CA2735302A1 - Blade and method of repair and manufacturing the same - Google Patents
Blade and method of repair and manufacturing the same Download PDFInfo
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- CA2735302A1 CA2735302A1 CA2735302A CA2735302A CA2735302A1 CA 2735302 A1 CA2735302 A1 CA 2735302A1 CA 2735302 A CA2735302 A CA 2735302A CA 2735302 A CA2735302 A CA 2735302A CA 2735302 A1 CA2735302 A1 CA 2735302A1
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- Prior art keywords
- blade
- alpha
- airfoil
- per
- beta
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
- B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
- B23P15/02—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass turbine or like blades from one piece
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
- B21K3/00—Making engine or like machine parts not covered by sub-groups of B21K1/00; Making propellers or the like
- B21K3/04—Making engine or like machine parts not covered by sub-groups of B21K1/00; Making propellers or the like blades, e.g. for turbines; Upsetting of blade roots
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/20—Bonding
- B23K26/32—Bonding taking account of the properties of the material involved
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/34—Laser welding for purposes other than joining
- B23K26/342—Build-up welding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/24—Selection of soldering or welding materials proper
- B23K35/32—Selection of soldering or welding materials proper with the principal constituent melting at more than 1550 degrees C
- B23K35/325—Ti as the principal constituent
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
- B23P6/00—Restoring or reconditioning objects
- B23P6/002—Repairing turbine components, e.g. moving or stationary blades, rotors
- B23P6/007—Repairing turbine components, e.g. moving or stationary blades, rotors using only additive methods, e.g. build-up welding
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C14/00—Alloys based on titanium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
- C22F1/18—High-melting or refractory metals or alloys based thereon
- C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
- F01D5/005—Repairing methods or devices
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2101/00—Articles made by soldering, welding or cutting
- B23K2101/001—Turbines
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2103/00—Materials to be soldered, welded or cut
- B23K2103/08—Non-ferrous metals or alloys
- B23K2103/14—Titanium or alloys thereof
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2103/00—Materials to be soldered, welded or cut
- B23K2103/18—Dissimilar materials
Abstract
A blade for turbine engines comprises a stressed section of an airfoil and a blade retainer manufactured of a near alpha or .alpha.-.beta. titanium alloys having equiaxed alpha and intergranular beta phases that is produced by a consecutive forging and heat treatment cycles to enhance high rupture properties and a leading edge, which is produced by a laser cladding using the similar filler materials and parameters or differential heat treatment allowing formation of a microstructure with a plate-like alpha and retained beta phase having high fracture toughness.
Description
BLADE AND METHOD OF REPAIR AND MANUFACTURING THE SAME
The invent ion is related to the airfoil of turbine engine and can be used for a manufacturing and repair of blisks, fan and compressor blades made of near alpha and alpha-beta titanium alloys.
It is well known that titanium and it alloys undergo the allotropic phase transformation also known as a polymorphous transformation at a temperature of 885 C that results in changing of a crystallite lattice from a close-package hexagonal (alpha) to a body centered cubic know also as beta phase.
The temperature of a polymorphous transformation know also as a beta transus temperature depends on interstitial impurities and alloying elements that either increase or reduce a temperature of a polymorphous transformation.
Based on structure and phase compositions titanium alloys belong to one of following classes:
alpha, near alpha, alpha-beta and metastable beta. These classes denote peculiarities of microstructure, mechanical and corrosion properties of all titanium alloys after welding and heat treatment.
Alpha alloys usually do not contain beta phase after cooling from a high temperature neither after welding nor after heat treatment.
Near alpha alloys contain limited amount of beta phase occupying a transition place between alpha and alpha-beta alloys that can produce a large amount of equilibrium alpha, further (a) or martensitic a'-phase, which is an oversaturated solid solution of alloying elements in a close-package hexagonala-phase and beta, furtherf3-phase.
A metastable beta alloys tend to retain the high temperaturef3-phase at ambient temperature.
This invention is applicable for blades manufactured of near alpha and toa-f3titanium alloys.
Therefore, it might be useful to discuss a structure transformation of this group of alloys in more details using as an example the well know Ti-6%AI-4%V, further 6-4-Ti (titanium) alloy, after cooling from temperature exceeding fi- transus that represents the welding metal and heat affected zone (HAZ).
During welding and heat treatment depending on a cooling rate, welds and HAZ
of Ti-6V-4V
alloy can from three different types of a micro structure.
The water quench results in a formation of a martensitica'-phase with a precipitation off3-phase prior to beta grain boundaries.
The martensitica' +fstructure microstructure forms also during air cooling, which is close to a cooling rate of welding joints that are produced by a conventional fusion welding such as gas tungsten arc welding, plasma, electron beam or laser welding. However, the content of vanadium in the oversaturated solid solution of martensitic a'-phase in this case is usually less than after a water quenching.
The equilibrium plate-like a-phase and retained C3-phase prior grain boundaries is usually formed during a furnace cooling in vacuum or argon at a very low cooling rate.
As it was shown in the `Fatigue Data Book: Light Structural Alloys, ASM
International , 2008, 397 p', near alpha Ti-8%Al-1%Mo-1%V alloy, also known as 8-1-1 titanium alloy, after beta anneal has impact toughness of 104 MPax while after alpha anneal just 50 MPax \Im-.
