Patent Application
20240173770
This application claims priority to United Kingdom Patent Application GB 2218011.1, filed Nov. 30, 2022, the entire contents of which is hereby incorporated by reference.
The present invention relates generally to hot isostatic pressing. Certain aspects of the present disclosure relate to canisters for use in forming components by way of hot isostatic pressing, and other aspects of the present invention relate to methods for hot isostatic pressing.
Powder Metallurgy Hot Isostatic Pressing (PM-HIP) is a near net shape manufacturing method, filling low cost capsules with high value metallic powders. PM-HIP titanium alloys have comparable mechanical properties to wrought titanium. However, PM-HIP titanium has superior machining characteristics.
PM-HIP processes are often used in the aerospace field for creating large metallic parts, for example large titanium parts used in aircraft. Forging similar sized parts would typically require long lead times for the part to be created, but PM-HIP allows for the same part to be created in a much quicker timeframe.
A summary of a typical PM-HIP process is shown in
In step A1 a canister 1 is formed to the approximate shape of the final desired product. It can be formed, for example, as a welded steel fabrication. In A2, the metallic powder 2 is loaded into the canister 1. In steps A3 and A4, the powder-filled canister 1 is degassed and then sealed, ensuring there is no risk of there being any air pockets in the body of the final product. The Hot Isostatic Pressing (HIP) process is carried out in step A5. In HIP processes in which a canister is used, 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 3.
Once the HIP process has been completed, the canister 1 is removed as shown in A6, and the result is the finished component 3 in step A7. Canister removal is typically carried out by machining or acid etching the canister off. After the canister 1 has been removed, depending on the requirements of the product, and the application of it, the product may go through a number of machining steps to finish the product to the required specification.
It has been found during machining removal of the canister that material dissimilarity between the canister and the product can make the swarf generated during the machining stages more difficult to recycle. In addition, the strain energy present in the canister after HIP deformation, combined with the input energy of the cutter being used can lead to large pieces of the canister breaking off, and in some cases being ejected. This poses a serious risk to the operator of the machinery.
Acid etching away of the canister can be used as an alternative to machining, but it can take a significant amount of time for the material of the canister to be dissolved by the acid, and this method also prevents the waste material of the canister from being recycled.
It is an object of the present invention to address the limitations described above.
According to a first aspect of the invention, there is provided 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.
With such an arrangement it may be possible to separate the canister into parts quicker and more safely following Hot Isostatic Pressing, and parts of the canister can be recycled after use.
Optionally, the body may comprise a plurality of weakened areas. This can result in the body of the canister being separated into a number of smaller sections following HIP, and may speed up the time taken to recover the final HIP product.
Optionally, the weakened area may comprise a notch formed in the body. The thickness of the material at the notch will therefore be smaller, and it will be quicker for the material within the notch to be dissolved than the reminder of the body.
Optionally, the body may be coated in an etching-resistant coating. As a result, parts of the canister will not be affected by an acid bath, allowing for easier removal after a HIP process.
Optionally, the weakened area may be an area on the body which is not coated in an etching-resistant coating.
Optionally, the acid etching-resistant coating may be a polymeric coating.
A further aspect of the invention provides 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.
Optionally, the step of weakening an area of the body may comprise machining a notch into the body.
Optionally, the method may further comprise coating the body in an acid etching-resistant coating, and the step of weakening an area of the body may comprise ensuring an area of the body is not coated by the coating.
Optionally, ensuring an area of the body is not coated by the coating may comprise 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.
A further aspect of the invention provides 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; the method further comprising the steps of evacuating at least a portion of air from the canister through the fill stem; hermetically sealing the canister; and hot isostatically pressing the canister.
Optionally, the method may comprise 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.
The method may comprise a subsequent step of removing at least a part of the body from the chemical bath using a robotic arm.
The method may further comprise a step of removing a hot isostatic pressed product from the chemical bath using a robotic arm.
Embodiments of the invention will now be described with reference to the accompanying drawings, in which:
The body 201 comprises a number of weakened areas 204. In the embodiment of
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.
The body 301 comprises a number of weakened areas 304. In the embodiment of
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.
In
Once the canister 40 is full, then it is degassed and then sealed.
In the next step, illustrated in
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.
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
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.
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
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.
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.
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.
As another example, two embodiments of a canister are described above in relation to
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.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2218011.1 | Nov 2022 | GB | national |
