GB2455194A

GB2455194A - Processing sulphur contaminated metal powder

Info

Publication number: GB2455194A
Application number: GB0821508A
Authority: GB
Inventors: Thomas E Strangman
Original assignee: Honeywell International Inc
Current assignee: Honeywell International Inc
Priority date: 2007-11-30
Filing date: 2008-11-26
Publication date: 2009-06-03
Also published as: GB0821508D0; US20090142221A1; CA2644713A1

Abstract

A method of forming a component by introducing gas which includes H2 into a can containing sulphur contaminated metal powder, the can being usable in a consolidation process. At least some gas is removed from the can, and by means of sensing the hydrogen sulphide content of this gas, the sulphur content of the metal powder is determined. When the sulphur content of the metal powder is below 5 parts per million by weight it is consolidated by hot isostatic pressing, extrusion or forging, either in the can which holds the metal powder during desulphurization, or in another can. Gas is introduced into the can for 1-20 hours and the method is performed within 300 {C of the incipient melting temperature of the metal powder. The method can be used to form a turbine hub, a turbine disc, a rotating seal, a compressor or an impeller from a nickel-based superalloy.

Description

ENGINE COMPONENTS AND METHODS OF FORMING ENGINE COMPONENTS

TECHNICAL FiELD

100011 The inventive subject matter generally relates to engine components, and more particularly relates to methods of forming engine components for use in high temperatures.

BACKGROUND

100021 Components, such as turbine disks, may be subjected to relatively high temperatures (e.g., temperatures up to about 675°C). These components may be formed by several manufacturing methods. For example, the components may be formed from a metal powder, such as a nickel-based superalloy material, which is placed in a container that is subsequently evacuated and sealed, and then consolidated to full density at high temperatures (e.g., temperatures greater than about 1150°C). Consolidation may be performed by techniques known in the art (e.g., by hot isostatic pressing, extrusion and forging) to compact the metal powder to full density. The compacted metal powder may then be machined, or otherwise shaped, to form a turbine component, such as a turbine disk, a hub insert for a dual alloy turbine, or a rotating seal.

100031 Although the above-mentioned alloys are adequate for forming engine components that operate at temperatures up to 675°C, they may be improved. In particular, the powder metallurgy superalloys used to make the engine components typically have sulfur contents of up to 50 parts per million by weight. The presence of the sulfur in such amounts may contribute to grain boundary fracture under high-temperature sustained-peak low cycle fatigue and creep conditions, which may prevent the alloys from being used to make components for use in temperatures greater than about 675°C. Thus, it would be desirable to have a method for forming components that operate at temperatures higher than 675°C.

More particularly, it would be desirable to have a method to form components, such as turbine disks, that arc capable of operating at temperatures in the 675°C to 815°C range.

BRiEF SUMMARY

100041 Methods arc provided for forming high temperature engine components, such as turbine disks.

100051 In an embodiment, by way of example only, the method includes flowing a gas into a can with a metal powder therein, the gas comprising hydrogen, the can configured to be used for a consolidation process, and the metal powder comprising sulfur, removing at least a portion of the gas from the can, determining a sulfur content of the removed gas, and subjecting the can and the metal powder therein to a consolidation process, if a determination is made that a sulfur content of the metal powder is below a threshold value, the threshold value being a value below about 5 parts per million by weight.

100061 In another embodiment, the method includes flowing a gas into a can with a metal powder therein, the gas comprising hydrogen, the can configured to be used for a hot isostatic pressing process, and the metal powder comprising sulfur, removing at least a portion of the gas from the can, determining a sulfur content of the removed gas, after a determination is made that the sulfur content of the metal powder is below a threshold value, the threshold value being below about 1 part per million by weight, subjecting the can and the metal powder therein to the hot isostatic pressing process to form compacted metal powder 100071 In still another embodiment, an engine component is provided. The engine component includes a compacted powder material comprising a nickel-based superalloy having less than 5 parts per million sulfur, by weight.

BRIEF DESCRIPTION OF THE DRAWINGS

100081 The inventive subject matter will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and I 0009J FIG. I is a perspective view of a component, according to an embodiment.

100101 FIG. 2 is a flow diagram of a method of manufacturing the component, according to an embodiment; 100111 FiG. 3 is a cross-sectional view of a can implemented into a desulfurization treatment system that may be used for the method depicted in FIG. 2, according to an embodiment; and 100121 FIG. 4 is a flow diagram of a method of de-sulfurizing a metal powder, according to an embodiment.