The fan blades are most critical engine components. Therefore, they are manufactured of Ti-6Al-4V or 8-1-1 titanium alloys by multi steps forging and heat treatment cycles to produce the equiaxed globular structure of the equilibriums alpha phase with fine precipitation of beta phase to enhance high rupture and low cycle fatigue properties. However, this structure does not have the best impact toughness that is extremely important for the leading edge of fan blades that are in a permanent risk of a FOD such as bird strike, ice pellets and stones.
Also, erosion reduces a chord width making eminent a weld repair of fan blades to restore the leading edge geometry and chord width using the electron beam patch and other types of weld repairs that were disclosed in prior arts US 4,118,147; 5,092,942; 5,142,778; 5,479,704 ; 5,795,412 and 6,339,878. However, the electron beam patch weld repair is a low productivity and high cost process.
A laser cladding that was disclosed in patents US 5,897,801; 6,269,540;
6,659,332, 6,972,390 and 7,137,544 is more cost effective process. However, it has not been used for a full leading edge (LE) repair because it has been believed that casting structure of fusion welds produced by a conventional gas tungsten arc welding (GTAW), plasma and laser will not be able to withstand a potential FOD without fan blade failure or fracture.
Therefore, the development of a new blade that can combine a high impact fracture of the leading edge to withstand the probable foreign object damage (FOD) and high rapture and tensile properties in most stressed section of the airfoil and blade retainer will be of a great commercial value to the aviation industry.
A further objective of this invention is a development of a new method for a repair of these blades using a laser cladding aiming to produce the required structure composition in "as welded" condition.
Another objective of the invention is a development of a new method aiming to produce the desirable structure of blade by a heat treatment during a manufacturing cycle.
We have found that due to achieve these objectives a blade should comprise a stressed section of airfoil and a blade retainer manufactured of a near alpha or alpha-beta titanium alloy having a structure of equiaxed alpha and intergranular beta phases or a similar structure composition, which is produced by a consecutive forging and heat treatment cycles to enhance high rapture and tensile properties, and a leading edge that is made of the same alpha-beta titanium alloy having a plate-like alpha phase structure with a retained beta phase within and along alpha plates and prior grain boundaries having high impact toughness, and wherein a leading edge is bonded to an airfoil via a transition layer having a variable morphology of alpha and beta titanium phases.
In accordance with another preferable embodiment, a trailing edge and a tip of the airfoil are produced with the similar to the leading edge structure and phase composition.
This invention can be used also to produce shrouded blades.
Manufacturing or repair of blades as per the preferable embodiment includes step of a multi pass laser cladding to a stub of a defect free airfoil to produce at least the leading edge using powder with similar chemical composition, laser beam power of 200-400 watt per each 1 mm width of the airfoil, laser beam diameter of 0.75-1.8 mm, welding speed of 12.5-100 mm per minute and powder feed rate of 0.4-2 grams per minute, which results in a formation of a microstructure consisting of a plate-like alpha phase with a retained beta phase along alpha plates and prior grain boundaries.
To allow cladding of blades with a variable thickness, a welding head is oscillated across a cladding direction with a traveling speed of 8-12 greater than the welding speed at an amplitude of maximum of three times greater that the laser beam spot diameter, proportionally increasing the laser beam power to maintain a ratio of the beam power to the width of the oscillation from 1 to 3.
As per other preferable embodiment due to produce the same microstructure throughout the leading edge at least one technological pass should be deposited to the top of the repaired leading edge followed by a machining off the latter to restore required geometry of the blade.
To perform a stress relief without affecting the desirable microstructure in the leading edge blades should be subjected to a post weld heat treatment below of the transus temperature, that is selected with range of 475 - 650 C in accordance with a relevant OEM
standards.
And finally, to produce the desirable micro structure in the leading edge preserving a forging equiaxed structure in most stressed sections of the airfoil and blade retainer during preferably in manufacturing cycle as well as in repair, the fan blade might be subjected to a differential heat treatment, wherein the leading edge is heated to a temperature above the beta transus at least for 3 minutes while maintaining a temperature of stressed sections of the blade at a temperature below of 680 C followed by a controlled cooling of the leading edge with at a rate of 0.1-2 C
per min during the polymorphous 0 -* a transformation.
Figure 1 is the schematic presentation of the blade, wherein 1 is airfoil, 2-shroud, 3-blade retainer also known as a dove tail, 4-leading edge, 5-transition layer, 6-tip, 7-trailing edge.
Figure 2 depicts the laser cladding of the fan blade in the Liburdi LAW5000 laser system.
Figure 3 shows the microstructure of the laser cladding using optimal parameters prior to a heat treatment, further in `as welded' condition.
Figure 4 is the micrograph of the transition layer that is also known as a heat affected zone (HAZ).
Figure 5 depicts the typical microstructure of the base material also known as a parent material.
Figure 6 is a distribution of microhardness from the airfoil parent material via HAZ and 10 passes of clad welds that were produce on the leading edge of a fan blade.
The fan blades are most critical engine components. Therefore, they are manufactured of Ti-6A1-4V or Ti-8A1-1 Mo-1 V titanium alloys by multi steps forging and heat treatment cycles to produce the equiaxed globular structure of the equilibriums alpha phase with fine precipitation of beta phase to enhance high rupture and low cycle fatigue properties.
The depicted in Figure 1 fan blade have the complex of microstructure and phase compositions that guaranty the highest level of impact toughness at the leading edge (4) and maximum rupture properties in the most stressed areas of airfoil (1) and blade retainer (3).
