CA2850698C - Welding material for welding of superalloys - Google Patents

Abstract

Improvement of Inconel 625 as well as other nickel and iron based welding materials is required to increase mechanical properties of welds at a high temperature avoiding at the same time heat affected zone (HAZ) cracking of Inconel 738, GTD111 and other superalloys with high content of .gamma.' phase. Disclosed is a welding material for welding of superalloys containing 0.4 to 0.8 wt.% Boron; 0.2 to 0.8 wt.% Carbon; 20 to 23 wt.% Chromium; 8 to 12 wt.% Molybdenum; 3.15 to 4.14 wt.% Niobium; trace amount to 5 wt.% Iron; trace amount to combined 1.4 wt.% of micro alloying elements (Titanium, Silicon and Manganese); and Nickel with impurities to balance; which can help to produce high strength welds to minimize and eliminate cracking in the HAZ of Inconel 738, GTD 111 and other nickel based superalloys and improve mechanical properties of welds on various nickel and iron based alloys.

Description

WELDING MATERIAL FOR WELDING OF SUPERALLOYS
[0001] Alloy 625 also known as Inconel 625 manufactured to AMS 5879, which comprises 20 ¨ 23 wt. % Cr, 8 ¨ 10 wt. % Mo, 3.15 ¨ 4.15 wt. % Nb, 0.1 wt. % C

and nickel with impurities to balance, has good oxidation resistance at temperatures up to 980 C (1800 F), mechanical properties up to 870 C (1598 F) and provides good resistance to aqueous corrosion. As a result, this alloy has been widely used in aerospace, chemical and power generation industries for decades.

[0002] Also, due to unique metallurgical propertied Inconel 625 manufactured as per AMS 5837 in a form of welding wire and rods has been used for crack repair and dimensional restoration of turbine engine components by GTAW, laser and plasma welding and cladding.

[0003] Inconel 625 produces sound welds but the heat affected zone (HAZ) of Inconel 738, GTD 111, GTD 222, Inconel 713 and some other precipitation hardening superalloys with high content of gamma prime phase (y') is prone to micro cracking known also as microfissuring as per Banerjee K., Richards N.L., and Chaturvedi M.C.
"Effect of Filler Alloys on Heat Affected Zone Cracking in Pre-weld Heat Treated IN-738 LC Gas-Tungsten-Arc Welds", Metallurgical and Materials Transactions, Volume 36A, July 2005, pp.1881 ¨ 1890.

[0004] Low creep properties is another major disadvantage of this alloy that limits it application for the repair of highly stressed structural and containment engine components. Currently, Haynes 230 welding wire manufactured to AMS 5839 as well as other more superior materials are used in lieu of Alloy 625 for a weld repair of these engine components. However, welding of Inconel 738 and GTD 111 superalloys with Haynes 230 welding wire aggravates the HAZ cracking.

Date Recue/Date Received 2020-07-20

[0005] Boron and some other melting point depressants are used to prevent HAZ
cracking by the reducing the solidus ¨ liquidus range of a welding pool and overheating of HAZ. However, large amount of boron further reduces creep and rupture properties of welds produced using Inconel 625 alloy.

[0006] From other hand, the insufficient boron content in nickel based alloy that was described in US RE 29920 and RE 28681, which are similar to Inconel 625, and comprise 0.05 ¨ 0.3 wt. % B, up to 0.35 wt. % C from 5 to 22 wt. % Cr, up to 8 wt. %
and up to 3 wt. % Nb, do not prevent HAZ cracking of GTD 111 alloy as was found by experiments.

[0007] Niobium free nickel-chromium-molybdenum based alloys with boron content of (0.04 wt. % ¨ 0.8 wt. %) and carbon (0.12 wt. % ¨ 1.2 wt. %) such as alloys described by US39 18964, as well as similar alloys described in patents US4363659, US3428442 have been used mostly only for hardfacing. As a rule hard facing alloys have low rupture and low cycle fatigue properties and can't be used for a structural repair of turbine engine components.

