Composite welding wire and method of manufacturing

Abstract

The present invention is a composite welding wire for fusion welding of components manufactured of superalloys. The composite weld wire includes a surface layer applied to the core wire in a green condition and bonded to the core wire. The surface layer includes alloying elements selected from among B and Si, the total bulk content of B and Si representing 0.5 to 4.0 wt. % of the composite welding wire. The boron and silicon alloying elements reduce the melting temperature and increase the solidification range of the weld pool, minimizing the incidence of weld cracking compared to welding without the coating. The green condition surface layer is comprised of more than 80 wt. % of the bulk content of the composite welding wire selected from the combination of B and Si.

Claims

1. A composite welding wire for fusion welding of components manufactured of superalloys, the composite weld wire comprises: a) a coated core wire configured for fusion welding of components manufactured of superalloys; b) the coating includes a surface layer applied to the core wire in a green condition and bonded to the core wire; c) the surface layer includes alloying elements which act to depress the melting point of a weld pool during welding, the alloying elements selected from a combination of B and Si in the surface layer, wherein the combination has a total bulk content of B and Si in representing 0.5 to 4.0 wt. % of the composite welding wire, wherein the boron and silicon alloying elements reduce the melting temperature and increase the solidification range of the weld pool and adapted to minimize the incidence of weld cracking compared to welding without the coating; and d) wherein the green condition surface layer comprises more than 80% wt. % of the bulk content of the composite wire of the alloying elements selected from the combination of B and Si.

2. The composite welding wire claimed in claim 1 wherein in a green condition the surface layer consists of at least 50 wt. % of a combination of B and Si with a sacrificial organic binder to make up the balance of the surface layer.

3. The welding wire claimed in claim 1 wherein the total bulk content of B does not exceed 2.5 wt. %.

4. The welding wire claimed in claim 1 wherein the total bulk content of Si does not exceed 2.1 wt %.

5. The welding wire claimed in claim 1 wherein the total bulk content of B is 0.5 to 0.8 wt % and the bulk Si content is 0 wt %.

6. The welding wire claimed in claim 1 wherein the total bulk content of Si is 1.5 to 1.8 wt,% and the bulk B content is 0 wt %.

7. The welding wire claimed in claim 1 wherein a thickness T of the surface layer being less than 25% of a total diameter D of the weld wire.

8. The welding wire claimed in claim 1 wherein the surface layer is adhesively bonded to the core wire, selected from among: adhesively bonding, sintering in the solid state, and metallurgically bonding by diffusion bonding.

9. The welding wire claimed in claim 1 further including a transition layer sandwiched between the core wire and the surface layer.

10. The welding wire claimed in claim 9 wherein the surface layer is metallurgically bonded to the core wire by diffusion bonding of B and Si into the core wire.

11. The welding wire claimed in claim 1 wherein the surface layer is metallurgically bonded to the core wire by a diffusion bonding method selected from among; solid diffusion, solid-liquid diffusion, and liquid diffusion.

12. The welding wire claimed in claim 8 wherein the adhesive bonding is carried out in a temperature range from 30 C. to 500 C.

13. The welding wire claimed in claim 8 wherein the sintering bonding is carried out in a temperature range from 500 C. to 900 C.

14. The welding wire claimed in claim 8 wherein the metallurgical bonding is carried out in a temperature range from 900 C. to 1400 C. and below of a melting temperature of the core wire.

15. The welding wire claimed in claim 1 wherein the core wire composition is selected from among nickel based alloys, nickel based superalloys, cobalt based alloys, cobalt based superalloys, iron based alloys, iron based superalloys.

16. The welding wire claimed in claim 1 wherein the core wire is a solid core wire and the surface layer is applied to an outer surface of the solid core wire.

17. The welding wire claimed in claim 1 wherein the core wire is a hollow tubular core wire and wherein the surface layer is applied to an outer surface of the hollow tubular core wire.

18. The welding wire claimed in claim 17 wherein the surface layer is applied to an inner surface of the hollow tubular core wire.

19. The welding wire claimed in claim 17 wherein the surface layer is applied to an inner surface of the hollow tubular core wire and applied to an outer surface of the hollow tubular core wire.

20. The welding wire claimed in claim 17 wherein the surface layer is bonded to the core wire by selected from among adhesively bonded, sintering in the solid state, and by diffusion bonding.

