Patent Description:
Cost effective manufacturing of a fabricated integrally bladed rotor (IBR) typically involves joining a plurality of airfoils to a titanium forged hub. A conventional manufacturing process for an IBR includes machining a titanium forging (typically Ti-<NUM>-<NUM> alloy) to a pre-heat treat shape, solution heat treating, then liquid quenching to obtain a rapid cooling rate from the solution heat treat temperature, then subsequently annealing. Following annealing, the forging is machined to a rectilinear sonic inspection shape, then sonic inspected prior to additional machining. Another conventional process incorporates a machining step of the pre-heat treat shape to produce airfoil stubs such that increased cooling rates may be achieved further inboard toward a final inner diameter flow path.

<CIT> discloses a method according to the preamble of claim <NUM>.

<CIT> discloses local heat treatment and thermal management system for engine components, and <CIT> discloses a localised heat treating apparatus for blisk airfoils.

According to a first aspect, there is provided a tool for simultaneous local stress relief of each of a multiple of linear friction welds as set forth in claim <NUM>.

According to a further aspect, there is provided a method as set forth in claim <NUM>.

These features and elements as well as the operation of the invention will become more apparent in light of the following description and the accompanying drawings. It should be appreciated, however, that the following description and drawings are intended to be exemplary in nature and non-limiting.

The gas turbine engine <NUM> as disclosed herein is a two-spool turbofan that generally incorporates a fan section <NUM>, a compressor section <NUM>, a combustor section <NUM>, and a turbine section <NUM>. The fan section <NUM> drives air along a bypass flowpath while the compressor section <NUM> drives air along a core flowpath for compression and communication into the combustor section <NUM>, then expansion through the turbine section <NUM>. Although depicted as a high bypass gas turbofan engine architecture in the disclosed non-limiting embodiment, it should be appreciated that the concepts described herein are not limited only thereto.

The engine <NUM> generally includes a low spool <NUM> and a high spool <NUM> mounted for rotation around an engine central longitudinal axis A relative to an engine case structure <NUM> via several bearings <NUM>. The low spool <NUM> generally includes an inner shaft <NUM> that interconnects a fan <NUM>, a low pressure compressor ("LPC") <NUM> and a low pressure turbine ("LPT") <NUM>. The inner shaft <NUM> drives the fan <NUM> directly or through a geared architecture <NUM> to drive the fan <NUM> at a lower speed than the low spool <NUM>. An exemplary reduction transmission is an epicyclic transmission, namely a planetary or star gear system. The high spool <NUM> includes an outer shaft <NUM> that interconnects a high pressure compressor ("HPC") <NUM> and high pressure turbine ("HPT") <NUM>. A combustor <NUM> is arranged between the HPC <NUM> and the HPT <NUM>.

The fan <NUM> includes a rotor hub <NUM> with a plurality of circumferentially spaced fan blades <NUM>. A nose cone <NUM> may be fastened to an upstream end of the rotor hub <NUM>. The rotor may be provided in the form of an integrally bladed rotor (IBR; also, known as a blisk) which may be manufactured of a high-strength, low weight material such as a titanium alloy (typically Ti-<NUM>-<NUM> alloy), high strength nickel base alloy, or other material. Although an example fan is illustrated and described in the disclosed embodiments, other components may also benefit herefrom.

With reference to <FIG>, the plurality of fan blades <NUM> are integrally formed with, and substantially radially extending from, the rotor hub <NUM>. Each of the fan blades <NUM> defines an airfoil <NUM> which has a leading edge <NUM> and trailing edge <NUM> that extends from a blade root <NUM> to a blade tip <NUM>. The fan blades <NUM> are integrated with the rotor hub <NUM> such that the fan blades <NUM> are integrally formed as a monolithic component with the rotor hub <NUM> to form an integrally bladed rotor. Each airfoil <NUM> is formed from an airfoil stub <NUM> that is machined into the rotor hub <NUM> and an airfoil section <NUM> that is linear friction welded (LFW) to the airfoil stub <NUM> at a linear friction weld <NUM> in a predetermined area <NUM>.