[0008] Therefore, a significant improvement of Inconel 625 is required to increase mechanical properties of welds at a high temperature avoiding at the same time HAZ
cracking of Inconel 738, GTD111 and other superalloys with high content of y' phase.
BRIEF DESCRIPTION OF THE INVENTION

[0009] We have found that the welding material comprising 0.4 ¨ 0.8 wt. % of boron (B), 0.25 ¨ 0.8 wt. % of carbon (C), 20 ¨ 23 wt. % of chromium (Cr), 8 ¨ 10 wt. %
of molybdenum (Mo), 3.15 ¨ 4.15 wt. % of niobium (Nb) and nickel with impurities to balance produces high strength welds which minimize and often eliminate cracking in the HAZ of Inconel 738 and GTD 111 superalloys.

Date Recue/Date Received 2020-07-20

[00010] ADVANTAGES OF THE CURRENT (INVENTED) ALLOY
1) Produces welds with superior mechanical properties at temperature up to 980 C
(1800 F). Rupture properties of welds at 980 C (1800 F) exceeds rupture properties of standard Inconel 625 and Haynes 230 as shown in Table 3.
2) Allows welding of Inconel 738 and GTD 111 and other high gamma prime nickel based superalloys at an ambient temperature while minimizing or eliminating HAZ cracking.
3) Produces ductile welds at an ambient temperature allowing cold working of repair sections.
4) Welding wire can be manufactured using standard low cost drawing processes.
5) A preferable embodiment of the current alloy having carbon content of 0.25 ¨
0.5 wt. % can be used for the crack repair of engine components while embodiments with carbon content of 0.6 ¨ 0.8 wt. % can be used for hard facing.

[00011] The nickel based welding material may be a welding wire.

[00012] The nickel based welding material may also be a welding powder.

[00013] The nickel based welding material may be a repair section of a turbine engine component, where in the welding material with a carbon content of 0.25 ¨ 0.5 wt. %
substitutes the cracked section of the engine component, and welding material with a carbon content of 0.6 ¨ 0.8 wt. % is applied to the section of the engine component that is subjected to wear and fretting in service conditions.

[00014] As per other preferable embodiments the nickel based material may be an article of a particular engine component such as shrouds, vanes, casings, shroud support rings, air seal rings.

[00015] DESCRIPTION OF DRAWINGS

Date Recue/Date Received 2020-07-20 FIGURE 1 is the cross section of clad welds that was produced on Inconel 738 substrate by GTAW-MA welding using the invented welding material.
FIGURE 2 is a micrograph of the weld that was produced on GTD 111 base material using welding rods comprised 0.4 wt.% B and 0.4 wt. % C that depicts the crack free HAZ at the bottom and weld build up on the top.
FIGURE 3 is a micrograph of the homogeneous GTAW weld produced using the standard Inconel 625.
FIGURE 4 is a micrograph of GTAW weld produced using the invented welding material that depicts precipitation of high strength cuboidal borides and carbides in ductile nickel ¨ chromium ¨ boron matrix.
FIGURE 5 depicts the microstructure of the invented alloy in the annealed condition with a uniform precipitation of high strength cuboidal borides and carbides within equiaxed grains and intergranular precipitation of carbides.
FIGURE 6 is a micrograph of the weld that was produced on GTD 111 base material using Alloy 2 welding rods that comprised 0.3 wt.% B and 0.1 wt. % C followed by annealing at a temperature of 1200 C and standard aging heat treatment that depicts HAZ micro cracking.
FIGURE 7 is a micrograph of the weld that was produced on GTD 111 base material using Alloy 2A welding rods comprised 0.35 wt. % B and 0.35 wt. % C after annealing at a temperature of 1200 C f and standard aging heat treatment that depicts the propagation of micro crack from HAZ into weld metal.
FIGURE 8 is a micrograph of the weld that was produced on GTD 111 base material using welding rods comprised 0.85 wt.% B and 1.2 wt. % C after annealed heat treatment at a temperature of 1205 C that depicts unacceptable interdendritic solidification shrinkage.
FIGURE 9 depicts the stage 1 high pressure turbine blade manufactured of GTD

alloy with the tip weld (1) produced using ductile welding wire comprised 0.25 wt. %
C and 0.4 wt. % B and wear resistance angel wing weld (2) produced with hardfacing wire that comprised 0.6 wt. % B and 0.8 wt. C.

