JP4973301B2 - Ni3 (Si, Ti) intermetallic compound excellent in oxidation resistance and corrosion resistance, the intermetallic compound rolled foil, and a method for producing the intermetallic compound rolled foil - Google Patents

Description

The present invention is excellent in oxidation resistance and corrosion resistance, and has an intermetallic compound having a basic composition of Ni ₃ (Si, Ti) (hereinafter referred to as “Ni ₃ (Si, Ti) intermetallic compound”), the metal. The present invention relates to an intermetallic compound rolled foil and a method for producing the intermetallic compound rolled foil.

Ni ₃ (Si, Ti) -based intermetallic compounds are expected to be used as high-temperature structural materials because they exhibit inverse temperature dependence of strength. Further, by processing a Ni ₃ (Si, Ti) intermetallic compound into a foil, application to, for example, a catalyst carrier of an automobile exhaust gas purification device or a structural material for an aircraft is expected.
In Patent Document 1, a study was made on the mechanical properties of a foil made from a Ni ₃ (Si, Ti) intermetallic compound, and this foil has a mechanical strength that exceeds that of conventional nickel alloys and titanium alloys. It was confirmed that
JP 2007-84903 A

However, Patent Document 1 does not sufficiently study the oxidation resistance and corrosion resistance of Ni ₃ (Si, Ti) -based intermetallic compound foils.
It is desirable for the inventors to study the oxidation resistance and corrosion resistance of the Ni ₃ (Si, Ti) intermetallic compound foil described in Patent Document 1 and further improve the oxidation resistance and corrosion resistance of the foil. I thought.

The present invention has been made in view of such circumstances, it is to provide a Ni ₃ (Si, Ti) based intermetallic compound having an excellent oxidation resistance and corrosion resistance.

Means for Solving the Problems and Effects of the Invention

According to the present invention, Si: 7.5-12.5 atomic%, Ti: 3.5-8.5 atomic%, Nb: 0.5-3 atomic%, Cr: 0.5-3 atomic%, The balance is provided with a Ni ₃ (Si, Ti) -based intermetallic compound containing B: 25 to 500 ppm by weight with respect to the total weight of the composition comprising Ni.

As a result of intensive studies, the present inventors have found that 0.5 to 3 atomic% of Nb and 0.Ob in Ni ₃ (Si, Ti) -based intermetallic compounds (hereinafter also referred to as “intermetallic compounds”). It has been found that an intermetallic compound having excellent oxidation resistance, corrosion resistance and mechanical properties can be obtained by containing 5 to 3 atomic% of Cr, and the present invention has been completed. The intermetallic compound of the present invention can be suitably used for applications requiring excellent oxidation resistance, corrosion resistance and mechanical properties, such as a catalyst carrier of an automobile exhaust gas purification apparatus.
Moreover, the intermetallic compound of the present invention can be easily processed into a foil. The rolled foil made of the intermetallic compound of the present invention can be used, for example, to adhere to the surface of another structural member to protect the surface of the structural member, and to produce a honeycomb structural member or the like. Can be used.
In the present specification, “to” includes end points.

1. Ni ₃ (Si, Ti) intermetallic compound Ni ₃ (Si, Ti) intermetallic compound of an embodiment of the present invention, Si: 7.5 to 12.5 atom%, Ti: 3.5 to 8 .5 atomic%, Nb: 0.5-3 atomic%, Cr: 0.5-3 atomic%, and the balance contains B: 25-500 ppm by weight with respect to the total weight of the composition composed of Ni.
Hereinafter, each element will be described in detail.

  The content of Si is 7.5 to 12.5 atomic%, for example, 10.0 to 12.0 atomic%. Specific contents of Si are, for example, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0, 11.5, 12.0. Or 12.5 atomic%. The range of the Si content may be between any two of the numerical values exemplified here.

  The Ti content is 3.5 to 8.5 atomic%, for example, 4.5 to 6.5 atomic%. Specific contents of Ti are, for example, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0. Or 8.5 atomic%. The range of the Ti content may be between any two of the numerical values exemplified here.

  The content of Nb is 0.5 to 3 atomic%, for example, 1.5 to 2.5 atomic%. The specific content of Nb is, for example, 0.5, 1.0, 1.5, 2.0, 2.5, or 3.0 atomic%. The range of the Nb content may be between any two of the numerical values exemplified here.