DETAILED DESCRIPTION

[0013j The following detailed description is merely exemplary in nature and is not intended to limit the inventive subject matter or the application and uses of the inventive subject matter. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.

100141 FIG. I is a perspective view of a component 100, according to an embodiment.

The component 100 is capable of being subjected to high temperatures (e.g., temperatures greater than about 675°C) and may be any component that may be used in an engine. For example, the component 100 depicted in FIG. I may be a dual alloy turbine, which may comprise a hub 102 bonded to a blade ring 104 for use in a turbine section of an engine.

The hub 102 and the blade ring 104 may or may not comprise the same materials. In an embodiment, the hub 102 may comprise a compacted powder metallurgy superalloy, and the blade ring 104 may be a cast superalloy blade ring 104. However, other materials may alternatively be employed. Alternatively, the component 100 may be other engine components such as a turbine disk, rotating seal, a compressor or impeller. In some embodiments, the component 100 alternatively may be used in cooler temperature environments (e.g., temperatures b1ow about 675°C').

100151 The component 100 may comprise a powder metallurgy superalloy material. In an embodiment, the powder metallurgy superalloy material may be a nickel-based powder metallurgy superalloy. Suitable superalloys include, but are not limited to, Alloy 10 (available through Honeywell International, Inc. of Morristown, New Jersey). To ensure that the component 100 may be capable of operating at high temperatures, the component may include by weight about 5 parts per million of sulfur or less. In some embodiments, the component 100 may have about one part per million of sulfur. In still other embodiments, the component 100 may be substantially free of sulfur (e.g. less than one part per million of sulfur by weight).

100161 To form the above-described component 100, a method 200 of manufacturing the component 100 depicted in FIG. 2 may be employed. In an embodiment, a metal powder is disposed in a can, step 202. The can is healed, step 204. Then, the metal powder is de-sulfurized and desulfurizing gas is removed from the can, step 206. Next, the can and the de-sulfurized metal powder are consolidated to form a compacted metal powder, step 208.

The compacted metal powder may be machined to form the component, step 210.

Following consolidation, the can is removed and the compacted metal powder may be heat treated, step 212. Each of these steps will be discussed in detail below.

100171 As briefly mentioned above, a metal powder is disposed in a can, step 202. The metal powder may be any one of numerous powders that may be suitable for use during a powder metallurgy process. For example, the metal powder may be a nickel-base powder metallurgy superalloy, such as Alloy 10. In an embodiment, the metal powder may include sulfur as an impurity. In another embodiment, the metal powder may include trace amounts of sulfur (e.g., up to about 50 parts per million by weight of sulfur). In another embodiment, more or less sulfur may alternatively be included in the metal powder.

100181 The can may be configured to contain the metal powder during the desulfurization process. In an embodiment, the can may be configured such that it may be subsequently used in the consolidation process of step 208. FIG. 3 is a cross-sectional view of a can 304 disposed in a desulfurization treatment system 302, according to an embodiment. The can 304 may be made of any one of numerous materials having an incipient melting point that is above that of the metal powder. Thus, for example, if the metal powder comprises Alloy 10, the can 304 may comprise steel or a nickel-based superalloy. In an embodiment, the can 304 may be capable of supporting and maintaining a vacuum.

100191 The can 304 may have walls 316 (e.g., top, bottom, and side walls) that form a cavity 318 to receive the metal powder. In an embodiment, the cavity 318 may have a cylindrical shape, and an opening 320 may be formed in one of the walls 316. The opening 320 may have a diameter that is suitable for receiving the metal powder and for flowing gas therethrough. For example, the diameter of the opening 320 may be between about 0.5 cm and about 5.0 cm. In an embodiment, the can 304 is completely closed, except for the opening 320.

100201 As shown in FIG. 3, in an embodiment, a fill pipe 306 is attached to the opening 320. The fill pipe 306 receives the metal powder and enables gas ulow into and out of the cavity 3 1 8 when the treatment system 302 is in use. In an embodiment, the fill pipe 306 has a diameter that is between about 0.5 cm and 5 cm, but in other embodiments, the diameter may be smaller or larger. The fill pipe 306 may have a length sufficient to extend outside a heater 334 of the treatment system 302 when the can 304 is disposed therein. In other embodiments, the length of the fill pipe 306 may be shorter or longer. In any case, the fill pipe 306 has a valve 309 which is capable of maintaining a vacuum within the can 304 or permitting gas flow into or out of the powder filled can 304. The fill pipe 306 may be made of the same or similar material as the can 304 and may also be capable of supporting and maintaining a vacuum.

