Abstract:
A method and apparatus for removing a canister  12  from a component  18  by forming an opening  30  in the canister wall thickness  14, 16  and introducing a pressurised fluid into the opening  14, 16  causing hydrostatic pressure build up between an internal canister surface  14  and the component  18,  leading to the removal of the canister  12.  This method and apparatus obviates the need to expend significant machining or chemical processing to remove the canister  12.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to method and apparatus for separating a component from a canister post Hot Isostatic Pressing (HIP). 
       BACKGROUND TO THE INVENTION 
       [0002]    A HIP process is known in which the alloy raw material, in powder form, is introduced into a specially shaped deformable canister which defines the shape of the desired component, and is usually formed from a mild steel or stainless steel. The canister is filled with a metal or a composite powder, the chamber is evacuated and sealed, and the canister is subjected to hot isostatic pressing using elevated temperatures and pressures, thereby consolidating the powder particles, and bonding these powder particles to form the resultant near net shaped component. 
         [0003]    The canister is then removed either mechanically using machining or chemically using a pickling process, or a combination of these processes. The cost and timescales involved in both processes can make near net processing less attractive from both an environmental and cost perspective. A method of removing the metal canister post HIP that does not require either of these processes would be advantageous. It is an object of the present invention to seek to provide an improved method of separating a canister from a processed component. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention is set out in the appended claims. 
         [0005]    According to a first aspect of the present invention, there is provided a method of separating a hipping (HIP) canister from a hot isostatically pressed component, the method comprises steps of: providing at least one opening extending through a wall of the hipping canister; and supplying a fluid under pressure through the opening to separate the canister surface from the component. 
         [0006]    Optionally the canister wall has a thickening in the region of the opening and the method comprises removing a portion of the thickening to uncover a blocking material. 
         [0007]    Optionally the blocking member is provided in an aperture in the canister and is removed to provide an opening. 
         [0008]    Preferably the portion of the thickening is removed by drilling or grinding. 
         [0009]    The removal method does not interfere with the processed component surface, hence the processed near net shaped component is protected. 
         [0010]    Preferably the blocking material is removed by applying a solution to the material that dissolves the material. 
         [0011]    Preferably the applied solution is alkaline and the material is a ceramic. 
         [0012]    The ceramic preferably exhibits chemical properties enabling it to be leached out using an alkaline solution. 
         [0013]    Preferably the thickening portion has an attachment feature for a fluid supply conduit, wherein the method comprises the step of attaching a fluid supply conduit to the attachment feature. 
         [0014]    The attaching of fluid supply conduit to the attachment portion is made by a mechanical fastening technique. Optionally the step of attaching the fluid supply conduit comprises screwing the conduit onto a screw thread formed on an external surface of the attachment portion. 
         [0015]    The attaching of fluid supply conduit to the attachment portion is made by a mechanical fastening technique. Optionally the step of attaching the fluid supply conduit comprises screwing the conduit onto a screw thread formed on an internal surface of the attachment portion. The attachment may be made by any mechanical fastening technique. 
         [0016]    The attaching of fluid supply conduit to the attachment portion is made by a mechanical fastening technique. Optionally the step of attaching the fluid supply conduit comprises clipping or welding the conduit to the attachment portion. The attachment may be made by any mechanical fastening technique. 
         [0017]    According to a second aspect of the present invention, a canister for a hot isostatic press (HIP) process comprising: a canister wall having a first surface and an opposite second surface, wherein an aperture opens to the first surfaces and contains a blocking member, the second surface having an attachment member for attachment to a fluid supply conduit. 
         [0018]    Optionally the attachment member comprises a thickened portion extending from the second surface. The thickened portion having a thickness which is at least greater than canister wall thickness. 
         [0019]    Preferably the aperture extends from the first surface into the attachment member. The blocking member may fill the opening within the canister wall or may also extend at least partially into the blind aperture of the attachment member. 
         [0020]    Preferably the blocking member extends into the attachment member. The blocking member may partially extend into the blind aperture within the attachment member. 