21. The welding wire claimed in claim 5 wherein the surface layer comprises an organic binder, wherein the binder is selected from among the following synthetic or natural resins: acrylics, polyesters, epoxy, vinyl-acrylics, vinyl acetate-ethylene (VAE), melamine resins, epoxy, alkyds, and oils.

22. The welding wire claimed in claim 1 wherein the surface layer is applied using a method selected from among; painting, electrostatic powder painting, slurry coating, boriding, chemical vapour depositing, physical vapour depositing, electron beam depositing, and electron beam physical vapour depositing.

23. The welding wire claimed in claim 1 wherein the total bulk content of B is 0.5 to 0.8 wt % and the bulk Si content is 1.2 to 1.5 wt %.

24. The welding wire claimed in claim 1 wherein the total bulk content of B is 1.0 to 2.5 wt % and the bulk Si content is 1.2 to 1.5 wt %.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 depicts the cross section of the composite weld wire and includes ductile core wire 10, outer surface layer 102 that is enriched with melting point depressants and a transition layer 103, wherein D 112 is the outer diameter of the composite welding wire and T 110 is the thickness of the outer surface layer 102.

(2) FIG. 2 depicts in cross sectional view a powder cored filler composite welding wire 200 which includes a ductile core wire 201 with the outer surface layer 202 that is enriched with melting point depressants, coaxial opening 204, inner surface layer 205 with melting point depressants, and wherein coaxial opening 204 may be filled with filler powder core 206.

(3) FIG. 3 is a macrograph of the cross section of the nickel based composite filler wire having the boron enriched surface layer produced by electrochemical boriding.

(4) FIG. 4 is a macrograph of the cross section of the nickel based composite filler wire with the boron enriched surface layer produced by boriding.

(5) FIG. 5 is a micrograph of the cross section of the nickel based composite filler wire with the boron enriched surface layer (a) and silicon enriched surface layer (b) produced by an application of boron slurry to the surface of the core wire followed by a vacuum heat treatment at a temperature of 1200 C.

(6) FIG. 6 is a 304 stainless steel plate with a nickel based LPM top layer produced according to the teachings of U.S. Pat. No. 5,156,321 prior to welding.

(7) FIG. 7 depicts the same sample after GTAW weld-brazing using the boron modified Composite Welding Wire A with chemical composition shown in Examples on LPM.

(8) FIG. 8 is a micrograph of the sample shown in FIG. 7.

(9) FIG. 9 is a micrograph of the fusion zone between the LPM deposit and boron modified Composite Welding Wire A with chemical composition shown in Examples.

(10) FIG. 10 is the micrograph of welds produced on the LPM deposit using the boron modified Composite Welding Wire B with chemical composition shown in Examples.

(11) FIG. 11 depicts the crack free welds produced on Inconel 738 alloy using the boron modified Composite Welding Wire B with chemical composition shown in Examples.

(12) FIG. 12 is the micrograph of the weld produced using silicon modified Composite Welding Wire C with chemical composition shown in examples regarding Rene 77.

(13) FIG. 13 depicts the sections of a spooled composite welding wire with the surface layer comprised 40% of boron and welding rod on the bottom with the surfaces layer comprised 12% or boron and the polyester binder to balance.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

(14) Binder: a material possessing properties enabling it to hold solid particles together to constitute a coherent mass of for example boron and/or silicon containing slurries and/or paints.

(15) Organic Binder: binder comprising substantially all organic compounds.

(16) Diffusion bonding: a material condition or process whereby due to a thermal activation, constituents such as for example B and Si spontaneously move into surrounding material such as the core wire material which has lower concentrations of these constituents. Diffusion may change the chemical composition and produce a transition or dissimilar interlayer.

(17) Superalloys: Are metallic materials that exhibit excellent mechanical strength and resistance to creep at high temperatures, up to 0.9 melting temperature; good surface stability, oxidation and corrosion resistance. Superalloys typically have a matrix with an austenitic face-centered cubic crystal structure. Superalloys are used mostly for manufacturing of turbine engine components.

(18) Nickel based superalloys: materials whereby the content of nickel exceeds the content of other alloying elements.

(19) Cobalt based superalloys: materials whereby the content of cobalt exceeds the content of other alloying elements.

(20) Iron based superalloys: materials whereby the content of nickel exceeds the content of other alloying elements.