The invented method allows manufacturing of new blades during manufacturing and modification of serviceable ones during repair.
Undersized or rejected due to other reasons serviceable fan blades are usually routed to OEM or FAA approved repair stations for further inspection and repairs that creates an excellent opportunity for their modification as per the invented method.
The typical repair work scope includes the sequence of the following below standard steps that might be performed based on the applicable OEM Standard Process Manual (SPM).
The first and obvious step after a visual inspection of fan blades is degreasing using either the applicable SPM alkaline process or aqueous cleaning followed by a fluorescent penetration inspection (FPI) also known as non destructive testing.
In case if no rejectable defects are found in the highly stressed area, fan blades are routed further for machining to remove defective materials at the leading or trailing edge or tip to a standard dimension leaving a stub of a defect free airfoil material as shown in Figure 2.
To remove machining residues and prepare fan blades for a laser cladding parts should undergo alkaline degreasing followed by cold and hot water rinsing and air draying. To prevent blades from contamination it is essential to vacuum seal parts using plastic bags.
Restoration of tip, leading and trailing edges is done by a laser cladding using either filler wire or powder having chemical composition similar to a parent material.
Usually, laser cladding is performed using a laser beam power from 200 to 1400 watt depending on material thickness to maintain a thermal conductive mode and prevent plasma formation. The combination of a thermal conductive mode and low traveling speed also known as welding speed produces an excellent boding of clad welds with minimum penetration of a substrate. Also, it slows down a cooling rate, which is critical for a formation of a desirable microstructure.
Due to a high affinity of titanium and it alloy for oxygen and nitrogen, argon, helium, and mixture of these gasses may be used for a protection of a welding or repair area from a contamination. However, taking into consideration a sensitivity of a microstructure of near alpha and a - 0 titanium alloys to cooling rate argon with low heat conductivity is a preferable inert gas.
The laser cladding can be made using filler wire or powder made of similar filler materials. In both cases a laser beam is focused onto a repair area of a fan blade to create a molten paddle of a parent material. After that, filler material in a form of powder or filler wire is introduced into the welding puddle to produce clad welds. The laser head is moved forward and oscillated across the repair are wherein the thickness of latter is exceeding the laser spot diameter. This process produces a near net shape repair minimizing final machining and polishing.
The key element of the invented method is laser cladding parameters. Usually, a conventional laser cladding and welding result in a formation of a typical for air cooling martensitic like structure on near alpha and a - (3 titanium alloys. In the invented method, the multi pass laser cladding with a relatively high heat input, which is produced by a combination of a low power laser beam and low welding speed, as well as multiple reheating of previous weld deposits above a beta transus temperature and multiple polymorphous 13 -p a transformation and recrystallization during deposition consecutive layers results in a formation of a plate-like alpha phase structure with a retained beta phase along alpha plates and prior grain boundaries as shown in Figure 3 with a superior impact toughness. As it was found by experiments, deviation of laser cladding parameters from the specified range results in a formation of a martensitic structure that has low fracture and impact toughness typical for welds produced by the conventional fusion welding. Also, the last layer has a transition structure between typical martensitic like and furnace cooled. Therefore, the preferable embodiment should include the deposition of at least one technological layer for a heat treatment of the previous layer followed by removing of latter by machining or other means due to produce desirable structure throughout the leading edge.
After laser cladding, the fan blade is subjected to non destructive testing (NDT) by the FPI as per AMS 2647 or relevant OEM standards. The laser cladding area is also subjected to x-ray inspection for weld discontinuities as per applicable OEM standards. Usually, no linear indications and pores exceeding of 0.15 mm in diameter are allowed.
After NDT accepted parts are degreased using alkaline and subjected to a heat treatment in the alpha region at a temperature from 475 to 650 C that does not result in a polymorphous transformation and recrystallization of near alpha and alpha-beta titanium alloys. This heat treatment reduce residual stresses and results in a decomposition of martensitic a'-phase. This process is also known as an aging that is accompanied by a precipitation of fine particles of (--phase along boundaries and within a-plates without changing of morphology of last ones. Aging also increase hardness of clad deposits as shown in Figure 6 and tensile properties of Ti-6A1-4V
alloy.
After heat treatment repaired areas of fan blades are machined to final dimensions followed by polishing and ball burnishing to restore a surface roughness.
The final steps of a modification and repair of fan blades as per the preferable embodiment is NDT and dimensional inspection to relevant OEM standards followed by a shot peening of blade retainers and glass bead peening of airfoils to induce compressive stresses increasing a high cycle fatigue (HCF).
The described above method was developed mostly for a modification of serviceable fan blades during a repair cycle.
The differential heat treatment of fan blades is more cost effective process for a manufacturing of fan blades, wherein the leading edge of forged blades may be subjected to a heat treatment at a temperature exceeding beta transus, usually from 890 to 950 C at least for 3 minutes, at the leading edge while maintaining a temperature of stressed sections of the airfoil and blade retainer at a temperature below of 650 C followed by a controlled cooling of the leading edge with at a rate of 0.1-2 C per min during a polymorphous (3 -* a transformation.
The differential heat treatment of fan blades as per another preferable embodiment can be made in a vacuum furnace using the press form with a provision of a temperature control of the blade in stressed area below of 650 C that is shielded from the heating elements that are situated either side of the leading edge by several rows of heat shields. Titanium has very low heat conductivity.