         [0021]    Optionally a diffusion bonding resistant layer is deposited on the first canister surface. The diffusion bonding resistant layer prevents the component bonding to the canister first surface during processing. Post processing, the diffusion bonding resistant layer acts as brittle interface between the canister first surface and the component surface, allowing separation of the canister from the component without the need for chemical processing or mechanical removal processes. 
         [0022]    Preferably the diffusion bonding resistant layer is a ceramic, an intermetallic or a glass. The specific diffusion bonding resistant layer material dependent on the powder material or solid material, or combination of powder material and solid material being processed. The selection of diffusion bonding resistant layer material is also dependent on the HIP temperatures and pressures used and the geometry of the component being formed. 
         [0023]    Preferably the blocking member is formed from a dissolvable material. 
         [0024]    Preferably the blocking member is formed from ceramic. 
         [0025]    The blocking member is a consumable item, and once the component has been processed, the blocking member has to be removed, providing access to the first canister surface and component surface interface. A ceramic blocking member can be readily dissolved using a suitable alkaline based solution. 
         [0026]    Optionally the aperture has a cross section selected from the group comprising: a vee, a semi-circle, a stepped or parallel cross-section. Preferably the corresponding preformed blocking member has a corresponding cross-section to be mateably received in the aperture. 
         [0027]    Preferably the aperture is symmetrical about an axis extending from the first surface. 
         [0028]    Optionally the blocking member is secured into the aperture of the canister wall by a screw threaded region formed around the external surface of the blocking member, which is mateably received with a corresponding internal screw threaded region on the internal surface of the aperture. 
         [0029]    The attachment of a blocking member into the attachment portion is made mechanically. Optionally the blocking member is secured into the aperture of the canister wall by an interlocking mechanism. 
         [0030]    The attachment of a blocking member into the attachment portion is made by bonding. Optionally the blocking member is secured into the aperture of the canister wall by an adhesive bonding agent. 
         [0031]    The attachment of a blocking member into the attachment portion is made by a frictional fitment. Optionally the blocking member is secured into the aperture of the canister wall through interference fit between the blocking member and the aperture in the canister wall. 
         [0032]    Optionally the attachment member has a screw threaded region formed on an external attachment member surface for engaging a complementary screw threaded region on an inner bore of a fluid supply conduit. 
         [0033]    Preferably the attachment member is welded to the second surface of the canister wall. 
         [0034]    Preferably the canister walls are fabricated from mild steel or a stainless steel. 
         [0035]    According to a third aspect of the present invention, there is provided a method of the method comprising the steps of forming an aperture in a canister wall and filling the aperture with a blocking material. 
         [0036]    Optionally the blocking material is applied to the aperture as a fluid or paste to fill the aperture and solidified in situ. 
         [0037]    Optionally the blocking material is applied to the aperture as a preformed article. 
         [0038]    Optionally the blocking member is secured into the canister wall by one or more of the following techniques: fastening the blocking member into the corresponding screw threaded region in the aperture of the canister wall; providing an interlocking mechanism between the blocking member and first or second surface of the canister; adhesively bonding the blocking member into the canister wall aperture; introducing an interference fit between blocking member and canister wall aperture. 
         [0039]    Optionally the method further comprising the step of applying a diffusion bonding resistant layer on the first surface. The diffusion bonding resistant layer prevents the component bonding to the canister first surface during processing. 
         [0040]    Preferably the diffusion bonding resistant layer is applied by electroplating, physical vapour deposition, chemical vapour deposition, thermal spraying or painting. 
         [0041]    Optionally the attachment member can be provided by machining from a solid, fabricating using sheet material or through a casting operation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0042]    The present invention will be more fully described by way of example with reference to the accompanying drawings in which: 
           [0043]      FIG. 1   a  shows a plan view of the metal canister and attached boss. 
           [0044]      FIG. 1   b  shows a cross-sectional view of the canister configuration prior to HIP processing. 
           [0045]      FIG. 1   c  shows a cross-sectional view of the canister configuration post HIP processing. 
           [0046]      FIG. 1   d  shows a cross-sectional view of the canister and access to the blocking member, inclusive of an optional blocking member location feature. 
