Hard solder made of a nickel-based superalloy

Abstract

Ductile welding consumable, comprising: to 11.2 wt.%-15.6 wt.% chromium; to 9.6 wt.%-11.4 wt.% cobalt; to 2.4 wt.%-5.0 wt.% molybdenum; to 4.4 wt.%-7.5 wt.% tungsten; to 1.4 wt.%-2.6 wt.% tantalum; to 3.0 wt.%-4.8 wt.% aluminium; to 0.4 wt.%-1.0 wt.% titanium; to a maximum of 0.15 wt% iron; to a maximum of 0.1 wt% manganese; to a maximum of 0.04 wt% silicon; to 0.07-0.08 wt% carbon; up to a maximum of 0.015 wt% boron; to 0.005-0.02 wt.% zirconium; to 0.5-1.4 wt% hafnium; up to a maximum of 0.1 wt% vanadium; and as residual nickel.

Description

BACKGROUND 1. Subject

[0001] The present disclosure relates generally to the field of materials technology and in particular to a welding filler made of a nickel-based superalloy. 2. Description of the state of the art

[0002] According to the applicant's internally known prior art, of all high-temperature materials, nickel-based superalloys exhibit the most favorable combination of mechanical properties, corrosion resistance, and workability for gas turbine construction in aircraft and power plants. This is partly due to the fact that nickel-based superalloys can be strengthened by the precipitation of a γ' phase. Nevertheless, over time, cracks can still develop in nickel-based superalloy components operating in harsh environments, such as a gas turbine engine. Since the manufacture of these components is complex and costly, efforts are made to repair damaged sections rather than scrapping them entirely. Accordingly, welding nickel-based superalloy components is a desirable and cost-effective option for their repair.

[0003] Welding materials made from nickel-based superalloys is known to be difficult. To overcome the challenging weldability of γ'-hardened nickel-based superalloys, welding is often performed using ductile filler materials. Commonly used ductile filler materials, such as IN-625, IN-617, Hast-W, and HA-282, were developed when gas turbine temperatures were comparatively lower than current and future designs. When used on current gas turbine components operating at increasingly higher temperatures than those of the recent past, these ductile filler materials may not be able to withstand the oxidation that occurs at these higher operating temperatures. EP 3 153 271 A1 discloses a method for repairing and manufacturing turbine engine components using nickel-based filler material.US patent 9 902 021 B2 discloses a nickel-based welding material.

[0004] For this reason, there is a need for ductile welding consumables that can withstand higher temperatures than those used in the past. SUMMARY

[0005] In short, aspects of the present disclosure relate to a ductile welding filler and a method for welding components made of a nickel-based superalloy.

[0006] One aspect is the provision of a ductile welding additive which has the following composition: to 11.0 wt.%-15.5 wt.% chromium; to 9.5 wt.%-11.0 wt.% cobalt; to 2.0 wt.%-5.0 wt.% molybdenum; to 4.5 wt.%-7.5 wt.% tungsten; to 1.5 wt.%-2.6 wt.% tantalum; to 3.0 wt.%-5.0 wt.% aluminium; to 0.4 wt.%-1.0 wt.% titanium; to a maximum of 0.8 wt% iron; up to a maximum of 0.3 wt% manganese; to a maximum of 0.3 wt% silicon; to a maximum of 0.1 wt% carbon; up to a maximum of 0.015 wt% boron; to a maximum of 0.02 wt% zirconium; up to a maximum of 1.2 wt% hafnium; to a maximum of 0.1 wt% vanadium; to a maximum of 1 mg magnesium; and as residual nickel.