Date Recue/Date Received 2020-07-20

[00016] STANDARD ACROMYMS
AMS - Aerospace Material Specification (standards) ASTM - American Society for Testing and Materials (standards) AWS - American Welding Society (standards) HAZ ¨ Heat Affected Zone NDT ¨Non Destructive Testing OEM - Original Equipment Manufacture PWHT ¨ Post Weld Heat Treatment

[00017] GLOSSARY AND TERMS (DEFINITIONS) Alloys -metal compounds consisting of a mixture of two or more materials.
Superalloys -metallic materials with oxidation resistance and mechanical properties for service at elevated temperatures.
Argon Quench - introducing argon into a vacuum heat treatment chamber at annealing temperature that results in a rapid cooling of alloys to an ambient temperature.
Austenite ¨ a solid solution of one or more elements in the face-centered cubic phase. Base Metal or Material - one of the two or more metals to be welded together to form a joint.
Borides ¨ compounds consisting of two elements of which boron is the more electronegative one. Boron form borides with metal and non-metal elements.
Carbides ¨ compounds composed of carbon and a less electronegative element.
Carbon can produce carbides with metals (such as chromium, niobium, molybdenum, tantalum, titanium, tungsten, and other metals of IVB, VB and VIB groups) and non-metal (such as boron, calcium, or silicon). Metal carbides are characterized by their extreme hardness and resistance to high temperatures.
Cast Nickel Alloys - alloys containing nickel that has been poured or cast as a liquid into a mold and cooled into a solid shape.
Date Recue/Date Received 2020-07-20 Cladding - the process of the application of a relatively thick layer (> 0.5 mm (0.02 in.)) of welding material and/or composite welding powder for the purpose of improved wear and/or corrosion resistance or other properties and/or to restore the part to required dimensions with minimum penetration into the base material.
Cold Rolling ¨ a process that carried out at a temperature below of the recrystallization temperature of alloy.
Cold Working - shaping of metal at temperatures substantially below the point of recrystallization. Cold working adds strength and hardness.
Crack¨ fracture-type discontinuity that is characterized by a sharp tip and high ratio of length to width, usually exceeding three (3).
Crack Free Weld - weld that are free of linear indications with length equal or greater of 0.004 inch (0.1 mm) detected either by radiographic or fluorescent penetration inspection without magnification or metallographic examination of welds Cracking - fracture that develops in the weld during or after solidification of a welding pool is completed.
Creep (Properties) ¨ is the tendency of a solid material to move slowly or deform permanently under the influence of stresses. Creep occurs when a metal is subjected to a constant tensile load at an elevated temperature.
The Creep and Rupture Tests ¨ are tests that carried out by applying a constant load to a tensile specimen maintained at a constant temperature according to ASTM
E 139. The rupture test in carried out in a similar manner to the creep test but at a higher stress level until the specimen fails and the time at failure is measured.
Time prior to rupture at given loading is used to characterize rupture properties of materials.
Dilution - the change in a chemical composition of a welding material caused by the admixture of the base material or previous weld metal in the weld bead that is measured by the percentage of the base metal or previous weld metal in the weld bead.
Discontinuity ¨ an interruption of the typical structure of a weld metal, such as a lack of homogeneity in the mechanical, metallurgical or physical characteristics of the base or weld metal.

