KR100336803B1 - Polycrystalline Nickel Superalloy with Excellent Oxidation Resistance - Google Patents

Abstract

Equivalent nickel superalloys having excellent oxidation resistance under conditions such as those in jet engines are disclosed. Superalloys comprise 0.25-0.40 weight percent zirconium and 0.004-0.010 weight percent boron. Under burner equipment oxidation conditions, the alloy can form a zirconium stabilized alumina barrier layer that greatly reduces the oxidation rate of the alloy. Also disclosed are methods of producing superalloys and methods of casting engine parts made of such superalloys.

Description

Polycrystalline Nickel Superalloy with Excellent Oxidation Resistance

The present invention relates to a nickel superalloy and a method for producing nickel superalloy with high oxidation resistance and containing a controlled amount of boron and zirconium. The nickel superalloys are suitable for use in articles requiring good oxidation resistance and good strength at high temperatures, including engine combustors, nozzles and low speed turbine components.

Various nickel based superalloys are known in the art. Superalloys are such alloys that maintain high strength at high temperatures. Examples of nickel-based superalloys are in US Pat. It is merged into this circle as if fully reproduced. Other commercially available nickel based superalloys include B1900 + Hf and Mar-M247, whose nominal compositions are by weight

Due to their ability to maintain good mechanical strength at high temperatures, these alloys are particularly useful as materials for jet engine component manufacturing.

Boron is typically added to conventional cast superalloys in the range of 0.010 to 0.020 weight percent to enhance grain interface strength and ductility. Typically zirconium is added in the range of 0.03 to 0.13% by weight for additional particle interface properties enhancement. Yttrium may be added to the nickel superalloy to enhance oxidation resistance.

Prior art nickel superalloys that exhibit good oxidation resistance at high temperatures (over 1093.3 ° C. (about 2000 ° F.)) are too soft. Accordingly, there is a continuing need for metals that have excellent oxidation resistance at high temperatures and at the same time have good ductility. There is also a need for turbine components in jet engines with good strength and excellent oxidation resistance within the temperature range of 760.0 ° C. (1400 ° F.) to 1037.8 ° C. (1900 ° F.).

It is therefore an object of the present invention to provide a nickel based superalloy that has good oxidation resistance and high ductility at high temperatures.

It is a further object of the present invention to provide a nickel based superalloy suitable for use as part of a jet engine which maintains good strength within the temperature range of 760.0 ° C to 1037.8 ° C.

The above and these objects of the present invention are achieved by a polycrystalline nickel based superalloy having about 0.25 to 0.40% zirconium and about 0.004 to 0.010% by weight boron. The alloys of the present invention demonstrated excellent oxidation resistance below 1093.3 ° C., and preferably below 1204.4 ° C. (2200 ° F.). The nickel superalloy of the present invention demonstrated excellent strength in the temperature range of 760.0 ° C to 1037.8 ° C. The superior oxidation resistance of the superalloy of the present invention makes it suitable for use in high temperature applications such as jet engine combustors, nozzles and low speed turbine components. In a preferred embodiment, the superalloy of the present invention contains 5.0 to 8.0% by weight of aluminum to form an effective barrier layer to prevent oxidation of the superalloy. The presence of zirconium in the superalloy promotes the formation of an alumina barrier layer.

Burner equipment oxidation tests showed a deleterious effect of boron on high temperature (1093.3-1204.4 ° C) oxidation resistance. Removing boron from the nickel superalloy solves the oxidation problem, but the resulting alloy has unacceptable ductility. Low levels (0.002-0.010 wt%) of boron were added to provide acceptable oxidation behavior but ductility was at its lowest. The addition of yttrium also had a problem of softness due to the formation of surface oxide particles during casting, resulting from the reaction between yttrium and the cast ceramic. Additional experiments have found that combinations of zirconium and boron in the amounts specified herein typically can greatly enhance the oxidation resistance of cast nigel superalloys while maintaining particle boundary layer properties and avoiding inclusion formation during casting.

In addition to the critical concentrations described above for zirconium and boron, the nickel superalloys of the present invention have been found to work when the elements are added in the following weight percent:

The following alloying elements can be added to strengthen the alloy:

Elemental manganese, phosphorus, sulfur, silicon, iron, bismuth, lead, selenium, tellurium, and thallium are adjusted in small amounts to prevent degradation into superalloy properties.

