WO2002027067A1 - Heat-resistant material of niobium base alloy - Google Patents

Abstract

A heat-resistant material for a niobium base alloy which comprises a substrate of a niobium base alloy, a first alloy coating film comprising Re and at least two other metal elements formed on the surface of the substrate and, formed on the surface of the first alloy coating film, a second alloy coating film comprising one element of Al and Si and at least one metal element except these elements. The above combination of coating films exhibits excellement performance in the interception of oxygen and is less susceptible to deterioration owing to diffusion of an element. Suitable compositions of the first alloy coating film and the second alloy coating film are disclosed for each case wherein the second alloy coating film comprises Al or Si, and preferred compositions of alloy coating films for some compositions of the niobium base alloy of the substrate are also disclosed.

Description

Description Heat resistant materials for niobium-based alloys

 The present invention relates to a heat-resistant material used as a member of a high-temperature combustion device such as a gas turbine or a jet engine, and particularly to a niobium-based alloy in which a film for suppressing high-temperature oxidation is formed on the surface of a niobium-based alloy substrate. 'Regarding heat-resistant materials. Background art

 In recent years, the operating temperature of power generation gas turbines has been required to be even higher, and new heat-resistant materials that have higher operating temperature limits than Ni-based alloys that have been frequently used as turbine members have become necessary. . Examples of such materials include niobium (Nb) -based heat-resistant materials, such as solid-solution strengthened or precipitation-strengthened Nb alloys and Nb-A1 intermetallic compounds (in the present invention, these are referred to as " Materials are called niobium-based alloys). Although these niobium-based alloys have high high-temperature strength, they are all easily oxidized in a high-temperature range, for example, at a temperature of 800 ° C or higher, and are used as such in a high-temperature oxidizing atmosphere such as a gas turbine. It is difficult. For this reason, various studies have been made on applying a coating for the purpose of oxidation resistance to the surface of a niobium-based alloy substrate.

Conventionally, a method of forming a Cr or A1 diffusion layer and a method of ceramic coating have been studied as a heat and oxidation resistant coating of a metal member used in a high-temperature oxidizing atmosphere. Especially for Ni-based alloys, a method called Thermal Barrier Coating (TBC) is used. It has become mainstream. This is made by laminating a metal bonding layer on the surface of a base material and a heat shielding layer of ceramics on the surface. MC is the metal bonding layer r A 1 Y alloy (M is N i, C o, etc.> is ceramics in thermal barrier layer to generate content of Z r 0 ₂ is often used.

 As an oxidation-resistant coating of a niobium-based alloy, Japanese Patent Application Laid-Open No. H10-1403333 discloses that an Ir surface coating layer is formed or that an Ir surface coating layer and a Ta An Nb alloy heat-resistant member in which a diffusion preventing layer that forms at least one of R, W, and W is formed is disclosed. Also, Japanese Patent Application Laid-Open No. H10-140347 describes that Ir is vacuum-deposited on the surface of a substrate and A1 ion irradiation is performed at the same time to form a coating layer composed of an Ir_A1 alloy. A method for producing an oxidation-resistant coating layer is disclosed. Disclosure of the invention

 In general, ceramic coatings often have cracking or peeling due to thermal stress due to insufficient toughness of the ceramic itself and insufficient adhesion to the base material, leaving a problem in durability. Also in the above-mentioned TBC, oxygen is cut off mainly at the metal bonding layer. Therefore, the film intended for oxidation resistance is an alloy film having high adhesion to the base material, and has the same blocking performance of non-metal components such as oxygen and nitrogen as the above-mentioned metal bonding layer. It is desirable.

Further, the Nb-based alloy which is the object of the present invention is intended to be used at a higher service temperature than the Ni-based alloy, for example, at a temperature exceeding 140 ° C. In such a high temperature range, the diffusion of elements between the film and the substrate is inevitable, so that the film deteriorates in a relatively short time and loses its original function in many cases. Therefore, in order to ensure the durability of the oxidation-resistant film, the diffusion should be suppressed as much as possible, and even if there is some diffusion, the film will not deteriorate. It is necessary to have a light covering structure.

 Therefore, the present invention provides a heat-resistant niobium-based alloy material in which an alloy film that is excellent in blocking performance of non-metal components such as oxygen and nitrogen and that is hardly deteriorated by diffusion is formed on the surface of the niobium-based alloy substrate. The purpose is to do.

 The present invention for achieving the above object,

 (1) A first-layer alloy film composed of Re and at least two other metal elements is formed on the surface of a niobium-based alloy substrate, and the surface is coated with either one of A 1 and Si. It is a heat-resistant niobium-based alloy on which a second-layer alloy film made of at least one other metal element is formed.

(2) The composition of the alloy film of the first layer is substantially the same as the general formula Re e _ab M _a R _b (where M is selected from the group consisting of G r, Ni and A 1 R is one or more elements selected from the group consisting of Nb, M0, W, Hf, Zr and C, and a and b are the atomic ratios of M and R, respectively.) And the composition of the alloy film of the second layer is substantially the general formula Q or _e A (wherein Q is at least one element of Cr and Ni) , C is the atomic ratio of A 1), which is the heat-resistant material of the niobium-based alloy according to the above (1).