[0007] A second aspect presents a process for welding components made of a nickel-based superalloy. This process involves providing a nickel-based superalloy substrate for welding. For the welding process, a ductile filler metal, as described above, is applied to the surface of the substrate. This filler metal has a coefficient of thermal expansion precisely matched to that of the substrate. Heat is applied to melt the filler metal, forming a molten weld pool. The filler metal is then used in the welding process at ambient temperature. The molten filler metal can then solidify again, forming a hardened, joined material. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a diagram illustrating the relative weldability of different superalloys. Fig.Figure 2 is a diagram of the coefficient of thermal expansion of various welding consumables and superalloy base materials and Fig. Figure 3 illustrates a perspective view of a guide vane or a guide vane. DETAILED DESCRIPTION

[0008] To facilitate an understanding of the embodiments, principles, and features of this disclosure, these are explained below with reference to their implementation in illustrative embodiments. However, embodiments of this disclosure are not limited to use in the described systems or methods.

[0009] The components and materials described below as constituting the various embodiments are intended for illustration and not for limitation. Many suitable components and materials that would perform the same or a similar function as the materials described herein are to be included within the scope of the embodiments of this disclosure.

[0010] Now, referring to the figures, in which the representations serve only to illustrate embodiments of the subject matter within the scope of the present invention and not to limit it, Fig.Figure 100 illustrates the superalloy weldability of various base metal and welding filler materials as a function of their aluminum and titanium content. Generally, the higher a material's aluminum content, the more difficult it is to weld. Line 110 represents a recognized upper limit of a weldability range. Alloys above this line are considered difficult to weld. For example, as the diagram illustrates, Alloy-247LC is a very difficult alloy to weld, while IN-617 is readily weldable using a conventional TIG (tungsten inert gas) welding process. Regarding welding filler materials, the diagram further illustrates that HA-282 is readily weldable.For the welding professional, HA-282 is a very good ductile welding filler, but it will soon no longer be able to withstand the oxidation that occurs at the comparatively higher operating temperatures of current and future gas turbine engine designs.

[0011] Rene-80 is a nickel-based superalloy and a very popular base metal for aircraft engines, but it has proven to be oxidation-limited in current gas turbine applications. IN-617 is a very good ductile welding filler metal made from a nickel-based superalloy. IN-617 is particularly suitable because it exhibits increased ductility in the temperature range of 700–900 °C, a range in which gas turbines operate, while most other superalloys show a decrease in ductility in this temperature range.

[0012] The inventors of the present invention have recognized that the chemical composition of HA-282 is essentially a 50 / 50 mixture (in wt.%) of Rene-80 and IN-617 with some minor differences (the W and Fe content, for example). This is illustrated in Table 1 below, which lists the chemical compositions of the base metal Rene-80 in row 1, the welding filler IN-617 in row 2, the 50 / 50 mixture (in wt.%) of Rene-80 and IN-617 in row 3, and the welding filler HA-282 in row 4. Accordingly HA−282≈Rene−80+IN−617.

[0013] In current gas turbine castings, Alloy-247LC is a base metal of choice because it can withstand the ever-increasing gas turbine operating temperatures, which allow the gas turbines to run ever more efficiently. Accordingly, the inventors propose, according to the invention, to replace the base metal Rene-80 in equation (1) with Alloy-247LC to obtain a new ductile welding filler metal, which is essentially a mixture of the base metal Alloy-247LC and the ductile welding filler metal IN-617. The ductile welding filler metal according to the invention is accordingly described by equation (2). Ductile welding filler metal≈Alloy−247LC+IN−617.

[0014] The presented welding filler is more oxidation-resistant than those previously used and therefore more compatible with currently used base metal alloys such as Alloy-247LC and IN-738. For example, the properties of the ductile welding filler are precisely matched to those of Alloy-247LC and IN-738.