Date Recue/Date Received 2020-07-20 Drawing ¨ a process in which wire is pulled through either a single drawing die or series of dies.
Ductility - ability of metals and alloys to be drawn, stretched, or formed without breaking. Fissuring ¨ small crack-like discontinuities with only slight separation (opening displacement) of the fracture surfaces. The prefixes macro ¨ or micro ¨
indicate relative size.
Fusion Welding ¨ the welding process that used fusion of the base metal to make the weld.
Gamma (y') Phase ¨ the continuous matrix (called gamma) is a face-centered-cubic (fcc) nickel-based austenitic phase that usually contains a high percentage of solid-solution elements such as Co, Cr, Mo, and W.
Gamma Prime (y') Phase ¨ the primary strengthening phase in nickel-based superalloys is a compound consisting of nickel and either aluminum or titanium Ni3A 1 or Ni3Ti that coherently precipitates in the austenitic y matrix.
Gas Atomization ¨ the process to manufacture high quality metal powders by forcing a molten metal stream through an orifice and atomizing it by inert gas jets into fine metal droplets followed by rapid cooling.
Gas Tungsten Arc Welding (GTAVV) ¨ in accordance with the AWS definition it is the arc welding process that produces coalescence of metals by heating them with an arc between a tungsten (non-consumable) electrode and the work also know as a base material. Shielding is obtained from a gas or a gas mixture. Pressure may or may not be used and filler metal may or may not be used.
Hardness- ability of metals and alloys to resist indentation, penetration, and scratching. Heat Affected Zone (HAZ) - the portion of the base metal that has not been melted, but whose mechanical properties or microstructure were altered by the heat of welding.
Heat Treatment - the controlled heating and cooling processes used to change the structure of a material and alter its physical and mechanical properties.
Hot Rolling ¨ a process that carried out at a temperature exceeding the recrystallization temperature of alloy.

Date Recue/Date Received 2020-07-20 Induction Melting ¨ a process in which an induced electrical current known also as Eddy Current heat and melt metals and alloys.
Laser Beam Welding and Cladding (LBW) - in accordance with AWS definition it is a welding process that produces coalescence of materials with the heat obtained from the application of concentrated coherent light beam impinging upon the joint or base material respectively.
Linear Discontinuities ¨ weld defects with the ratio of a length to a with 3:1 or greater. Multi Pass Cladding and Welding ¨ a weld that is formed by two or more passes. Nickel Based Superalloys - materials whereby the content of nickel exceeds the content of other alloying elements.
Plasma Arc Welding (PAW) ¨ in accordance with AWS definition it is an arc welding process that produces coalescence of metals by heating them with a constricted arc between an electrode and the workpiece (base metal) known also as transferred arc or the electrode and the constricting nozzle known also as non-transferred arc.
Precipitation Heat Treatment or Hardening - the process of heating of alloys to a temperature at which certain elements precipitate, forming a harder structure, and then cooling at a rate to prevent return to the original structure.
Recrystallization ¨ is a formation of a new, strain-free grain structure from existing one that usually accompanied by grain growth during heating.
Recrystallization Temperature is an approximate temperature at which complete recrystallization of an existing grain structure occurs within a specified time.
Rolling ¨ a process in which metal stock is passed through a set of mechanically driven rolls.
Rupture Strength ¨ is a nominal stress developed in a material at rupture, which in not necessarily is equal to ultimate strength.
Solidification Shrinkage ¨ the volume contraction of a metal during solidification.
Solution Heat Treatment - the heat treatment method that is used to heat alloys to a specific temperature for a certain period of time allowing one or more alloying elements to dissolve in a solid solution and then cool rapidly.

Date Recue/Date Received 2020-07-20 Ultimate Tensile Strength (UTS) ¨ the resistance of a material to longitudinal stress, measured by the minimum amount of longitudinal stress required to rupture the material. Weld ¨ a localized coalescence of metal or non-metals produced either by heating the materials to the welding temperature, with or without the application of pressure, or by the application of pressure alone, with or without the use of welding material.
Weld Bead - a weld resulting from a pass.
Weld Defects ¨ discontinuities that by nature or accumulated effect render a part or product unable to meet minimum applicable acceptance standards or specifications.
Weld Pass ¨ a single progression of a welding or cladding operation along a joint, weld deposit or substrate. The result of a pass is a weld bead, layer or spray deposit.
Weld Pool ¨ the localized volume of molten metal in a weld prior to its solidification as weld metal.
Weld ability - ability of a material to be welded under imposed conditions into a specific, suitable structure and to perform satisfactorily for its intended use.
Welding ¨ the material joining processes used in making welds.
Welding Powder - the welding material in a form of powder that is added in making of welded joints or clad welds.
Welding Rods - welding wire cut to a standardized length.
Welding Wire - welding material in a form of wire that is added in making of welded joints or clad welds.
Wrought Nickel Alloys - nickel based alloys that have been bent, hammered, forged or physically formed into a desired shape. Wrought nickel alloys are often welded under the same conditions as certain types of steel.
Yield Strength ¨ the ability of a metal to tolerate gradual progressive force without permanent deformation.
DETAILED DESCRIPTION OF THE INVENTION

