Heat-resistant IrPt alloy

Abstract

To provide a heat-resistant Ir alloy, which is further improved in Vickers hardness while maintaining satisfactory processability.SOLUTION: Provided is a heat-resistant Ir alloy, including: 5 mass% to 30 mass% of Pt; 0.5 mass% to 5 mass% of Ta; and 0.003 mass% to 0.15 mass% of at least one selected from the group consisting of Sc, Hf and W, with the balance being Ir.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a heat-resistant Ir alloy used for high-temperature crucibles, heat-resistant appliances, gas turbines, spark plugs, high-temperature sensors, jet engines, and the like.

Background Art

[0002] Various alloys have been developed as heat-resistant materials used for high-temperature crucibles, heat-resistant appliances, gas turbines, spark plugs, high-temperature sensors, jet engines, and the like. Main heat-resistant materials include heat-resistant steel, nickel-based superalloys, platinum alloys, tungsten, and the like. Heat-resistant steel, nickel-based superalloys, platinum alloys, etc. have a solidus point of less than 2000°C and cannot be used at higher temperatures. On the other hand, high-melting-point metals such as tungsten and molybdenum are severely oxidized and consumed in a high-temperature atmosphere. Therefore, Ir alloys have been developed as heat-resistant materials that have a high melting point and high oxidation and corrosion resistance.

[0003] Patent Document 1 describes that by incorporating a predetermined amount of platinum and a predetermined amount of an alkaline earth metal element into an iridium alloy, the Ir alloy can be stably used for a long time in a high-temperature environment.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] It is desired that the Ir alloy used as a heat-resistant material can be stably used for a long time. For example, when used in a gas turbine, mechanical strength to withstand the centrifugal force of the turbine is required. Therefore, there is a problem that it is desired to further improve the hardness.

[0006] Therefore, an object of the present invention is to provide a heat-resistant Ir alloy having further improved Vickers hardness while maintaining good workability.

Means for Solving the Problems

[0007] The inventors have found that in an IrPt alloy, high hardness can be achieved by adding Ta and trace amounts of Sc, Hf, and W, and thus the present invention has been completed.

[0008] The present invention is a heat-resistant Ir alloy characterized by containing 5 to 30 mass% of Pt, 0.5 to 5 mass% of Ta, and at least one of Sc, Hf, and W in an amount of 0.003 to 0.15 mass%, with the balance being Ir.

Effects of the Invention

[0009] According to the present invention, it is possible to provide a heat-resistant Ir alloy that further improves Vickers hardness while maintaining good workability.

Modes for Carrying Out the Invention

[0010] The present invention is a heat-resistant Ir alloy characterized by containing 5 to 30 mass% of Pt, 0.5 to 5 mass% of Ta, and at least one of Sc, Hf, and W in an amount of 0.003 to 0.15 mass%. When containing two or more of Sc, Hf, and W, the total content is 0.003 to 0.15 mass%. Note that an Ir alloy is an alloy mainly composed of Ir. The Ir alloy according to the present invention may contain inevitable impurities in addition to the aforementioned elements.

[0011] In an Ir alloy containing 5 to 30 mass% of Pt, oxidation and volatilization of Ir from grain boundaries are suppressed in a high-temperature atmosphere or an oxidizing atmosphere, and oxidation resistance and wear resistance are significantly improved. When the Pt content is less than 5 mass%, the oxidation resistance and wear resistance of the Ir alloy are insufficient. On the other hand, when the Pt content exceeds 30 mass%, although the oxidation resistance and wear resistance of the Ir alloy are good, the recrystallization temperature decreases, so the upper limit of the temperature range in which the strength can be maintained decreases.

[0012] An IrPt alloy containing 0.5 to 5 mass% of Ta has its hardness improved by solid solution hardening due to Ta. The content of Ta is more preferably 0.7 mass% or more. When the content of Ta is less than 0.5 mass%, the solid solution hardening is insufficient. On the other hand, when the amount of Ta exceeds 5 mass%, the plastic deformation ability decreases and processing becomes difficult.

[0013] An IrPtTa alloy containing at least one of Sc, Hf, and W in an amount of 0.003 to 0.15 mass% has its hardness improved by solid solution hardening and / or grain refinement. Sc and Hf, which have a lower melting point than the IrPtTa alloy, preferentially dissolve in the grain boundaries, which are the last solidified part, and suitably strengthen the brittle grain boundaries of the Ir alloy. W, which has a higher melting point than the IrPtTa alloy, serves as a nucleation site during solidification to refine the solidification structure of the IrPtTa alloy.

[0014] The content of at least one (in the case of two or more, the total) of Sc, Hf, and W is preferably 0.005 mass% or more. The content of at least one (in the case of two or more, the total) of Sc, Hf, and W is more preferably 0.01 mass% or more. When the content of at least one (in the case of two or more, the total) of Sc, Hf, and W exceeds 0.15 mass%, the hardness is improved but the workability decreases.

[0015] The heat-resistant Ir alloy of the present invention has a Vickers hardness of 600 HV or more.

[0016] Since the above alloys are single-phase solid solutions each having no second phase, they have good ductility and can be plastically processed into various shapes and dimensions by known warm working or hot working, and machining and welding are also easy.

Examples

[0017] Examples of the present invention will be described. First, each raw material powder (Ir powder, Pt powder, Ta powder, Sc powder, Hf powder, W powder) was mixed at a predetermined ratio to prepare a mixed powder. Next, the obtained mixed powder was formed using a uniaxial pressing machine to obtain a green compact. The obtained green compact was melted by an arc melting method to produce an ingot.

[0018] Subsequently, the as-prepared ingot was hot-forged into a square bar with a width of 15 mm. This square bar was subjected to hot grooving rolling and die wire drawing to obtain a wire with a diameter of φ0.5 mm.

[0019] The hardness was measured under the conditions of a load of 200 gf and a holding time of 10 seconds using a micro-Vickers hardness tester on the longitudinal section of the wire cut to a predetermined length.

[0020] The workability was evaluated in the above processing steps from the ingot to the wire drawing. Those from which a wire with a diameter of φ0.5 mm was obtained were marked as ○, and those from which a wire with a diameter of φ0.5 mm could not be obtained were marked as ×.

[0021] Table 1 shows the compositions of the alloys of the examples and comparative examples, as well as the test results.

[0022]

Table 1

[0023] Examples 1 to 15 are those in which at least one of Ta, Sc, Hf, and W is added to IrPt. The hardness has increased compared to Comparative Examples 1 and 2 in which neither Sc, Hf, nor W is added. On the other hand, for Comparative Examples 3 and 4 in which 0.20 mass% of Sc or Hf is added, the workability has significantly deteriorated.

[0024] It was confirmed that the alloys of the examples have a hardness of 600 HV or more and a workability of ○, achieving both high hardness and good workability, and having excellent properties as heat-resistant Ir alloys.

Claims

【Claim 1】 A heat-resistant Ir alloy characterized by containing 5 to 30 mass% of Pt, 0.5 to 5 mass% of Ta, and at least one of Sc, Hf, and W in an amount of 0.003 to 0.15 mass%, with the balance being Ir.

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