[0015] The presented ductile welding additive has the following composition: to 11.0 wt.%-15.5 wt.% chromium; to 9.5 wt.%-11.0 wt.% cobalt; to 2.0 wt.%-5.0 wt.% molybdenum; to 4.5 wt.%-7.5 wt.% tungsten; to 1.5 wt.%-2.6 wt.% tantalum; to 3.0 wt.%-5.0 wt.% aluminium; to 0.4 wt.%-1.0 wt.% titanium; to a maximum of 0.8 wt% iron; up to a maximum of 0.3 wt% manganese; to a maximum of 0.3 wt% silicon; to a maximum of 0.1 wt% carbon; up to a maximum of 0.015 wt% boron; to a maximum of 0.02 wt% zirconium; up to a maximum of 1.2 wt% hafnium; to a maximum of 0.1 wt% vanadium; to a maximum of 1 mg magnesium; and as residual nickel.

[0016] The following table, Table 2, summarizes three embodiments of the ductile welding filler (values ​​in wt.%), Ductilloy, SieWeld-A-247LC, and SieWeld-B-247LC, including the elemental ranges and the beneficial effects of each element on the alloy. Ductilloy is essentially a 50 / 50 mixture (wt.%) of Alloy 247 and IN-617. SieWeld-A-247LC essentially comprises a 75 / 25 mixture (wt.%) of the base metal Alloy 247 and welding filler IN-617, while SieWeld-B-247LC essentially comprises a 66.6 / 33.3 mixture (wt.%) of the base metal Alloy 247 and welding filler IN-617. Table 2 (all values ​​in wt.%) element Ductilloy SieWeld-A-247LC SieWeld-B-247LC Effect, beneficial Cr 14,6-15,6 11,2-12,2 12,3-13,3 Surface protection, corrosion resistance Co 10,4-11,4 9,6-10,6 9,8-10,8 Precipitation modification improves the annealing properties of the solution. Mon 4,6-5,0 2,4-2,8 3,1-3,5 Solid solution strengthening W 4,4-5,2 6,7-7,5 5,9-6,7 Solid solution strengthening Ta 1,4-1,8 2,2-2,6 2,2-2,6 Solid solution strengthening Al 3,0-3,7 4,2-4,8 3,8-4,4 Excretory agents Ti 0,4-1,0 0,4-1,0 0,4-1,0 Excretory agents Fe max 0.15 max 0.15 max 0.15 Connection base element Mn max 0.1 max 0.1 max 0.1 Si max 0.04 max 0.04 max 0.04 Excretory agent, increases the formation of hot cracks C 0,07-0,08 0,07-0,08 0,07-0,08 Grain boundary phases B max 0.015 max 0.015 max 0.015 Grain boundary phases Zr 0,005-0,02 0,005-0,02 0,005-0,02 Increases resistance to hot cracking Hf 0,5-1,0 0,9-1,4 0,7-1,2 Grain refinement V max 0.10 max 0.10 max 0.10 Solid solution strengthening Ni rest rest rest

[0017] It can be desirable to have a welding filler metal whose composition and properties are matched as closely as possible to the base metal to which it is welded. For example, by matching the coefficient of thermal expansion as closely as possible to the base material, high stress levels due to differing thermal expansion can be avoided. Accordingly, the SieWeld-A-247LC welding filler metal, for instance, would be the closest match to the Alloy-247 base metal. Currently, welds where the base metal is a nickel-based superalloy and the welding filler metal are identical, as tested at room temperature using conventional welding processes, are not possible due to the formation of cracks in the heat-affected zone and the weld metal.

[0018] Based on its ductility or tensile elongation, the proposed ductile welding filler will exhibit good welding properties at room temperature. Furthermore, based on its coefficient of thermal expansion, the ductile welding filler will demonstrate acceptable performance during turbine operation at elevated temperatures. Fig. Figure 2 illustrates the coefficient of thermal expansion of several base metals, Alloy-247LC, IN-738 and Rene 80, welding consumables IN-617 and HA 282, and the featured welding consumables, Ductilloy, SieWeld-A-247LC and SieWeld-B-247LC. Fig.As shown in Figure 2, the coefficient of thermal expansion of the proposed embodiments of the welding filler is precisely matched to that of Alloy 247LC. Having a welding filler with a coefficient of thermal expansion precisely matched to that of the base metal is advantageous because the materials would heat up similarly during the welding process when high temperatures are applied to the alloys. By reducing the temperature difference and, consequently, the stress gradient between the weld and the substrate, cracking in the weld can be avoided.

