DESC:NOZZLE GUIDE VANE AND MANUFACTURING METHOD FOR THE SAME

FIELD OF THE INVENTION
[0001] The present invention relates to additive manufacturing of aerospace part.

[0002] Particularly, this invention relates to nozzle guide vane (NGV) and its casing and a method of manufacturing of nozzle guide vane (NGV) and its cage and cage ring in jet engine turbine section.

BACKGROUND OF THE INVENTION
[0003] A nozzle guide vane plays an important role in an aero engine exhaust (Turbine) section. Stator blades of the NGV are convex and shaped like air foils. They direct airflow onto turbine blades, of the turbine section, while, at the same time, converting pressure energy into kinetic energy. Gases coming from the combustion chamber pass through nozzle guide vanes where, because of their convergent shape, they accelerate. On passing through the nozzle guide vanes, gases are given a “spin” or a “swirl” in the direction of rotation of the turbine rotor blades. The latter absorb this energy, causing the turbine to rotate at a high speed. Manufacturing of nozzle guide vanes has always been a challenging task due to complex shape of blades (vanes) and integral cage and cage ring. Traditionally, a nozzle guide vane is manufactured by vacuum investment casting followed by machining or electro-chemical machining or machining from a solid block (turning, milling, drilling, broaching, grinding, etc.).

[0004] The traditionally manufactured parts have the following drawbacks:
? The traditional (or prior art) method requires a huge amount of melt material for one heat.
? One of the biggest disadvantages is its size limitation.
? The nozzle guide vanes, its cage and cage ring have to be manufactured separately and then joined using precision joining techniques. This is a very complex process and also reduces the overall strength of the part due to presence joints.
? The machining processes demands various specialized tools for vacuum investment casting dies and that is economical for mass production only.
? The main disadvantage is the overall cost, especially for short-run productions.
? Many operations are involved such as making a mould, die manufacturing, making wax patterns, along with a lot of labour.
? Enormous initial investments are required for this process. The preparation of the wax patterns and shell moulds require much time and effort to ensure a quality product. Large machinery is required for this process.

[0005] Accordingly, there is a need for an improved nozzle guide vane and also for a method of manufacturing the improved nozzle guide vane.

OBJECTS OF THE INVENTION
[0006] It is an object of the present invention to provide an integral (single piece) nozzle guide vane and its cage and cage ring with its features.

[0007] It is another object of the present invention to provide a manufacturing method for an integral nozzle guide vane through additive manufacturing.

[0008] Other objects and advantages of the present disclosure will be more apparent from the following description which is not intended to limit the scope of the present disclosure.

SUMMARY OF THE INVENTION
[0009] To overcome the above-mentioned drawbacks, additive manufacturing method has been proposed in the present invention. The additive manufacturing is a novel manufacturing method in which nozzle guide vanes, its cage (16) and cage ring (14) with integral features like vanes (12) and cage ring holes (18) are produced. In this manufacturing method, an integral nozzle guide vane (100) is made by using digital model and layer by layer material build-up approach. This tool-less manufacturing method can produce uniform nozzle guide vanes, along with cage and cage ring, in a short time with high precision.

[00010] Increased productivity and reduced cost of production is achieved by the reducing number of steps in manufacturing processes. The additive manufacturing approach eliminates vacuum investment casting, rough machining, and press fitting of cage and cage ring processes in a nozzle guide vane manufacturing.

[00011] According to one embodiment of the present invention, nozzle guide vanes, its cage and cage ring are manufactured in a single print by additive manufacturing.

[00012] The present invention describes elimination of vacuum investment casting and rough machining to make an integral part. It also eliminates the problem of maintaining the exact clearance between NGV vanes and cage and cage ring by press fitting.

[00013] In one embodiment, the process for the manufacturing an integral nozzle guide vane (100) comprises the following steps:
? providing metal powder as a raw material;
? spreading said powder layer by layer on a predetermined platform;
? selectively fusing said powder using at least one energy source selected from the group consisting of laser, electron beam and the like to perform printing operation to obtain integral nozzle guide vane with build platform;
? transferring said integral nozzle guide vane with build platform to a furnace in order to heat treat said integral nozzle guide vane with build platform to obtain heat processed integral nozzle guide vane with build platform; and
? subjecting said heat processed integral nozzle guide vane with build platform to wire cutting operation to separate the integral nozzle guide vane from the build platform followed by shot blasting to generate compressive residual stresses on the surfaces of the integral nozzle guide vane and buffing operation to obtain the integral nozzle guide vane with pre-determined surface finish.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
[00014] The invention will now be described in relation to the accompanying drawings, in which:

[00015] Figure 1 illustrates the typical integral nozzle guide vane (100) printed in additive manufacturing; and

[00016] Figure 2 shows the flow chart of an invented process for nozzle guide vane manufacturing.