           [0047]      FIG. 1   e  shows a cross-sectional view of the canister blocking member removed. 
           [0048]      FIG. 1   f  shows a cross-sectional view of the canister inclusive of an attachment feature and a fluid supply conduit. 
           [0049]      FIG. 1   g  shows a cross-sectional view of the canister inclusive of an alternative attachment feature and a fluid supply conduit arrangement. 
           [0050]      FIG. 1   h  shows a cross-sectional view of the canister blocking member removed, and inclusive of an optional blocking member location feature. 
           [0051]      FIG. 1   j  shows a cross-sectional view of separation of component from canister. 
           [0052]      FIG. 2  is a cross sectional view of an alternative canister configuration prior to HIP processing. 
           [0053]      FIGS. 3   a - 3   d  show blocking member cross sections. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0054]      FIGS. 1   a  and  1   b  show in plan view and cross-sectional view respectively a HIP canister configuration prior to processing. The canister configuration  10  comprising a canister  12 , the canister having a first surface  14  and a second surface  16 , the canister first surface  14  defining the shape of the desired component  18 . The canister is fabricated from mild steel or stainless steel sheet material. The wall thickness of the canister will depend on the type of near net shape component that is processed. A thinner canister wall thickness can be used when processing components of a solid nature. A thicker canister wall thickness may be required when processing hollow components, the thicker wall thickness ensuring the canister does not collapse or slump during processing. 
         [0055]    The first canister surface  14  can have a diffusion bonding resistant layer  20  deposited thereon. This diffusion bonding resistant layer acts as a layer between the first canister surface  14  and the processed component  18 , and either forms a brittle interface or a complete barrier to diffusion. The diffusion bonding resistant layer  20  is typically selected from a ceramic, an inter-metallic or a glass material. The specific choice of diffusion bonding resistant material is dependent on a number of factors, including the canister material, the thickness of the canister walls  14  to  16 , the structural and chemical properties of the HIP starting material to be processed, and the pressure and temperature ranges used during the HIP process. The diffusion bonding resistant layer  20  can be deposited by a number of deposition techniques and not limited to electroplating, physical vapour deposition, chemical vapour deposition, thermal spraying or painting. 
         [0056]    An attachment member is provided on the second canister surface. The attachment member has a thickness that is substantially greater than the canister wall thickness  14  to  16 . The attachment member  22  is typically machined from solid, fabricated using sheet material, or formed from a casting route. A blind aperture  24  is machined substantially into the centre of one face of the attachment member  22 . The blind bore  24  can be machined to reach half the depth of the attachment member  22 . If cast, the casting method would result in the attachment member  22  and the blind aperture  24  formed in a single casting method. The attachment member  22  may have a screw threaded region  45  formed on an external surface of the attachment member  22  and or may have an internal screw thread region  46  formed on an internal surface of the attachment member  22 . This screw threaded region  45  formed on the external surface of the attachment member  22  is used to attach a fluid supply conduit  47  post the completion of the HIP processing and when the component is to be separated from the canister  12 , and particularly from the canister first surface. The screw threaded regions may be provided by machining or alternatively the screw threaded regions may be formed during the casting process. 
         [0057]    A blocking member  28  is provided and is mainly chosen from a ceramic material, where the ceramic material exhibits material properties enabling the blocking material  28  to be removed post HIP processing by a chemical leaching process. The blocking member  28  can be in the form of fluid, a paste or in the form of a preformed article. A preformed blocking member would generally be processed using a sintering route, thereby providing a structurally robust and rigid blocking member  28 . The ceramic blocking member  28  can be integrally included as a core, if the attachment member  22  is manufactured using a casting process. 
