EP0225270B1 - Weldable cast nickel base superalloy - Google Patents

Weldable cast nickel base superalloy Download PDF

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Publication number
EP0225270B1
EP0225270B1 EP86630172A EP86630172A EP0225270B1 EP 0225270 B1 EP0225270 B1 EP 0225270B1 EP 86630172 A EP86630172 A EP 86630172A EP 86630172 A EP86630172 A EP 86630172A EP 0225270 B1 EP0225270 B1 EP 0225270B1
Authority
EP
European Patent Office
Prior art keywords
alloy
limiting
level
heat affected
inconel
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP86630172A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0225270A3 (en
EP0225270A2 (en
Inventor
John Edward Flynn
Mathew J. Arnold
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Raytheon Technologies Corp
Original Assignee
United Technologies Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by United Technologies Corp filed Critical United Technologies Corp
Publication of EP0225270A2 publication Critical patent/EP0225270A2/en
Publication of EP0225270A3 publication Critical patent/EP0225270A3/en
Application granted granted Critical
Publication of EP0225270B1 publication Critical patent/EP0225270B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel
    • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel
    • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
    • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
    • C22C19/055—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 20% but less than 30%

Definitions

  • the present invention concerns a process for improving the weldability of an alloy according to the precharacterizing portion of claim 1 and an alloy according to the precharacterizing portion of claim 2.
  • This invention relates to compositional modifications of, a nickel base superalloy, Inconel R 718 (a product of the International Nickel Co., Inc.) to render it consistently weldable.
  • Inconel 718 is a nickel base superalloy developed in the 1960s which has particular application in gas turbine engines. The nominal content of the required elements is 5.12% niobium plus tantalum, 19% chromium, 52.5% nickel, 3.05% molybdenum , 0.9% titanium, 0.6% aluminum, balance iron. Additionally, limits are placed on certain impurity elements such as silicon with a maximum of 0.3%, carbon with a maximum of 0.8% sulfur with a maximum of 0.015%, and manganese with a maximum of 0.35%. Inconel 718 is a moderate strength material particularly useful in the temperature range of about 538°C-816°C (1000 - 1500°F) and is apparently the subject of U.S. Patent No. 3 046 108.
  • the alloy has been used in wrought form in which case it can be bent or otherwise formed into useful shapes, and in cast form in which case the geometry of the shape is essentially established by the casting process. Intricate shapes and close tolerance dimensions in both wrought and cast forms can also be achieved through machining.
  • Modern gas turbine engines contain parts of substantially increased complexity compared to those of past generation engines.
  • there is a great impetus to reduce the weight of engines so that whereas in past engines excessive material in castings was tolerated, in present engines there is a desire to remove all excess material.
  • Concurrently there have been advances in the casting art so that parts of increased complexity can now be cast in almost final or net shape requiring minimum finish machining.
  • there has also been an increase in both use temperature and applied stresses so that there has been a driving force to go to stronger materials.
  • the cracking encountered in welding Inconel 718 has been analyzed and it was observed that the cracking, more properly described as microcracking, occurs in grain boundaries in the heat affected zone.
  • the heat affected zone is that zone immediately adjacent the weld zone which has not itself melted during welding.
  • FIG. l is a photomicrograph at a magnification of 1000X showing the appearance of a grain boundary in the heat affected zone (in Inconel 718) which has melted and resolidified after welding. A clear indication of extraneous phases can be seen in the center of the melted boundary, and there is evidence of cracking and/or void formation in the boundary, associated with the extraneous phase.
  • Figure 2 is a 1000X scanning electromicrograph photograph of a crack or a void found at the center of a grain boundary in a heat affected zone, the lumpy or rounded crack surface morphology strongly suggests that the crack surface was formed from molten metal, i. e. the cracking occurred before solidification was complete.
  • Table l shows the composition of the base alloy material, the composition of the grain boundary away from the weld zone and the composition of the grain boundary near the weld zone where cracking was observed.
  • the reference letters in Table I corresponds to the letters in Fig. 1.
  • the grain boundary near the weld zone also contain the previously referred to Laves phase. From the table it is seen that the composition at the grain boundary near where the weld zone has solidified is substantially increased in silicon (by about 10X) and in niobium (by about 6X) from the base metal composition.
  • Figure 3 shows a S.E.M. photomicrograph in which techniques have been employed to enhance the contrast of MC carbides and it can be seen that there is a pronounced concentration of MC carbides in the heat affected zone grain boundary.
  • the sulfur, zirconium, boron and phosphorus levels are preferably reduced to the lowest values commercially practical. It is theorized that the success in eliminating weld cracking which is observed in the compositions modified according to the present invention may be the result of a two-step sequence of events. First by reducing the boron, sulfur, zirconium and phosphorus (all of which are prone to concentrate at grain boundaries and are melting point depressants) melting of the grain boundaries in the heat affected zone may be substantially reduced. Second, for the reduced amount of grain boundary melting which does occur in the modified composition, the reduction of the niobium and silicon substantially eliminates the formation of the deleterious Laves phase. In addition by limiting the carbon content the amount of the MC carbide phase which forms is also reduced.
  • Figure 1 is a photomicrograph of a grain boundary in the heat affected zone.
  • Figure 2 is a S.E.M. photomicrograph showing voids associated with grain boundaries.
  • Figure 3 is a S.E.M. photomicrograph showing M.C. carbides in grain boundaries.
  • the best mode for carrying out the invention is first to limit the total content of niobium plus tantalum in the Inconel 718 composition to be between 4.75 and 5.125%, to limit the silicon level to a maximum of 0.05% and to change the carbon range to 0.03-0.06%. Also it is highly preferred to limit the sulfur, zirconium, boron and phosphorus contents to be as low as possible in consistent with commercial practice. The reduction of the sulfur, zirconium, boron and phosphorus is best achieved through the use of good modern practice in conjunction with the use of virgin starting materials, that is to say the use of pure individual starting elements rather than the use of revert or scrap material as starting material.
  • Table II shows composition and weld test results of ten samples of Inconel 718 material. Seven of the ten samples were special test samples with controlled chemistries (according to the present invention) produced from virgin material, the remaining three samples were commerical engine parts produced in one case from virgin material and in two cases from revert or scrap material.
  • the Table generally supports the thesis of the invention, that excessive amounts of silicon, niobium and/or carbon result in increased microcracking.
  • the Table also supports the desirability of using virgin material inasmuch as the two samples produced in part from revert or scrap material had by far the highest microcracking.
  • Samples number three and five which had niobium level at the high at or above upper end of the invention limit displayed the highest cracking levels of any of the virgin samples tested. Samples three and five also had carbon contents at the high end of those permitted by the invention limits. Accordingly it is believed that this data substantiates the affects of carbon, silicon and niobium, and the weldability of alloy Inconel 718 and that by limiting these elements as previously set forth the weldability of Inconel 718 can be substantially enhanced.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Arc Welding In General (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Chemically Coating (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
EP86630172A 1985-11-26 1986-11-20 Weldable cast nickel base superalloy Expired - Lifetime EP0225270B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US80198285A 1985-11-26 1985-11-26
US801982 1985-11-26

