NL8602578A - NICKEL ALUMINUM ALLOY. - Google Patents

Description

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Nickel aluminum alloy

Ordered metal alloys based on trinickle aluminum (N13AI) are attractive because of their properties for architectural applications at elevated temperatures. They have the unusual property that the yield strength increases at a higher temperature, whereas the yield strength decreases with conventional alloys. Trinickaluminide is the major constituent of nickel-based superalloys and is responsible for its good strength and high temperature creep resistance. The main limitation in using these nickel aluminides as a construction material lies in their tendency to brittleness and low ductility.

Recently, it has been proposed to improve alloys of this type by adding iron to increase yield strength, boron to increase ductility, and titanium, manganese, and niobium to improve cold formability (U.S. Patent No. 519,941, August 3, 1983). . It has further been proposed to add to the base alloy N13AI iron and boron for the aforementioned purposes as well as hafnium and zirconium to increase the strength at higher temperature (US patent application 564,108 of December 21, 1983).

Although these improved alloys have many good properties, they also still have shortcomings. Thus, ductility and ductility deteriorate with increasing temperature, so that shaping into the desired shape must be done by rolling or forging at temperatures below 700 ° C. These alloys would be more valuable if the hot formability could take place at temperatures up to 1200 ° C, since the industrial capacity is calculated on them 8602578: * 4 -2-. A higher temperature deformation also means a reduction in manufacturing costs and less need for high power deformation equipment.

It is therefore an object of the invention to provide a nickel-aluminum alloy which is deformable by hot rolling or forging at temperatures up to 1200 ° C.

Furthermore, it aims to provide a nickel-aluminum alloy that has a good yield strength, good ductility and good oxidation resistance at high temperature. It also aims to provide a nickel-aluminum alloy with the above properties, which can be obtained with relatively low costs and conventional methods.

The invention provides an alloy based on N13AI, which contains additions of other elements to achieve the desired purpose. The additional elements are iron and boron, one or more elements from group IVb of the periodic table to increase high temperature strength and one or more rare earths to improve hot formability. Additions of molybdenum and carbon can also be used to improve the oxidation resistance, respectively. the tear resistance. The iron is used in an amount of 14-17% by weight and the boron in an amount sufficient to increase ductility.

The Group IVb elements are present together in an amount of less than 1% by weight while the rare earths are added in trace amounts sufficient to allow the hot formability to take place at temperatures above 700 ° C. Molybdenum is added in an amount sufficient to reduce the susceptibility to oxidation. Carbon is used in sufficient amount to suppress cracking resulting from molybdenum addition. The rest of the alloy consists of nickel and aluminum with the base composition N13AI.

In a preferred embodiment, the amount of boron to increase the ductility is 0.01 and 0.03 wt% to increase ductility. The Group IVb element is preferably hafnium, although zirconium functions in much the same way. As a rare earth, cerium is preferred, the amount required to bring the hot deformability at about 1200 ° C to be between 0.002 and 0.007% by weight and preferably about 0.005% by weight. Yttrium, thorium and lanthanum are believed to act in the same way as cerium.

The amount of molybdenum required to improve the oxidation resistance is up to 4% by weight, while the amount of carbon required to suppress cracking during the hot distortion is up to 0.1% by weight.

The 4 nickel aluminum alloys of the invention have the advantage of good ductility, hot formability, high tensile strength up to about 600 ° C and good oxidation resistance. In addition, these alloys have low density and low manufacturing costs compared to the commercial nickel-based superalloys.

Alloy castings according to the invention can be obtained by fusing together pure metal flakes and nickel master alloys with 4 wt.% B and 4 wt.% Ce in the correct proportion using an arc. The master alloys are used for precise control of the concentrations of B and Ce in the final alloy. The castings can then be deformed by hot rolling at 1200 ° C, with three passes at 12% reduction per Dorogang. The ductility and hot formability of these nickel iron aluminide nickel alloys are sensitive to iron concentration, iron to nickel ratio, and rare earth additives such as cerium.

Table A lists a series of nickel-aluminum alloys made in this manner. The basis is the alloy IC-47, which contains 10.4 wt.% Aluminum, 16.1 wt.% Iron, 0.05 wt.% Boron and 860257-8-4- the balance of nickel. The other alloys additionally contain 0.25 to 0.5 atomic% Hf or Zr and optionally still Ce and C. The table shows the composition in% by weight.

5:

TABLE A

IC-47 Ni-10.4 Al-16.1 Fe-0.05 B

10 IC-105 Ni-10.0 Al-15.9 Fe-1.7 Hf-0.02 B

IC-124 N1-10., 2 Al-16.0 Fe-0.9 Hf-0.02 B

IC-126 N1-10 ^ 2 Al-16.0 Fe-0.9 Hf-0.02 B-0.005 Ce IC-159 Ni-10.2 Al-16.6 Fe-0.9 Hf-0.015 B- 0.005 Ce 15 IC-165 Ni-10.2 Al-16.6 Fe-0.4 Zr-0.015 B-0.005

Ce-0.03 C

IC-166 Ni-10.2 Al-16.3 Fe-0.9 Ze-0.015 B-0.005 Ce-0.03 C.