         [0058]    An aperture  30  is introduced extending from the first canister surface  14  and the canister second surface  16 . The aperture  30  can have a cross section selected from a vee; a semi-circle; a stepped; or a parallel cross section. The next stage is to fasten the blocking member  28  in the aperture  30 . A fluid or paste based blocking material  28  can be applied to the aperture  30 , where upon application, the blocking member  28  solidifies in situ. When considering the preformed blocking member  28 , the blocking member  28  can be secured into the aperture  30  within the canister wall  14 ,  16 , by a number of methods. In a first example, the blocking member  28  can have a screw threaded region  48  formed on the external blocking member  28  surface, and is mateably received with a corresponding internal screw threaded region  49  formed on the internal opening surface. In a second example, the blocking member  28  can be secured into the canister wall aperture  30  by an interlocking mechanism. In a third example, the blocking member  28  is secured into the canister wall aperture  30  by using an adhesive bonding agent. In a fourth example, the blocking member  28  is secured into the aperture  30  of the canister wall through an interference fit between the blocking member  28  and the aperture in the canister wall  30 . 
         [0059]    The attachment member  22 , with the secured ceramic blocking member  28  protruding from the blind aperture  24  is aligned to the aperture within the canister wall  30  with the blind aperture face  26  sitting in close relationship with the second canister surface  16 . The ceramic blocking member  28  is therefore mateably received into the through opening  30 . The ceramic blocking member  28  protrudes and in the main sits flush with the diffusion bonding resistant layer  20  as shown in  FIG. 1   b.    
         [0060]    The use of the ceramic blocking member  28  brings a number of advantages over conventional machining to remove the canister. Firstly the ceramic blocking member  28  provides a means to access the interface between component  18  and the canister first surface  14  post processing. Secondly, before the ceramic blocking member  28  is leached out, material is removed from the attachment member  22 , e.g. by drilling, to access the ceramic blocking member  28 , and this drilling action does not damage the processed component. Thirdly, the use of the ceramic blocking member  28  negates difficult drilling or machining to the already accurately processed near net shape. 
         [0061]    Once the attachment member  22  is aligned as mentioned above, the attachment member  22  can be secured to the external canister surface  16 . A weld  34 , as shown in  FIG. 1   b  is formed around the outer surface of the attachment member  22  with the canister second surface  16 . The welding process used will generally be tungsten inert gas welding, providing high integrity welds. The attachment member  22  may also be secured to the external canister surface  16  by friction welding. 
         [0062]    In operational use, the canister configuration can have numerous attachment members  22  secured to the canister second surface  16 . The location of each attachment member  22 , will be dependent on the geometry of the final component  18 , and positioned to provide the most efficient way to separate the canister first surface  14  from the component  18 . 
         [0063]    The canister is now configured, and the HIP process can be initiated. A method of HIP to produce a component is known to the person skilled in the art. Briefly the steps include, introducing raw material into the canister cavity, e.g. powder or solid material or a combination of powder material and solid material  32 ; evacuating and sealing the canister, applying a combination of high pressure and high temperature to the canister. A near net shaped component  18  is produced, and bounded by the canister first surface  14 , see  FIG. 1   c.    
         [0064]    The next stage is to remove the canister  12  from the component  18 . An opening needs to made from the thickened region of the attachment member  22  and uncover the blocking member  28 . In one example, an opening  36  is made in the boss  22  by a drilling operation, extending from the top surface of the boss  38  to expose a portion of the blind bore  24  and uncovering the blocking member  28  see  FIG. 1   d . In a second example, a portion of the thickened region of the attachment member  22  can be removed by a grinding operation, and thereby uncovering the blocking member  28 . Once access to the blocking member  28  is gained, the blocking member  28  can be chemically leached out. 
         [0065]    The blocking member  28  can be removed by applying a solution that dissolves the ceramic blocking member material  28 . The solution for leaching out a ceramic based material is normally chosen from an alkali based solution. The specific selection of alkaline based solution is dependent on the material properties of the blocking member  28 . It is important that the chosen alkaline based solution does not react with the component surface  18 . By way of example, a blocking member plug  28  manufactured from silica rich ceramic may be removed by introducing the ceramic plug  28  with a solution of sodium hydroxide and water. This creates an opening  36  interconnected to an area  40 , the area left by the leached blocking member  28 , see  FIG. 1   e    
         [0066]    The final stage is to provide a mechanism for attaching a fluid supply conduit  47  to the attachment member  22 , and applying fluid under pressure through the opening to separate the canister surface from the component. There are a number of ways to connect the fluid supply conduit  47  to the attachment member  22 . As mentioned above, the attachment member  22  can have an external screw threaded region  45  or an internal screw threaded region  46 . In a first example the step of attaching the fluid supply conduit is conducted by screwing the conduit  47  onto a screw threaded region formed on an external surface  45  of the attachment member  22 . In a second example, the step of attaching the fluid supply conduit is conducted by screwing the conduit onto a screw thread formed on an internal surface  46  of the attachment member  22 . In a third example, the step of attaching the fluid conduit is conducted by welding the conduit to a portion of the attachment member  22 . In a fourth example, the step of attaching the fluid conduit to a portion of the attachment member is by introducing clipping. 
