JP3148211B2 - Nickel-based superalloy, article made of nickel-based superalloy, method of heat treatment of cast article made of nickel-based alloy, method of manufacturing cast article made of columnar particle nickel-based superalloy, and turbine blade of gas turbine engine made of columnar particle nickel-based superalloy Manufacturing method of cast member - Google Patents

Description

Description: The present invention relates to a cast article comprising a nickel-based alloy of directional solidified columnar particles, and more particularly to an excellent high temperature surface stability as represented by oxidation resistance. Articles, especially thin hollow articles, and alloys and heat treatments for the manufacture of such articles.

BACKGROUND OF THE INVENTION A significant portion of the known and well-known casting techniques for hot working articles, for example, turbine blades for gas turbine engines, are characterized by the elimination of some or all of the grain boundaries in the microstructure of the final article. Is aimed at improving. Such structures are usually
It is manufactured by a well-known precision casting method in which a molten metal is oriented so as to elongate crystals or particles to be solidified and solidified (directional solidification). During solidification, growing only one particle in the article, for example, by stopping the growth of other particles or using a seed crystal, results in a single crystal article having few grain boundaries. However, as many particles solidify in the area of the casting mold and heat is removed from the molten metal in the casting mold and grows in a generally single direction, a large number of elongations in the solidified casting, i.e. Columnar particles are present. Such structures may be referred to herein as "DS multiparticulates" with respect to cast articles. The direction of elongation is called the longitudinal direction, and the direction substantially perpendicular to this longitudinal direction is called the lateral direction.

Since almost all grain boundaries in such articles are longitudinal grain boundaries, such as stress rupture life and ductility, as well as good transverse mechanical properties and good alloy surface stability in cast articles. It is important that the mechanical properties in the longitudinal direction are very good. If this property is balanced in the article, the article alloy should be capable of being cast into complex shapes and directional solidification, usually with complex internal voids and relatively thin walls without cracks. With. In so-called "thin-wall" hollow castings, founders using well-known "lost wax" type precision casting methods with alloys designed to have improved properties face difficult quality problems are doing. That is, while the properties of the alloy are within good and desirable ranges, thin-walled castings, such as those having walls less than about 0.035 inches thick, will crack during multi-columnar grain-directed solidification. Is common.

SUMMARY OF THE INVENTION Briefly, in one aspect, the present invention provides, in one form, the result of an alloy specification enhanced by an improved combination and balance between heat treatment and longitudinal and transverse stress fracture properties. An improved columnar particle nickel-based alloy cast article characterized by outstanding high temperature surface stability to a solidified article is provided. In this case,
The article has at least one internal gap,
Includes an integral cast wall with less than about 0.035 inch thickness with few large cracks.

In the alloy according to the present invention, the essential addition of C, Hf, Co and Ta and the intentional limitation of the elements V, Zr and Ti are employed in a special combination, resulting in Cr, Mo, W, Al, Re. And B, and may contain Cb and Y in arbitrary amounts.
Outstanding high temperature oxidation resistance, good castability, and resistance to grain boundaries and fatigue crack initiation are obtained in Ni alloys.

In one form, the alloys of the present invention have essentially 0.1-
0.15C, 0.3-2Hf, 11-14Co, 5-9Ta, Zr less than 0.05,
It contains a combination of V and Ti (up to about 1 each) of almost 0 (weight is mathematical) so that from this alloy:
With good castability and resistance to grain boundary and fatigue crack initiation, as well as outstanding oxidation resistance, it is possible to make DS multiparticulate articles. The balance of the alloy of the present invention is 5-10Cr, 0.5-3Mo, 4-7W, 5-7Al, 1.5-4R.
e, 0.005-0.03B, Cb up to 1.5, Y up to 0.5 and the balance Ni and accompanying (unavoidable) impurities.

In another aspect, the invention dealing with such an alloy is a heat treatment used in a method of making an article. Such heat treatment comprises a combination of at least three stepwise heating steps, including a solution treatment step, a preliminary first aging step, and a second aging step, which improves the stress fracture properties of the article.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Nickel-based alloys according to the present invention have, in particular, relatively high C
It is characterized by a combination of content and addition of relatively large amounts of Hf and Co and Ta. This and the elements V, Zr and
Due to the conscious control and limitation of Ti, the alloy as a whole has outstanding oxidation resistance and good
DS castability and resistance to grain boundaries and fatigue crack initiation can be achieved, allowing DS walls to be cast with less than 0.035 inch thin walls with most crack-free elongated particles. Other elements that contribute to its unique mechanical properties and surface stability in this nickel-based alloy are Cr, Mo, W, Al, Re, B and optionally limited amounts of Cb and Y. The resulting article has an unusual and unique combination of mechanical properties and surface stability, such as blade members (ie, blades or wings) of the type used in the harsh environment of the turbine section of a gas turbine engine. It is particularly useful for manufacturing such hollow air-cooled high temperature working parts. For rotating turbine blades that are subject to high stress, but to high temperature oxidation and thermal corrosion, crack-free conditions associated with repeated internal cooling are essential for safe and efficient engine operation.