With reference to <FIG>, one non-limiting embodiment of a method <NUM> for producing the integrally bladed rotor <NUM> is disclosed. Initially, a cast ingot is forged (<NUM>). The forged ingot is then solution heat treated and annealed (<NUM>). The solution heat temperature varies from heat-to-heat of material due to chemistry variation. Each heat of Ti-<NUM>-<NUM> material has a beta transus established by the mill. A solution heat treatment temperature is defined for each part based on the beta transus temperature, which is the lowest temperature at which a <NUM> percent beta phase can exist. For example, the forged ingot may be heated in argon, a vacuum, or air, to a temperature within the range of <NUM> - <NUM> degrees F (<NUM>-<NUM> degrees C) below beta transus; then held at the selected temperature ±<NUM> degrees F (± <NUM> degrees C) for <NUM> hour; then cooled at a rate equivalent to rapid air cool or faster; then annealed at <NUM> degrees F (<NUM> degrees C) in argon, a vacuum, or air; held at heat for <NUM> hours; then cooled at a rate equivalent to air cool; and descaled as necessary.

The forged ingot is then machined to a sonic shape (<NUM>). A sonic shape is a rectilinear machined shape that is created from the forged ingot. The rectilinear shape facilitates sonic inspection. The sonic shape is then sonic inspected (<NUM>).

Next, the sonic shape is machined (<NUM>) to fabricate a stub-containing rotor hub forging. The stub-containing rotor hub forging is a nearer-net shape for linear friction welding (LFW) to the stubs <NUM>. Optionally, a warm-working step (<NUM>) of the machined stubs <NUM> is provided for potential mechanical property/grain structure improvement.

The stub-containing rotor hub forging is then re-solution heat treated (<NUM>) using the same beta transus temperature that the mill used for its solution heat treatment. In one example, the stub-containing rotor hub forging is re-solution heat treated to a temperature in an upper portion of an acceptable solution temperature range.

Next, the solution heat treated stub-containing rotor hub forging is then water quenched (<NUM>). Alternatively, a warm-working step (<NUM>) of the machined stubs is next provided for enhanced aging and enhanced mechanical properties within the stub-to-inner flow path region. The water quenched stub-containing rotor hub forging is then aged (<NUM>). In one example, the stub-containing rotor hub forging is aged within a furnace at 1000F for <NUM> hours.

The aged hub is then further machined to prepare for linear friction welding of the airfoils to the stubs (<NUM>).

An airfoil is then linear friction welded onto each of the stubs (<NUM>). One example shows the temperature at the linear friction weld <NUM> to be <NUM> degrees F (<NUM> degrees C) and the temperature <NUM> inches (<NUM>) on either side of the linear friction weld <NUM> is below <NUM> degrees F (<NUM> degrees C). Upon completion of all linear friction welding, the IBR is machined to remove the airfoil collars, remove the LFW flash, and reduce the size of the stubs to which the airfoils were linear friction welded (<NUM>).

Next, each of the multiple of linear friction welds <NUM> is concurrently locally stress relieved within the predetermined area <NUM> (<FIG>) (<NUM>). In one example, the predetermined area <NUM> is stress relieved at <NUM> degrees F (<NUM> degrees C) for <NUM> hours. Localized stress relief within the predetermined area <NUM> stress relieves the linear friction weld <NUM>, yet ensures that the stubs <NUM> near a hub outer diameter <NUM> (<FIG>) and the airfoil <NUM> outwardly span-wise to some design-determined outer diameter will not exceed <NUM> degrees F (<NUM> degrees C). This protects the improved fatigue and tensile properties previously achieved in (<NUM>). In one example, the predetermined area <NUM> is located at a distance greater than <NUM> inches (<NUM>), but less than <NUM> inches (<NUM>) from the hub outer diameter <NUM>. In a more specific example, the predetermined area <NUM> is greater than <NUM> inches (<NUM>) from the hub outer diameter <NUM>. The total width of the predetermined area <NUM> in this example is approximately <NUM> inches (<NUM>), but varies depending upon the IBR size.

With reference to <FIG>, the predetermined area <NUM> may be stress relieved with a heat treat fixture <NUM> that mounts around each airfoil <NUM> at the interface between the respective airfoil stub <NUM> and airfoil section <NUM> to span the predetermined area <NUM>. The heat treat fixture <NUM> may be manufactured of a ceramic material to contain a multiple of heaters <NUM> (<FIG>) that produce the desired radiant heat. The heaters <NUM> may be, for example, calorimetric heating rods or Calrod® tubular heaters manufactured by Wattco Inc. of Lachine, QC Canada. A multiple of thermocouples <NUM> may also be located in the heat treat fixture <NUM> to closely control the temperature of the multiple of heaters <NUM> in the predetermined areas <NUM> for each airfoil <NUM> in response to a control system <NUM> (<FIG>).

