Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
  • B23P6/00—Restoring or reconditioning objects
  • B23P6/04—Repairing fractures or cracked metal parts or products, e.g. castings
  • B23P6/045—Repairing fractures or cracked metal parts or products, e.g. castings of turbine components, e.g. moving or stationary blades, rotors, etc.
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/49972—Method of mechanical manufacture with separating, localizing, or eliminating of as-cast defects from a metal casting [e.g., anti-pipe]

Definitions

• a metal casting of an alloy based on an element selected from the group consisting of Ni, Co, Fe and Ti and having internal discontinuities, such as porosity, microfissures and internal tears, is improved by applying pressure to an outer surface of the casting surrounding the discontinuities while at the same time heating the casting, at least in its portion including the discontinuities, at a temperature less than that which will cause substantial degradation of the mechanical properties of the metal.
• the casting outer surface is coated with a coat ing of sufficient thickness to bridge the surface openings of the surface-connected discontinuities and to prevent penetration of the pressurizing fluid into such surface discontinuities.
• the combined amount of and time of application of pressure and the heating is suflicient to press together and to difiFusion bond walls of the discontinuity.
• the method of the present invention for improving the structural integrity and mechanical properties of the metal casting having discontinuities in its internal structure comprises applying pressure to the outer surfaces of the casting surrounding the discontinuity while at th esame time heating the casting at least in that portion including the discontinuities.
• the temperature at which heating occurs is less than that which will cause substantial degradation in mechanical properties of the metal.
• the combination of the applied pressure and the heating, for the time of such application is suflicient to press together and to diffusion bond walls of the discontinuities.
• the present invention is particularly useful in connection with the stronger alloys, such as those sometimes referred to as the superalloys based on the transition triad elements Ni, Co and Fe, as well as on Ti.
• the broad treatment temperature range for such materials is from about 1300-2250 F., depending upon the alloy being treated.
• the temperature is selected so that, at the pressure for example about 1-30,000 p.s.i. and for the time of application for example about /2 to 16 hours, there will be no substantial degradation in mechanical properties of the metal after treatment.
• discontinuities can be tolerated in some castings from which cast articles are made. However, in castings from which are made certain jet engine components, such as turbine blades and vanes which experience relatively severe operating conditions, discontinuities can be cause for rejection of such castings. Any discontinuities will cause less than optimum mechanical properties.
• Some of the cast test bars were treated, according to the present invention, by placing them in an autoclave, evacuating air from the autoclave and then applying pressure to the test bars within the autoclave through an inert gas, in this example argon. At the same time as pressure was applied, the bars within the autoclave were heated to about 2225 F. at which point a pressure of about 10,000 p.s.i. was being applied. The bars were held in the autoclave under these conditions for about 8 hours before cooling and removing.
• an inert gas in this example argon
• EP means Elongation
• R.A. means Reduction of Area.
• Both the untreated and treated specimens were given the same heat treatment of solutioning at 2225 F. for 2 hours in a vacuum then inert gas quenching to room temperature followed by 2000 F. for 4 hours in a vacuum and then inert gas quenching to room temperature. These specimens were aged at 1925 F. for 4 hours then furnace cooled to 1200 F. where they were held for 1 hour prior to air cooling to room temperature. Then they were heated at 1550" F. for 16 hours in argon and then cooled to room temperature.
• EXAMPLE 2 A cast turbine bucket of Ren 80 alloy was found through eddy current tests to have subsurface defects which, through fluorescent penetrant tests, were found to be surface connected. These were in amounts sufficient to cause rejection of the casting. Prior to treatment of such casting according to the present invention, the surface of the casting was nickel electroplated to a thickness of about 0.001 to bridge the openings of surface connected defects and thus to prevent pressurizing fluid penetration within such surface defects. Then the casting was treated as in Example 1.