(21) Adhesive bonding: also referred to as gluing; the act or process by which the surface layer and core wire are bonded together using a binder as glue.

(22) Sintering: a process that results in bonding between particles and possibly also a parent material. Sintering for example can take place between B and Si particles which may be powder form. and also a core wire due to atom diffusion during heating at a temperature below a melting temperature. Atoms of B and Si may for example diffuse across boundaries of the particles and core wire bonding these together and creating one solid piece without melting of any of constituencies.

(23) Welding Wire: A form of welding filler metal, normally supplied as coils or spools that may or may not conduct electrical current depending upon the welding process with which it is used.

(24) Welding Rod: A form of welding filler metal if form or rods that may or may not conduct electrical current depending upon the welding process with which it is used. In this application the terms weld rod and weld wire are used interchangeably since the inventive concept applies equally to either a weld wire or weld rod.

(25) GTAWGas Tungsten Arc Welding

(26) Brazing: A process in which a filler metal is heated above its melting point and distributed by capillary action between closely fitted repair component faying surfaces. The repair components are not heated above their melting temperatures.

(27) Braze Welding: A fusion welding process variation in which a filler metal, having a liquidus above 450 C. and below the solidus of the repair component metal, is used. Unlike brazing, in braze welding the filler metal is not distributed in the joint by capillary action.

(28) Buttering: A surfacing variation that deposits surfacing metal on one or more surfaces to provide metallurgically compatible weld metal for the subsequent completion of the weld.

(29) Heat Affected Zone: Also known as HAZ, is the portion of the base metal that has not been melted, but whose mechanical properties or microstructure have been altered by the heat of welding, brazing, soldering, or cutting.

(30) Fusion Welding: Any welding process that uses fusion of the base metal to make the weld.

(31) Solidus temperaturethe highest temperature at which a metal or alloy is completely solid.

(32) Liquidus temperaturethe lowest temperature at which all metal or alloy is liquid.

(33) Solidusliquidus range or melting range also referred to as solidification rangethe temperatures over which the metal or alloy is in a partially solid and partially liquid condition.

(34) Description

(35) The present invention is a composite welding the wire or rod for fusion welding shown generally as composite welding wire 100 and the method of making composite welding wire 100. Composite welding wires 100 are used for the repair of various articles, preferably for repair of turbine engine components, manufactured of Ni, Co and Fe based superalloys, directionally solidified and single crystal alloys that were previously repaired using ADH, LPM or high temperature brazing as well as superalloys that are prone to cracking in the HAZ while welded using standard welding materials.

(36) Composite welding wires 100 include a ductile core wire 101 shown in FIG. 1 produced for example by a hot or cold drawing of ductile standard or custom produced nickel, cobalt and iron based alloys having required chemical composition. Composite welding wires 100 also includes a surface layer 102, which is enriched with melting point depressants, such as boron, silicon or combination of these two chemical elements. Core wire 101 has an outer surface 111 and may be a solid core wire 113 as depicted. The surface layer 102 may include a transition layer 103 depending upon the method of manufacture of the composite welding wire 100. In FIG. 1 the surface layer 102 includes transition layer 103 for a total thickness of the surface layer 102 of T 110. The total diameter of the composite welding wire 100 is shown as D 112.

(37) FIG. 2 depicts in cross sectional view a weld wire which is a powder cored filler composite welding wire 200 which includes a ductile core wire 201 which may be a hollow tubular core wire 209 as depicted with the outer surface layer 202 that is enriched with melting point depressants, coaxial opening 204, inner surface layer 205 with melting point depressants, and wherein coaxial opening 204 may be filled with filler powder core 206. Hollow tubular core wire 209 includes an outer surface 211 and an inner surface 213.

(38) To produce welding on variety of superalloys, ADH, LPM and brazed joints ductile core wires and rods are currently manufactured using standard and custom made nickel, cobalt, iron based wires.

(39) Several examples of boriding are discussed below to produce the outer surface layer 102 and 202 shown in FIGS. 1 and 2 of a required thickness T 110.

(40) For example a paste also known as slurry boriding, in which a mix of boronaceous medium made of boron powder with a volatile solvent such as alcohol or methanol or water is applied by brushing, or spraying or dipping onto the surface of core wires or rods.

