JP7252621B2 - High strength Ir alloy - Google Patents

Description

TECHNICAL FIELD The present invention relates to an Ir alloy having excellent high-temperature strength.

Ir, which is a platinum group element, has a high melting point and is less consumed by oxidation. Therefore, it is used as an excellent high temperature material in a wide range of fields such as crucibles for growing single crystals, heat-resistant equipment, and gas turbines. On the other hand, the oxidation resistance of Ir at high temperatures is superior to other high-melting-point metals such as W and Mo, but it is not sufficient. known to do. Therefore, alloy development so far has focused mainly on improving its oxidation resistance.

Patent Document 1 describes a heat-resistant material based on iridium, with rhodium added as a second element in the range of 0.1 to 30 wt%, and further as a third element platinum, ruthenium, rhenium, chromium, and vanadium. , Molybdenum is added within a solid solubility range of 0.1 to 20 wt%, and the total amount of the third element and the second element added is within a solid solubility range of 0.2 to 50 wt%. An iridium-based alloy is disclosed that is characterized by: It is described that it has excellent oxidation resistance at 1050° C. in the air.

Patent No. 3135224

Although the IrRh alloy has a high melting point and good oxidation resistance, it does not have sufficient mechanical strength. For example, when used in crucibles, gas turbines, etc., it must be able to withstand the expansion of the contents of the crucible and must have mechanical strength to withstand the centrifugal force of a turbine rotating at high speed. Therefore, Ir alloys with high high-temperature strength are always required in these fields.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an Ir alloy having excellent high-temperature strength.

As a result of diligent research to improve the high-temperature strength of IrRh alloys, the inventors have developed an Ir alloy with excellent high-temperature strength by simultaneously adding Ru and a small amount of Nb. In addition, 4 mass % or less of Ni may be contained instead of part of Ir.

The present invention is an Ir alloy containing 5 to 35 mass% of Rh, 0.1 to 25 mass% of Ru, 0.1 to 3 mass% of Nb, 0 to 4 mass% of Ni, and the balance being Ir. is.

According to the present invention, an Ir alloy having excellent high-temperature strength can be provided.

is a structural photograph of Example 7. is a photograph of the structure of Comparative Example 1.

The present invention is an Ir alloy containing 5 to 35 mass% of Rh, 0.1 to 25 mass% of Ru, 0.1 to 3 mass% of Nb, 0 to 4 mass% of Ni, and the balance being Ir. is. Here, "containing 0 to 4 mass% of Ni" means that Ni is not contained or that Ni is contained in an amount of 4 mass% or less.

The Ir alloy of the present invention contains Ir in an amount of 40 mass% or more, preferably 45 mass% or more, more preferably 50 mass% or more, and still more preferably 55 mass% or more of all components constituting the alloy.

The total content of Rh and Ru is preferably 55 mass% or less. The total content of Rh and Ru is more preferably 50 mass% or less. The total content of Rh and Ru is more preferably 45 mass% or less.

If the Rh content is less than 5 mass%, the oxidation wear resistance of the Ir alloy is insufficient. On the other hand, when the content of Rh exceeds 35 mass %, the melting point and recrystallization temperature of the Ir alloy are lowered although the resistance to oxidation consumption of the Ir alloy is good.

The addition of Ru to the IrRh alloy improved the oxidation resistance, but the high temperature strength was insufficient.

By adding Nb in addition to Ru in the above content, synergistic solid-solution hardening of Ru and Nb is exhibited while oxidation wear resistance is secured, and an alloy with significantly improved high-temperature strength can be obtained. Addition of Nb raises the recrystallization temperature of the alloy, and exhibits the effect of suppressing crystal growth during use at high temperatures. As a result, the processed structure can be maintained up to high temperatures, and the alloy has high high-temperature strength suitable as a heat-resistant material.

If the Ru content is less than 0.1 mass %, the oxidation wear resistance is lowered. On the other hand, when the Ru content exceeds 25 mass %, the plastic deformability is lowered, which not only makes processing difficult, but also lowers oxidation wear resistance. The content of Ru is preferably 0.5 mass % or more. The content of Ru is more preferably 1 mass % or more.

If the Nb content is less than 0.1 mass%, synergistic solid-solution hardening with Ru is small, resulting in insufficient high-temperature strength. On the other hand, if the Nb content exceeds 3 mass %, the plastic deformability is reduced, making working difficult, and the oxidation of Nb is significant, resulting in reduced oxidation wear resistance. The content of Nb is preferably 2.5 mass% or less. On the other hand, the content of Nb is preferably 0.2 mass% or more. Furthermore, the content of Nb is more preferably 0.3 mass % or more.

As an element for improving the strength of the alloy, Ni may be added in a range of 4 mass% or less. When the Ni content exceeds 4 mass %, the oxidation consumption of Ni becomes significant, and the resistance to oxidation consumption deteriorates. The Ni content is preferably 3.5 mass% or less. On the other hand, the Ni content is preferably 0.1 mass% or more, more preferably 0.3 mass% or more. Further, the content of Ni is more preferably 0.5 mass % or more.

A single-phase solid solution alloy can be obtained by using the alloy within the above composition range. Therefore, the alloy according to the invention is ductile and can be formed into various shapes using known processing methods such as rolling and wire drawing. Processing methods such as machining and welding are also applicable.