Date Recue/Date Received 2020-07-20

[00018] The invented alloy can be used in a form of casting, wrought materials, plates, strips, sheets, powders and other welding materials. Welding materials in a form of welding wires, rods and powders as the major application of the invented alloy are discussed below in more details.

[00019] Ingots, also known as billets, for a manufacturing of welding wire and powder are produced in vacuum or argon using standard induction melting technologies and equipment or other melting processes.

[00020] For a manufacturing of welding wire billets are usually produced in a form of rods with a diameter exceeding 0.75 inch that are reduced to a diameter of 0.5 inch by rolling or extrusion at a high temperature followed by standard surface finishing.

[00021] Nickel based alloys in accordance with the present concept for a manufacturing of a welding wire for a crack repair with boron content of 0.4 ¨ 0.5 wt. % and carbon content of 0.25 ¨ 0.4 wt. % are ductile at temperatures below the recrystallization temperature. Therefore, manufacturing of welding wire using alloys with low content of boron and carbon can be done by cold rolling. During cold rolling the rod stock with the initial diameter of 0.5 ¨ 0.75 inch is reduced down to 0.020 ¨ 0.062 inch. The cold rolling increases the yield strength and hardness. Therefore, to increase ductility the metal stock is subjected to annealing heat treatment every so often to allow restoration of workability.

[00022] High strength and hardness welding wire also known as hardfacing welding wire with content of boron and carbon respectively of 0.6 ¨ 0.8 wt. % has low ductility at low temperatures. For manufacturing of hardfacing weld wire standard hot rolling or extrusion processes are used. The hot extrusion process consists of assembling of a billet housing that contains coated alloyed rods of desired chemical composition. The billet is then prepared for the extrusion. Billets are heated to a temperature exceeding the recrystallization temperature to avoid hardening and ease extrusion.
Date Recue/Date Received 2020-07-20

[00023] During final processing the wire is passed through a standard rigorous cleaning procedure that ensures the welds are free from contamination.

[00024] After cold or hot rolling the wire is cut to a required length for a manufacturing of welding rods for a manual GTAW-MA or butt welded together and spooled for the automatic GTAW-ME, LBW or PAW welding.

[00025] Welding powder of 45 ¨ 75 gm in diameter is manufactured by standard gas atomization processes. During this process the melded alloy is atomized by inert gas jets into fine metal droplets, which cool down during their fall in the atomizing tower.
Metal powders obtained by gas-atomization have a perfectly spherical shape and high cleanliness level. Welding powder is used for plasma, microplasma and laser welding and cladding. Welding powder is fed into the welding pool with a jet of argon using standard powder feeders.

[00026] After solidification welding powder is fused with the base material producing the weld metal. To reduce overheating and prevent HAZ cracking, welding and cladding are carried out with minimum dilution. The best results in cladding were achieved with a dilution of 5 ¨15 %.

[00027] Boron and carbon within the specified ranges produce two beneficial effects for achieving the objectives of the current invention.

[00028] First of all, boron combining with nickel reduced the melting temperature of a welding pool and overheating of the HAZ allowing a formation of crack free welds on Inconel 738 and GTD 111 as shown in FIG. 1 and 2.

[00029] Secondly, due to solidification of the welding pool carbon and boron formed cuboidal high strengths carbides and borides respectively with Nb, Mo and Cr in the Date Recue/Date Received 2020-07-20 relatively ductile Ni ¨ Cr ¨ B matrix as shown in FIG. 4 and 5 that significantly increase ultimate (UTS) and yield strengths as well as rupture properties of the welds as shown in Tables 2 and 3.