(41) Electrolytic boriding, in which the filler core wires are immersed into a melted boric acid (H.sub.3BO.sub.3) at a temperature of 950 C. with a graphite electrode that works as an anode, wherein boron atoms that are released due the electrochemical dissociation of boric acid, are absorbed by the core wire material.

(42) Liquid boriding, in which the filler core wires are immersed into a salt bath. Pack boriding in which the boronaceous medium is a solid powder.

(43) Gas boriding, in which the boronaceous medium is a boron-rich gases, such as B.sub.2H.sub.2H.sub.2 mixtures.

(44) Plasma boriding, which also uses boron-rich gases at lower than gas boriding temperatures.

(45) Fluidized bed boriding, which uses special boriding powders in conjunction with an oxygen-free gases such as hydrogen, nitrogen and their mixtures.

(46) Boriding by a chemical vapour deposition (CVD), wherein boron atoms are diffused into core wires forming an intermetallic compounds on the surface of core wires in which the uniform diffusion of boronized layer is controlled by a thermo-chemical reactions.

(47) Boriding by a Physical Vapour Deposition also knows as the PVD process, wherein the sputtering rich in boron material is evaporated by an electric arc in vacuum at working pressure of 10.sup.2 torr or better. This process results in coating of the outer surface of core wires by boron atoms that diffuse at a high temperature into core wires producing coatings with a thickness that is regulated by a temperature of core wires and duration of the PVD process. Boriding by the Electron Beam Physical Vapour Deposition also known as the EB-PVD process which is similar to PVD but heating and evaporating of the sputtering material is performed by an electron beam.

(48) Slurry, electrolytic and pack boriding are most cost effective for a manufacturing of the invented composite filler materials.

(49) In paste boriding, the slurry containing boron powder and a easily vaporized. solvent is applied to the core wire by painting, spraying or dipping followed by drying at an ambient or elevated temperature in an oven if water was used to produce the slurry. Methanol is a preferable solvent due to easy evaporation at ambient temperature, low content of impurities, low health and safety hazardous and reasonable cost.

(50) The required thickness of this coating depends on the core wire diameter and desirable chemical composition of melting point depressants.

(51) The content of boron, silicon or boron and silicon in the surface layer and thickness of this layer should produce a bulk content of melting points depressants in a composite filler wire within a range of 0.1-10% reducing a melting temperature of this filler wire below the solidus-liquidus range of a brazing materials that were used to produce LPM, ADH as well as to eliminate HAZ cracking of Inconel 713, Inconel 738, Rene 77 and other difficult to weld superalloys with a high content of gamma-prim () phase. Bulk content is the B in surface layer+B in core wire. Bulk content refers to the total amount of an element in the composite welding wire.

(52) The total amount of the low melting temperature depressants in the composite filler wire depends on the wire diameter and thickness of the outer surface layer that can be estimated using the equitation below:

(53) $C_{.Math.}=\frac{D^{}.Math.C_{\mathrm{SL}}}{T}$
wherein:

(54) C.sub.total content of melting point depressants in the melted welding wire,

(55) Dwelding wire diameter,

(56) C.sub.SLcontent of melting point depressant in the surface layer

(57) T thickness of the surface layer.

(58) After drying, the filler wire or rod with the applied slurry is subjected to a heat treatment in protective gasses (argon, helium or hydrogen) or in a vacuum to prevent oxidation of the melting point depressants at a temperature above 900 C. but below the melting temperature of the core wire material. This value can be found from available handbooks for each type of alloy. However, the best results were achieved in heat treatment within the temperature range of 1180-1205 C.

(59) As shown in FIGS. 4 and 5 the heat treatment of filler wires within this temperature range produced the surface layers of thickness T=75-111 m, which includes the transition layer 103. The content of boron reduces from a maximum on the surface to zero or to the original content of boron in the parent material at the parent material-transition layer interface.

(60) Increasing the boriding time from 2 to 6 hours increases the thickness of the boronized layer to 140-250 m. That is close to previously published by X. Dong et al Microstructure and Properties of Boronizing Layer of Fe-based Powder Metallurgy Compacts Prepared by Boronizing and Sintering Simultaneously, Science of Sintering, 41 (2009) 199-207.

(61) These surface layers exhibit excellent bonding with core wires allowing easy handling of composite filler weld wires and rods during welding.

(62) The thickness of the boriding or boronizing layer is regulated by time and temperature of a heat treatment. During heat treatment boron diffuses into the substrate pwireucing a surface layer with a good bonding to the core wire.