20

After hot rolling at 1200 ° C with three passes (12% per pass), the condition of these alloys was as follows: 25 IC-47 many surface cracks IC-105 many surface cracks and edges IC-124 some surface cracks but not in the edges IC-126 two cracks in the surface. No 30 cracks in the edges IC-159 no cracks

IC-165 no cracks after hot rolling at 1100 ° C

only small cracks in the surface after hot rolling at 1200 ° C

35 IC-166 some surface cracks

Hafnium or zirconium is added to improve the strength of the alloy at high temperature 8602578-5. However, the amount of hafnium and zirconium should be limited to less than 1 wt% (or 0r5 atom%), otherwise the hot formability of the alloy will deteriorate. Surprisingly, the deformation of the alloy by a small amount of cerium (0.002 to 0.007 wt%) is significantly improved. The alloy IC-159 with 0.005 wt.% Cerium and 16.6 wt.% Iron was best hot-deformable, since no cracks occurred after hot-rolling at 1200 ° C.

Table B shows yet another series of alloys based on the alloy IC-47 by adding hafnium, cerium, molybdenum and / or carbon.

15 TABLE B

IC-47 Ni-10.4 Al-16.1 Fe-0.05 B

IC-109 Ni-9.8 Al-13.8 Fe-1.7 Hf-3.7 Mo-0.025 B

IC-117 Ni-10.0 Al-13.9 Fe-0.9 Hf-3.7

Mo-0.025 B

IC-123 Ni-10.0 Al-15.8 Fe-0.9 Hf-3.7

Mo-0.02 B

IC-152 Ni-10.0 Al-15.8 Fe-0.9 Hf-3.7

25 Mo-0.015 B-0.005 Ce-0.06 C

IC-157 Ni-10.0 Al-15.8 Fe-0.9 Hf-3.7 Mo-0.015 B-0.005 Ce IC-158 Ni-10.1 Al-16.4 Fe-0.9 Hf- 2.7 Mo-0.015 B-0.005 Ce 30 ---

After hot rolling at 1200 ° C with three passes (12% reduction per pass), the condition of these alloys was as follows: IC-47 many surface cracks IC-109 many surface cracks and edges IC-117 many surface cracks but not in edges 8602578 * -βίοι 23 some cracks in surface but not in edges 10152 no cracks 10157 three cracks in surface, none in the 5 edges.

10158 one crack in surface, no cracks in edges.

The molybdenum was added to improve the oxidation resistance. At a molybdenum concentration of 3.7% by weight, the hot formability of the alloy was highly dependent on minor composition changes. At an iron concentration of less than 14.5% by weight, a lot of cracking occurred during hot-forming. However, a combination of 0.005 wt% cerium and 0.06 wt% carbon at an iron content of 15.8 wt% was sufficient to completely suppress cracking, so that the composition of this alloy (10152) is preferred. The iron content in the alloys is limited to less than 17.5%, otherwise the alloys may lose some of their strength at high temperature.

These are examples of two alloys of the nickel iron aluminide type, which can be easily deformed by hot rolling or forging at 1200 ° C. In contrast, the commercial nickel aluminide alloys cannot be deformed by hot rolling or forging at temperatures above 700 ° C.

In metallographic examination of the two alloys, after quenching with water from 1200 ° C, a significant amount (20-30 volume%) of a second phase was found, which is probably of the type B2 (an ordered BCC phase similar to FeAl) .

The volume fraction of the B2 phase decreases at a lower annealing temperature, so that after 16 hours of annealing at 1800 ° C

less than 2% of the B2 phase is present. A comparison of the microstructures of the alloys furthermore shows that addition of molybdenum 8602578 ....... m> 2 -7- reduces the formation of the disordered phase in the alloys.

Table C contains the yield strength, tensile strength and elongation at break values for the 5 alloys from Tables A and B, determined at various temperatures up to 1200 ° C. The test samples were plate-shaped with a measuring section of 12.7 x 0.8 mm and the crosshead speed was 25 mm / min in vacuum.

Alloys IC-152 and IC-159 with Ί0 additionally used were an alloy IC-136 of the composition: 11.9 wt% aluminum, 1.7 wt% hafnium, 0.015 wt% boron and the balance nickel.