[00030] Microstructure of welds produced using standard Inconel 625 comprised almost homogeneous low strength gamma grains as shown in FIG. 3. The weld metal with this structure demonstrated extremely low rupture and insufficient tensile properties as shown in Tables 3 and 2 respectively.

[00031] Welds produced using the invented alloy had a unique combination of required ductility, high strength and good rupture properties at a temperature of 982 C (1800 F) that significantly exceeds properties of welds produced using base line Alloy 625 and more superior Haynes 230 alloy due to formation cuboidal borides and carbides.

[00032] Weld metal comprised 0.4-0.5 wt. % B and 0.25 ¨ 0.4 wt. % C
demonstrated good ductility as shown in Table 4 that allowed reshaping of engine components by cold working.

[00033] The invented alloy can be also used for a manufacturing of engine components by casting and forging followed by annealing that forms high strength equiaxed structure with precipitation of cuboidal carbides and borides in the Ni ¨ Cr ¨ B based matrix shown in FIG. 5.

[00034] The weld repair of engine components using the invented alloy in a form of welding wire, rods or powder is made in accordance with AMS 2694, AMS 2685 or relevant OEM specifications and includes removing of defective area or cracks, cleaning of engine components, welding, post weld heat treatment (PWHT) that for a repair of engine components manufactured of precipitation hardening superalloys might constitute annealing and aging or just aging, machining and polishing to restore the original geometry of engine components followed by non-destructive testing of welds (NDT) and Date Recue/Date Received 2020-07-20 dimensional inspection. Standard repair processes are well known in the art.
However, the example of a turbine blade repair manufactured of GTD 111 superalloy and welded at an ambient temperature is shown in FIG. 9.

[00035] The tip weld 1 was made using high ductility welding wire manufactured of Alloy 3 comprised of 0.4 wt. % B and 0.25 wt.% C to ensure high thermal fatigue properties while the angel wing weld 2 was produced using welding wire manufactured of Alloy 6 because this section of the blade is subjected mostly to wear.

[00036] Welds were free of discontinuities also known as weld defects exceeding of 0.002 inch in size in as welded condition and after PWHT that included annealing at a temperature of 1200 C (2192 F) and standard two stage aging at temperature of 1120 C (2048 F) for two hours followed by soaking for twenty four (24) hours at a temperature of 845 C (1553 F).
EXAMPLES OF WELDING OF INCONEL 738, GTD III and INCONEL 625 USING INVENTED ALLOY

[00037] Several welding wires with the chemical compositions shown in Table 1 were manufactured by adding different amount of boron and carbon to standard Inconel 625 alloy using standard metallurgical methods.

[00038] Multi pass clad welds of 2 ¨ 4 inch in length, 0.35 - 0.40 inch in width and 0.4 ¨0.5 inch height were produced using GTAW-MA welding and argon shielding gas on samples manufactured of Inconel 738 and GTD 111 superalloys.

[00039] Welding parameters were selected by experiment to produce clad welds with a dilution of 10 - 15%. Weld current varied form 60 - 75A, arc voltage was within the range of 12 ¨14, V and welding speed varied from 1.8 to 2.2 inch per minute.

Date Recue/Date Received 2020-07-20

[00040] Prior to welding samples were subjected to a pre-weld annealing heat treatment at a temperature of 1200 C (2192 F) for two (2) hours followed by an argon quench.

[00041] Clad welds on Inconel 738 and GTD 111 alloys were also produced using standard Inconel 625 and Haynes 230 welding wires to evaluate HAZ cracking of standard and invented welding materials.

[00042] After welding all samples were subjected to the PWHT comprised annealing at a temperature of 1200 C (2192 F) for two (2) hours followed by an aging at temperatures of 1120 C (2048 F) for two (2) hours and 845 C (1553 F) for twenty four (24) hours.

[00043] In addition to above, Inconel 625 samples of 6 x 3 x 0.060 inch in dimensions were butt welded using GTAW-MA with standard Inconel 625 (IN625) solution hardening nickel based superalloy were and invented welding alloys in a form of welding rods of 0.035 inch in diameter.