  The Cr content is 0.5 to 3 atomic%, for example, 1.5 to 2.5 atomic%. The specific content of Cr is, for example, 0.5, 1.0, 1.5, 2.0, 2.5, or 3.0 atomic%. The range of the Cr content may be between any two of the numerical values exemplified here.

The content of Ni is, for example, 78.5-81.0 atomic%, for example, 78.5-80.5 atomic%. The specific content of Ni is, for example, 78.5, 79.0, 79.5, 80.0, 80.5, or 81.0 atomic%. The range of the Ni content may be between any two of the numerical values exemplified here.
The content of each element is appropriately adjusted so that the total content of Si, Ti, Nb, Cr and Ni is 100 atomic%.

  The content of B is 25 to 500 ppm by weight, for example, 25 to 100 ppm by weight. The specific content of B is, for example, 25, 40, 50, 60, 75, 100, 150, 200, 300, 400, or 500 ppm by weight. The range of the B content may be between any two of the numerical values exemplified here.

  The specific composition of the intermetallic compound of the present embodiment is, for example, the composition shown in Tables 1 to 3 (or a composition in the range between any two of the compositions shown in Tables 1 to 3) with the above content. B is added.

2. Ni ₃ (Si, Ti) -based intermetallic compound rolled foil The Ni ₃ (Si, Ti) -based intermetallic compound having the composition of the above embodiment has a relatively high ductility, for example, compared with the ingot of the composition of the above-described embodiment. After performing homogenization heat treatment, rolling and annealing are repeatedly performed, and then cold rolling is performed to produce an intermetallic compound rolled foil having a thickness of, for example, 20 to 200 μm.
Hereinafter, each process will be described in detail.

2-1. Ingot making process First, a sample made of an ingot having the composition shown in the above embodiment is made. In one example, a sample made of an ingot obtained by melting and casting a Ni, Si, Ti, Nb, Cr ingot and B measured in an arc melting furnace can be produced.

2-2. Homogenization heat treatment Next, the obtained sample is subjected to homogenization heat treatment. The conditions for the homogenization heat treatment are not particularly limited. The homogenization heat treatment can be performed, for example, in vacuum at 1223K to 1373K for 24 to 48 hours.

2-3. Rolling and Annealing Repeat Step Next, the sample is processed into a thin plate by repeatedly rolling and annealing the sample for homogenization heat treatment. By recrystallizing the sample by annealing after rolling to remove work hardening by rolling and refining the crystal grains, it can be processed into a thin plate relatively easily.
Rolling can be performed, for example, at a temperature of 623K or less, preferably 523K to 623K. Rolling is preferably performed so that the rolling rate in one pass is 0.5 to 1.5%, and is preferably performed in 10 to 20 passes. The rolling is preferably performed so that the rolling rate is 10% or more, preferably 10 to 50%, more preferably 15 to 30%. In the present specification, unless it is clearly indicated as “in one pass”, the “rolling rate” means the ratio of the total thickness reduction due to rolling in a plurality of passes.
Any annealing condition may be used as long as the sample can be recrystallized. The annealing temperature can be set to 1173K to 1373K, for example. The annealing time can be 1 to 5 hours, for example.
Rolling and annealing are repeated until a thin plate having a desired thickness (for example, 2 mm or less) is obtained. Specifically, rolling and annealing are repeated 3 times or more, preferably 4 times or more.

2-4. Cold rolling step Next, the obtained sample is cold rolled at a rolling rate of 90% or more. By this cold rolling, an intermetallic compound rolled foil is obtained. The repeated rolling and annealing steps and the cold rolling step are preferably performed so that the thickness of the obtained foil is 200 μm or less, for example, 20 to 200 μm or less.
Also, if a foil with the desired thickness cannot be obtained by a single cold rolling, the thickness of the foil can be further reduced by performing annealing after cold rolling and then performing cold rolling again. . The annealing temperature at this time can be set to, for example, 1073K to 1273K. The annealing time can be 0.5 to 2 hours, for example.