[0019] In one embodiment, the detrimental trace elements, which can negatively affect the properties of the welding consumable composition, are kept within a narrow tolerance range. These detrimental trace elements can include silicon, carbon, boron, and zirconium. For example, the percentage of these elements must not exceed the concentrations listed in Table 2.

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

[0021] Referring again to the Fig. 1 and Fig.Section 2 presents a method for welding components made of a nickel-based superalloy. The ductile welding filler described above is used for welding onto a substrate of the nickel-based superalloy component. The method involves applying the ductile welding filler to a surface of the substrate. The presented ductile welding filler has a coefficient of thermal expansion precisely matched to that of the substrate. Heat can be applied to the welding filler to melt it, forming molten filler. At ambient temperature, the molten filler is used to weld the substrate. The welded substrate can then cool and re-solidify, forming a hardened joint on the substrate.For the purposes of this disclosure, it is precisely tailored to ensure that the coefficient of thermal expansion is within 3% of Alloy-247LC in the range of 600°–1000°C, the range in which gas turbines are currently operated.

[0022] Fig.Figure 3 illustrates a perspective view of a rotor blade 120 or guide blade 130 of a turbomachine extending along a longitudinal axis 121. The turbomachine can be a gas turbine of an aircraft or a power plant for electricity generation, a steam turbine, or a compressor. The blade 120, 130 has, successively along the longitudinal axis 121, a mounting area 400, an adjacent blade platform 403, and a main blade section 406. As a guide blade 130, the blade 130 can have an additional platform (not shown) as its blade tip 415. A blade root 183, used to attach the rotor blades 120, 130 to a shaft or disk (not a shaft), is formed in the mounting area 400. The blade root 183 is, for example, shaped like a hammerhead. Other designs, such as a fir tree or dovetail root, are possible.The blade 120, 130 has a leading edge 409 and a trailing edge 412 for a medium flowing past the main blade section 406. In the case of conventional blades 120, 130, for example, solid metallic materials, especially superalloys, are used in all areas 400, 403, 406 of the blade 120, 130. Accordingly, the ductile welding filler can be used, for example, to weld all areas of the blade. In addition, other combustion components can also be welded using the presented ductile welding filler.

[0023] Although embodiments of the present disclosure have been disclosed in exemplary forms, it is obvious to the person skilled in the art that many modifications, additions and removals can be made to it without deviating from the spirit and scope of the invention and its equivalents as set out in the following claims.

