic materials, particularly superalloys, are used in all regions (400, 403, 406) of the blade or vane (120, 130). Thus, a ductile weld filler can be utilized, for example, to weld all regions of the blade or vane. Additionally, other combustion components can also be welded using the proposed ductile weld filler.

[0023] Although the embodiments of the present disclosure have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions may be made as set forth in the following claims without departing from the spirit and scope of the invention and its equivalents.

Claims

Claim 1 As a ductile weld filler material, (SieWeld C) 14.6 to 15.6 wt% chromium; 10.4 to 11.4 wt% cobalt; 4.6 to 5.0 wt% molybdenum; 4.4 to 5.2 wt% tungsten; 1.4 to 1.8 wt% tantalum; 3.0 to 3.7 wt% aluminum; 0.7 to 1.3 wt% titanium; A ductile weld filler material comprising 0.14 to 0.16 wt% carbon; 0.0425 to 0.0575 wt% zirconium; 0.7 to 1.2 wt% hafnium; up to 0.15 wt% iron; up to 0.1 wt% manganese; up to 0.1 wt% silicon; up to 70 ppm wt% magnesium; up to 0.005 wt% sulfur; up to 0.1 wt% vanadium; up to 0.015 wt% boron; and the remainder nickel. Claim 2 A ductile welding filler material according to claim 1, wherein the filler comprises 14.9 to 15.2 weight percent of chromium. Claim 3 A ductile welding filler material according to claim 1, wherein the filler comprises 4.6 to 4.9 weight percent molybdenum. Claim 4 A ductile welding filler material according to claim 1, wherein the ductile welding filler comprises powder. Claim 5 A ductile weld filler material according to claim 1, wherein the ductile weld filler comprises a wire.

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