In another embodiment of the present invention, the superalloy consists of the following elements given in weight percent.

Optionally, the superalloy of the present invention may contain up to the indicated weight percent maximum additive materials as follows: manganese (0.20), phosphorus (0.015), sulfur (0.015), silicon (0.10), iron (0.25), Titanium (0.10), CB (0.10), Bismuth (0.00005, 0.5 ppm), Lead (0.0002, 2 ppm), Selenium (0.0001, 1 ppm), Tellurium (0.00005, 0.5 ppm), and thallium (0.00005, 0.5 ppm).

The invention is better understood by reading the detailed description of the preferred embodiments with reference to the attached drawings.

Detailed Description of the Preferred Embodiments

In accordance with the present invention, the product is secondary processed by taking the ingot of the essential composition, which is casted from the charge in a single piece under vacuum and vacuum remelted and recast using the investment casting procedure commonly used for nickel based alloys. Conventional investment main controls for superalloys, procedures for forming ingots of superalloys, and other general information about superalloys are superalloys II, Sims et al., Eds., John Wiley & Sons, incorporated herein by reference as if fully reproduced below. , New York, 1987. Typically, alloying elements in its commercial pure form are added to the primary heat source during ingot formation. In a preferred embodiment, the alloying elements are added with the following additive materials described under the heading “Summary of the Invention: Mn, P, S, Si, Fe, Ti, Cb (Nb), Bi, Pb, Se, Te, and T1 ( "max") or less than a specific amount.

The compositions of the specific alloys described herein are shown in Table 1.

In a non-limiting example of the invention, nickel superalloys having the compositions shown in Table 1 were prepared. The invention presented superior ductility compared to nickel alloys of similar composition and whose contents of boron and zirconium are outside the critical range defined in the present invention as demonstrated in Table II below.

Tensile elongation tests are described in the Metal Handbook, 9th Edition, American Metal Society, Vol. 8, 1985 (incorporated herein by reference). The tensile elongation properties of the inventive superalloys were tested according to the guidance described in ASTM E8.

In one embodiment, the ASTM E 8 tested average tensile elongation three times at 648.9 ° C. (1200 ° F.) is greater than 3.0%. In a preferred embodiment, the average tensile elongation of the inventive superalloys tested ASTM E 8 three times at 648.9 ° C. (1200 ° F.) is greater than 5.0%.

Burner equipment oxidation tests demonstrated that the alloy of the present invention had superior oxidation resistance compared to conventional nickel superalloys B1900 + H and Mar-M-247 (see Table I and FIGS. 1 and 2). After 70 replicates of 1204.4 ° C. (2200 ° F.) burner equipment oxidation test, the alloy of the present invention lost only about 2% of its weight compared to 55% for B1900 + HF and 75% for Mar-M + 247. .

In the repeated burner equipment test used to evaluate the superalloy of the present invention, the liquid fuel burner is adjusted by fuel pressure to maintain it at the temperature of interest. For repeated testing, remove the specimen or flame and allow it to cool by applying high pressure ambient air on the specimen. Specimens are generally cylindrical rods (0.47 "diameter by 1.19 cm (3.25") long in this case). Each sample can be tested. Multiple specimens are tested on the axis of rotation. Sample weights and diameters are measured at intervals during the test to report the loss of material through oxidative fracture. The oxidation rate is proportional to the weight loss (higher weights correspond to higher oxidation rates).

A second method of testing oxidation resistance can also be used to characterize the nickel superalloy of the present invention. In this method, a superalloy coupon is suspended on a wire and placed in a furnace maintained at 1148.9 ° C. (2100 ° F.) + / −− 31.65 ° C. (-25 ° F.) and exposed to ambient air.

In this method, the alloy sample is 1.27 cm (0.5 in) x 1.91 cm (0.75 in) +/- 0.20 cm (0.12 in) x 0.10 cm (0.040 in) +/- 0.025 cm (0.010 in). Prior to initial insertion into the furnace, round the corners and edges on the sample. Samples are heated during a 24 +/- 4 hour repeat test. At the end of each repeated test, the sample is removed from the furnace, cooled in ambient air and weighed. The material crushed during heating or cooling is not weighed. As an example of the oxidation resistance of the alloy of the invention, the weight loss due to the test at 1148.9 ° C. (2100 ° F.) under repeated test conditions in ambient air for 300 hours does not exceed 10% of the initial sample weight.