So, it is feasible to preheat the leading edge to a temperature from 890 to 1000 C for more than 3 minutes followed by a slow cooling of fan blades with the furnace at a range of 0.1-2 C per min during at least a polymorphous (3 -* a transformation to produce a plate-like alpha phase structure with a retained beta phase along alpha plates and prior grain boundaries, while stressed areas will have a the typical for forging globular equiaxed a-phase with the intergranular beta phase precipitations.
Therefore, as follows from above, the new and unique combination of microstructures in the leading and trailing edges and stressed sections of blades, which was not known from prior arts, was produced in different areas of the same fan blade manufactured of the same alloy having the same chemical composition by a laser cladding using the developed parameters or during manufacturing using a differential heat treatment.
The demonstration of a feasibility of this invention was made by a laser cladding repair on the leading edge and tip of fan blades manufacture of 6-4-Ti alloy by forging followed by a standard post weld heat treatment.
The laser cladding was made using Liburdi LAW 5000 system shown in Figure 2, IPG fiber laser, 6-4-Ti filler powder and following below cladding (welding) parameters:
Min laser beam power: 225 Watt (at a tin section of an article) Max laser beam power: 400 Watt Welding speed: 76.2 mm/min Oscillation speed: 762 mm/min Powder: 45-75 m Powder flow rate: 0.8 gram/min Focus distance: 150 mm Nozzle to the leading edge standoff distance: 9 mm Flow rate of argon to The laser head and trailer: 21 1/min Flow rate of a carrier Gas (argon): 1 1/min After cladding one fan blade was subjected to the post weld heat treatment at a temperature of 580 C for four (4) hours.
Second one was subjected to a metallographic evaluation of a thin section produced without oscillation and thickest section that was restored to required dimensions using the oscillation above.
Typical microstructures of Ti-6%Al-4%V clad welds in "as welded" condition are shown in Figures 3 and 4.
It was found that a laser cladding using the specified parameters produced a microstructure that constituted of plate-like a-phase and retained p-phase prior beta grain boundaries typical for a furnace cooling of alpha-beta titanium alloys from a temperature exceeding beta transus. This fact was not known before from prior arts. As a result, microhardness of laser clad deposits in "as welded" condition was at the level of a parent material as shown in Figure 6. The parent material had the typical forging equiaxed structure as shown in Figure 5.
The post weld heat treatment slightly increase microhardness of clad welds due to aging and precipitation of fine particles of beta phase within sub grains of alpha phase without affecting the desirable morphology of alpha phase. The transition area also knows as the HAZ
constituted of combination of equilibrium forging structure of alpha phase adjacent to a parent material to plate like alpha phase with retained beta adjacent to a fusion line.
The key element of the invented method is laser cladding parameters.
Increasing the welding speed and reducing the laser beam power had resulted in a formation or martensitic a'-phase typical for a conventional fusion welding.
Increasing the heat input was essential from a metallurgical point of view but it affected a formation of a net shape clad welds.
Therefore, as follows from the example above and description of the invention, objectives of latter were achieved by a creating of a plate-like alpha phase structure with a retained beta phase within and along alpha plates and prior grain boundaries having high impact and fracture toughness in the tip of the airfoil, leading and trailing edges and equiaxed alpha and intergranular beta phases or a similar forging structure in the highly stressed sections of the airfoil and blade retainer, as well as method of repair and modification of these blades by a laser cladding using developed parameters and manufacturing of new blades by a differential heat treatment.
The invent ion is related to the airfoil of turbine engine and can be used for a manufacturing and repair of blisks, fan and compressor blades made of near alpha and alpha-beta titanium alloys.
It is well known that titanium and it alloys undergo the allotropic phase transformation also known as a polymorphous transformation at a temperature of 885 C that results in changing of a crystallite lattice from a close-package hexagonal (alpha) to a body centered cubic know also as beta phase.
The temperature of a polymorphous transformation know also as a beta transus temperature depends on interstitial impurities and alloying elements that either increase or reduce a temperature of a polymorphous transformation.
Based on structure and phase compositions titanium alloys belong to one of following classes:
alpha, near alpha, alpha-beta and metastable beta. These classes denote peculiarities of microstructure, mechanical and corrosion properties of all titanium alloys after welding and heat treatment.
Alpha alloys usually do not contain beta phase after cooling from a high temperature neither after welding nor after heat treatment.
Near alpha alloys contain limited amount of beta phase occupying a transition place between alpha and alpha-beta alloys that can produce a large amount of equilibrium alpha, further (a) or martensitic a'-phase, which is an oversaturated solid solution of alloying elements in a close-package hexagonala-phase and beta, furtherf3-phase.
A metastable beta alloys tend to retain the high temperaturef3-phase at ambient temperature.
This invention is applicable for blades manufactured of near alpha and toa-f3titanium alloys.
Therefore, it might be useful to discuss a structure transformation of this group of alloys in more details using as an example the well know Ti-6%AI-4%V, further 6-4-Ti (titanium) alloy, after cooling from temperature exceeding fi- transus that represents the welding metal and heat affected zone (HAZ).
During welding and heat treatment depending on a cooling rate, welds and HAZ
of Ti-6V-4V
alloy can from three different types of a micro structure.
The water quench results in a formation of a martensitica'-phase with a precipitation off3-phase prior to beta grain boundaries.
