Classifications

• • 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
  • C22C19/057—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being less 10%
• • 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
• • 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%
• • 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
  • C22C19/056—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 10% but less than 20%

Definitions

• the present invention relates to improved superalloys and methods for improving superalloys.
• Superalloys are important materials used as hot components of gas turbines in aeroplanes, warships and industrial and traffic machines. Recently, they have also been widely used in aerospace nuclear reactors and chemical industries, etc. How to improve their resistant ability to oxidation and corrosion, and raise they strength and service temperature are of significant importance. And researches on these problems have been paid much attentions by many metallurgists and designers in the world. Since the late forties, superallloys have been developed rapidly. However, the progress of the development and improvement in composition design of superalloys has been slowed down after 1970's. the main reasons are as follows:
• the alloys of the present invention contain at least about 25% nickel (all percents expressed herein and in the claims are by weight unless otherwise specified) and up to about 0.001% phosphorus, for nickel-base superalloys the phosphorus content should be lower than 0.0005%, up to about 0.05% silicon, about 0.001 to about 0.015% boron.
• the balance of the alloy will consist of other elements which are conventionally alloyed with nickel to form superalloys such as elements selected from the group consisting of chromium, iron, cobalt, molybdenum, titanium, tantalum, tungsten, aluminum, niobium, carbon, vitriol and combinations thereof. These alloys will be zirconium-free.
• the alloy for the cast consists essentially of about 6.0% to about 22.0% chromium, up to about 16.0% cobalt, up to about 8% molybdenum, about 2% to about 5.5% titanium, about 2% to about 6.5 aluminum, up to about 12.0% tungsten, about 10 to about 150 ppm boron, up to about 4.0 niobium, up to about 12.0% tantalum, and about 0.02% to about 0.22% carbon, up to about 0.0005% phosphorus, up to about 0.05 silicon, hafnium-free, zirconium-free and the balance nickel.
• the alloy for the wrought consists essentially of about 25 to 55% nickel, about 0.01 to 0.1% carbon, about 0.1 to about 0.5% vitriol, about 10 to 22% chromium, up to about 3% tungsten, up to about 7% molybdenum, up to about 6% niobium, up to about 6% tantalum, about 0.1 to about 3% aluminum, about 0.5 to about 3% titanium, about 0.001 to about 0.01% boron, up to about 0.001% phosphorus, up to about 0.05% silicon, zirconium-free and the balance iron.
• the invention provides a new method of raising the incipient temperature, reducing the segregation, eliminating technological properties of the superalloys effectively by means of strictly controlling the contents of P and B and eliminating Zr.
• the key points are: the P content in the present superalloys must be reduced below 0.001 ( in wt%); for nickel-base superalloys the P content should be lower than 0.0005 (wt%); for the existing superalloys using Zr as the grain boundary strengthening element, besides reducing the P content less than 0.0005, it is also necessary to eliminate the Zr from the superalloys.
• the inventors developed a series of low segregration superalloys with excellent properties.
• the incipient melting temperature of Fe-Ni-Cr-base wrought superalloy GH901 (Namely Alloy IN 901) can be raised from 1140°C to 1260°C and the starting forging temperature can be raised to 1190-1225°C accordingly.
• the precision mould forging technology can be used very easily and the materials can be utilized very savingly without any loss in tensile and stress rupture properties, for cast superalloys the contents of Al and Ti can be added by 1% more without any loss in hot corrosion resistance and formation of harmful phases.
• This invention also provides the composition of new superalloy modified by the new method mentioned above. They are as follows: (1) an analogue of GH901 (IN 901) FE-Ni-Cr-base superalloys with low segregation. The characteristic specificity is to control the P content below 0.001.
• an analogue of M40 (IN 792) Ni-base superalloy with low segregation.
• the characteristic specificities are (A) to eliminate Zr and reduced P below 0.0005%, and (B) to raise the Al and Ti contents by 1(%).
• an analogue of M38 (IN 738) Ni-base superalloys with low segregation and high Al and Ti contents.
• the characteristics specificities are (A) to eliminate Zr and control P below 0.0005%, (B) to raise the Al and Ti contents by about 1(%).