(63) In accordance with another example the formation of the outer surface layer containing boron is performed by utilizing the electrochemical process, wherein the core wires are immersed into melted boric acid at a temperature approximately of 950 C.

(64) During boriding the boric acid dissociates releasing boron atoms that diffuse into the surface of ductile core wires forming Ni.sub.2B and other borides. During a post boriding heat treatment the metastable Ni.sub.2B borides are transformed into stable Ni.sub.3B compounds. Precipitation of borides, boride enrich solid solutions and phase containing up to 10% of boron takes place also on the surface of composite filler material and along grain boundaries.

(65) By experiment it was found, that during electrochemical boriding followed by a heat treatment within a temperature range of 900-1000 C. relatively thin boride layer is formed on the surface of filler wires. The thickness is approximately 75 m or 0.075 mm of boriding layer shown in FIGS. 3 & 4.

(66) As per another example, the outer surface layer containing melting temperature depressants is produced by pack boriding using Ekabor or similar powder comprised of 90% SiC, 5% B.sub.4C, 5% KBF.sub.4. During pack boronizing B.sub.4C is broken down to boron and carbon allowing boron diffusion into core wires.

(67) Ductile core wires are placed in the intimate contact with the Ekabor powder and then heated to a temperature from 820-980 C. under a protective atmosphere of argon and held within the optimal temperature range that is selected for each base material by experiments. The soaking time depends also on base material of core wires, required. thickness of the surface layer and core wire diameter. The optimal heat treatment time is defined by experiments for each type of core wire alloys. After a diffusion cycle and cooling the excessive Ekabor powder is removed using soft stainless steel wire brush or other cleaning method.

(68) Boriding also is carried out by CVD, PVD, EB-PVD and other processes using parameters developed for each type of material by experiments as well.

(69) Silicon does not have the same diffusivity as boron. Therefore, the most efficient way to apply silicon is brushing, spraying or dipping ductile core wires into a silicon containing slurry followed by a diffusion heat treatment at a temperature of 1100 C.-1200 C.

(70) In another embodiment the application of boron, silicon or boron-silicon powder or liquid paints are prepared using organic binders followed by electrostatic or brush painting followed by drying of welding wires. This produces an adhesive bond between the surface layer 102 and core wire 101 that allows automatic wire feeding for welding on nickel and cobalt based alloys that are not sensitive to carbon content or wherein additional alloying of welds with carbon is essential.

(71) During welding organic binder is evaporated and decomposed releasing B and Si that are absorbed by the welding pool.

(72) In Use

(73) Composite welding wires were manufactured using slurries made of boron, silicon and boron-silicon powders with purity of 99% and a particle size of 1-5 m and organic binders. Slurries were applied by brushing to standard welding wires AMS 5837, AMS 5839, AMS 5801, Rene 80 and Rene 142 of 1.0-1.5 mm in diameter, wherein AMS stands for Aerospace Material Specification. New name of composite welding wires and bulk content of alloying elements in wt. % shown below:) a) Composite Welding Wire A (manufactured of AMS 5837: 20-22% Cr, 9-11% Mo, 3.5-4% Nb, 0.5-0.8% B. Ni and impurities to balance. b) Composite Welding Wire B (manufactured of AMS 5839 wire): 21-23% Cr, 1.5-2.5% Mo, 13-45% W, 0.3-0.5% Al, 1.5-1.8% Si, 0.5-0.8% Mn, Ni and impurities to balance. c) Composite Welding Wire C (manufactured of AMS 5801 wire): 21-23% Cr, 21-23% Ni, 14-15% W, 0.05-0.08% La, 0.5-0.8% B, 1.2-1.5% Si, Co and impurities to balance. d) Composite Welding Wire D (manufactured of AMS 5694 wire): 23-25% Cr, 11-13% Ni, 1-2.5% B, 1.2-1.5% Si, Fe and impurities to balance.

(74) After drying filler wires were subjected to a heat treatment in a vacuum with a minimum pressure of 10.sup.4 ton within at a temperature range 1120 and 1205 C. at a soaking time of two (2) hours followed by a furnace cooling in vacuum.

(75) Visual and metallographic examination of produced composite filler wires demonstrated formation of continues boriding layer with a thickness that varied from 105 to 175 m. A typical microsturcture of a welding wire produced using this method is shown in FIGS. 4 and 5.

