HOT ISOSTATIC PRESSING CANISTER

Abstract

A canister for hot isostatic pressing is disclosed including a body arranged to define a cavity for containing a powder arranged to be subjected to hot isostatic pressing; and an opening defined in the body through which a powder can be inserted into the body, and the opening being closeable so as to seal the canister for hot isostatic pressing; wherein the body comprises a weakened area, the weakened area defining a part of the body which is designed to dissolve in acid faster than the rest of the body.

Claims

1. A canister for hot isostatic pressing, the canister comprising: a body arranged to define a cavity for containing a powder arranged to be subjected to hot isostatic pressing; and an opening defined in the body through which a powder can be inserted into the body, and the opening being closeable so as to seal the canister for hot isostatic pressing; wherein the body comprises a weakened area, the weakened area defining a part of the body which is designed to dissolve in acid faster than the rest of the body.

2. A canister as claimed in claim 1, wherein the body comprises a plurality of weakened areas.

3. A canister as claimed in claim 1, wherein the weakened area comprises a notch formed in the body.

4. A canister as claimed in claim 1, wherein the body is coated in an etching-resistant coating.

5. A canister as claimed in claim 4, wherein the weakened area is an area on the body which is not coated in an etching-resistant coating.

6. A canister as claimed in claim 4, wherein the acid etching-resistant coating is a polymeric coating.

7. A method of producing a canister suitable for hot isostatic pressing, the method comprising: constructing a canister by forming a body defining a cavity; and weakening an area of the body such that the weakened area will dissolve in acid faster than the rest of the body.

8. A method of producing a canister as claimed in claim 7, wherein the step of weakening an area of the body comprises machining a notch into the body.

9. A method of producing a canister as claimed in claim 7, wherein the method further comprises coating the body in an acid etching-resistant coating, and the step of weakening an area of the body comprises ensuring an area of the body is not coated by the coating.

10. A method of producing a canister as claimed in claim 9, wherein ensuring an area of the body is not coated by the coating comprises one of either removal of the coating in a desired area or masking off an area prior to the coating being applied and then removal of the mask.

11. A method for hot isostatic pressing a powdered material, the method comprising: disposing at least one powdered material in a canister, wherein the canister comprises: a body arranged to define a cavity for containing the powdered material, and the body comprising a weakened area, the weakened area defining a part of the body which is designed to dissolve in acid faster than the rest of the body; and an opening defined in the body through which the powder can be inserted into the body, and the opening being closeable so as to seal the canister for hot isostatic pressing; evacuating at least a portion of air from the canister through the fill stem; hermetically sealing the canister; and hot isostatically pressing the canister.

12. The method as claimed in claim 11, the method comprising a further step after the step of hot isostatically pressing the canister, the further step comprising placing the canister into a chemical bath to remove the material in the weakened area.

13. The method as claimed in claim 12, further comprising a subsequent step of removing at least a part of the body from the chemical bath using a robotic arm.

14. The method of as claimed in claim 12, further comprising a step of removing a hot isostatic pressed product from the chemical bath using a robotic arm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

[0027] FIG. 1 shows a summary of a PM-HIP process as known in the prior art;

[0028] FIG. 2 shows a first embodiment of a canister for hot isostatic pressing;

[0029] FIG. 3 shows a second embodiment of a canister for hot isostatic pressing; and,

[0030] FIGS. 4 to 9 show various steps in a method for hot isostatic pressing a powdered material.

DETAILED DESCRIPTION OF EMBODIMENT(S)

[0031] FIG. 2 shows a canister 20 suitable for use in a hot isostatic pressing process. The canister 20 comprises a body 201. The body 201 is arranged such that it defines a cavity 202 inside the body 201. An opening 203 is provided in the body 201 through which a powder can be inserted into the body 201 during a HIP process. The opening 203 is closeable so that the canister 20 can be sealed for hot isostatic pressing. This sealing process may be, for example, by welding the opening closed, and will typically result in the canister 20 being hermetically sealed.