DETAILED DESCRIPTION
[00017] The present invention relates to the manufacturing of an integral nozzle guide vane for jet engines using selective laser sintering process. The nozzle guide vanes are manufactured along with their respective cage and cage ring. The inventive step of this invention lies in the design and development of the integral nozzle guide vane (100) and a manufacturing process to make the same.

[00018] According to the invented process, the manufacturing process starts with metal powder as a raw material. The material used as metal powder includes but is not limited to Nickel based alloys (IN718, IN713C, IN625 etc.), titanium alloys, steels and the like. This powder is spread on a bed / build platform, layer by layer, and selectively fused by using an energy source like a laser or electron beam. After completion of the print, part with build platform is transferred to the furnace, where heat treatment is conducted and required properties are achieved. Then, final parts are separated from the build platform using wire cutting operation. Then, the final part is transferred to shot blasting to generate compressive residual stresses on surface. Then, micro machining process/buffing is carried out on the final part to achieve required surface finish. Finally, X- ray tomography (i.e. non-destructive test) is conducted on the integral nozzle guide vane for surface crack detection and quality inspection.

[00019] In one embodiment, the process for the manufacturing of an integral nozzle guide vane using IN718 (Nickel based alloy) as a raw material in the form of metal powder comprises the following steps:

[00020] In the first step, metal powder as a raw material and a 3D printing device is provided or kept ready. In the second step, the metal powder is spread layer by layer on a predetermined platform of 3D printing device. Typically, the temperature of said platform is set in the range of 80 to 160°C, preferably, at 120°C.

[00021] Typically, the layer has a thickness in the range of 0.02 to 0.08 mm and a laser strip width in the range of 3 to 10 mm. Typically, the overlap between the layers is in the range of 0.10 to 0.15 mm. In one preferred embodiment, the layer has a thickness of 0.02 mm, a laser strip width 5 mm and the overlap between the layers is 0.12 mm.

[00022] In one embodiment, the spreading comprises controlled deposition of the layers of metal powder to form the integral nozzle guide vane. In one embodiment, the spreading comprises depositing layers of a metal powder sequentially one upon the other to form features.

[00023] After spreading, the powder is selectively fused using at least one energy source at predetermined conditions to perform a printing operation to obtain an integral nozzle guide vane. Typically, the energy source is selected from the group consisting of laser beam and electron beam. The energy source has a scanning speed of about 800 to 1400 mm/second and has power of 80 to 400 watt. In one preferred embodiment, the energy source has a scanning speed of about 1000 mm/second and, has power of 195 watt.

[00024] In the third step, the integral nozzle guide vane with build platform is heated in a furnace at a predetermined temperature followed by cooling to room temperature to obtain heat treated integral nozzle guide vane with build platform.

[00025] In one preferred embodiment, the heat treatment step involves the following steps:
Step A: annealing the integral nozzle guide vane with build platform at a temperature ranging from 900 to 1200°C for a period ranging from 30 minutes to 120 minutes in an inert Argon atmosphere followed by cooling to room temperature. The output of this stage is annealed integral nozzle guide vane with build platform.
Step B: ageing the annealed integral nozzle guide vane with build platform by holding the part at a temperature ranging from 700 to 800°C for a time period ranging from 5 to 10 hours in an inert Argon atmosphere followed by cooling to a temperature ranging from 625 to 675°C in 1 to 3 hours and holding at a temperature ranging from 625 to 675 °C for 6 to 10 hours in an inert Argon atmosphere. The output of this stage is aged integral nozzle guide vane with build platform.
Step C: air cooling said aged integral nozzle guide vane with build platform to room temperature to obtain a heat treated integral nozzle guide vane with build platform.
[00026] In fourth step, the heat treated integral nozzle guide vane with build platform is subjected to wire cutting operation to separate the integral nozzle guide vane from the build platform and thus obtain a separated integral nozzle guide vane.

[00027] In the fifth step, the separated integral nozzle guide vane is subjected to shot blasting to generate compressive residual stresses on the surfaces to obtain a shot blasted integral nozzle guide vane.

[00028] In the sixth step, a buffing operation is performed on the shot blasted integral nozzle guide vane to obtain the integral nozzle guide vane with predetermined surface finish.

[00029] In one embodiment, the process comprises a pre-step of printing a support having predetermined configuration meant for holding said integral nozzle guide vane and transferring heat from the material being 3D printed to the build platform during printing operation.