• an analogue of M 38(IN 738) Ni-base superalloy with low segregation and high Cr content The characteristic specificities are (A) to eliminate Zr and control P content below 0.0005% and (B) to increase the Cr content by about 4(%).
• the service temperature of the exisiting cast superalloys can be raised by 100-300°C. Meanwhile, the invented new method is also very helpful to solve the difficult problem in hog working processing of wrought superatlloys and greatly improve the hot workability of the alloys.
• the new method of the present invention is carried out as follows: Firstly, the P and Si contents of raw materials (Fe and Cr) must be strictly controlled. If the P and Si contents in Fe and/or Ce are a little high, it is necessary that to refine Fe into powder form by wet metallurgy and to purify Cr several times by electrolysis.
• the P content in raw materials of Fe and Cr is below 0.0005%, and Si content is below 0.05%.
• the qualified raw materials are melted in a vacuum induction furnace and the added boron content is controlled at the range from about 0.001 to about 0.015%.
• the alloy is remelted in the vacuum induction furnace with the same melting technology to the ordinary one.
• a superalloy (our name: M17E) with low segregation for the cast was produced by melting a composition of about 0.08 to about 0.21% C, about 8.0 to about 10.0% Cr, about 10.0 to about 16.0% Co, about 2.5 to about 3.5% Mo, about 5.5 to about 6.5% Al, about 4.5 to about 5.5% Ti, about 0.005 to about 0.015% B, and the balance of Ni, controlling incidental impurities, such as: ⁇ 0.0005% P, ⁇ 0.05% Si, in a vacuum induction furnace.
• the melted alloy was cast into ceramic molds to form sticks. And cuting down the ends of the sticks, then remelting the sticks in a vacuum induction furnace.
• the melted alloy was cast into shaped molds to produce parts or specimens.
• a superalloy (our name: M17F) with low segregation for the cast was produced by melting a composition of about 0.08 to about 0.21% C, about 8.0 to about 10.0% Cr, about 8.0 to about 10.0% Co, about 3.0 to about 5.0% W, about 1.0 to about 3.5% Mo, about 3.0 to about 5.0% Ta, about 4.5 to about 5.5% Al, about 4.0 to about 5.0% Ti, about 0.005 to about 0.015% B, and the balance of Ni, controlling incidental impurities, such as: ⁇ 0.0005% P, ⁇ 0.05% Si, in a vacuum induction furnace. The melted alloy was cast into ceramic molds to form sticks. And cuting down the ends of the sticks, then remelting the sticks in a vacuum induction furnace. The melted alloy was cast into shaped molds to produce parts or specimans.
• a superalloy (our name: M40) with low segregation for the cast was produced by melting a composition of about 0.08 to about 0.21% C, about 12 to about 14% Cr, about 8 to about 10% Co, about 1.0 to about 3% Mo, about 3.2 to about 4.3% Al, about 4.2 to about 5.3% Ti, about 0.005 to about 0.015% B, about 3 to about 5% W, about 3 to about 5% Ta and the balance of Ni, controlling incidental impurities, such as: ⁇ 0.0005% P, ⁇ 0.05% Si, in a vacuum induction furnace.
• the melted alloy was cast into ceramic molds to form sticks. And cuting down the ends of the sticks, then remelting the sticks in a vacuum induction furnace.
• the melted alloy was cast into shaped molds to produce parts or specimans.
• a superalloy (our name: M38G) with low segregation for the cast was produced by melting a compositon of about 0.08 to about 0.21% C, about 15 to about 17% Cr, about 7 to about 9% Co, about 2 to about 4% W, about 1 to about 3% Mo, about 1 to about 2.5% Ta, about 3.5 to about 4.5% Al, about 3.3 to about 4.3% Ti, about 0.005 to about 0.015% B,about 0.5 to about 1.5% Nb and the balance of Ni, controlling incidental impurities, such as: ⁇ 0.0005% P, ⁇ 0.05% Si, in a vacuum induction furnace. The melted alloy was cast into ceramic molds to form sticks. And cuting down the ends of the sticks, then remelting the sticks in a vacuum induction furnace. The melted alloy was cast into shaped molds to produce parts or specimans.
• a superalloy (our name: M36) with low segregation for the cast was produced by melting a composition of about 0.08 to about 0.21% C, about 19 to about 21% Cr, about 7 to about 9% Co, about 2 to about 4% W, about 1 to about 3% Mo, about 3.5 to about 4.5% Al, about 3.5 to about 4.5% Ti, about 0.005 to about 0.015% B,about 0.5 to about 1.5% Nb and the balance of Ni, controlling incidental impurities, such as: ⁇ 0.0005% P, ⁇ 0.05% Si, in a vacuum induction furnace.
• the melted alloy was cast into ceramic molds to form sticks. And cuting down the ends of the sticks, then remelting the sticks in a vacuum induction furnace.
• the melted alloy was cast into shaped molds to produce parts or specimans.
• the most preferred version of the superalloys of the present invention were produced by following compositions of elements in Table I-A.