TABLE C

Alloy yield strength TreJ [Ulfikt ReJc fracture

Room temperature IC-136 52.0 195.3 38.1 IC-159 77.4 195.0 40.3 IC-152 97.5 222.0 29.0

600 ° C

IC-136 92.6 158.8 50.6 IC-159 94.9 140.0 47.9 IC-152 112.0 150.0 26.8

850 ° C

IC-136 86.2 111.9 18.6 IC-159 68.0 72.2 29.8 IC-152 78.1 84.2 26.4

1,000 ° C

IC-136 46.2 52.2 16.2 IC-159 26.6 28.6 40.6 IC-152 27.1 33.9 48.1

1,200 ° C

IC-136 21.2 22.3 25.0 IC-159 2.5 2.8 152.5 IC-152 2.2 2.2 199.5 8602578 * -8 - Table C shows that the yield strength of the both alloys of the invention are higher than those of IC-136 at room temperature and at 600 ° C. At higher temperatures, however, the yield point 5 drops so that both alloys above 850 ° c become less strong than IC-136. In contrast, the two alloys of the invention are much more ductile than IC-136 at 1000 ° C and at 1200 ° C, while at 1200 oc they exhibit superplastic behavior with elongation at break of greater than 150%. The high ductility of the two alloys corresponds to their excellent hot formability at 1200 ° C.

Furthermore, the creep properties of the alloy IC-159 according to the invention have been determined at 15 760 ° C. The time to break was resp. 300 at 138 MPa and 12 at 276 MPa. This is considerably less than with alloys of the nickel-aluminide (without iron) type which respectively. values of more than 2000 and from 300 to more than 800 (depending on the Hf content in the 20 alloys). For comparison, the known alloys Hastelloy-X and Waspalloy were used. Hastelloy-X is a commercial nickel alloy with 21.8 wt% Cr, 2.5 wt% Co, 9.0 wt% Mo, 0.6 wt% W, 18.5 wt% Pe and the remainder is nickel and has a creep value of 200. Waspalloy is a commercial nickel alloy with limited ductility, consisting of 19.5 wt% Cr, 13.5 wt% Co, 4.3 wt% Mo, 3 .0 wt% Ti, 1.4 wt% Al, 2.0 wt% Pe, 0.0006 wt% B, 0.07 wt% Zr, 0.07 30 wt% C and for the rest nickel. This Waspalloy had a creep value of 1000.

To determine the oxidation stability, alloys samples were recrystallized in an oven at 1050 ° C for 1 hour and then exposed to air. The samples were taken periodically (every 1 to 3 days) from the oven for visual inspection and weight measurement. They showed a coherent weight gain during the 8602578-9 cyclic oxidation at 800 OC and 1000 ° C. The oxidation rate of the molybdenum-containing nickel-iron aluminum aluminides was comparable at 800 ° C and 1000 ° C, while the oxidation rate of the 5 molybdenum-free nickel iron aluminides was lower at 1000 ° C than at 800 ° C. This slower rate indicates that the aluminum atoms at 1000 ° C quickly diffuse from the interior to the surface, so that an aluminum oxide film is formed on the surface which protects the base metal from further oxidation. The alloys exhibited an oxidation resistance comparable to that of nickel aluminide alloys at 1000 ° C.

This shows that the alloys according to the invention (nickel iron aluminides) show a good combination of ductility, hot formability, strength and oxidation resistance.

In addition, they have the advantage of low density and low cost compared to the known commercial superalloys. The density of the alloys of the invention is 10-15% less than that of a nickel-containing superalloy.

An important difference of the alloys according to the invention with earlier alloys is that the iron concentration has increased in the presence of hafnium and boron. The addition of small amounts of other elements such as cerium, molybdenum and carbon results in an alloy with greatly improved high temperature formability.

8602578

Claims (9)

1. Nickel-aluminum alloy based on N13AI, characterized by a sufficient concentration of elements of the group IVB to increase the strength at high temperature, a sufficient concentration of iron and rare earths to increase the hot formability, and a sufficient concentration boron to increase ductility. . 2. Alloy according to claim 1, characterized in that the iron concentration is between 14.5 and 17.5% by weight. Alloy according to claim 1 or 2, with a sufficient amount of molybdenum to reduce the oxidation rate and a sufficient amount of carbon to reduce cracking by molybdenum addition. Alloy according to claims 1-3, characterized in that the elements of the group IVB consist of hafnium, zirconium or mixtures thereof and are present in an amount of less than 1% by weight. Alloy according to claims 1-4, characterized in that the rare earths consist of cerium in an amount of not more than 0.01% by weight. 6. Alloy according to claims 1-5, characterized in that boron is present in an amount of 0.01 to 0.05% by weight. Alloy according to claims 1-6, characterized in that it has the following composition: 10.2 wt% aluminum, 16.6 wt% iron, 0.9 wt% hafnium, 0.015 wt% boron 0.005 wt.% Cerium and the remainder nickel. Alloy according to claim 3, characterized in that the molybdenum is present in an amount of not more than 4% by weight and the carbon 35 in an amount of not more than 0.01% by weight. __ 8602578 -11- «* Alloy according to claims 1-8, characterized in that it has the following composition: 10.0 wt% aluminum, 15.8 wt% iron, 0.9 wt% hafnium, 3.7 wt% molybdenum 0.015 wt% boron, 0.005 wt% cerium, 0.06 wt% carbon and the balance nickel. 8602578