The measurement and scale of the castability and crack resistance of nickel-based superalloys of columnar particles solidified at high temperature are described in Ukusick et al., U.S. Pat.
No. 9,742, column 2, line 41, starting from column 3, following the castability test and rating reported. The disclosure of this patent is incorporated herein by reference. The ratings are listed in Table I below.

Some of the nickel-base superalloys designed and used for gas turbine engine turbine components, along with certain alloys in one form according to the present invention, are shown in Table II below. The alloy designated Rene'N5 was devised for use in the manufacture of single crystal alloy articles, and was filed on October 15, 1985, now pending by Wukusick et al. It is described in Patent Application No. 790,439. Alloys marked Rene 'N150 are DS
It was devised for use as a columnar particle article and is described in Wukusick et al., US Pat. No. 4,169,742, which is incorporated by reference above. The above-mentioned co-pending U.S. patent application is assigned to the assignee of the present invention, and its disclosure is incorporated herein by reference. Table II also shows the castability grades of such alloys.

In order to improve the castability of the alloy designated as Rene'N5 in Table II, the alloys were evaluated by varying the amounts of Hf, Co and B in the alloy. The results of such an evaluation are shown in Table III.

First of all, the data in Table III shows that greater than 7.5% by weight (eg, about 1%) in combination with Hf in the range of about 0.3-1.6% by weight.
0% by weight) shows the effect and criticality of including up to about 12% by weight of Co. However, even with such improved castability, with a C content of about 0.05% by weight,
By changing the alloy composition of Rene'N5 alloy, more Co is added to the basic chemistry of Rene'N5 alloy in Table II above.
As a result of diluting the curable element to add, the stress rupture strength in the longitudinal direction was reduced. Add nominal 3% Co to Rene'N5 alloy composition (Co total 10.5%), Hf
Is nominally 1%, the longitudinal stress rupture life is about 65% of Rene'N5 alloy, and Co is nominally 0.5% Hf.
With an additional 4.5% (12% total Co), the longitudinal stress rupture life was 30% that of Rene'N5 alloy. This illustrates one critical balance between the elements used in the present invention. That is, the alloy composition contains C
In the range of about 0.1 to 0.15% by weight, and 11 to 1
It contains 4% by weight of Co and 0.3-2% by weight of Hf.

Regarding the balance between castability and grain boundaries and fatigue cracking, too little Co results in loss of castability and grain boundary strengthening, while Co above about 14% by weight has the effect of some alloy strengthening elements. It is recognized that may be diluted. If the element Hf is too low below about 0.3% by weight, D
Hf may increase the tendency to intergranular cracking during S-casting and use, and if too high above 2% by weight, Hf can cause problems with casting reactivity and initial melting during heat treatment. If Ta and Al are too large, they become too strong and affect castability, which may cause grain boundary cracks. In addition, topologically closest packing (TC
P) phase can be formed. Therefore, in the practice of the present invention, the Ta content is preferably maintained in the range of about 6-7% by weight, and the Al content is preferably 5.5-6.5% by weight. As is known in the art, a small amount of Cb
Can be used.

In evaluating some of the alloys in Table II, vanadium may impair surface stability, i.e., thermal and oxidation resistance, Zr may increase cracking potential, and Ti may increase It was recognized that oxidation resistance could be significantly reduced. Therefore, these elements have V of about 1
Wt%, Zr less than 0.05 wt%, Ti less than 1.5 wt%, preferably V less than 0.1, Zr less than 0.03, Ti less than 0.02
Controlled to less than. Yttrium is effective in improving oxidation resistance but can weaken grain boundaries, thus limiting the alloy of the invention to less than about 0.1%. Cr is mainly included because it contributes to oxidation and hot corrosion resistance, Mo, W and Re are mainly added for strengthening the matrix, and B is included for increasing the grain boundary strength.