100211 After the can 304 is filled with the metal powder, it may be evacuated. For example, residual powder atomization gas (e.g., argon) or air impurities may be removed from the can 304. Following evacuation, the valve 309 in the fill pipe 306 may be closed to prevent entry of air while the powder-filled can 304 is transferred into the desulfurizat ion treatment system 302.

100221 The can 304 may be disposed in the treatment system 302 to dc-sulfurize the metal powder. Generally, as shown in FIG. 3, the treatment system 302 has a gas source 330, a vacuum source 332, and a controller 336. The gas source 330 may be in flow communication with the open end of the fill pipe 306 via a gas connection tube 322. The gas source 330 may be a canister or any other gas storage device that may store hydrogen gas. In an embodiment, the hydrogen gas may be pure hydrogen gas. In another embodiment, the hydrogen gas may be mixed with an inert gas. Suitable inert gases include, but are not limited to, argon and helium. The vacuum source 332 communicates with the can 304 via a vacuum connection tube 308. The vacuum source 332 may be a vacuum pump or other device capable of pulling a vacuum through the treatment system 302 and may be positioned in any location within the system 302 that is downstream from the gas source 330. ln an embodiment, the diameter of the vacuum connection tube 308 may be substantially equal to or larger than the diameter of the fill pipe 306. In other embodiments, the diameter of the vacuum connection tube 308 may be smaller.

100231 In an embodiment, the fill pipe 306, the gas connection tube 322, and the vacuum connection tube 308 arc connected to a junction fixture 325. The junction fixture 325 is configured to enable communication between the can 304, the gas source 330, and the vacuum source 332. To control flow through the system 302, in some embodiments, one or more valves 309, 310, 312 may be included. In an embodiment, one or more of the valves 309, 3 10, 3 12 may be vacuum-capable valves capable of opening and closing a flowpath. Suitable valves include, but arc not limited to, gate valves. As mentioned to briefly above, a first valve or "fill pipe valve" 309 may be disposed in the fill pipe 306 and may control gas flow into and out of the can 304. A second valve 3 12 controls gas flow into the vacuum connection tube 308 and may be positioned therein. A third valve 310 controls gas flow out of the gas source 330 and may be disposed in the gas connection tube 322.

100241 The treatment system 302 may also include a heater 334. In an embodiment, the heater 334 may be a furnace, oven, or other device suitably sized to receive and heat the can 304.

100251 The controller 336 is adapted to provide commands to and receive data from, either wirclessly or via other transmission means, the gas source 330, the vacuum source 332, and the valves 309, 310, 312 to control the flow of gas through the system 302. The particular commands from the controller 336 may depend on data related to an amount of sulfur that may be present in the metal powder in the can 304. In this regard, one or more sensors 338, adapted to detect the amount of hydrogen sulfide in the evacuated gas and to communicate the detected amount to the controller 336, may be appropriately placed to evaluate gas exposed to the metal powder. In an embodiment, the sensor 338 may be disposed in the vacuum line 308, as shown in FIG. 3. In any event, the sensor 338 may be any suitable sensor capable of detecting a sulfur amount from a volume of gas. The sensor 338 may be capable of sensing an amount of sulfur that may be equal to or less than I part per million by weight. Based in part on the communications from the sensor 338, the controller 336 may determine whether to repeat the steps of flowing gas into the can 304 and removing gas from the can 304. In an embodiment, the controller 336 may also be adapted to provide commands to the heater 334 to control the rate at which the can 304 will be heated and to what temperature the can 304 will be heated.

100261 Referring again to FIG. 2, after the can 304 is suitably incorporated into the treatment system 302, the can 304 is heated to a temperature sufficient to desulfurize the metal powder, step 204. In an embodiment, a vacuum may he applied to the can 304 during heating. For example, the vacuum source 332 may be used to exhaust gases that may be in the can 304. Next, the can 304 and the metal powder therein may be heated to a predetermined temperature. The predetermined temperature may be a temperature that is within 300°C of the incipient melting temperature of the metal powder. In an embodiment, the temperature is between about 50 °C and about 100°C lower than the incipient melting point of the metal powder. In an embodiment, the metal powder may be Alloy JO and the predetermined temperature may be between about 1150°C' and about 1200°C. The predetermined temperature may be more or less, depending on the particular metal powder in the can 304.