The martensitica' +fstructure microstructure forms also during air cooling, which is close to a cooling rate of welding joints that are produced by a conventional fusion welding such as gas tungsten arc welding, plasma, electron beam or laser welding. However, the content of vanadium in the oversaturated solid solution of martensitic a'-phase in this case is usually less than after a water quenching.
The equilibrium plate-like a-phase and retained C3-phase prior grain boundaries is usually formed during a furnace cooling in vacuum or argon at a very low cooling rate.
As it was shown in the `Fatigue Data Book: Light Structural Alloys, ASM
International , 2008, 397 p', near alpha Ti-8%Al-1%Mo-1%V alloy, also known as 8-1-1 titanium alloy, after beta anneal has impact toughness of 104 MPax while after alpha anneal just 50 MPax \Im-.
The fan blades are most critical engine components. Therefore, they are manufactured of Ti-6Al-4V or 8-1-1 titanium alloys by multi steps forging and heat treatment cycles to produce the equiaxed globular structure of the equilibriums alpha phase with fine precipitation of beta phase to enhance high rupture and low cycle fatigue properties. However, this structure does not have the best impact toughness that is extremely important for the leading edge of fan blades that are in a permanent risk of a FOD such as bird strike, ice pellets and stones.
Also, erosion reduces a chord width making eminent a weld repair of fan blades to restore the leading edge geometry and chord width using the electron beam patch and other types of weld repairs that were disclosed in prior arts US 4,118,147; 5,092,942; 5,142,778; 5,479,704 ; 5,795,412 and 6,339,878. However, the electron beam patch weld repair is a low productivity and high cost process.
A laser cladding that was disclosed in patents US 5,897,801; 6,269,540;
6,659,332, 6,972,390 and 7,137,544 is more cost effective process. However, it has not been used for a full leading edge (LE) repair because it has been believed that casting structure of fusion welds produced by a conventional gas tungsten arc welding (GTAW), plasma and laser will not be able to withstand a potential FOD without fan blade failure or fracture.
Therefore, the development of a new blade that can combine a high impact fracture of the leading edge to withstand the probable foreign object damage (FOD) and high rapture and tensile properties in most stressed section of the airfoil and blade retainer will be of a great commercial value to the aviation industry.
A further objective of this invention is a development of a new method for a repair of these blades using a laser cladding aiming to produce the required structure composition in "as welded" condition.
Another objective of the invention is a development of a new method aiming to produce the desirable structure of blade by a heat treatment during a manufacturing cycle.
We have found that due to achieve these objectives a blade should comprise a stressed section of airfoil and a blade retainer manufactured of a near alpha or alpha-beta titanium alloy having a structure of equiaxed alpha and intergranular beta phases or a similar structure composition, which is produced by a consecutive forging and heat treatment cycles to enhance high rapture and tensile properties, and a leading edge that is made of the same alpha-beta titanium alloy having a plate-like alpha phase structure with a retained beta phase within and along alpha plates and prior grain boundaries having high impact toughness, and wherein a leading edge is bonded to an airfoil via a transition layer having a variable morphology of alpha and beta titanium phases.
In accordance with another preferable embodiment, a trailing edge and a tip of the airfoil are produced with the similar to the leading edge structure and phase composition.
This invention can be used also to produce shrouded blades.
Manufacturing or repair of blades as per the preferable embodiment includes step of a multi pass laser cladding to a stub of a defect free airfoil to produce at least the leading edge using powder with similar chemical composition, laser beam power of 200-400 watt per each 1 mm width of the airfoil, laser beam diameter of 0.75-1.8 mm, welding speed of 12.5-100 mm per minute and powder feed rate of 0.4-2 grams per minute, which results in a formation of a microstructure consisting of a plate-like alpha phase with a retained beta phase along alpha plates and prior grain boundaries.
To allow cladding of blades with a variable thickness, a welding head is oscillated across a cladding direction with a traveling speed of 8-12 greater than the welding speed at an amplitude of maximum of three times greater that the laser beam spot diameter, proportionally increasing the laser beam power to maintain a ratio of the beam power to the width of the oscillation from 1 to 3.
As per other preferable embodiment due to produce the same microstructure throughout the leading edge at least one technological pass should be deposited to the top of the repaired leading edge followed by a machining off the latter to restore required geometry of the blade.
To perform a stress relief without affecting the desirable microstructure in the leading edge blades should be subjected to a post weld heat treatment below of the transus temperature, that is selected with range of 475 - 650 C in accordance with a relevant OEM
standards.
And finally, to produce the desirable micro structure in the leading edge preserving a forging equiaxed structure in most stressed sections of the airfoil and blade retainer during preferably in manufacturing cycle as well as in repair, the fan blade might be subjected to a differential heat treatment, wherein the leading edge is heated to a temperature above the beta transus at least for 3 minutes while maintaining a temperature of stressed sections of the blade at a temperature below of 680 C followed by a controlled cooling of the leading edge with at a rate of 0.1-2 C
per min during the polymorphous 0 -* a transformation.
Figure 1 is the schematic presentation of the blade, wherein 1 is airfoil, 2-shroud, 3-blade retainer also known as a dove tail, 4-leading edge, 5-transition layer, 6-tip, 7-trailing edge.
Figure 2 depicts the laser cladding of the fan blade in the Liburdi LAW5000 laser system.
Figure 3 shows the microstructure of the laser cladding using optimal parameters prior to a heat treatment, further in `as welded' condition.