Claims

[1] Ductile welding filler material, comprising: to 11.2 wt.%-15.6 wt.% chromium; to 9.6 wt.%-11.4 wt.% cobalt; to 2.4 wt.%-5.0 wt.% molybdenum; to 4.4 wt.%-7.5 wt.% tungsten; to 1.4 wt.%-2.6 wt.% tantalum; to 3.0 wt.%-4.8 wt.% aluminium; to 0.4 wt.%-1.0 wt.% titanium; to a maximum of 0.15 wt% iron; to a maximum of 0.1 wt% manganese; to a maximum of 0.04 wt% silicon; to 0.07-0.08 wt% carbon; up to a maximum of 0.015 wt% boron; to 0.005-0.02 wt.% zirconium; to 0.5-1.4 wt% hafnium; up to a maximum of 0.1 wt% vanadium; and as residual nickel. [2] Ductile welding filler material according to claim 1, comprising (ductilloy): to 14.6-15.6 wt% chromium; to 10.4-11.4 wt.% cobalt; to 4.6-5.0 wt% molybdenum; to 4.4-5.2 wt% tungsten; to 1.4-1.8 wt% tantalum; to 3.0-3.7 wt.% aluminium; to 0.4-1.0 wt% titanium; to 0.07-0.08 wt% carbon; to a maximum of 0.02 wt.% zirconium; to a maximum of 0.15 wt% iron; up to a maximum of 0.3 wt% manganese; to a maximum of 0.3 wt% silicon; up to a maximum of 0.015 wt% boron; and as residual nickel. [3] Ductile welding filler material according to claim 2, wherein the addition comprises 14.9-15.2 wt.% chromium. [4] Ductile welding filler material according to claim 2, wherein the addition comprises 4.6-4.9 wt.% molybdenum. [5] Ductile welding filler material according to claim 1, comprising (SieWeld-A-247LC): to 11.2 wt.%-12.2 wt.% chromium; to 9.6 wt.%-10.6 wt.% cobalt; to 2.4 wt.%-2.8 wt.% molybdenum; to 6.7 wt.%-7.5 wt.% tungsten; to 2.2 wt.%-2.6 wt.% tantalum; to 4.2 wt.%-4.8 wt.% aluminium; to 0.4 wt.%-1.0 wt.% titanium; to 0.07 wt.%-0.08 wt.% carbon; to 0.005 wt.%-0.2 wt.% zirconium; to 0.9 wt.%-1.4 wt.% hafnium; to a maximum of 0.15 wt% iron; to a maximum of 0.1 wt% manganese; to a maximum of 0.04 wt% silicon; up to a maximum of 0.015 wt% boron; up to a maximum of 0.1 wt% vanadium; and as residual nickel. [6] Ductile welding filler material according to claim 5, wherein the addition comprises 11.6-11.9 wt% chromium. [7] Ductile welding filler material according to claim 5, wherein the addition comprises 2.5-2.7 wt.% molybdenum. [8] Ductile welding filler material according to claim 1, comprising (SieWeld-B-247LC): to 12.3 wt.%-13.3 wt.% chromium; to 9.8 wt.%-10.8 wt.% cobalt; to 3.1 wt.%-3.5 wt.% molybdenum; to 5.9 wt.%-6.7 wt.% tungsten; to 1.9 wt.%-2.3 wt.% tantalum; to 3.8 wt.%-4.4 wt.% aluminium; to 0.4 wt.%-1.0 wt.% titanium; to 0.07 wt.%-0.08 wt.% carbon; to 0.005 wt.%-0.02 wt.% zirconium; to 0.7 wt.%-1.2 wt.% hafnium; to a maximum of 0.15 wt% iron; to a maximum of 0.1 wt% manganese; to a maximum of 0.04 wt% silicon; up to a maximum of 0.015 wt% boron; up to a maximum of 0.1 wt% vanadium; and as residual nickel. [9] Ductile welding additive according to claim 8, wherein the additive comprises 12.7-13.0 wt% chromium. [10] Ductile welding additive according to claim 8, wherein the additive comprises 3.2-3.4 wt.% molybdenum. [11] Method for welding components made of a nickel-based superalloy, comprising: Providing a nickel-based superalloy substrate; applying a ductile welding filler according to claim 1 to a surface of the substrate, wherein the welding filler has a coefficient of thermal expansion precisely matched to a surface of the substrate; Applying heat to melt the welding filler material, forming molten welding filler material; Welding of the substrate with the welding filler at ambient temperature; resolidification of the molten welding filler to form a solidified bonded material. [12] Method according to claim 11, wherein the nickel-based component is a turbine blade. [13] Method according to claim 11, wherein the substrate is selected from the group consisting of Mar-M-247, CM-247LC, PWA-1483, Alloy-247, IN-738, Mar-M002, Rene-N5, Rene-N4, CMSX-4, CMSX-2, Rene-142, GTD-111, MGA-1400 and IN-939. [14] Method according to claim 11, wherein the welding filler material has a coefficient of thermal expansion within 3% of Alloy-247 in the range of 600°-1000°C.

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