Publications (3)

Publication Number Publication Date
EP0225270A2 EP0225270A2 (en) 1987-06-10
EP0225270A3 EP0225270A3 (en) 1989-01-18
EP0225270B1 true EP0225270B1 (en) 1991-10-30

Family

ID=25182523

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86630172A Expired - Lifetime EP0225270B1 (en) 1985-11-26 1986-11-20 Weldable cast nickel base superalloy

Country Status (7)

Country Link
EP (1) EP0225270B1 (xx)
JP (1) JPS62130252A (xx)
KR (1) KR920000035B1 (xx)
BR (1) BR8605725A (xx)
DE (1) DE3682258D1 (xx)
IL (1) IL80535A (xx)
NO (1) NO864420D0 (xx)

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1250642B (xx) * 1958-11-13 1967-09-21
US4231795A (en) * 1978-06-22 1980-11-04 The United States Of America As Represented By The United States Department Of Energy High weldability nickel-base superalloy

Also Published As

Publication number Publication date
JPS62130252A (ja) 1987-06-12
IL80535A0 (en) 1987-02-27
DE3682258D1 (de) 1991-12-05
NO864420D0 (no) 1986-11-06
KR870005111A (ko) 1987-06-04
BR8605725A (pt) 1987-08-18
KR920000035B1 (ko) 1992-01-06
IL80535A (en) 1989-08-15
EP0225270A3 (en) 1989-01-18
EP0225270A2 (en) 1987-06-10

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