In another embodiment, the airfoil section <NUM> that is linear friction welded (LFW) to the airfoil stub <NUM> may be of an equivalent or different material to hybrid nickel. For example, a hybrid nickel alloy stub <NUM> may be a semi-heat treated (or fully heat treated) nickel alloy hub of one material, with airfoils of a different nickel alloy linear friction welded onto the airfoil stubs <NUM>, then subsequently locally stabilization and/or precipitation heat treated within the predetermined area <NUM>, while maintaining a specified maximum temperature near the hub outer diameter <NUM> and outwardly span-wise to the airfoil tips <NUM>.

The control system <NUM> may include at least one processor (e.g., a controller, microprocessor, microcontroller, digital signal processor, etc.), a memory, and an input/output (I/O) subsystem. The control system <NUM> may be embodied as any type of computing device. The processor and the I/O subsystem are communicatively coupled to the memory. The memory may be embodied as any type of computer memory device (e.g., volatile memory such as various forms of random access memory). The I/O subsystem may be communicatively coupled to a number of hardware, firmware, and/or software components, including a data storage device, a display, a communication subsystem, a user interface (UI) subsystem, the multiple of heaters <NUM>, the multiple of thermocouples <NUM>, and a power source <NUM>.

The integrally bladed rotor <NUM> is then finish machined to a final configuration (<NUM>).

The method <NUM> for producing the integrally bladed rotor <NUM> potentially increases high cycle fatigue (HCF) strength by as much as <NUM>% at <NUM> degrees F (<NUM> degrees C), plus increases <NUM>% yield and tensile strengths by as much as <NUM>% at <NUM> degrees F (<NUM> degrees C) compared to conventional processes. The increased HCF and tensile strengths can be leveraged to increase life for an existing weight. Alternatively, if life is held constant, the improved mechanical properties enables reduced part weight.

With reference to <FIG>, a tool <NUM> supports an upper heat treat fixture portion 300A and a lower heat treat fixture portion 300B of the heat treat fixture <NUM> along an axis W. Each of the upper heat treat fixture portion 300A and the lower heat treat fixture portion 300B include airfoil shaped openings which mount around each airfoil <NUM> at the interface between the respective airfoil stub <NUM> and airfoil section <NUM> to span the predetermined area <NUM>.

The tool <NUM> includes an upper support structure <NUM> and a lower support structure <NUM> that translate and rotate the upper heat treat fixture portion 300A and the lower heat treat fixture portion 300B along a respective columnar track 506A, 506B. The integrally bladed rotor includes airfoils <NUM> at a predetermined fixed pitch such that the upper heat treat fixture portion 300A and the lower heat treat fixture portion 300B must respectively translate and rotate along axis W to fit around and then enclose the predetermined area <NUM> of each airfoil <NUM>.

The upper heat treat fixture portion 300A and the lower heat treat fixture portion 300B are simultaneously positioned by a lead screw <NUM> driven by a geared motor <NUM>. The respective columnar tracks 506A, 506B, and the lead screw <NUM>, extend along the axis W.

The lower heat treat fixture portion 300B is located on the columnar track 506B adjacent to a fixed support plate <NUM> with respect to a base <NUM>. The fixed support plate <NUM> positions the integrally bladed rotor <NUM> and may house the geared motor <NUM>. The upper heat treat fixture portion 300A is located on the columnar track 506A and the columnar track 506A is positioned by a structure <NUM> that is mounted to the base <NUM>. The structure <NUM> may rotate about an axis to facilitate loading and unloading of the integrally bladed rotor <NUM>.

The upper heat treat fixture portion 300A and the lower heat treat fixture portion 300B each include a collar assembly <NUM> that provides the coordinated rotational and translational movement of the upper heat treat fixture portion 300A and the lower heat treat fixture portion 300B along the respective columnar track 506A, 506B. Although only a single collar assembly <NUM> will be described in detail, each is essentially the same.