Although the castability of alloys such as Rene'150 was very good and acceptable for thin-walled castings, their surface stability has been improved in some harsh environments. Was unacceptable for high temperature applications. Rene (Re
ne ') The surface stability of the alloy of the present invention at 150 ° C was compared with that of the alloy of the present invention. It was found that Rene' 150 exposed to Mach 1 air at 2075 ° F for 100 hours. The alloys of the invention in the form shown in Table II, while exposed to 50-65 mils of coated metal, had a higher temperature of 2150 ° F. for 1.5 hours exposed to 1.5 It has been shown that only mils are lost, ie less than about 5 mils per side according to the invention. In another test as an additional comparison, Rene'150 alloy lost 40 mils per specimen after 82 hours at a Mach 1 air flow of 2075 ° F.

One nickel-based alloy that appeared to have outstanding high-temperature oxidation resistance is the MA754 alloy shown in Table II. Although such alloys are not cast alloys but forged,
Included in the table above for further comparison with the oxidation resistance of the present invention. Exposing MA754 coupons to air at 2150 ° F. and a flow of Mach 1 resulted in a loss of 10 mils per coupon after 140 hours. The excellent high-temperature oxidation resistance of the present invention is:
This was confirmed by tests performed on specimens obtained by heating 3000 lbs of the alloy of the present invention. Mach at 2150 ゜ F
When exposed to air at a flow rate of 1 for 170 hours, the metal loss of the specimen was only 1.6 mils per side, and after 176 hours under the same conditions the metal loss was only 2 mils per side.

The results of another form of comparison of the outstanding high temperature surface stability of the present invention, expressed in terms of oxidation resistance, with other alloys are shown in grams in the accompanying figures. This comparison is based on Mach (Mac
h) Surface loss of the specimen versus time exposed to high speed air (HVO) moving at 1 speed. As used herein, a Mach 1 oxidation test specimen has a diameter of 0.23 ″ and a length of 0.23 ″.
3.5 ″. 24 specimens were placed on a round metal plate,
The test was performed in a furnace heated with aircraft jet fuel. These specimens were inspected approximately every 24 hours. As can be seen, the present invention results in a casting having significant surface stability.

As noted above, an important feature of the present invention is that, along with the outstanding surface stability discussed above, improved longitudinal stress fracture strength and improved balance of longitudinal and transverse stress fracture properties. That is being done. The alloy of the present invention
Among the DS columnar grain alloys, the good stress rupture strength of Rene '150 alloy and the Rene' shown in Table II above
9 shows the outstanding oxidation resistance of single crystal articles of N5 composition. Table IV below compares some of the stress fracture properties.

For the alloys of the present invention, as seen in Table V below,
At 00 ° F, nominally 32,000 psi (32 ksi), the transverse stress rupture strength ranged from about 80 to 120 hours.

Several heat treatments were studied during the evaluation of the present invention. In a first-speed heat treatment test, the alloys according to the present invention whose nominal compositions are listed in Table II were subjected to DS casting to produce 1/4 "thick x 2" wide x 4 "long columnar grain thick plates. The plate was heat treated and then machined to produce a standard stress fracture specimen, which has been previously evaluated, for example, in the case of columnar particle articles made of Rene '150 alloy, a partial However, sufficient solution (90-95%) severely reduced the transverse stress fracture properties, however, an almost complete solution heat treatment (to achieve the desired properties). It has been found that at least 90% solution of the γ-γ ′ eutectic and coarse secondary γ ′ and an initial melting of up to about 4%) are required.
Besides almost complete solution, a combination of successive additional aging steps is included. A basic first aging to improve ductility and transverse stress fracture properties;
Two additional aging treatments are performed at a continuous temperature below the basic aging temperature to further optimize the properties of the aging.

Table V below gives an overview of another series of heat treatments evaluated and the resulting stress rupture strength. The heat treatments labeled A, B, C and D indicate heat treatment steps, the first being 2300
Treated at a solution temperature in the range of 22335 ° F. for 2 hours and then heat treated in each combination. These designations are recognized and widely used in the metallurgical industry. The solution and aging steps were performed in a non-oxidizing atmosphere, ie, vacuum, argon or helium. In such an atmosphere, there was no need to cool to 1200 ° F. or lower performed during the aging step. Among the heat treatments evaluated, heat treatment D employed a unique and relatively slow cooling step from the first aging temperature to the second aging temperature, in which case the best combination of properties was obtained.