Figure 4 is the micrograph of the transition layer that is also known as a heat affected zone (HAZ).
Figure 5 depicts the typical microstructure of the base material also known as a parent material.
Figure 6 is a distribution of microhardness from the airfoil parent material via HAZ and 10 passes of clad welds that were produce on the leading edge of a fan blade.
The fan blades are most critical engine components. Therefore, they are manufactured of Ti-6A1-4V or Ti-8A1-1 Mo-1 V titanium alloys by multi steps forging and heat treatment cycles to produce the equiaxed globular structure of the equilibriums alpha phase with fine precipitation of beta phase to enhance high rupture and low cycle fatigue properties.
The depicted in Figure 1 fan blade have the complex of microstructure and phase compositions that guaranty the highest level of impact toughness at the leading edge (4) and maximum rupture properties in the most stressed areas of airfoil (1) and blade retainer (3).
The invented method allows manufacturing of new blades during manufacturing and modification of serviceable ones during repair.
Undersized or rejected due to other reasons serviceable fan blades are usually routed to OEM or FAA approved repair stations for further inspection and repairs that creates an excellent opportunity for their modification as per the invented method.
The typical repair work scope includes the sequence of the following below standard steps that might be performed based on the applicable OEM Standard Process Manual (SPM).
The first and obvious step after a visual inspection of fan blades is degreasing using either the applicable SPM alkaline process or aqueous cleaning followed by a fluorescent penetration inspection (FPI) also known as non destructive testing.
In case if no rejectable defects are found in the highly stressed area, fan blades are routed further for machining to remove defective materials at the leading or trailing edge or tip to a standard dimension leaving a stub of a defect free airfoil material as shown in Figure 2.
To remove machining residues and prepare fan blades for a laser cladding parts should undergo alkaline degreasing followed by cold and hot water rinsing and air draying. To prevent blades from contamination it is essential to vacuum seal parts using plastic bags.
Restoration of tip, leading and trailing edges is done by a laser cladding using either filler wire or powder having chemical composition similar to a parent material.
Usually, laser cladding is performed using a laser beam power from 200 to 1400 watt depending on material thickness to maintain a thermal conductive mode and prevent plasma formation. The combination of a thermal conductive mode and low traveling speed also known as welding speed produces an excellent boding of clad welds with minimum penetration of a substrate. Also, it slows down a cooling rate, which is critical for a formation of a desirable microstructure.
Due to a high affinity of titanium and it alloy for oxygen and nitrogen, argon, helium, and mixture of these gasses may be used for a protection of a welding or repair area from a contamination. However, taking into consideration a sensitivity of a microstructure of near alpha and a - 0 titanium alloys to cooling rate argon with low heat conductivity is a preferable inert gas.
The laser cladding can be made using filler wire or powder made of similar filler materials. In both cases a laser beam is focused onto a repair area of a fan blade to create a molten paddle of a parent material. After that, filler material in a form of powder or filler wire is introduced into the welding puddle to produce clad welds. The laser head is moved forward and oscillated across the repair are wherein the thickness of latter is exceeding the laser spot diameter. This process produces a near net shape repair minimizing final machining and polishing.
The key element of the invented method is laser cladding parameters. Usually, a conventional laser cladding and welding result in a formation of a typical for air cooling martensitic like structure on near alpha and a - (3 titanium alloys. In the invented method, the multi pass laser cladding with a relatively high heat input, which is produced by a combination of a low power laser beam and low welding speed, as well as multiple reheating of previous weld deposits above a beta transus temperature and multiple polymorphous 13 -p a transformation and recrystallization during deposition consecutive layers results in a formation of a plate-like alpha phase structure with a retained beta phase along alpha plates and prior grain boundaries as shown in Figure 3 with a superior impact toughness. As it was found by experiments, deviation of laser cladding parameters from the specified range results in a formation of a martensitic structure that has low fracture and impact toughness typical for welds produced by the conventional fusion welding. Also, the last layer has a transition structure between typical martensitic like and furnace cooled. Therefore, the preferable embodiment should include the deposition of at least one technological layer for a heat treatment of the previous layer followed by removing of latter by machining or other means due to produce desirable structure throughout the leading edge.
After laser cladding, the fan blade is subjected to non destructive testing (NDT) by the FPI as per AMS 2647 or relevant OEM standards. The laser cladding area is also subjected to x-ray inspection for weld discontinuities as per applicable OEM standards. Usually, no linear indications and pores exceeding of 0.15 mm in diameter are allowed.
After NDT accepted parts are degreased using alkaline and subjected to a heat treatment in the alpha region at a temperature from 475 to 650 C that does not result in a polymorphous transformation and recrystallization of near alpha and alpha-beta titanium alloys. This heat treatment reduce residual stresses and results in a decomposition of martensitic a'-phase. This process is also known as an aging that is accompanied by a precipitation of fine particles of (--phase along boundaries and within a-plates without changing of morphology of last ones. Aging also increase hardness of clad deposits as shown in Figure 6 and tensile properties of Ti-6A1-4V
alloy.
After heat treatment repaired areas of fan blades are machined to final dimensions followed by polishing and ball burnishing to restore a surface roughness.
The final steps of a modification and repair of fan blades as per the preferable embodiment is NDT and dimensional inspection to relevant OEM standards followed by a shot peening of blade retainers and glass bead peening of airfoils to induce compressive stresses increasing a high cycle fatigue (HCF).
