Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
  • B23K20/02—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating by means of a press ; Diffusion bonding
  • B23K20/021—Isostatic pressure welding
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2101/00—Articles made by soldering, welding or cutting
  • B23K2101/001—Turbines

Definitions

• the invention relates to metal working processes and more particularly to improved HIP Bonding processes particularly suited for bonding austenitic materials.
• the invention which is the subject matter of this patent application comprises an improved Pressure Bonding process.
• the invention was reduced to practice as a result of and is described with respect to its use to implant a fault of known characteristic in a larger body of austenitic material.
• the hereinafter described bonding process has many uses.
• a fault having the desired characteristics was formed in a surface of a first body of austenitic material and implanted in a larger body of austenitic material by bonding the first body of austenitic material to a second similar body.
• the larger body of austenitic material was machined to form a cylindrical structure (fault sample) containing the fault with the fault positioned at a predetermined location therein.
• a cylindrical cavity having a diameter less than the diameter of the cylindrical structure was machined in a third body of austenitic material .
• the cylindrical structure and the third body were respectively cryogenically cooled and heated to insert the cylindrical structure into the cavity. After insertion of the cylindrical structure, the combined structure was stabilized to a uniform temperature causing an interference fit creating sufficient pressure at the interface formed by the interior of the cavity and the outer surface of the cylindrical structure to cause localized cold working of the interface surfaces.
• a non-oxidizing atmosphere was established around the combined structure and the interface sealed.
• a bond free of detectable variations in grain structure was formed along the interface using a HIP bonding cycle without significantly altering the original grain structure of portions of the austenitic material which had not been subjected to cold working.
• Figure 1 is a drawing illustrating two bodies of austenitic material used to form the fault sample.
• Figure 2 is a drawing illustrating two bodies of austenitic material assembled for HIP bonding.
• Figure 3 is a drawing illustrating a fault implanted in a body of austenitic material.
• Figure 4 is a drawing illustrating the fault sample after final machining .
• Figure 5 is a drawing illustrating a third body of austenitic material including a cylindrical cavity machined therein.
• Figure 6 is a drawing illustrating the test structure after final assembly.
• Figure 7 is a drawing illustrating the test structure after bonding and final machining.
• Figure 8 is a flow chart illustrating a process for preparing the defect sample.
• Figure 9 is a flow chart for the Bonding Process comprising the invention.
• Figures 1 through 4 illustrates the fault sample at various stages of assembly.
• the desired fault is implanted into a fault sample which is in turn implanted into a larger body to form a test structure.
• first and second bodies, 20 and 22, of austenitic material are utilized to form the fault sample 34 (Figure 4).
• Two similar interfaces, 24 and 26, of the bodies of materials, 20 and 22, are severely cold-worked using any suitable machining technique.
• a fault 28 having the desired characteristics is formed in one surface, for example surface 26 of body 22, using any suitable prior art techniques.
• the first and second bodies of materials, 20 and 22, are positioned in contacting end-to-end relationship to each other and sealed around the periphery of the interface formed by the contacting surfaces by welding in a protective atmosphere.
• the seal weld is illustrated at reference numeral 30.
• a single unitary body 32 is formed by HIP bonding the bodies, 20 and 22, together. The body 32 is then machined to form a cylindrical fault sample 34 containing the fault 28 therein.
• the fault 28 may be formed as complementary portions in the surfaces, 24 and 26, of the bodies, 20 and 22. While conventional HIP bonding processes have been successfully used to bond relatively small components, such as for forming the fault sample 34, they have not proved successful in bonding larger components. These difficulties with the prior art processes are believed to be caused by an inability of these processes to maintain a suitable interface between the components to be bonded as the size of the interfacing surfaces of the components increases.
• the fault sample 34 was implanted into a third larger body of identical material at a predetermined location. Specifically, the fault sample 34 was inserted into a cylindrical cavity 40 in a third body 42 of austenitic material. The diameter of the cavity 40 is smaller than the outer diameter of the fault sample 34 producing an interference fit.
• Insertion of the fault sample 34 into the cavity 40 was facilitated by heating the third body 42 and cryogenically cooling the fault sample 34. After insertion of the fault sample 34 into the body of material 42 the resulting test structure was stabilized to a uniform temperature resulting in extreme pressure at the interface of the body of austenitic material 42 and the fault sample 34. This pressure causes cold-working of the interfacing surfaces. Seal welding in a protective atmosphere was utilized along the upper and lower surfaces of the third body of material 42 and the fault sample 34 to seal the interface. This results in the assembled test structure illustrated in Figure 6.
• the assembled test structure was subjected to a HIP bonding cycle to form a unitary body free of abnormalities at the interface of the third body of austenitic material 42 and the fault sample 34 without causing undesirable metallurgical changes in the other portions of the structure.
• the bond forms as the grains comprising the cold-worked surfaces reform into larger grains extending across the interface. As previously discussed, this grain regrowth restores the original grain structure along the bond and progresses to completion without altering the grain structure of portions of the austenitic material which have not been subjected to cold working.
• test component can be machined into any desired configuration.
• development program it was machined into a rectangular body as illustrated in Figure 7 which was subjected to various tests to demonstrate that the improved bonding process performed as desired.
• Figure 8 is a flow chart of the process utilized to form the fault sample 34.
• the first step is to cut the austenitic material to form the two substantially identical bodies, 20 and 26, which are subsequently HIP bonded to form the fault sample 34 ( Figure 4) .
• This step is functionally illustrated at reference numeral 60, Figure 8.
• Cold worked surfaces, 24 and 26 are produced by machining selected surfaces of the two rectangular bodies, 20 and 22.
• a fault 28 is fabricated using any desired process. These steps are functionally illustrated at reference numerals, 62 and 64.
• the fault 28 is installed in at least one surface of the bodies, 20 and 22. Protection for the interface is provided by a seal weld as illustrated in Figure 2. Process steps producing these results are illustrated at reference numerals, 66 and 68.
• the fault sample is HIP Bonded and machined into final form to produce the fault sample 34 as illustrated at reference numerals, 70 and 72.
• the first step in the process is to machine the cavity 40 in the third body of austenitic material 42, as functionally illustrated at reference numeral 80.
• the fault sample 34 is installed into the cavity by heating the third body of austenitic material 42 and cooling the fault sample 34.
• This process is functionally illustrated at reference numeral 82.
• the interface is welded to seal the junction and the combined structure HIP bonded, as functionally illustrated at Reference Numerals, 84 and 86.
• the test structure is machined into the desired configuration, as functionally illustrated at Reference Numeral 88.
• Process parameters such as pressure and temperature for performing the above described bonds are determined by the characteristics of the materials . Selection of these parameters is within the capability of those skilled in the art. Also, the process can be used to bond materials other than the austenitic materials described above.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Pressure Welding/Diffusion-Bonding (AREA)

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• 1989
  • 1989-01-10 EP EP89902114A patent/EP0380593A1/de not_active Withdrawn
  • 1989-01-10 WO PCT/US1989/000098 patent/WO1989006583A1/en not_active Application Discontinuation

Non-Patent Citations (2)

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