• the conventional superalloys for the cast containing essentially about 0.004 to about 0.009% P, about 0.03 to about 0.15% Zr, about 0.005 to about 0.02% B, about 0.05 to about 0.3% Si. Because of the segregation, the microstructure of the conventional superalloys are found to have stable laves phase on solidification, to form 3-5% (gamma+gamma′) phase, and to produce delta phase after exposure in the elevated temperatures.
• the nickel-­base superalloys in present invention showed improved elevated temperature strength properties over their proir art and these properties were even further improved by use of the preferred heat treatment.
• a superalloy (our name :LSDS738) with low segregatin for the directional solidification was produced by melting a composition of about 0.08% C, about 16% Cr, about 8.5% Co, about 2.6% W, about 1.7% Mo, about 0.7% Nb, about 1.7% Ta, about 3.5% Al, about 3.3% Ti, about 0.008% B, Hf-free and the balance of Ni, controlling incidental impurities, such as: ⁇ 0.0005% P, ⁇ 0.05% Si, in a vacuum induction furnace.
• the melted alloy was cast into ceramic molds to form sticks. And cutting down the ends of the sticks, then remelting the sticks in a vacuum induction furnace.
• the melted alloy was cast into shaped molds to produce parts or specimans.
• the conventional superaloys for the directional solidification containing essentially Hf and about 0.08% C, about 0.012% B, about 0.10% Zr, about 0.005% P, about 0.1% Si.
• the very expensive metal Hf have to be added in the said alloy.
• the present invention make it possible that the transverse properties of the directional solidified superalloys can be improved obviously without any addition of Hf. So, the invention benefits to the application of the directional solidification technology and makes it easy to combine with the air-cooling technique.
• the directional solidified superalloys for the cast of the present invention exhibit substantially increased elevated temperature strength and stress Rupture Time, especially increased the transverse properties of the directional solidified suporalloys.
• a superalloy (our name: LSIN901) with low segregation for the wrought was produced by melting a composition of 0.03% C, 12% Cr, 5.7% Mo, 0.2% Al, 3% Ti, 43% Ni, 0.003% B, and the balance of Fe, controlling incidental impurities, such as: ⁇ 0.0005% P, ⁇ 0.05% Si, in a vacuum inductiong furnace.
• the melted alloy was cast into ceramic molds to form slabs.
• the slabs were remelted by vacuum drip melting to form ingot.
• a superalloys (our name:LSA286) with low segregation for the wrought was produced by melting a compositiong of about 0.08% C, about 13.5 to about 16.0% Cr, about 24% to about 27% Ni, about 1.0% to about 1.5% Mo, about 1.9% to about 2.35% Ti, ⁇ 0.35% Al, about 0.1% to about 0.5% V, about 0.001% to about 0.004% B, and the balance of Fe, controlling incidental impurities, such as: ⁇ 0.001% P, ⁇ 0.05% S, in a vacuum induction furnace the malted alloy was cast into ceramic molds to form slabs. The slabs were remelted by vacuum drip melting to form ingot.
• the superalloys of the present invention showed improved elevated temperature strength properties over the prior art and these properties were even further improved by the use of the preferred heat treatment.
• the new method of the present invention is suitable to both Fe-Ni-Cr-base superalloys and Ni-base superalloys. It is obvious that the characteristics of the low segregation superaloys of the present invention lie in: (1) no addition of Zr; (2) P content is below 0.001 or 0.0005%; (3) contents of Al and Ti increased by 1%; (4) Cr content increased by 4%.
• the properties of the superalloys provided by this invention are shown in Table IV, V,VI and VII.
• Table IV shows the comparison of the properties of GH901 (IN901) alloy with those of the low segregation GH90; alloy. It can be seen that the tensile strength at room temperature, stress repture property and incipient temperature of the low segregation GH901 alloy are raised obviously.
• Table V shows the comparison of 100 hour stress repture strength data in the M38 (IN738) and M17(IN100) alloys with those in the corresponding low segregation ones. The properties of the low segregation alloys are obvously higher than those in conventional ones.
• Table VI gives the comparison of the stress rupture life (hour) and hot corrosion resistance in both series of the alloys (M38 & M36 with low segregation M38 & M36 alloys).
• Table VII lists the data of the stress reputre strength at elevated temperatures in both IN 792 and low segregation IN 792 alloys. It is clear that the properties of low segregation superalloys are obviously higher than those of the corresponding conventional ones.

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• 1989
  • 1989-03-15 CN CN 89105034 patent/CN1045607A/zh active Pending
• 1990
  • 1990-03-14 EP EP19900250070 patent/EP0387976A3/fr not_active Withdrawn

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