[00030] Typically, the temperature of the platform is set in the range of 80 to 160 ºC preferably at 120 ºC.

[00031] In one embodiment, the integral nozzle guide vane being designed and rendered using a rendering software, is used as an input for the additive manufacturing process. In one embodiment, the spreading comprises depositing layers of a metal powder sequentially one upon the other to form features.

[00032] The material used as metal powder includes but is not limited to Nickel based alloys (IN718, IN713C, IN625 etc.), titanium alloy, steel, and the like. This powder is spread on a bed (which is its build platform), layer by layer, and selectively fused by using an energy source like a laser or an electron beam.

[00033] Typically, the energy source is selected from the group consisting of laser beam and electron beam, wherein the energy source has a scanning speed of about 800 to 1400 mm/second, preferably 1000mm/second and has power of 80 to 400 watt, preferably 195 watt.

[00034] According to the present invention several types of supports which can be used during the 3D printing are tried. The type of support to be used is decided based on the quantity of material required for supports, heat dissipation of product to surrounding, geometry of model etc. Different types of supports which are tried include Block type, Line type, Point type, Web Type, Contour type, Gusset type, Hybrid type and Volume type etc. The support structure with different features like hatching, hatching teeth, fragmentation, borders, border teeth, perforations, gusset borders etc. are experimented. Based on the considerations and experimentations, during the manufacturing of the integral nozzle guide vane, the preferred type of supports used are combination of block support with hatching teeth and perforation type support, volume support and hybrid support.

[00035] As shown in Figure 2, the invented manufacturing process typically involves the following steps:

[00036] CAD Model generation:
Producing a digital model is the first step in the additive manufacturing process. The digital model is produced using computer aided design (refer figure1). Then this CAD model is converted into the stereo lithography / Surface Tesselation Language / Standard Triangulation Language file (STL) which is used by further portions and processes of this invention.

[00037] Additive Manufacturing program generation:
Once a STL file has been generated, the file is imported into a MAGICS materialise software. In MAGICS, part orientation and support generation takes place. Then, STL file is sent to the slicer software for slicing. After slicing, the file is imported in EOSPRINT software. In EOSPRINT software, build parameters are assigned and optimized for CAD data. Then, parameters like laser power, scanning speed, hatch distance, and layer thickness are selected. Finally, the file is exported to the 3D printing machine for final printing.

[00038] Additive Manufacturing or 3D printing:
Different types of materials can be used for manufacturing integral nozzle guide vane which include but are not limited to Nickel based alloys (IN718, IN713C, IN625 etc.), titanium alloys, steels and the like. Material is provided in the form of powder. Then powder is spread on the platform, layer by layer, with a layer thickness ranging from 0.020 mm to 0.080 mm. During this activity, platform temperature is maintained 120 ºC throughout the process. After each layer, powder is selectively fused by using a laser (max. 400 watt laser power) with a scanning speed ranging from 1000 mm/Sec for parts and 500 mm/Sec for support in an Argon environment. The output of this process is an integral NGV with a build platform. The above parameters are performed for IN718. A summary of parameters used to produce the integral NGV in additive manufacturing using IN718 are mentioned in table 1.

Table 1
Parameters Value
Part (Integral NGV)
Layer thickness 0.020 mm to 0.080 mm
Platform temperature 120ºC
Chamber environment Argon
Hatching strip width 3 mm to 9 mm
Skip Layer 0
Scanning speed 800 mm/Sec to 1400 mm/Sec
Laser Power 80 Watt to 400 Watt
Strip Width 3 mm to 9 mm
Strip Overlap 0.1 mm to 0.15 mm
Beam offset 0.015
Supports for Integral NGV
Layer thickness 0.020 mm to 0.080 mm
Platform temperature 120ºC
Chamber environment Argon
Skip Layer 1
Scanning speed 500 mm/Sec
Laser Power 90 Watt

[00039] Heat treatment:
Heat treatment is carried out on the 3D printed integral nozzle guide vane with build platform to achieve the mechanical properties. Firstly, the integral nozzle guide vane with build platform is solution annealed at 1065 °C for one hour in an inert Argon atmosphere, followed by air cooling to room temperature. A second heat treatment is ageing. In this treatment, the integral nozzle guide vane with build platform is held at a 760 °C temperature for 10 hours in an inert Argon atmosphere, after which it is furnace cooled to 650°C in two hours and then held at 650°C for eight hours in an inert Argon atmosphere. Finally, the integral nozzle guide vane with build platform is air cooled to room temperature. The above heat treatment is performed for IN718. The different types of materials can be used for manufacturing integral nozzle guide vane which include but are not limited to Nickel based alloy, Titanium alloys, Steels and the like. The mechanical properties achieved after heat treatment are summarised in table 2 (Material: IN718). The below provided properties and values are illustrative and not considered as limitation to scope of the present invention.