• EXAMPLE 3 A casting of Ren 100 alloy with internal discontinuities was treated in accordance with Example 1 except that the treatment temperature was 2000 F. Examination of the casting after treatment showed that the voids in the casting did not close.
• the temperature of treatment according to the method of the present invention be greater than 2000 F.
• EXAMPLE 4 A titanium base alloy having the composition of Ti 6-4 and with internal discontinuities was treated in accordance with the method of Example 1. Although the discontinuities were healed in accordance with the method of the present invention, it was found that such a temperature was too high and resulted in degradation of the properties of the alloy. Heating of such titanium base alloys should not exceed the beta transus temperature of such alloy and should be maintained in the range of about l300-1850 F. Normally, diffusion bonding of such titanium alloys as Ti 6-4 can be accomplished at about 1750 F. under pressure of about 1000 p.s.i. for 1 hour to complete bonding.
• EXAMPLE 5 An iron base alloy of the composition identified by 17-4 PH and having internal discontinuities was treated in accordance with the conditions of. Example 1. Although the discontinuities were healed in accordance with the method of the present invention, it was found that the temperature of 2225 F. resulted in degradation of the mechanical properties. Therefore, treatment of such alloys should be conducted at about 2000 F. or less. For example, an undesirable delta ferrite will form in alloys such as A181 403 stainless steel, at about 2100 R. or above. Therefore, it is believed that these alloys should be treated at about 2000 F. or less, for example at about 5000 p.s.i. for about 1 hour.
• the treatment produced significant improvement in mechanical properties compared with ordinary castings. Such treatment did not substantially affect the external configuration of the casting but merely resulted in a densification of the metal.
• the present invention has been described in connection with the above specific examples, it will be understood that the application of heat and pressure and the combination of the two can vary over relatively wide limits so long as the applied temperature is less than that which will cause substantial degradation in mechanical properties of the metal and that the pressure applied to the outer surface is sufficient to cause for example, creep in the metal at the selected temperature. If it is desired to seal surface connected voids, the method of the present invention contemplates first coating the surface of the casting to bridge surface openings of such voids.
• a method for improving the structural integrity and mechanical properties of a metal casting of an alloy based on an element selected from the group consisting of Ni, Co, Fe and Ti and having in its internal structure surface-connected discontinuities, defined by discontinuity walls, and having surface openings through a casting outer surface comprising the steps of:
• the temperature of heating is (i) no greater than the incipient melting point of the alloy and up to about 2,250 F. when the element selected is Ni or C0,
• the alloy is a nickel base alloy; the temperature of heating is in the range of greater than 2000 F. up to about 2250 F.; the pressure is applied through a gas and is in the range of about 1000-30,000 p.s.i.; and the time of holding the casting at such temperature and pressure is about /2-16 hours. 4.
• the alloy is a titanium base alloy
• the temperature of heating is in the range of about the pressure is applied through a gas and is in the range of about 100030,000 p.s.i.;

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Physics & Mathematics (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Turbine Rotor Nozzle Sealing (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Pressure Welding/Diffusion-Bonding (AREA)
• Heat Treatment Of Nonferrous Metals Or Alloys (AREA)
• Heat Treatment Of Steel (AREA)

Applications Claiming Priority (1)

Publications (1)

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ID=22279718

Family Applications (1)

Country Status (7)

Cited By (22)

Families Citing this family (1)

Family Cites Families (2)

• 1970
  • 1970-12-21 US US00100426A patent/US3758347A/en not_active Expired - Lifetime
• 1971
  • 1971-08-28 JP JP6558971A patent/JPS5551008B1/ja active Pending
  • 1971-09-02 GB GB4099571A patent/GB1338917A/en not_active Expired
  • 1971-11-03 BE BE774828A patent/BE774828A/xx not_active IP Right Cessation
  • 1971-11-22 DE DE2157752A patent/DE2157752C2/de not_active Expired
  • 1971-12-03 IT IT32005/71A patent/IT943696B/it active
  • 1971-12-20 FR FR7145815A patent/FR2119510A5/fr not_active Expired

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