[0032] The body 201 comprises a number of weakened areas 204. In the embodiment of FIG. 2, the weakened areas are provided in the form of notches 205a-d formed in the walls of the body 201. The notches 205a-d are machined into the body 201 in this embodiment, but it will be understood that notches may be formed in a number of ways. The weakened areas 204 define a part of the body 201 which is designed to dissolve in acid faster than the rest of the body. In this embodiment, the reduced thickness of the wall of the body at the point of the notches 205a-d mean that the remaining material at the notch will dissolve faster than the rest of the body 201.

[0033] Notches 205a and 205b are formed in the side walls toward the top end of the canister 20 close to the corners of the top end, and notches 205c and 205d are formed in the side walls toward the bottom end of the canister 20 close to the corners at the bottom end. The location of the notches 205a-d are designed to allow for the easiest possible removal of the parts of the canister from the finished product after the HIP process has happened. Whilst the notches 205a-d have been shown at the corners in this embodiment, it will be appreciated that alternative locations for notches may be selected depending on the shape and requirements of the final product. For example, notches may be provided in the middle of each of the sides.

[0034] FIG. 3 shows a second embodiment of a canister 30 suitable for use in a hot isostatic pressing process. The canister 30 comprises a body 301. The body 301 is arranged such that it defines a cavity 302 inside the body 301. An opening 303 is provided in the body 301 through which a powder can be inserted into the body 301 during a HIP process. The opening 303 is closeable so that the canister 30 can be sealed for hot isostatic pressing. This sealing process may be, for example, by welding the opening closed, and will typically result in the canister 30 being hermetically sealed.

[0035] The body 301 comprises a number of weakened areas 304. In the embodiment of FIG. 3, the body is coated in an etching-resistant coating (not shown) which resists the dissolving effects of acid. However, the etching-resistant coating is not provided at the weakened areas 304 of the body 301. The etching-resistant coating may have been applied all over the body 301 and then removed at the places where a weakened area is desired. Alternatively, the areas where it is desired to have a weakened area may have been masked off prior to the coating being applied, and then the masking material removed along with the coating at the weakened areas 304. Due to the lack of the etching-resistant coating, the weakened areas 304 define a part of the body 301 which is designed to dissolve in acid faster than the rest of the body.

[0036] Some weakened areas 304 are located at the side walls toward the top end of the canister 30 close to the corners of the top end, and other weakened areas are formed in the side walls toward the bottom end of the canister 30 close to the corners at the bottom end. The location of the weakened areas 304 are designed to allow for the easiest possible removal of the parts of the canister from the finished product after the HIP process has happened. Whilst the weakened areas 304 have been shown at the corners in this embodiment, it will be appreciated that alternative locations for weakened areas may be selected depending on the shape and requirements of the final product. For example, weakened areas may be provided in the middle of each of the sides.

[0037] FIGS. 4 to 9 show various steps in a method for hot isostatic pressing a powdered material.

[0038] In FIG. 4 a canister 40 is provided. The canister 40 can be formed as a welded steel fabrication, and has an opening 403 in the body 401 through which a powder 450 is inserted into the cavity 402 within the body 401 as indicated by arrow A. The powder is a powdered metal alloy, for example a powered titanium alloy may be used.

[0039] Once the canister 40 is full, then it is degassed and then sealed. FIG. 5 shows the sealed canister 40 full of powder 450.

[0040] In the next step, illustrated in FIG. 6, the sealed full canister 40 is machined using milling tools 460 or similar to create a number of notches at points 404 around the body 401 of the canister. The notches, which can more easily be seen in FIG. 7 referenced as 405a-d, result in the points 404 becoming weakened areas around the body 401. The machined notches 405a-d extend partially through the thickness of the walls of the body 401. A notch may, for example extend into between 10% and 90% of the overall thickness of the wall into which it is machined, this being referred to as the depth of the notch. The depth of a notch can be tailored to the desired requirements of the canister. A deeper notch will reduce the amount of time required for acid to separate the canister into separated parts and therefore speed up the time to produce the final product, however will also reduce the mechanical strength of the canister. As such, the most appropriate notch depth can be selected for the application. For example, in one embodiment, a notch may be chosen which extends into 50% of the overall thickness of the wall.