The heat treatment of the present invention involves an almost complete solution treatment step. This is in contrast to the partial solution commonly used for DS articles made from the alloys listed in Table II, such as Rene'150. Rene'150
In such cases, complete solution heat treatment impairs some of its properties. In the present invention, at least about
Solution of 90% of γ-γ 'eutectic and coarse secondary γ'
An initial melting of less than% is important. This is because the stress rupture life increases as the solution of γ ′ eutectic and coarse secondary γ ′ increases. Table VI below compares the amount of solution and the stress rupture life for the alloys of the present invention.

After solution, cooling to, for example, about 2025-2075 ° F is preferably performed at a rate of at least 100 ° F / min. Faster cooling rates have a more beneficial effect on properties such as stress rupture strength as described in co-pending US Patent Application No. 790,439, incorporated above.

The heat treatment of the present invention is further characterized by a combination of successive aging steps after solution. The first basic aging is performed in a non-oxidizing atmosphere at a temperature in the range of about 2025-2075 ° F., for example, for about 1-10 hours to improve the ductility and stress rupture strength of the article. After the first solution, for example, about 1950
Cooling to the range of 2000 ° F. is preferably at a rate of about 75 ° F./min, followed by further cooling. A second aging step, performed at a temperature lower than the temperature of the first aging, for example, at a temperature in the range of about 1950-2000 ° F. for about 4-12 hours, usually 4-8 hours, allows for the growth of γ, Is improved.
As can be seen from the data in Table V, this unique combination of continuous heating steps resulted in a structure with improved mechanical properties, and did not adversely affect the walls of the casting with thin walls. Can be heat treated.

After the above aging step, the final aging step is usually beneficially carried out, for example, in the range of about 1625 to 1675 ° F for about 2 to 10 hours, usually about 4 to 8 hours.

In the context of DS cast articles using the alloy according to the invention, the heat treatment according to the invention maximizes the longitudinal stress rupture strength, while retaining acceptable transverse strength and ductility. This is due, at least in part, to the increased solution of γ 'at relatively high temperatures. Basic or first-order effect in the range of about 2025-2075 ° F, followed by about 1950-20
Relatively slow cooling to a temperature in the range of 00 ° F. (eg, about 1 hour) and further cooling resulted in further improved longitudinal stress fracture life and improved transverse stress fracture properties. .

The combination of alloy selection, casting conditions, and heat treatment in accordance with the present invention results in an improved DS columnar particle article having less than about 0.035 inch thin walls with little cracking. In the form of a gas turbine engine turbine blade having a radial centerline, the grain boundaries and the primary dendritic orientation are straight and parallel. Further, in such articles,
Any particles emanating from the airfoil of such a blade intersect the leading or trailing edge of the airfoil at an angle of no more than 15 °, and all other grain boundaries and primary dendrites will be 15 ° from the radial centerline. It is preferably within the range, and according to the present invention, it is possible.

As a result of the above evaluation, it was found that the article and the heat treatment of the present invention can be used in a specific alloy range. The particular alloy range is particularly unique when combined with the heat treatment of the present invention. Table VII below shows a range of such useful and novel alloys.

Although the present invention has been described with respect to particular embodiments and examples, it will be apparent to those skilled in the metallurgy industry that the present invention is capable of various other forms and aspects which fall within the scope of the appended claims. You can understand.

[Brief description of the drawings]

The attached figure is a graph comparing the oxidation resistance of the alloy according to the present invention with another alloy.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kevin Swain O'Hara No. 9, Wild Meadow Road, Boxford, Mass., USA (56) References JP-A-54-58612 (JP, A) JP-A-61-223155 (JP, A) JP-A-61-223171 (JP, A) (54) [Title of the Invention] Nickel-based superalloys, articles made of nickel-based superalloys, and cast articles made of nickel-based alloys Heat treatment method, method for producing columnar particle nickel-base superalloy cast article, and method for producing turbine blade cast member for columnar particle nickel-base superalloy gas turbine engine

Claims (11)