When the method described above was applied to a sample of the inventive superalloy for 302 hours (11 replicates), the sample was observed to lose 4.7% of its initial weight.

Additional non-limiting examples of superalloys can also be made within the scope of the present invention, the compositions are shown in Table III below.

In a preferred embodiment, the nickel superalloy parts of the present invention are heated to 1079.5 ± 14 ° C (1975 ± 25 ° F) for 4 hours in air and air cooled to at least 4.4 ° C / min (40 ° F / min). The heat treatment improves the tensile and creep properties of the superalloy part.

In a preferred embodiment, the polycrystalline nickel superalloy of the present invention is equiaxed: In another embodiment, the polycrystalline nickel superalloy of the present invention is columnar.

The nickel superalloys of the present invention shown in Table I have been used successfully as part of float wall combustors.

While the present invention has been described in conjunction with certain preferred embodiments, those skilled in the art will readily appreciate that modifications and variations can be made without departing from the scope and spirit of the invention. Such modifications and variations are considered to be within the limits and scope of the invention and the appended claims.

1 shows the results of burner equipment oxidation at 1093.3 ° C. (2000 ° F.), comparing the weight loss versus time of the nickel superalloy of the present invention and other commercially available nickel superalloys, B1900 + Hf and MAR M-247. The compositions of these alloys are shown in Table 1.

2 illustrates the results of burner equipment oxidation at 1093.3 ° C. (2000 ° F.), comparing the weight loss versus time of the nickel superalloy of the present invention and other commercially available nickel superalloys.

Claims (11)

0.25-0.40 wt% zirconium and 0.004-0.010 wt% boron, 5.0-8.0 wt% aluminum, 5.0-12.0 wt% chromium, 0.75-2.0 wt% hafnium, and up to 10.0 wt% cobalt; The remainder is nickel, and the particles are equiaxed or columnar, and have a high oxidation resistance at a high temperature. The alloy of claim 1, wherein after exposure to severe oxidation conditions, an alumina layer is formed on the surface of the alloy that can reduce the oxidation rate of the superalloy. The alloy of claim 1 further comprising an element in the following weight percent range: The method of claim 1, wherein manganese, phosphorus, sulfur, silicon, iron bismuth, lead, selenium, tellurium, and thallium are used to prevent a substantial decrease in the ductility of the superalloy as measured by the tensile elongation of the superalloy. Each of which is present at 0.20%, 0.015%, 0.015%, 0.10%, 0.25%, 0.5 ppm, 2 ppm, 1 ppm, 0.5 ppm, 0.5 ppm. The alloy of claim 1, wherein the alloy contains up to 0.007% by weight of boron. The alloy of claim 1 comprising the elements in the following weight percent. The alloy of claim 6, further comprising the following additive materials containing up to the indicated amounts: manganese (0.20), phosphorus (0.015), sulfur (0.015), silicon (0.10), iron (0.25), titanium (0.10) ), CB (0.10), bismuth (0.00005, 0.5 ppm), lead (0.0002, 2 ppm), selenium (0.0001, 1 ppm), tellurium (0.00005, 0.5 ppm), and thallium (0.00005, 0.5 ppm). The method of claim 1 wherein the average tensile elongation of the three ASTM 8 tests at 648.9 ° C. is greater than 3.0%, and 1.27 × 1.91 cm (at 1148.9 ° C. under repeated conditions of 24 +/− 4 hours in ambient air for 300 hours). 0.50 × 0.75 in) +/- 0.30 cm (0.12 in) × 0.10 (0.040 in) +/- 0.025 cm (0.010 in) Weight loss from testing of superalloy samples greater than 10% of initial sample weight Does not alloy. The method of claim 8 wherein the average tensile elongation of the three ASTM 8 tests at 648.9 ° C. is greater than 5.0% and 1.27 × 1.91 cm (114114 ° C.) at 300 ° C. under repeated conditions of 24 +/- 4 hours in ambient air for 10 hours. Weight loss from testing of a superalloy sample having dimensions of 0.50 × 0.75 in) +/- 0.30 cm (0.12 in) × 0.10 cm (0.040 in) +/- 0.025 cm (0.010 in) yields 5.0% of the initial sample weight. Alloy not exceeding. A jet engine component composed of the nickel superalloy of claim 1. The component of claim 10 selected from the group consisting of a combustor, a nozzle, and a low speed turbine component.