  The foil after cold rolling has a very high tensile strength and can be used as a structural material as it is. However, when used for applications that require large elongation, the foil after cold rolling is preferably annealed at 973-1173K. The annealing is preferably performed for about 0.5 to 2 hours. By this annealing, the sample is recrystallized, and the tensile strength is slightly reduced, but the elongation is greatly improved.

3. Demonstration Experiment Next, a demonstration experiment showing the effect of the present invention will be described. In the following experiment, the oxidation resistance, corrosion resistance, mechanical properties, etc. of the foil prepared from the intermetallic compound having the composition shown in the above embodiment and the foil prepared from the intermetallic compound having the composition described in Patent Document 1 are described. An evaluation was conducted to demonstrate that the intermetallic compound of the present invention is excellent in oxidation resistance, corrosion resistance and mechanical properties.

3-1. Production of Intermetallic Compound Rolled Foil Intermetallic compound rolled foil was produced by the following method.

3-1-1. Ingot production process First, Ni, Si, Ti, Nb, Cr ingots (purity 99.9 ppm by weight) and B were weighed in an arc melting furnace so as to have the two types of compositions shown in Table 4. A sample made of a molten and cast ingot having a thickness of 10 mm was prepared. The arc melting furnace was first evacuated and then replaced with an inert gas (argon gas). The electrode was a non-consumable tungsten electrode and the mold was a water-cooled copper hearth.
A sample containing Nb and Cr is an example of the present invention, and is hereinafter referred to as an “example sample”. The sample that does not contain Nb and Cr is the sample described in Patent Document 1, and is hereinafter referred to as “comparative sample”.

3-1-2. Homogenization heat treatment step Next, vacuum heat treatment (furnace cooling) was performed at 1323 K for 48 hours to eliminate casting segregation and to homogenize the sample.

3-1-3. Warm rolling and annealing process Next, a thin plate having a thickness of 2 mm was prepared by repeating the warm rolling and annealing for the sample obtained in the above process 5 times.
In the warm rolling, the sample was heated to 573 K in the atmosphere, and rolling of 10 to 20 passes was performed using a two-high rolling mill with a reduction amount of 1 pass of about 0.1 mm. The sample was heated every pass. The annealing was performed in a vacuum at 1273 K for 5 hours (furnace cooling).

3-1-4. Cold Rolling Step Next, the thin plate obtained in the above step was cold rolled at room temperature to produce a foil. Cold rolling was performed so that the rolling rate would be 90% without annealing. Cold rolling was performed by changing rolling mills in the order of large-diameter two-high rolling mill → small-diameter two-high rolling mill → small-diameter four-high rolling mill as processing progressed. The thickness of the produced foil was 0.2 mm. A foil obtained by cold rolling and not annealed after cold rolling is hereinafter referred to as “cold rolled foil”.

3-2. Evaluation 3-2-1. Oxidation resistance test A cold rolled foil was subjected to an oxidation resistance test. The oxidation resistance test was performed by TG-DTA (Thermogravimetry-Differential Thermal Analysis). Specifically, the oxidation resistance test was performed by measuring the amount of mass increase per unit surface area of the sample when the cold rolled foil was exposed to the atmosphere at 1173K. The result is shown in FIG. FIG. 1 is a graph showing the relationship between time and mass increase, showing the results of an oxidation resistance test. FIG. 1 also shows the results for nickel alloy (Inconel X750) and stainless steel (SUS310).
According to FIG. 1, it can be seen that the increase in mass was considerably smaller in the example sample than in the comparative example sample. This indicates that the oxidation resistance of the example sample is excellent, and it was demonstrated that the oxidation resistance is greatly improved by adding Cr and Nb to the sample. Further, according to FIG. 1, it can be seen that the oxidation resistance of the example sample is superior to that of nickel alloy or stainless steel.

3-2-2. Corrosion resistance test Corrosion resistance tests were conducted on cold rolled foil. The corrosion resistance test was performed by immersing the cold rolled foil in hydrochloric acid (concentration: 36%) at room temperature for 24 hours and measuring the corrosion loss (weight loss due to corrosion) at that time. The smaller the corrosion weight loss, the better the corrosion resistance.
Fig. 2 shows the corrosion weight loss during the corrosion resistance test and the appearance of the foil after the corrosion resistance test. FIG. 2 also shows the results for nickel alloy (Inconel X750) and stainless steel (SUS304).
According to FIG. 2, it can be seen that the weight loss of corrosion was considerably smaller in the example sample than in the comparative example sample. This indicates that the corrosion resistance of the example sample is excellent, and it was proved that the corrosion resistance is greatly improved by adding Cr and Nb to the sample. Further, according to FIG. 2, it can be seen that the corrosion resistance of the example sample is much better than that of nickel alloy or stainless steel.