[00044] Welds on Inconel 738 and Gill 111 were evaluated for HAZ cracking. No cracks and other linear discontinuities exceeding 0.002 inch in length were observed.
Due to high susceptibility to cracking and wide range of industrial applications IN738 and GID111 nickel based precipitation hardening superalloys and IN625 solution hardening superalloy were selected for welding examples.
IN738 and GTD111 superalloys have been used for a manufacturing of buckets (blades) of Industrial Gas Turbine (IGT) engines for decades and exercise tip thermal fatigue cracking, oxidation and wear of angel wings shown in FIG. 9.
IN625 superalloy was used as welding wire and for manufacturing of combustion chambers and other parts of IGT and aero turbine engines.

[00045] Clad welds were subjected to tensile and rupture testing at a temperature of 982 C (1800 F) as per ASTM E21 and E139 respectively.

Date Recue/Date Received 2020-07-20

[00046] Inconel 625 butt joints were subjected to a tensile testing at a room temperature as per ASTM E8 and bend test as per ASTM E190-92.

[00047] Acceptable compositions include those that produce crack free welds, interdendritic shrinkage with a length less than 0.004 (0.1 mm) inch and tensile and rupture properties exceeding Inconel 625 and Haynes 230 respectively on various substrates as per the tables below.

[00048] Unacceptable inter-dendritic shrinkage is a linear indication with a size exceeding 0.004 inch.

[00049] Tensile properties of clad welds and HAZ cracking of Inconel 738 and GTD111 alloys are summarised in Table 2. Rupture properties in a comparison with tensile properties of standard Inconel 625 and Haynes 230 are shown in Table 3.

[00050] Tensile properties of butt joints of Inconel 625 alloy produced using standard Inconel 625 and invented welding rods in as welded condition are presented in Table 4.
Date Recue/Date Received 2020-07-20 Table 1 Chemical Composition of Alloys in Wt. %
Material Ni Cr Mo Nb Inconel 625 To balance 20 - 23 8- 10 3.15 - 4.14 - 0.1 Standard Base Line Alloy 1 To balance 20 - 23 8 - 10 3.15 - 4.14 0.2 0.1 Alloy 2 To balance 20 - 23 8 - 10 3.15 - 4.14 0.30 0.1 Alloy 2A To balance 20 - 23 8 - 10 3.15 - 4.14 0.35 0.35 Alloy 3 To balance 20 - 23 8- 10 3.15 - 4.14 0.40 0.25 Alloy 4 To balance 20 - 23 8- 10 3.15 - 4.14 0.40 0.50 Alloy 5 To balance 20 - 23 8 - 10 3.15 - 4.14 0.60 0.65 Alloy 6 To balance 20 - 23 8- 10 3.15 - 4.14 0.80 0.80 Alloy 7 To balance 20 - 23 8 - 10 3.15 - 4.14 1.00 1.25 Alloy 8 To balance 20 - 23 8- 10 3.15 - 4.14 0.85 1.2 Date Recue/Date Received 2020-07-20 Table 2 Tensile Properties of Clad Welds at 982 C (18000 f) and Susceptibility of HAZ to Crackin Material 0.2% Offset Ultimate Elongati Weld & HAZ Weld & HAZ
Yield Tensile on, Cracking of Cracking of Strength, KSI Strength, KSI % IN738 Alloy GTD111 Alloy Inconel 625 12.1 24.1 43.8 HAZ Cracking HAZ Cracking Standard Base Line' Haynes 230 24.8 29.4 25.5 HAZ Cracking HAZ Cracking Standard Base Line2 Alloy 1 - - - HAZ Cracking HAZ Cracking Alloy 2 - - - No Cracks HAZ Cracking Alloy 2A - - - No Cracks HAZ Cracking Alloy 3 24.5 30.0 22.5 No Cracks No Cracks Alloy 6 29.3 34.5 7.5 No Cracks No Cracks Alloy 7 - - - Weld Weld Solidification Solidification Shrinkage Shrinkage Exceeding 0.004 Exceeding 0.004 inch in length inch in length Alloy 8 - - - Weld Weld Solidification Solidification Shrinkage Shrinkage Exceeding 0.004 Exceeding 0.004 inch in length inch in length Note: 1, 2 Weld metals produced using standard Inconel 625 and Haynes 230 welding wires were tested to obtain base line data for a comparison. Other weld alloys that produced HAZ or exhibited cracking and other unacceptable weld discontinuities such as solidification shrinkage were rejected and therefore were not subjected to mechanical testing.