With respect to <FIG>, the collar assembly <NUM> includes a connecting arm <NUM> and a carrier <NUM>. The connecting arm <NUM> and the carrier <NUM> are supported along the columnar track <NUM> by the lead screw <NUM>.

With respect to <FIG>, the connecting arm <NUM> includes an internal thread <NUM> that receives the lead screw <NUM> to provide the motive power for the upper heat treat fixture portion 300A and the lower heat treat fixture portion 300B. The internal thread <NUM> may include a cavity <NUM> that receives a lubricant from a grease fitting <NUM>. The connecting arm <NUM> includes a first arm <NUM> and a second arm <NUM> that are rotationally offset by, for example, about <NUM> degrees (<FIG>). The first arm <NUM> supports a crowned roller <NUM> that engages a through-wall helical slot <NUM> in the columnar track <NUM> (<FIG>). The second arm <NUM> mounts to the carrier <NUM> (<FIG>) via a fastener that is received within, for example, a threaded blind hole <NUM>. The second arm <NUM> extends through the helical slot <NUM> in the columnar track <NUM> (<FIG>).

The carrier <NUM> rides along an outer surface of the columnar track <NUM>. Bearings <NUM> (<FIG> and <FIG>), such as linear ball bearing, are located within the carrier <NUM> to ride along the columnar track <NUM> to support the connecting arm <NUM> in response to rotation of the lead screw <NUM>.

With reference to <FIG>, one non-limiting embodiment of a method <NUM> for positioning the heat treat fixture <NUM> on the integrally bladed rotor <NUM> is disclosed. Initially, the integrally bladed rotor <NUM> is retained upon the fixed support plate <NUM> (<NUM>). Next, the geared motor <NUM> rotates the lead screw <NUM> in response to the control system <NUM> to translate and rotate the upper heat treat fixture portion 300A and the lower heat treat fixture portion 300B along axis W to enclose each airfoil <NUM> at the interface between the respective airfoil stub <NUM> and airfoil section <NUM> (<NUM>). That is, the upper heat treat fixture portion 300A and the lower heat treat fixture portion 300B translate and rotate along axis W to follow the pitch of each airfoil <NUM>. The adjacent upper heat treat fixture portion 300A and the lower heat treat fixture portion 300B when closed span the predetermined area <NUM>.

Next, each of the multiple of linear friction welds <NUM> are then concurrently locally stress relieved (<NUM>) within the predetermined area <NUM> with the heat treat fixture <NUM> as detailed above in step <NUM>. After being locally stress relieved, the geared motor <NUM> rotates the lead screw <NUM> in response to the control system <NUM> to translate and rotate the upper heat treat fixture portion 300A and the lower heat treat fixture portion 300B along axis W to retract the upper heat treat fixture portion 300A and the lower heat treat fixture portion 300B from around each airfoil <NUM> so that the integrally bladed rotor <NUM> can be removed (<NUM>).

The tool <NUM> readily facilitates proper positioning and simultaneous local stress relief of each of the multiple of linear friction welds <NUM> on the integrally bladed rotor hub <NUM>.

Although the different non-limiting embodiments have specific illustrated components, the embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments.

It should be appreciated that relative positional terms such as "forward", "aft", "upper", "lower", "above", "below", and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting.

It should be appreciated that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be appreciated that although a particular component arrangement is disclosed in the illustrated embodiments, other arrangements will benefit herefrom.

Although particular step sequences are shown, described, and claimed, it should be appreciated that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure.

Claim 1:
A tool (<NUM>) for simultaneous local stress relief of each of a multiple of linear friction welds (<NUM>), the tool (<NUM>) comprising:
a columnar track (506A, 506B) defined along an axis (W), the columnar track (506A, 506B) having a helical slot (<NUM>); and
a support structure (<NUM>, <NUM>) engaged with the helical slot (<NUM>) to translate and rotate a heat treat fixture portion (300A, 300B) along the axis (W), wherein the support structure (<NUM>) comprises:
an upper support structure (<NUM>) engaged with the helical slot (<NUM>) to translate and rotate an upper heat treat fixture portion (300A) along the axis (W); and
a lower support structure (<NUM>) engaged with the helical slot (<NUM>) to translate and rotate a lower heat treat fixture portion (300B) along the axis (W), wherein the lower support structure (<NUM>) translates and rotates opposite the upper support structure (<NUM>).