Table 2
Mechanical properties Value
Tensile strength Min 1241 MPa
Yield strength 1150 MPa
Elongation 12 %
Hardness 47 HRC

[00040] Wire cutting and support removal:
The heat treated integral nozzle guide vane with build platform is separated from the build platform using wire cutting operation. Next, support formed during the 3D printing operation is machined off.

[00041] Shot Blasting:
After wire cutting support removal, a shot blasting operation is performed to generate compressive residual stresses on integral nozzle guide vane surface. The shot blasting is carried out using steel balls of 0.7 mm dia. and ceramic balls of 0.1 mm diameter.

[00042] Micro Machining Process (MMP) / Buffing For Polishing:
Micro machining process / Buffing operation is performed to obtain desired finish to the integral nozzle guide vane. Micro machining process technology can continually reproduce mirror-like finishes with unrivalled aesthetic consistency and technical precision. Micro machining process reduces friction, has extremely low material removal, and provides homogeneity of treatment across entire surface in respect of tolerances.

[00043] Non-destructive testing
Finally, the integral nozzle guide vane is tested for surface quality and cracks by X – Ray tomography.

[00044] In accordance with another aspect of the present invention there is also provided integral nozzle guide vane made by the 3D printing method of the present invention. Said integral nozzle guide vane characterized by predetermined structural configuration and characteristics.

[00045] In one embodiment, the integral nozzle guide vane (100) comprises Vanes / Blades (12), Cage (16), Cage ring (14) and Cage Ring Holes (18). Figure 1 illustrates integral nozzle guide vane (100) in which NGV vanes/blades are shown by numeral 12; cage ring by numeral 14; NGV cage by numeral 16 and NGV cage ring hole by numeral 18.

[00046] In accordance with still another aspect of the present invention there is also provided a system for manufacturing integral nozzle guide vane by 3D printing method, said system comprises 3D printing device and support. It is critical to design an optimized support which can be suitable for printing integral nozzle guide vane, as other type of support makes marks on surface of parts. In one embodiment, the support comprises teeth/grooves. The teeth/grooves enable easy removal of supports. Support height is optimised for better heat transfer (heat dissipation) between build platform and job at the time of part building. It also avoids distortion in the part. The amount of support required to build the part is based on the orientation of part. The optimised orientation is selected based on least amount of material required for support generation, minimum laser travel time for generating the support, support free critical areas of the component and height of support that dissipates better heat transfer to build platform from job. Based on above factors for optimized orientation of NGV, the preferred type of supports used are combination of block support with hatching teeth and perforation type support, volume support and hybrid support and the height of supports is selected from the range of 15.49 mm to 2 mm.

[00047] While this detailed description has disclosed certain specific embodiments for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

,CLAIMS:We Claim:
1. A process for the manufacturing an integral nozzle guide vane; said process comprising the following steps:
a) providing metal powder as a raw material wherein the metal powder is selected from a group consisting of Nickel based alloys, titanium alloys, steels and the like;
b) providing a 3D printing device;
c) spreading said powder layer by layer on a predetermined platform;
d) selectively fusing said powder using at least one energy source selected from the group consisting of laser, electron beam and the like to perform printing operation to obtain integral nozzle guide vane with build platform;
e) transferring said integral nozzle guide vane with build platform to a furnace in order to heat treat said integral nozzle guide vane with build platform at a predetermined temperature to obtain heat processed integral nozzle guide vane with build platform; and
f) subjecting said heat processed nozzle guide vane with build platform to wire cutting operation to separate the nozzle guide vane from the build platform followed by shot blasting to generate compressive residual stresses on the surfaces of the integral nozzle guide vane and buffing or micro machining operation to obtain the integral nozzle guide vane with pre-determined surface finish.

2. The process as claimed in claim 1, wherein the process comprises a pre-step of printing supports having predetermined configuration meant for holding said integral nozzle guide vane and transferring heat from the material being 3D printed to the platform during printing operation.

3. The process as claimed in claim 1, wherein the metal powder is Inconel 718 and the temperature of the platform is set in the range of 80 to 160 ºC, preferably at 120 ºC.

4. The process as claimed in claim 1, wherein the integral nozzle guide vane being designed and rendered using a rendering software, is used as an input for the additive manufacturing process.