An embodiment of the present invention will be described. The compositions of the alloys of Examples and Comparative Examples are shown in Table 1, and the test results are shown in Table 2.
First, each raw material powder (Ir powder, Rh powder, Ru powder, Nb powder, and Ni powder) was mixed at a predetermined ratio to prepare a mixed powder. Next, the obtained mixed powder was molded using a uniaxial pressure molding machine to obtain a green compact. The compact thus obtained was melted by an arc melting method to prepare an ingot.

Then, the produced ingot was hot forged into a plate material having a thickness of 4 mm. This plate material was hot-rolled into a plate material having a thickness of 1 mm. To prepare a test piece for high-temperature strength measurement, it was further hot-rolled to a thickness of 0.6 mm.

The workability was evaluated in the above working steps from ingot to rolling. In Table 2, ◯ indicates that a plate material with a thickness of 0.6 mm was obtained, and x indicates that a plate material with a thickness of 0.6 mm was not obtained due to cracking occurring in the middle.

Evaluation of oxidation wear resistance was carried out by a high-temperature oxidation test using each cylindrical test piece cut from a plate material having a thickness of 1 mm. In the high-temperature oxidation test, a test piece was placed in an electric furnace and held in the atmosphere at 1200°C for 20 hours. Oxidative wear resistance was defined as mass change in the high temperature oxidation test. The mass change ΔM (mg/mm ² ) is calculated by taking the mass of the test piece before the test as M0 (mg), the mass after the test as M1 (mg), the surface area of the test piece before the test as S (mm ² ), and ΔM =(M1-M0)/S. Also, the surface area S (mm ² ) of the test piece was calculated from the dimensions of the test piece.

In the evaluation of resistance to oxidation at 1200° C., alloys with a mass change ΔM up to −0.05 were judged to have particularly good resistance to oxidation (the amount of oxidation was small). Alloys with a mass change ΔM of less than −0.05 and −0.20 or more are considered to have good oxidation wear resistance, and are indicated by symbol B in Table 2. Alloys with a mass change ΔM of less than −0.20 are considered to have poor resistance to oxidation wear (the amount of oxidation wear is large), and are indicated by symbol C in Table 2.

As for the recrystallization temperature, the test piece was treated in an electric furnace in an Ar atmosphere at 950°C, 1000°C, 1050°C, 1100°C, 1150°C, and 1200°C for 30 minutes, the cross section of the test piece was polished, and the polished surface was It was determined by etching and observing the structure with a metallurgical microscope (200x magnification). One specimen was heat treated at one temperature.

As a result of structural observation, the heat treatment temperature of the test piece in which recrystallized grains were observed was defined as the recrystallization temperature of the alloy. For example, when recrystallized grains were not observed at 1050°C and recrystallized grains were observed at 1100°C, the recrystallization temperature was set to 1100°C. The evaluation of the recrystallization temperature is indicated by symbol A in Table 2 for alloys with a temperature of 1100°C or higher, symbol B in Table 2 for alloys at 1000°C or higher and lower than 1100°C, and symbol C in Table 2 for alloys with a temperature lower than 1000°C.

FIG. 1 is a photograph of the structure of the alloy of Example 7 heat-treated at 1100° C. for 30 minutes, and FIG. 2 is a photograph of the structure of the alloy of Comparative Example 1 heat-treated under the same conditions as in FIG. As shown in the figure, recrystallization occurs in Comparative Example 1, but the alloy of Example 7 maintains the worked structure.

In order to clarify the effects of the additive elements, the high-temperature strength was evaluated according to the following procedure, using Comparative Example 1 as a reference as a representative IrRhRu alloy to which Nb was not added. A test piece with a parallel part of 0.5 × 0.6 and a length of 3 mm was cut out from a plate material with a thickness of 0.6 mm by wire electric discharge machining. calculated. The obtained tensile strength of Comparative Example 1 is T0, and the tensile strength of the example is Tx (x is the number of the example)
, and the high-temperature strength ratio T (%) was obtained from the equation T=Tx/T0×100 and shown in Table 2. Here, excellent high-temperature strength specifically means that the high-temperature strength ratio T (%) calculated according to the above formula is 130 or more, preferably 140 or more.

From the results shown in Table 2, it can be seen that the high-temperature strength of the example in which Ru and Nb are added at the same time is significantly higher than that of the IrRhRu alloy of the comparative example. Specifically, when comparing Comparative Example 1 with the same Rh and Ru concentrations and Example 6 and Example 7, the high temperature strength ratio T (%) of Example 6 and Example 7 was 195 and 221, respectively. , and the high-temperature strength ratio is greatly improved to 1.95 times and 2.21 times that of Comparative Example 1. In addition, when comparing Example 1 and Example 2, and Example 6 and Example 10, which have the same Rh, Ru, and Nb concentrations, the high temperature strength ratio T (%) is 197 in Example 1, and 197 in Example 2. is 239, Example 6 is 195, while Example 10 is 229, and the high-temperature strength is further improved by adding Ni as compared to the case where only Nb is added. While the high-temperature strength is improved, the alloys of Examples show properties comparable to those of Comparative Example 1 in terms of recrystallization temperature and oxidation resistance. Thus, it was confirmed that the alloys of the examples have favorable properties as heat-resistant materials.

In addition, the alloy of the example was able to be plastically worked to a plate material with a thickness of 0.6 mm, indicating that it has the same workability as that of the comparative example 1.

Claims (1)

5 to 35 mass% of Rh,
0.1 to 25 mass% of Ru,
0.1 to 3 mass% of Nb,
Contains 0 to 4 mass% of Ni,
balance is Ir,
An Ir alloy characterized by:

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