         [0067]      FIG. 1   f  shows a fluid  42  injected into the aperture  36  resulting in hydrostatic pressure build up between component  18  and the diffusion bonding resistant layer  20 . The fluid used is usually a liquid. The build-up of fluid and hydrostatic pressure acting to force apart and cause separation of canister  12 , and canister second surface  16  from the component  18 , as shown by arrow F. 
         [0068]    The first embodiment was described using a solid attachment member. In a further embodiment of the present invention, the attachment member and plug have different configurations, providing a canister configuration  110 . This embodiment is described with the support of  FIGS. 2 and 3   a - 3   d  showing a cross-sectional view of a tubular attachment member and blocking member configurations respectively. The focus of this embodiment will therefore be on the tubular attachment member, the blocking member configurations, the interaction of the blocking member and the tubular attachment member prior to HIP processing, and initial stage post HIP processing, i.e. uncovering and gaining the blocking member. For the purposes of this embodiment, the features that are common to both embodiments have their reference numerals increased by  100 . Additional features only mentioned in this embodiment are added, starting with  111  and numerically indexed up with odd numerals. 
         [0069]    The attachment member  122  has a tubular shape as opposed to a solid attachment member described in the first embodiment. The tubular attachment member is formed from a fabrication manufacturing route and formed from a mild steel or stainless steel. The tubular attachment member  122  has a wall  115  bounding a hollow central region  124 . 
         [0070]    The longitudinal ends of the tubular attachment member  122 , having a first open end  117  and a second open end  119 . The first open end  117  used to insert the blocking member  128  within the hollow central region  124 . The second open end  119  region has a tubular cross-section configured to locate and position the blocking member  128 . This second open end  119  region has a cross-section where the walled thickness  115  increases towards the second open end  119 . This increasing wall thickness can be provided by a vee; a semi-circle; or a stepped, wall configuration. The wall thickness configuration is not limited to a particular shape configuration, and needs to have an upper portion capable of receiving a larger part of the blocking member  128 , and conversely a lower portion capable of containing the larger portion of the blocking member  128 . The configuration of the cross section in the region of the second open end  119  preventing the blocking member from falling into the canister cavity (not shown in the figures). 
         [0071]    The end walls  126  of the second open end  119  of the tubular attachment member  122  are positioned and secured to the canister second surface  116  by welding. 
         [0072]    The blocking member  128  has an external dimension such that the blocking member  128  can be inserted into the hollow region  124  of the tubular attachment member  122 . 
         [0073]      FIGS. 3   a - 3   d  show a number of blocking member  128  configurations that can mate up to an opposing configuration formed in the wall thickness configuration in the second open end  119  region. 
         [0074]      FIG. 3   a  shows a cross sectional view of a blocking member  128 , where the blocking member having a uniform diameter to a depth where the cross section gradually tapers to a second diameter (the second diameter smaller than the first diameter), and the second diameter extending with a uniform cross section to a depth. The blocking member  128  can be configured to have a stepped cross section as shown in  FIG. 3   b . The stepped cross section having at least a larger uniform cross section at an upper region of the blocking member reducing to a smaller uniform cross section at lower region. The blocking member shown in  FIG. 3   b  can have multiple steps. The blocking member  128  can be configured to have a vee shaped cross section as shown in  FIG. 3   c . The vee configuration having a large first diameter at an upper portion of the blocking member plug  128 , and the first diameter gradually reducing to a smaller second diameter.  FIG. 3   d  shows a blocking member  128  having a semi-circle configuration. The semi-circle configured blocking member  128  has a first cross section at an upper region of the blocking member  128 . The first cross-section gradually decreasing to form a hemispherical shape to a depth and width, where the width is wider than the longitudinal centre line of the blocking member  128 , and a uniform cross section extending to the bottom. 