5. The process as claimed in claim 1, wherein the layer has a thickness in the range of 0.02 to 0.08 mm, preferably 0.02 mm and a laser strip width in the range of 3 to 10 mm, preferably 5 mm.

6. The process as claimed in claim 1, wherein the overlap between the layers is in the range of 0.10 to 0.15 mm, preferably 0.12 mm.

7. The process as claimed in claim 1, wherein the spreading comprises depositing layers of a metal powder sequentially one upon the other to form features.

8. The process as claimed in claim 1, wherein the energy source is selected from the group consisting of laser beam and electron beam, wherein the energy source has a scanning speed of about 800 to 1400 mm/second, preferably 1000 mm/second and has power of 80 to 400 watt, preferably 195 watt.

9. The process as claimed in claim 1, wherein the heat treating step involves the following steps:
? annealing the integral nozzle guide vane with build platform at a temperature ranging from 900 to 1200 °C for a period ranging from 30 minutes to 120 minutes in an inert Argon atmosphere followed by cooling to room temperature;
? ageing the integral nozzle guide vane with build platform by holding the integral NGV with build platform at a temperature ranging from 700 to 800 °C for a time period ranging from 5 to 10 hours in an inert Argon atmosphere followed by cooling to a temperature ranging from 625 to 675 °C in 1 to 3 hours and holding at a temperature ranging from 625 to 675 °C for 6 to 10 hours in an inert Argon atmosphere; and
? air cooling said integral nozzle guide vane with build platform to room temperature.

10. The process as claimed in claim 1, wherein the heat treatment comprises solution annealing the integral nozzle guide vane with build platform at 1065 °C for one hour in an inert Argon atmosphere, followed by air cooling to room temperature; holding the integral nozzle guide vane with build platform at 760 °C for ten hours followed by furnace cooled to 650 °C in two hours in an inert Argon atmosphere, holding at 650 °C for eight hours in an inert Argon atmosphere and air cooling to the room temperature.

11. The process as claimed in claim 1, wherein the support is selected from Block type, Line type, Point type, Web Type, Contour type, Gusset type, Hybrid type and Volume type, preferably, the support is combination of block support with hatching teeth and perforation type support, volume support and hybrid support, wherein the height of said supports is selected from the range of 15.49 mm to 2 mm.

12. A process for manufacturing integral nozzle vane guide, said process comprising the following steps:
a) generating a CAD model using computer aided design;
b) converting the model into a Stereolithography /Surface Tesselation Language / Standard Triangulation Language file (STL);
c) generating additive manufacturing program by importing STL file into a MAGICS MATERIALISE software adapted to define part orientation and generate support;
d) transferring the STL file to a slicer software for slicing;
e) importing the file in an EOSPRINT software adapted for assigning the build parameters which are further optimized for CAD data;
f) designing parameters selected from laser power, scanning speed, hatch distance and layer thickness;
g) exporting the file to the 3D printing machine for producing the integral nozzle guide vane;
h) spreading metal powder layer by layer on a predetermined platform;
i) selectively fusing said metal powder using at least one energy source at predetermined conditions to perform a printing operation to obtain the integral nozzle guide vane with build platform;
j) heat treating said integral nozzle guide vane with build platform in a furnace at a predetermined temperature to obtain heat treated integral nozzle guide vane with build platform;
k) subjecting said heat treated integral nozzle guide vane with build platform to wire cutting operation to separate the integral nozzle guide vane from the build platform, followed by shot blasting to generate compressive residual stresses on the surfaces of the integral nozzle guide vane, and buffing operation to achieve the integral nozzle guide vane with pre-determined surface finish.

13. An integral nozzle guide vane (100) obtained by the process as claimed in claim 1 to 12; said integral nozzle guide vane (100) comprises Vanes / Blades (12), NGV cage (16) and NGV Cage Ring (14) and NGV cage ring hole (18).

14. The integral nozzle guide vane as claimed in claim 13, characterized in that said nozzle guide vane exhibits a tensile strength of >1241 MPa, a yield strength of about 1150MPa and a hardness of about 47 HRC.

15. A system for manufacturing integral nozzle guide vane by 3D printing method, said system comprises a 3D printing device and a support, wherein the support comprises teeth/grooves adapted to enable easy removal of supports, wherein height of support corresponds to height of build platform in order to dissipate heat between build platform and job at the time of part building and avoiding distortion of the Integral NGV.

Dated this 30th day of March, 2019

CHIRAG TANNA
of NOVO IP
APPLICANT’S PATENT AGENT