(57) [Claims] 1% by weight of carbon, 1.5% by weight of hafnium, 12% by weight of cobalt, 6.35% by weight of tantalum, 6.8% by weight of chromium, 1.5% by weight of molybdenum,
4.9% by weight of tungsten, 6.15% by weight of aluminum, 2.8% by weight of rhenium, 0.015% by weight of boron, substantially free of zirconium, substantially free of titanium, A nickel-based superalloy consisting essentially of vanadium, which is not present in, and the balance nickel and incidental impurities. 2. An article comprising the alloy of claim 1 having an internal gap in the outer surface of the article, wherein the gap has a substantially crack-free wall cross-sectional thickness of less than 0.035 inches. An article that includes an integral casting wall that is defined and defines at least one cooling passage. 3. The cast article of claim 2, wherein said internal gap is separated from said outer surface by an article wall having a thickness of less than 0.035 inches. 4. The cast article of claim 2 in the form of a turbine blade member having a radial centerline and including an airfoil having a leading edge and a trailing edge. The orientation of the boundaries and primary dendrites is substantially straight and parallel, and any emerging crystal grains intersecting the leading and trailing edges of the airfoil form an angle with the edge of up to 15 °; A cast article wherein all other grain boundaries and primary dendrites form an angle of less than 15 ° with said radial centerline. 5. An article comprising the alloy of claim 1 wherein the article is an airfoil of a gas turbine engine. 6. A method according to claim 1, wherein 0.1 to 0.15% by weight of C and 0.3 to 2% by weight of C are used.
Hf, 11-14% by weight of Co, 5-9% by weight of Ta, 0.05
Less than 5% by weight of Zr, V and Ti each being substantially absent without exceeding 1% by weight, and 5-10% by weight.
Cr, 0.5 to 3% by weight of Mo, 4 to 7% by weight of W,
~ 7 wt% Al, 1.5-4 wt% Re, 0.005-0.03
% Of B, up to 1.5% by weight of Cb, up to 0.5% by weight of Y, and the balance of Ni and alloys. A heat treatment method comprising: (a) at least 90% so that the initial melting is 4% or less.
% Γ-γ ′ eutectic and coarse secondary γ ′ are heated to a solution temperature in a non-oxidizing atmosphere for a time sufficient to solutionize the solution to 2025-2075 ° F. in said atmosphere. Cooling to a temperature in the range: (b) 2025-20 for 1-10 hours in a non-oxidizing atmosphere
Heating to a first aging temperature in the range of 75 ° F and cooling in said atmosphere to a temperature in the range of 1950-2000 ° F; (c) 1950-2000 lower than said first aging temperature.゜ F
Heating to a second aging temperature in the range of 4 to 12 hours. 7. The temperature range of 1625 to 1675 ° F.
7. The method according to claim 6, comprising a third aging step of heating for 0 hours. 8. The method of claim 6, wherein the solution temperature ranges from 2275 ° F. to 2360 ° F. and the heating time is at least 30 minutes. 9. A temperature range of 1625 to 1675 ° F.
9. The method according to claim 8, comprising a third aging step of heating for 0 hours. 10. A method for producing a columnar particle nickel-base superalloy cast article having excellent high-temperature oxidation resistance, wherein the article comprises:
Having an internal gap including an integral casting wall having a wall thickness of less than 0.035 inches, and (a) 0.1-0.15% by weight with the casting wall integrally formed with the columnar multi-particle directional solidification casting. C and 0.3 ~
2% by weight Hf, 11-14% by weight Co, 5-9% by weight
Ta, Zr less than 0.05% by weight, V and Ti each substantially not present without exceeding 1% by weight,
10 wt% Cr, 0.5-3 wt% Mo, 4-7 wt%
W, 5-7% by weight of Al, 1.5-4% by weight of Re,
0.005 to 0.03 wt% B, up to 1.5 wt% Cb, 0.5
7. precision casting the article from an alloy consisting essentially of up to% by weight Y and the balance Ni and incidental impurities; and (b) heat treating the cast article according to the method of claim 6. And a method for producing a columnar particle nickel-based superalloy cast article. 11. A method for manufacturing a cast turbine blade member for a gas turbine engine made of a columnar particle nickel-base superalloy having excellent high-temperature oxidation resistance, wherein said member is 0.035.
(B) having at least one internal gap including an integral cast wall having a wall thickness of less than inches, comprising: (a) 0.1-0.14% by weight C and 1.2-1.7% by weight Hf;
And 11.7-12.3 wt% Co, 6.2-6.5 wt% Ta,
V up to 0.1% by weight, Zr up to 0.03% by weight, 6.6-7
Wt% Cr, 1.3-1.7 wt% Mo, 4.7-5.1 wt%
Of W, less than 0.02% by weight of Ti, and 6 to 6.3% by weight of Al
2.6 to 3% by weight of Re, 0.01 to 0.02% by weight of B,
Up to 0.1% by weight of Cb, up to 0.2% by weight of Y and the balance of Ni
Providing a superalloy consisting essentially of: and (b) precision casting the superalloy, comprising at least one integrally cast wall having a wall thickness of less than 0.035 inches. A gas turbine engine made of a columnar particle nickel-based superalloy comprising: providing an article having two internal gaps; and (c) heat treating the cast article according to the method of claim 8. A method for producing a turbine blade cast member.