(76) To demonstrate method of a manufacturing of the invented composite welding wires by painting, 100 grams of boron powder of 99% purity was mixed with 100 grams of acrylic based binder and 150 grams of solvent Dowanol solvent. This mixture was carefully stirred to obtain a uniform slurry with the required brush painting viscosity. The slurry was applied to welding wires of I mm in diameter by brush with two layers and left to dry for two hours. Drying resulted in evaporation of solvents, and a boron rich surface layer with excellent bonding to the core wire.

(77) In another example of manufacturing of composite welding wires 60 grams of polyester resin were dissolved in 150 grams of pure acetone. This solution was vigorously stirred until full dissolution of polyester flakes followed by adding of 40 grams of Si powder with size of particles from 1 to 5 micrometers. Stirring was continued with adding of additional amount of acetone as required to obtain suitable for brush painting viscosity. Subsequently the welding wires were painted using a soft brush to apply layer and left in air to dry at an ambient temperature for 15 to 30 minutes. After evaporation of acetone, Si and polyester binder produced the uniform surface layer with good adhesion to the inner core wire that allowed easy handling of produced welding wires without damaging the uniformity of the Si surface layer.

(78) Composite welding wires in spools polyester powder paint with 10 to 45% B and polyester to balance was produced by the electrostatic painting method followed by oven curing at a temperature of 140-160 C. The thickness of the surface layer was regulated from 15 to 500 micrometers to produce welding wires with a bulk content of B from 0.1 to 10%. Standard equipment for the electrostatic powder paint was used. The sections of the spooled welding wire for the automatic GTAW welding is shown in FIG. 13.

(79) To demonstrate GTAW braze welding using the invented composite welding wires, experiments were performed using samples that comprised 304 stainless steel and Inconel 738 substrates and top layers LPM deposited according as shown in FIG. 8 of 1-4 mm in thickness and brazed joints produced by a high temperature brazing in a vacuum furnace using AMS 4777 brazing alloy.

(80) Manual GTAW braze welding process was carried out using the standard CK welding torch with 1/16 inch in diameter non consumable tungsten electrode further the electrode and argon for a protection of the repair area from oxidation and invented composite filler materials in a form of wires of 1-1.5 mm in diameter. The welding current was regulated within range of 20-40 A and arc voltage varied from 9 to 12 V depending on a distance between the tungsten electrode and samples. After establishing of the welding pool, the heating of the LPM was performed throughout the layer of melted filler material preventing latter from overheating and cracking.

(81) Composite welding wires with diameters between 1 and 2 mm were manufactured using electrostatic painting and brush application of B and Si paints. At this stage the wire is termed as being in the green condition. The process is followed by diffusion heat treatment for more than three hours. The coating of the composite welding wire in the green condition contains only B, Si and sacrificial binder. The green coating is made of B and Si and a sacrificial organic binder wherein the binder is not more than. 50 wt. % of the coating. The coating in green condition comprises at least 50% of B and Si with sacrificial binder to balance. The B and Si in the green surface layer represents at least 70% and preferably at least 80% of the total bulk B and Si content of the composite welding wire. After heat treatment and formation of the diffusion layer, the coating is comprised of all alloying elements of the core wire in addition to B and Si. No sacrificial hinder is present in the coating after heat treatment and formation of the diffusion layer.

(82) Composite Welding Wire Compositions

(83) Wire A

(84) Composite Welding Wire A (manufactured of AMS 5837 wire)

(85) Cr: 20-22 wt %, Mo: 9-11 wt %, Nb: 3.5-4%, B: 0.5-0.8 wt %, Ni and impurities to balance

(86) Core wire B content=0.00 wt % and Si content 0.00 wt %

(87) Wire B

(88) Composite Welding Wire B (manufactured of AMS 5839 wire)

(89) Cr: 21-23 wt %, Mo: 1.5-2.5 wt %, W: 13-15 wt %, Al: 0.3-0.5 wt %, Si: 1.5-1.8 wt %, n: 0.5-0.8 wt %, Ni and impurities to balance.

(90) Core wire B content 0.00 wt % and Si content=0.25 wt %

(91) Wire C

(92) Composite Welding Wire C (manufactured of AMS 5801 wire)

(93) Cr: 21-23 wt %, Ni: 21-23 wt %, W: 14-15 wt %, La: 0.05-0.08 wt %, B: 0.5-0.8%, Si: 1.2-1.5 wt %, Co and impurities to balance.