The described above method was developed mostly for a modification of serviceable fan blades during a repair cycle.
The differential heat treatment of fan blades is more cost effective process for a manufacturing of fan blades, wherein the leading edge of forged blades may be subjected to a heat treatment at a temperature exceeding beta transus, usually from 890 to 950 C at least for 3 minutes, at the leading edge while maintaining a temperature of stressed sections of the airfoil and blade retainer at a temperature below of 650 C followed by a controlled cooling of the leading edge with at a rate of 0.1-2 C per min during a polymorphous (3 -* a transformation.
The differential heat treatment of fan blades as per another preferable embodiment can be made in a vacuum furnace using the press form with a provision of a temperature control of the blade in stressed area below of 650 C that is shielded from the heating elements that are situated either side of the leading edge by several rows of heat shields. Titanium has very low heat conductivity.
So, it is feasible to preheat the leading edge to a temperature from 890 to 1000 C for more than 3 minutes followed by a slow cooling of fan blades with the furnace at a range of 0.1-2 C per min during at least a polymorphous (3 -* a transformation to produce a plate-like alpha phase structure with a retained beta phase along alpha plates and prior grain boundaries, while stressed areas will have a the typical for forging globular equiaxed a-phase with the intergranular beta phase precipitations.
Therefore, as follows from above, the new and unique combination of microstructures in the leading and trailing edges and stressed sections of blades, which was not known from prior arts, was produced in different areas of the same fan blade manufactured of the same alloy having the same chemical composition by a laser cladding using the developed parameters or during manufacturing using a differential heat treatment.
The demonstration of a feasibility of this invention was made by a laser cladding repair on the leading edge and tip of fan blades manufacture of 6-4-Ti alloy by forging followed by a standard post weld heat treatment.
The laser cladding was made using Liburdi LAW 5000 system shown in Figure 2, IPG fiber laser, 6-4-Ti filler powder and following below cladding (welding) parameters:
Min laser beam power: 225 Watt (at a tin section of an article) Max laser beam power: 400 Watt Welding speed: 76.2 mm/min Oscillation speed: 762 mm/min Powder: 45-75 m Powder flow rate: 0.8 gram/min Focus distance: 150 mm Nozzle to the leading edge standoff distance: 9 mm Flow rate of argon to The laser head and trailer: 21 1/min Flow rate of a carrier Gas (argon): 1 1/min After cladding one fan blade was subjected to the post weld heat treatment at a temperature of 580 C for four (4) hours.
Second one was subjected to a metallographic evaluation of a thin section produced without oscillation and thickest section that was restored to required dimensions using the oscillation above.
Typical microstructures of Ti-6%Al-4%V clad welds in "as welded" condition are shown in Figures 3 and 4.
It was found that a laser cladding using the specified parameters produced a microstructure that constituted of plate-like a-phase and retained p-phase prior beta grain boundaries typical for a furnace cooling of alpha-beta titanium alloys from a temperature exceeding beta transus. This fact was not known before from prior arts. As a result, microhardness of laser clad deposits in "as welded" condition was at the level of a parent material as shown in Figure 6. The parent material had the typical forging equiaxed structure as shown in Figure 5.
The post weld heat treatment slightly increase microhardness of clad welds due to aging and precipitation of fine particles of beta phase within sub grains of alpha phase without affecting the desirable morphology of alpha phase. The transition area also knows as the HAZ
constituted of combination of equilibrium forging structure of alpha phase adjacent to a parent material to plate like alpha phase with retained beta adjacent to a fusion line.
The key element of the invented method is laser cladding parameters.
Increasing the welding speed and reducing the laser beam power had resulted in a formation or martensitic a'-phase typical for a conventional fusion welding.
Increasing the heat input was essential from a metallurgical point of view but it affected a formation of a net shape clad welds.
Therefore, as follows from the example above and description of the invention, objectives of latter were achieved by a creating of a plate-like alpha phase structure with a retained beta phase within and along alpha plates and prior grain boundaries having high impact and fracture toughness in the tip of the airfoil, leading and trailing edges and equiaxed alpha and intergranular beta phases or a similar forging structure in the highly stressed sections of the airfoil and blade retainer, as well as method of repair and modification of these blades by a laser cladding using developed parameters and manufacturing of new blades by a differential heat treatment.
Claims (10)
1. Blade manufactured of near alpha or .alpha.-.beta. titanium alloys comprises an airfoil and a blade retainer, wherein a highly stressed sections of an airfoil and a blade retainer are manufactured of an alpha-beta titanium alloy having an equiaxed alpha and intergranular beta phases or a similar structure that is produced by a consecutive forging and heat treatment cycles and a leading edge having a plate-like alpha phase structure with a retained beta phase within and along alpha plates and prior grain boundaries, that is bonded to a stressed section of an airfoil via a transition layer having a variable morphology of an alpha and a beta titanium phases.