         [0075]    An aperture  130  is made extending from the first canister surface  114  and the second canister surface  116 . A blocking member  128  is inserted into the first open end  117  of the tubular attachment member  122 . The external dimension of the blocking member  128  in engagement with the internal surface  111  of the tubular attachment member  122 . 
         [0076]    The tubular attachment member  122  with the inserted blocking member  128  protruding from the second open end  119  is aligned to the aperture  130 , with the planar machined wall surface  126  sitting in close relationship with the external canister surface  116 . The blocking member  128  is therefore mateably received into the aperture  130 . The blocking member sits flush with the diffusion barrier resistant layer  120  deposited on the first canister surface  114  of the canister as shown in  FIG. 2 . The blocking member  128  may further protrude into the canister cavity and the powder material (not shown). 
         [0077]    Once the tubular attachment member  122  has been aligned as mentioned above, the tubular attachment member  122  can be secured to the second canister surface  116 . A weld  134  is formed around the external surface of the tubular attachment member  122  with the canister second surface  116 . The welding process of tungsten inert gas is generally used to produce high integrity welds. The ends of the tubular attachment member  122 , towards the first open end  117  are crimped shut  121 . At least one location is crimped shut using a mechanical crimping method. This method uses pressure welding, where the first open end  117  is heated and then crimped to form a closure by a pressure welding. 
         [0078]    The configured canister can then be HIP processed. Again, the main steps include, introducing raw material into the canister cavity, e.g. powder or solid material or a combination of powder material and solid material, evacuating and sealing the canister, applying a combination of high pressure and high temperature to the canister. A near net shaped component is produced, and bounded by the canister internal surface (not shown in  FIG. 2 ). 
         [0079]    Post HIP, the next stage is to remove the canister  112  from the component (not shown), and a method of gaining access to the ceramic plug is by mechanically removing at least a portion of the tubular attachment member  122 . A manual hand grinding operation can be used to remove a portion of the tubular attachment member material. Once the portion of tubular attachment member material is removed and the access to the blocking member  128  is gained, an alkali based solution can be applied to the blocking member  128 , thereby dissolving the blocking member material  128 . 
         [0080]    The final stage is to provide a mechanism for attaching a fluid supply conduit (not shown) to a portion of the tubular attachment member  122  or to the second canister surface  116 . This attachment is provided by welding the conduit to either a portion of the tubular attachment member  122  or to the second canister surface  116 . 
         [0081]    Fluid is injected into the attached fluid supply conduit resulting in hydrostatic pressure build up between component and the diffusion bonding resistant layer  120 . The build-up of fluid and hydrostatic pressure acting to force apart and cause separation of canister  112  from the component. Note that some of the features are not shown in this embodiment, and the removal of the canister  112  from the component during the injecting of pressure fluid causing hydrostatic pressure, is in the main the same as described in the first embodiment. 
         [0082]    In an example of the present invention, the internal canister surface  14 ,  114  may not require a diffusion bonding resistant layer  20 ,  120  deposited on it. In this method a material, e.g. a ceramic is processed in the same way as the aforementioned HIP process, and using a metal canister  12 ,  112 . Here, on HIP processing, the formed ceramic component  18  will not tend to adhere or bond to the internal canister surface  14 ,  114  due to the mismatch in chemical and structural properties of both metal canister  12 ,  112  and the ceramic component  18 . 
         [0083]    The features of the embodiments may be interchangeable. The shape of the blocking member, the method of gaining access to the blocking member, the methods of removing material from the attachment member to uncover blocking member are all interchangeable and not limited to one specific embodiment. Both attachment member and blocking member are not restricted to one particular shape, and the shapes used within the embodiments are to give one example. Where a singular attachment member is stated, it can also mean a plurality of attachment members. In practice the canister assembly may take the form of a combination of using tubular attachment members and solid attachment members.