(94) Core wire B content=0.00 wt % and Si content=0.20 wt %

(95) Wire D

(96) Composite Welding Wire D (manufactured of AMS 5694 wire)

(97) Cr: 23-25 wt %, Ni: 11-13 wt %, B: 1-2.5 wt %, Si: 1.2-1.5 wt %, Fe and impurities to balance.

(98) Core wire B content 0.00 wt % and Si content=0.30 wt %

(99) Wire E

(100) Composite Welding Wire E (manufactured from standard wire Rene 80)

(101) Co: 9.5 wt %, Cr: 14 wt %, W: 4 wt %, Mo: 4 wt %, Al: 3 wt %, Ta: 3.3 wt %, Zr: 0.06 wt,

(102) C: 0.17%, Ti: 5 wt %, Fe: 0.3 wt %, Si: 2.1 wt %, Ni and impurities to balance.

(103) Core wire B content=0.015 wt % and Si content=0.00 wt %

(104) Wire F

(105) Composite Welding Wire F (manufactured from standard wire Rene 142)

(106) Co: 12 wt %, Cr: 6.8 wt %, W: 4.9 wt %, Mo: 1.5 wt %, Al: 6.1 wt %, Ta: 6.3 wt %, Zr: 0.02

(107) wt %, C: 0.02 wt %, Re: 2.8 wt %, Ti: 1.0 wt %, Hf: 1.2 wt %, Mn: 0.2 wt %, Si: 1.88 wt %,

(108) Ni and impurities to balance.

(109) Core wire B content=0.015 wt % and Si content=0.00 wt %

(110) TABLE-US-00001 CHART A Boron Silicon Total Bulk Boron Bulk B Content Bulk Si Content and Silicon Composite in Composite in the Composite Content in the Welding Welding Welding Composite Welding Wire Wire, wt. % Wire, wt. % Wire, wt. % A 0.5-0.8 Nil 0.5-0.8 B Nil 1.5-1.8 1.5-1.8 C 0.5-0.8 1.2-1.5 1.7-2.3 D 1-2.5 1.2-1.5 2.2-4 E 0.015 2.1 2.115 F 0.015 1.88 1.895

(111) TABLE-US-00002 CHART B Boron Silicon % of Boron + Boron* Bulk Si Silicon* Total Bulk Silicon in the Bulk B Content Content Content Boron and Surface Layer Content in in the in the in the Silicon Relative to Composite Original Composite Original Content in the Bulk B + Composite Welding Core Welding Core Composite Si Content in Welding Wire, Wire, Wire, Wire, Welding the Composite Wire wt. % wt. % wt. % wt. % Wire, wt. % Welding Wire A 0.5-0.8 Nil Nil Nil 0.5-0.8 100 B Nil Nil 1.5-1.8 0.25 1.5-1.8 83.33-86.11 C 0.5-0.8 Nil 1.2-1.5 0.2 1.7-2.3 88.24-91.3 D 1-2.5 Nil 1.2-1.5 0.3 2.2-4.0 86.36-92.5 E 0.015 0.015 2.1 Nil 2.115 99.29 F 0.015 0.015 1.88 Nil 1.895 99.21

Weld Example 1

(112) Straight and circular coaxial V-grooves of 1-1.5 mm in depths were produced in nickel based LPM top layer that was applied on the 304 stainless steel plate as shown in FIG. 6.

(113) Two circular coaxial welds were made to induce extremely high residual stress aiming to initiate cracking in LPM similar to testing of standard low ductile materials for susceptibility to weld cracking.

(114) GTAW braze welding was made using the Composite Welding Wires A and B.

(115) As shown in FIG. 7, braze welding did not result in cracking of LPM deposit.

(116) The micrographic examination of the repair area in as welded condition did not reveal cracks and other linear indications as shown in FIG. 8.

(117) The depth of the HAZ varied between 7-8 m. No micro discontinuities were found in the HAZ as shown in FIG. 9 after a post weld heat treatment at a temperature of 1120 C.

Weld Example 2

(118) To establish reparability of LPM and Inconel 738 precipitation hardening difficult to weld superalloy high pressure turbine (HPT) blades with the LPM layer on the concave side of airfoils was GTAW welded as described above using Composite Welding Wires B. refer to FIG. 10.