2. Blade as per claim 1, wherein a trailing edge of the airfoil has the same structure as the leading edge.
3. Blade as per claim 1, wherein a tip of the airfoil has the same structure as the leading edge.
4. Blade as per claim 1 comprises a shroud.
5. Method of repair and manufacturing of the blade as per claim 1 includes steps of:
a) machining off a damaged portion of the airfoil removing minimum required material to leave the stub of a sound free of defects parent material, b) cleaning, c) multi pass laser cladding to the stub of the airfoil using a laser beam power of 200-400 watt per each 1 mm width of the airfoil, laser beam diameter of 0.75-1.8 mm, welding speed of 12.5- 100 mm per min and a powder feeding rate of 0.4-2 grams per minute.
d) heat treatment, e) machining of the repair area to reproduce the original geometry of the airfoil, and f) nondestructive testing of the blade.
a) machining off a damaged portion of the airfoil removing minimum required material to leave the stub of a sound free of defects parent material, b) cleaning, c) multi pass laser cladding to the stub of the airfoil using a laser beam power of 200-400 watt per each 1 mm width of the airfoil, laser beam diameter of 0.75-1.8 mm, welding speed of 12.5- 100 mm per min and a powder feeding rate of 0.4-2 grams per minute.
d) heat treatment, e) machining of the repair area to reproduce the original geometry of the airfoil, and f) nondestructive testing of the blade.
6. Method of repair and manufacturing of the fan blade as per claim 5, wherein during cladding of the airfoil having a variable width, a welding head is oscillated across a cladding direction with a speed of 8-12 greater than the welding speed at an amplitude of maximum of three times greater that the laser beam spot diameter, proportionally increasing the laser beam power to maintain a ratio of the beam power to the width of the oscillation within a range from 1 to 3.
7. Method of manufacturing and repair of the blade as per claim 5, wherein at least one technological pass is deposited to the top of the repaired edge of the airfoil.
8. Method of repair and manufacturing of the blade as per claim 7, wherein the technological pass is removed by a machining or other means.
9. Method of repair and manufacturing the blade as per claim 1, wherein the post weld heat treatment of the blade is produced below of the beta transus temperature.
10. Method of repair and manufacturing of the blade as per claim 1, the fan blade is subjected to a differential heat treatment, wherein the leading edge is heated to a temperature above beta transus at least for 3 minutes while maintaining a temperature of stressed sections of the blade at a temperature below of 650° C followed by a controlled cooling of the leading edge with a rate of 0.1-2° C per minute at least during a polymorphous beta-alpha transformation.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2735302A CA2735302A1 (en) | 2011-03-25 | 2011-03-25 | Blade and method of repair and manufacturing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2735302A CA2735302A1 (en) | 2011-03-25 | 2011-03-25 | Blade and method of repair and manufacturing the same |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2735302A1 true CA2735302A1 (en) | 2012-09-25 |
Family
ID=46889549
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2735302A Abandoned CA2735302A1 (en) | 2011-03-25 | 2011-03-25 | Blade and method of repair and manufacturing the same |
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| Country | Link |
|---|---|
| CA (1) | CA2735302A1 (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| DE102015209745A1 (en) * | 2015-05-28 | 2016-12-01 | MTU Aero Engines AG | Process for producing a Tl blisk |
| CN107063612A (en) * | 2017-04-18 | 2017-08-18 | 东北大学 | A kind of blisk kinematic similarity is test bed |
| RU2725469C1 (en) * | 2019-12-16 | 2020-07-02 | Общество С Ограниченной Ответственностью "Технологические Системы Защитных Покрытий" (Ооо "Тсзп") | Method for restoration and strengthening of antivibration shelves of titanium blades of gte compressor |
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-
2011
- 2011-03-25 CA CA2735302A patent/CA2735302A1/en not_active Abandoned
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102015209745A1 (en) * | 2015-05-28 | 2016-12-01 | MTU Aero Engines AG | Process for producing a Tl blisk |
| DE102015209745B4 (en) * | 2015-05-28 | 2018-12-20 | MTU Aero Engines AG | Process for producing a Tl blisk |
| CN107063612A (en) * | 2017-04-18 | 2017-08-18 | 东北大学 | A kind of blisk kinematic similarity is test bed |
| CN107063612B (en) * | 2017-04-18 | 2019-06-25 | 东北大学 | A kind of integral blade disk kinematic similarity is test bed |
| RU2725469C1 (en) * | 2019-12-16 | 2020-07-02 | Общество С Ограниченной Ответственностью "Технологические Системы Защитных Покрытий" (Ооо "Тсзп") | Method for restoration and strengthening of antivibration shelves of titanium blades of gte compressor |
| CN113084446A (en) * | 2021-03-30 | 2021-07-09 | 攀钢集团攀枝花钛材有限公司 | Method for repairing and regenerating blade of titanium sponge slicer |
| CN113084446B (en) * | 2021-03-30 | 2022-03-22 | 攀钢集团攀枝花钛材有限公司 | Method for repairing and regenerating blade of titanium sponge slicer |
| CN114086173A (en) * | 2021-11-04 | 2022-02-25 | 中车工业研究院有限公司 | Additive repairing method for axle |
| CN114086173B (en) * | 2021-11-04 | 2024-02-09 | 中车工业研究院有限公司 | Additive repairing method for axle |
| CN114959531A (en) * | 2022-06-01 | 2022-08-30 | 沈阳飞机工业（集团）有限公司 | Heat treatment method for directly depositing Ti65 titanium alloy by laser |
| CN115058674A (en) * | 2022-07-06 | 2022-09-16 | 中国航发湖南动力机械研究所 | Surface strengthening method of axial flow blade disc, axial flow blade disc and turbine engine |
| CN115058674B (en) * | 2022-07-06 | 2023-05-12 | 中国航发湖南动力机械研究所 | Surface strengthening method for axial flow blade disc, axial flow blade disc and turbine engine |
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