[0041] In this embodiment of the method, the notches are created in the body 401 of the canister 40 after it has been filled with powder and sealed. However, in alternative embodiments, it will be appreciated that the canister may be provided with the notches prior to being filled and sealed.

[0042] In addition, whilst there is no etch-resistant coating described in this embodiment, it will be understood that an alternative canister could be used with this method which comprises an etching-resistant coating as previously described in relation to FIG. 3. What is more, the milling operation could still be used to remove the coating and optionally even provide a notch as well.

[0043] Once the canister 40 has been filled, sealed, and it has weakened areas provided in the body, it can undergo the HIP process. The powder-loaded canister is placed in a pressure chamber and heated to a temperature at which the metallurgical powder inside the canister forms metallurgical bonds. The chamber is pressurized and held at high pressure and temperature. The canister deforms, and the metallurgical powder within the canister is compressed. The use of isostatic pressure ensures a uniform compaction pressure throughout the mass of metallurgical powder, which results in a consistent density distribution in the final product. FIG. 7 shows the canister 40 after the HIP process has taken place, and it can clearly be seen that the canister 40 has deformed and a final product 500 has been created inside the canister 40 from the powder.

[0044] To free the final product 500 from the canister 40, the canister 40 containing the final product 500 is placed into an acid bath 600 containing acid 610, as illustrated in FIG. 8. The remaining material of the body at each of the notches 405a-d is dissolved by the acid, which means that parts of the canister 40 are free to separate and fall away from the final product 500.

[0045] FIG. 9 shows the acid bath 600 containing the final product 500 and separated canister sections 410, 420, 430, 440 in the acid 610. The sections 410, 420, 430, and 440 have fallen away from the final product 500 as indicated by arrows B, C, D, E, and can now be recovered from the acid bath. This recovery can therefore happen much more quickly than if the whole canister 40 was required to dissolve in the acid 610, and as such the final product 500 can be made available more quickly. In addition, the recovered canister sections 410, 420, 430, 440 can be recycled instead of being entirely dissolved by the acid which helps conserve resources and reduces demand for materials.

[0046] In this embodiment, a robot 700 fitted with a robotic arm 701 is used to retrieve the canister sections 410, 420, 430, 440 and the final product 500 from the acid bath 600. The robotic arm 701 is fitted with an end effector 702 that allows it to capture the parts. The end effector 702 may capture the parts using one or a combination of a number of different methods, for example the end effector 702 may be magnetic or electromagnetic, and/or may have a grip which is able to physically grasp the parts. A magnetic end effector 702 may be able to capture parts of the canister magnetically. This is particularly beneficial when the canister 40 is made from steel as described earlier.

[0047] It will be clear to the skilled person that the examples described above may be adjusted in various ways, and features of some embodiments may be combined with other embodiments depending on the application and requirements.

[0048] For example, the canisters described herein are formed of steel. Steel is particularly beneficial as is can easily be welded during construction and also sealing, and also can allow for magnetic removal of the parts from the acid bath as described above. However, it will be appreciated that other materials may be used to for the canister.

[0049] As another example, two embodiments of a canister are described above in relation to FIGS. 2 and 3, one of which comprises notches, and the other comprises an etching-resistant coating. However, it will be appreciated that another embodiment of a canister may comprise both notches and also an etching-resistant coating.

[0050] Where the word or appears this is to be construed to mean and/or such that items referred to are not necessarily mutually exclusive and may be used in any appropriate combination.

[0051] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.