3-2-3. Room temperature tensile test Next, cold-rolled foil and foils obtained by annealing the cold-rolled foil at 873K for 1 hour or 1173K for 1 hour (referred to as "873K annealed foil" and "1173K annealed foil", respectively). A room temperature tensile test was conducted. The size of the foil used for the room temperature tensile test was a parallel part length of 10 mm and a width of 4 mm. The room temperature tensile test was conducted at room temperature and in air at a strain rate of 8.4 × 10 ⁻⁵ s ⁻¹ . The result is shown in FIG. FIG. 3 is a graph showing the relationship between the stress applied to the foil and the strain generated in the foil.
According to FIG. 3, the cold rolled foil and the 873K annealed foil have a tensile strength of 2 GPa or more in both the example sample and the comparative example sample, and these foils have a very high tensile strength. Was confirmed. Further, in the 1173K annealed foil, the plastic elongation is about 30% in both the example sample and the comparative example sample, and these foils have a high ductility comparable to that of a general metal material. It was confirmed.

3-2-4. High temperature tensile test Next, the high temperature tensile test was done about 1173K annealing foil. The size of the foil used for the high-temperature tensile test was 10 mm in parallel part length and 4 mm in width. The high temperature tensile test was performed in a vacuum at a strain rate of 8.4 × 10 ⁻⁵ s ⁻¹ and at a temperature of room temperature to 1023 K. The result of the high temperature tensile test about an Example sample and a comparative example sample is shown to Fig.4 (a)-(c). 4 (a) is a graph showing the relationship between the test temperature and tensile strength, FIG. 4 (b) is a graph showing the relationship between the test temperature and 0.2% proof stress, and FIG. It is a graph which shows the relationship between test temperature and elongation. In addition, examples and comparative samples, various general-purpose alloys (Inconel X750 (Ni-15.5Cr-7Fe-2.5Ti-1Nb), Hastelloy X (Ni-9Mo-22Cr-18.5Fe-1.5Co)), S 816 Graph showing the relationship between test temperature and tensile strength for (Co-20Ni-20Cr-4Mo-4W-4Nb-3Fe-1.2Mn), SUS304 (Fe-18Cr-8Ni), SUS430 (Fe-18Cr)) As shown in FIG. In FIG. 5, the data on the general-purpose alloy used is described in Metals Handbook Tenth Edition, (ASM International, Materials Park, OH, 1990).

According to FIG. 4A, the tensile strength of the example sample is larger than that of the comparative example sample at all temperatures, and it was demonstrated that the tensile strength is improved by adding Nb and Cr. . Also, according to FIG. 5, it can be seen that the tensile strength of the example sample showed a higher value than any of the general-purpose alloys in the temperature range of 900K or less.
According to FIG. 4B, the 0.2% proof stress of the example sample is larger than the 0.2% proof stress of the comparative sample at all temperatures, and 0.2% by adding Nb and Cr. It has been demonstrated that the yield strength is improved.
According to FIG. 4C, the elongation of the example sample is larger than that of the comparative example sample at a temperature of 773 K or higher, and it is demonstrated that the addition of Nb and Cr improves the elongation in the high temperature range. It was done.

  Here, the reason why the elongation of the example sample is larger than that of the comparative example sample in the high temperature range will be examined. FIGS. 6A to 6F show scanning electron microscope (SEM) photographs of the tensile fracture surface of the sample after the tensile test at room temperature, 773K, and 873K. 6A to 6C are SEM photographs of the example samples, and FIGS. 6D to 6F are SEM photographs of the comparative example samples. 6 (a) to 6 (f), in the comparative sample, when the tensile test temperature becomes high, the ratio of brittle grain boundary fracture surfaces increases, but in the experimental sample, the ductile dimple pattern is high even at high temperature. There are many fracture surfaces. For this reason, it is considered that the elongation in the high temperature range was improved in the example sample as compared with the comparative example sample.