(119) GTAW welding was also made on the convex side of blades directly on Inconel 738 alloy using the same filler material.

(120) Metallographic examination of weld beads produced by GTAW braze welding on LPM and Inconel 738 did not reveal any unacceptable linear discontinuities as shown in FIG. 11 in as welded condition and after heat treatment at a temperature of 1120 C.

Weld Example 3

(121) Successful repair of cracks on Rene 77 nozzle guide vane (NGV) was made using manual GTAW welding with Composite Welding Wires C and welding current of 50-60 A.

(122) Non distructive testing (NDT) and metallographic examination did not reveal any cracks along the fusion zone in as welded condition and after heat treatment at a temperature of 1205 C. for two (2) hours followed by the argon quench.

(123) Typical micrograph of a weld is shown in FIG. 12

Weld Example 4

(124) Successful weld build up on 304 stainless steel substrate using GTAW welding with Composite Welding Wires D and welding current of 40-50 A was carried out demonstrating applicability of the invented composite filler wires for cladding on ferrous materials (stainless steels). NT)T and metallographic examination did not reveal any cracks along the fusion zone and weld beads in as welded condition.

Welding Examples 5 & 6

(125) Composite Welding Wires E and F were manufacture by the application of silicon based slurry to standard welding wires Rene 80 and Rene 142 respectively followed by a vacuum heat treatment at a temperature of 1200 C. for two (2) hours. After heat treatment Composite Welding Wires comprised following below chemical elements in wt. %.

(126) Composite Welding Wires E: 9.5 wt % Co, 14% wt Cr, 4 wt % W, 4 wt Mo, 3 wt % Al, 3.3 wt % Ta, 0.06 wt Zr, 0.17% C, 5 wt % Ti, 0.3 wt % Fe, 2.1 wt Si, Ni and impurities to balance. Composite Welding Wire F: 12 wt % Co, 6.8 wt % Cr, 4.9 wt % W, 1.5 wt % Mo, 6.1 wt % Al, 6.3 wt % Ta. 0.02 wt % Zr, 0.02 wt % C, 2.8 wt % Re, 1.0 wt % Ti, 1.2 wt % Hf, 0.2 wt % Mn, 1.88 wt % Si, Ni and impurities to balance.

(127) Manufactured Composite Welding Rods E and F were used for manual GTAW butt welding of Inconel 738 and Mar M002 bars of 0.50 inch in diameter. Welding was made without any preheating at ambient temperature. Welding parameters were developed to control dilution below 40%.

(128) Welded joints were subjected to two stages standard aging heat treatment in vacuum at a temperature of 1120 C. for two (2) hours followed by 845 C. for twenty four (24) hours and argon quench.

(129) Standard round samples were manufactured and subjected to tensile testing at a temperature of 982 C. as per ASTM E21.

(130) Prior to mechanical testing samples were subjected to radiographic inspection. No indications exceeding 0.1 mm in size where found.

(131) Rupture testing of samples was made a temperature of 982 C. at stresses of 22 KSI as per ASTM E-139.

(132) Mechanical properties of Inconel 738 standard alloy and welding joints are shown in the Table 1.

(133) Table 1. Mechanical Properties of Inconel 738 Alloy and Welding Joints Produced on Inconel 738 and Mar M002 Using Composite Welding Wires E and F at a Temperature of 982 C.

(134) TABLE-US-00003 Material Tensile, Tensile, Tensile, Rupture, Being UTS, Yield, Elongation, Rupture*, Elongation, Tested KSI KSI % Hours % Incone 738 49.35 36.85 15.55 19.8 9.15 (base material) Inconel 738 52.4 38 21.5 16.15 6.55 Welded joints produced using Composite Welding Wire E Mar M002 80.95 60.95 9.35 173.3 12 Weld Joints produced using Composite Welding Wire F Note: Results are average of two tests.

(135) As follows from Table 1 welded joints produced using Composite Welding Wires E and F at an ambient temperature were free of cracks and had superior mechanical properties, while GTAW butt welding of Inconel 738 without preheating resulted in extensive cracking of weld beads and HAZ.

(136) The present invention has been described in a connection with most typical examples and embodiments. However, it will be understood by those skilled in the art that the invention is capable of other variations and modifications without departing from its scope as represented by the appended claims. The above are hereby incorporated by reference.