100271 The metal powder may then be de-sulfurized, and desulfurizing gas that comprises hydrogen and hydrogen sulfide may be removed from the can, step 206. FIG. 4 is a flow diagram of a method 400 of de-sulfurizing the metal powder, according to an embodiment. With additional reference to FIG. 3, gas may be flowed into the can 304 to react with the metal powder therein, step 402. As mentioned above, the gas may be a gas mixture, and the gas mixture may be flowed into the can. The gas mixture may comprise hydrogen and an inert gas, such as argon, for example. To flow the gas through the system 302, the valves 309 and 310 may be in an open position and valve 312 may be in a closed position to allow gas to be delivered into the cavity 318 of the can 304, in an embodiment.

After the cavity 3 18 is sufficiently filled with gas, the valve 3 10 may be closed. When the gas contacts the metal powder, the hydrogen in the gas may react with sulfur that may be present on a surface of the metal powder to form H2S (hydrogen sulfide) gas. in an embodiment, the gas may remain in the cavity 318 for a predetermined amount of time. The predetermined amount of time may be an amount of time sufficient for the sulfur on the surface of the metal powder to react with the hydrogen. For example, the gas may remain in the cavity 318 for between about 1 and about 180 minutes. It will be appreciated that alternatively the gas may remain in the cavity 3 18 for a longer or shorter period of time.

100281 After the predetermined amount of time has passed, at least a portion of the gas may be removed from the can 304, step 404. The gas may include H2S, hydrogen, and, in some embodiments, an inert gas. In an embodiment, substantially all of the gas is removed from the can 304. To remove the gas, the valve 3 12 may be opened and the vacuum source 332 may be activated to remove the gas from the can 304.

100291 In an embodiment, the steps 402 and 404 may be performed within a particular temperature range. For example, the steps may be performed within 300°C of an incipient melting temperature of the metal powder. In another example, the steps may be performed in a range of between about I 150°C and about 1200°C.

100301 A determination is then made as to a sulfur content of the metal powder, step 406. This determination may include establishment of a correlation between the amount of sulfur in the removed gas and the amount of sulfur remaining in the metal powder. In an embodiment, the sulfur content of the metal powder is calculated based upon data collected from the sensor 338. The sensor 338 may sense the sulfur content in the removed gas. For example, the sensor 338 may sense a hydrogen sulfide content of the removed gas. The sensor detection capability for sulfur may be about I part per million by weight, or may be lower. If the sulfur content is above the desired threshold value for the metal powder, steps 406 and 408 (e.g., the flowing and removing steps) may be repeated. In this way, each time steps 406 and 408 are repeated, a portion of the remaining sulfur in the metal powder is allowed to diffuse to an exposed surface of the metal powder, the gas flowed into the can 304 can react with the sulfur to form l-12S gas, and the gas may be removed. These steps may be repeated over a time period of between about one hour to twenty hours. The particular time period selected may depend on a quantity of metal powder that may be in the can 304 and/or the amount of sulfur that may have initially been included in the metal powder.

100311 Turning back to FIGs. 2 and 3, if a determination is made that the sulfur content is equal to or below a threshold value, the can 304 and the metal powder therein is consolidated to thereby form a compacted metal, step 208. In an embodiment, substantially all of the gas remaining in the can 304 is removed prior to compaction. To prevent the metal powder from being exposed to unwanted contaminants, such as to gases or other particles, the can 304 is evacuated and sealed before the consolidation process is performed.

For example, once the desulfurization treatment has been completed and the gas has been evacuated from the can 304, the valve 309 may be closed and the powder-filled can 304 may be cooled to room temperature. The fill pipe 306 may then be sealed at a location between the can 304 and the valve 309 (e.g., by crimping the pipe and/or welding). In some embodiments, the valve 309 may be removed for reuse. In other embodiments, prior to sealing the fill pipe 306, a chemical analysis sample of powder may be removed from the can 304 to vcri1' that the sulfur content of the metal powder has been reduced to below a desired threshold value (e.g., about 5 parts per million by weight, in an embodiment, or about I part per million by weight in other embodiments).

100321 The consolidation process may be performed on the can 304 and its contents by using particular process parameters that are suitable for forming a compacted solid having negligible porosity (e.g., having a porosity of less than 0. I percent by volume) For example, the consolidation process may be a hot isostatic pressing process in which parameters may include pressure, temperature, and time. In an embodiment, the hot isostatic pressing process may be performed at parameters where a selected temperature is in a range of between about 1090°C and 1290°C and a selected pressure is in a range of between about 15 to 30 ksi. The process may be performed for between about 2 to 8 hours.