3-2-5. Microstructure observation Next, SEM photographs of the 1173K annealed foil were taken and the microscopic observation was performed. The SEM photograph about an Example sample and a comparative example sample is shown to Fig.7 (a) and (b), respectively. FIGS. 7 (a), referring to (b), fccNi to Comparative Sample in FIG. 7 (b) has a L1 ₂ single phase structure, the example samples of FIG. 7 (a) in the L1 ₂ matrix It had a two-phase structure in which a solid solution phase appeared. The particle size of the L1 ₂ crystal grains of the example sample was fine as compared with the comparative example sample.

3-3. Summary As can be seen from the above evaluation results, the example samples have better oxidation resistance and corrosion resistance than the comparative example samples, and the mechanical properties such as tensile strength and elongation are equal to or higher than the comparative example samples. Is also excellent. Therefore, the example sample is suitably used for applications that require excellent oxidation resistance, corrosion resistance, and mechanical properties, such as a catalyst carrier of an automobile exhaust gas purification device. In addition, the example sample can be easily processed into a foil like the comparative example sample. The foil obtained from the example sample can be used, for example, to be applied to the surface of another structural member to protect the surface of the structural member, and to be used for manufacturing a honeycomb structural member or the like. Can do.

It is a graph which shows the relationship between time and the amount of mass increase which shows the result of the oxidation resistance test in the verification experiment of this invention. The corrosion weight loss during the corrosion resistance test in the demonstration experiment of the present invention and the appearance of the foil after the corrosion resistance test are shown. It is a graph which shows the result of the room temperature tensile test in the verification experiment of this invention, and shows the relationship between the stress added to foil, and the distortion which arose to foil. (A)-(c) shows the result of the high temperature tensile test in the demonstration experiment of the present invention, (a) is a graph showing the relationship between the test temperature and the tensile strength, and (b) shows the test temperature and It is a graph which shows the relationship of 0.2% yield strength, (c) is a graph which shows the relationship between test temperature and elongation. It is a graph which shows the result of the high temperature tensile test in the demonstration experiment of this invention, and shows the relationship between test temperature and tensile strength about an Example sample and a comparative example sample, and various general purpose alloys. (A)-(f) shows the scanning electron microscope (SEM) photograph of the tensile fracture surface of the sample after the tensile test in room temperature, 773K, and 873K in the demonstration experiment of this invention. (A)-(c) is a SEM photograph of an example sample, (d)-(f) is a SEM photograph of a comparative example sample. (A) And (b) shows the SEM photograph of the 1173K annealing foil of the Example sample and comparative example sample in the demonstration experiment of this invention, respectively.

Claims (4)

Si: 7.5 to 12.5 atomic%, Ti: 3.5 to 8.5 atomic%, Nb: 0.5 to 3 atomic%, Cr: 0.5 to 3 atomic%, the balance being Ni B relative to the total weight of: Ni ₃ (Si, Ti) intermetallic compound comprising 25 to 500 wt ppm. Si: 10.0-12.0 atomic%, Ti: 4.5-6.5 atomic%, Nb: 1.5-2.5 atomic%, Cr: 1.5-2.5 atomic%, B: The Ni ₃ (Si, Ti) -based intermetallic compound according to claim 1, which is 25 to 100 ppm by weight. A Ni ₃ (Si, Ti) intermetallic compound rolled foil comprising the intermetallic compound according to claim 1 or 2 and having a thickness of 20 to 200 µm. Si: 7.5 to 12.5 atomic%, Ti: 3.5 to 8.5 atomic%, Nb: 0.5 to 3 atomic%, Cr: 0.5 to 3 atomic%, the balance being Ni The sample consisting of an ingot containing B: 25 to 500 ppm by weight with respect to the total weight of
The sample after the homogenization heat treatment is repeatedly rolled at a rolling rate of 10% or more and annealed at 1173 to 1373K three times or more,
Thereafter, Ni ₃ comprising the step of performing cold rolling at a rolling rate of 90% or more with respect to the obtained sample (Si, Ti) based process for producing an intermetallic compound-rolled foil.