Date Recue/Date Received 2020-07-20 Table 3 Rupture Properties of Inconel 625, Haynes 230 and Alloy 3 Clad Welds at a Temperature of 982 C (1800 F) Material Stresses, Rupture Time, KSI Hours Inconel 625 8 1.8 Standard Base Line Haynes 230 8.0 10 Standard Base Line Alloy 3 8.0 242.8 Alloy 6 8.0 112.3 Table 4 Tensile Properties of Inconel 625 Butt Joints at a Room Temperature Welding Wire Ultimate Elongation, Bend Angle, Fracture Area Tensile % Deg.
Strength, KSI
Standard Inconel 625 127 46 180 HAZ
Alloy 3 129 38.5 180 HAZ

[00051] Welds produced on Inconel 738 and GTD 111 alloy using standard welding wire Inconel 625, Haynes 230, Alloys 1 and 2 welding wires exhibited unacceptable HAZ
micro cracking. Welds produced on GTD 111 alloy using Alloy 2A welding wire that comprised 0.35 wt. % B and 0.1 wt. % C exhibited HAZ micro cracking as well in as welded condition and heat treated conditions as shown in FIG. 6.

[00052] Elevated content of carbon in Alloy 2A welding wire with a boron content of 0.35 wt. % reduced ductility of welds that resulted in a propagation of cracks from HAZ
into weld as shown in FIG.7.

Date Recue/Date Received 2020-07-20

[00053] Therefore, Alloys 1, 2 and 2A with content of boron below of 0.3 ¨
0.35 wt.
% wt. % could not be used for a repair of engine components manufacturing of nickel based superalloys with high content of gamma prime phase such as GTD 111.

[00054] HAZ of welds produced using welding Alloys 7 and 8 with boron content of 1.0 wt. % and 0.85 wt. % respectively and carbon 1.25 wt. % and 1 wt. %
respectively was free of cracks but welds exhibited interdendritic shrinkage as shown in FIG. 8 and were considered unacceptable.

[00055] Therefore, as follows from examples above, invented welding alloy that comprised from about 0.4 wt. % to 0.8 wt. % B and from about 0.25 wt.% C to 0.8 wt.
% C produced crack free welds on Inconel 738 and GTD 111 superalloys with as well as superior mechanical properties due to unique combination of metallurgical properties, reduced melting temperature and precipitation of heat resistant cuboidal borides and carbides in the ductile Ni-Cr-B matrix.

Date Recue/Date Received 2020-07-20

Claims (7)

1. A welding material comprised of the following elements:
a) Boron: from 0.4 to 0.8 wt. %
b) Carbon: from 0.2 to 0.8 wt. %
c) Chromium: from 20 to 23 wt. %
d) Molybdenum from 8 to 12 wt. %
e) Niobium: from 3.15 to 4.14 wt. %
f) Iron from trace amount to 5 wt. %
g) micro alloying elements selected from among Titanium, Silicon and Manganese: from trace amount to combined 1.4 wt. %
h) Nickel with impurities: to balance.

2. The welding material according to claim 1, wherein the welding material is a welding powder.

3. The welding material according to claim 1, wherein the welding material is a welding wire.

4. The welding material according to claim 1, wherein the welding material is for repairing a section of a turbine engine component.

5. The welding material according to claim 1, wherein - the carbon content is from 0.2 to 0.5 wt.%, and - the boron content is from 0.4 to 0.8 wt.%.

6. The welding material according to claim 1, wherein - the carbon content is from 0.4 to 0.8 wt.%, and - the boron content is from 0.4 to 0.8 wt.%.

7. The welding material according to claim 6, wherein the welding material is a welding wire or welding powder for hard facing.