In another embodiment, the hot isostatic pressing process may be performed at a temperature within a range of between about 1140°C to 1260°C at a pressure in a range of between about 20 to 30 ksi for between about 2 to 6 hours. The process alternatively may be performed within different temperature and/or pressure ranges, and/or for different time periods, in other embodiments. In other embodiments, the consolidation process may be an extrusion or forging process. In particular, the compacted metal powder may be pushed through a die having a cutout of a particular shape to thereby form a particular profile. In still another embodiment, the compacted metal powder may be forged (e.g., plastically deformed) to form the engine component. It will be appreciated that two or more of the aforementioned embodiments may be combined, when performing this step. For example, the compacted metal powder may be initially compacted by hot isostatic pressing or extrusion to form a billet.

100331 In another embodiment, after desulfurization of the metal powder has been completed, all or a portion of the desulfurized metal powder may be transferred to another can for the consolidation process. For example, the can 304 and the metal powder may be removed from the treatment system 302 and transferred to a compaction apparatus (not shown). The compaction apparatus may be used for hot isostatic pressing, extrusion or forging. Using a compaction method, the powder may be consolidated to form a compacted metal billet or other geometry.

100341 After the metal powder is consolidated, the can 304 is removed, and the compacted metal powder may be contoured or machined to form the component, step 210.

In an embodiment, the compacted metal powder may be machined into a predetermined shape to form the component.

100351 The compacted metal powder may be heat treated to improve properties, step 212. In an embodiment, the component is heated treated after it is contoured (machined) in step 210. In another embodiment, heat treatment may occur after the powder is consolidated in step 208, but before the engine component is contoured, in step 2 JO.

100361 Methods have now been provided for forming components. By employing the above-described method for de-sulfurizing metal powder materials, the components formed by the manufacturing methods above may be capable of being subjected to higher temperatures (e.g., greater than 675°C). In particular, de-sulfurizing the metal powder to include less than 5 parts per million sulfur by weight allows very little sulfur from the metal powder material to diffuse to interfaces and/or grain boundaries. The substantial absence of sulfur in the alloy may inhibit intergranular cracking and, consequently, improve creep strength and sustained peak low cycle fatigue strength of the component.

100371 While at least one exemplary embodiment has been presented in the foregoing detailed description of the inventive subject matter, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the inventive subject matter in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the inventive subject matter. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the inventive subject matter as set forth in the appended claims.

Claims

What is claimed is: I. A method (200) of forming a component (100), the method comprising the steps of: flowing (402) a gas into a can (304) with a metal powder therein, the gas comprising hydrogen, the can (304) configured to be used for a consolidation process, and the metal powder comprising sulfur; removing (404) at least a portion of the gas from the can (304); and subjecting (208) the metal powder therein to the consolidation process, if a determination is made that a sulfur content of the metal powder is below a threshold value, the threshold value being a value below about 5 parts per million by weight.
2. The method of claim I, wherein the threshold value is a value less than about I part per million by weight.
3. The method of claim I, wherein the step of flowing (402) the gas comprises flowing (402) a gas mixture into the can (304), wherein the gas mixture comprises hydrogen and an inert gas.
4. The method of claim I, further comprising determining (406) a sulfur content of the removed gas by sensing a hydrogen sulfide content thereof.
5. The method of claim I, wherein the step of subjecting (208) comprises subjecting the metal powder to a consolidation process comprising a process selected from the group of hot isostatic pressing, extrusion, and forging.
6. The method of claim 1, further comprising the step of repeating the steps of flowing (402) and removing (404) until the sulfur content of the metal powder is below the threshold value.
7. The method of claim 6, wherein the step of repeating comprises performing the steps of flowing (402) and removing (404) over a time period of between about 1 hour and about 20 hours.
8. The method of claim 1, wherein the steps of flowing (402) and removing (404) are performed within 300°C of an incipient melting temperature of the metal powder.
9. The method of claim 1, wherein the steps of flowing (402) and removing (404) comprises placing the can (304) in a furnace and heating the can (304) to a temperature that is between about 50 °C and about 100 °C lower than an incipient melting point of the metal powder.
10. The method of claim 1, further comprising the step of transferring at least a portion of the desulfurized powder to another can (304), before the step of subjecting (208).