 In this heat-resistant material, the atomic ratio a is 0.01 or more, the atomic ratio b is 0.01 to 0.50, the a + b force is 0.95 or less, and the atomic ratio c is 0.0. It is preferably from 5 to 0.95.

In this heat-resistant material, the niobium-based alloy contains at least one of Mo and W and Cr with Nb as a pace, and optionally contains Si, Hf, Z An alloy containing at least one of r and C, wherein the element M in the alloy film of the first layer contains at least Cr (preferably, the element M is mainly composed of Cr). This includes a small amount of one or more of A 1 and Ni), and the element Q in the alloy film of the second layer is Cr or Cr and N Preferably i. Further, in this heat-resistant material, the niobium-based alloy may be an intermetallic compound containing Nb and A 1.

 (3) The composition of the alloy film of the first layer is substantially the general formula R e!-I-e T d R e

(Wherein T is one or more elements of Cr and Si, and R is one or more elements selected from the group consisting of Nb, Mo, W, Hf, Zr and C. , d, e are those represented by a ^1, an atomic ratio of R), and the composition of the alloy film of the second layer is substantially formula _{X -!! f S i f} ( wherein , X is one or more elements selected from the group consisting of Mo, W and Nb, and f is the atomic ratio of S i). It is a heat-resistant material.

 In this heat-resistant material, the atomic ratio d is 0.10 or more, the atomic ratio e is 0.01 to 0.50, d + e is 0.95 or less, and the atomic ratio f is 0.0. It is preferably between 5 and 0.95.

 In this heat-resistant material, the niobium-based alloy contains at least one of Mo and W and Si based on Nb, and further includes Cr, Hi, Z r, an alloy containing at least one of C, wherein the element T in the alloy film of the first layer is preferably Si, and in this case, More preferably, the element X in the alloy film is at least one of M 0 and W. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram for explaining the structure of the oxidation-resistant coating of the heat-resistant material of the present invention, and FIG. 2 shows changes in the skin after exposing the heat-resistant material of the present invention to a high-temperature atmosphere. It is a schematic diagram of a section for explaining. Fig. 3 is a schematic diagram showing the cross section of the film before the high-temperature oxidation test of the comparative test piece in the oxidation resistance evaluation. Fig. 3 (a) shows an example of the case of A1 alloy coating. b) is the Si alloy coating An example in the case of a cover is shown. Fig. 4 is a schematic diagram showing the cross section of the film after the high-temperature oxidation test of this comparative test piece. Fig. 4 (a) shows the case of A1 alloy coating, and Fig. 4 (b) shows the Si alloy coating. An example in the case of is shown. BEST MODE FOR CARRYING OUT THE INVENTION

 The oxidation-resistant coating of the heat-resistant material of the present invention comprises two layers of an alloy coating as shown in FIG. Since the surface of the second upper alloy film 3 is oxidized by oxygen in the atmosphere to form a dense oxide layer, it has a function of blocking non-metallic elements such as oxygen and nitrogen in the atmosphere. Have. At the same time, the alloy film 3 has a self-healing function. That is, since the alloy film 3 contains a metal element that is a source of oxide, if the oxide layer formed on the surface peels off, the metal element is immediately oxidized and the oxide layer is formed on the surface. Is regenerated, and the effect of blocking oxygen, nitrogen and the like in the atmosphere can be maintained. On the other hand, the main purpose of the lower first alloy film 2 is to prevent diffusion of elements between the base material 1 and the second alloy film 3.

 In the present invention, the metal element from which the oxide in the second alloy film 3 is based is A1 or Si. If both are present at the same time, an oxide having a low melting point is generated, so only one of them is added to the alloy film 3. When the metal element that forms the oxide is A 1 (hereinafter referred to as “A1 alloy coating”) and when it is Si (hereinafter referred to as “Si alloy coating”), the first layer The preferred composition of the alloy film is different between the first and second layers.

First, in the case of A1 alloy coating, the composition of the second alloy film 3 is substantially the same as that of the general formula 0 _C Ca lc (where Q is at least one element of Ni and Cr). , A 1 is aluminum and c is the atomic ratio of A 1). As already mentioned, A 1 Q is an element necessary to form a dense oxide layer when oxidized in a high-temperature oxidizing atmosphere. Q is a high-temperature stable phase (alloy or intermetallic compound) between it and A 1. ) Is an essential element for ensuring the heat resistance and durability of the second layer coating.

The composition of the first alloy film 2 in the A1 alloy coating is substantially the general formula R e _ab M _a R _b (where R e is rhenium and M is C r, N i and And one or more elements selected from the group consisting of A1 and R is one or more elements selected from the group consisting of Nb, M0, W, Hf, Zr and C. A, b are the atomic ratios of M and R, respectively.

 Re is an element that plays a major role in preventing diffusion. The element M is mainly contained in the first layer coating and the second layer coating (may be partially contained in the base material), and the first layer coating and the second layer coating (and the first layer coating and the base layer). This is effective in reducing the diffusion between materials. The element R is mainly contained in the first layer film and the substrate (partially may be contained in the second layer film), and between the first layer film and the substrate (and the first layer film and the first layer film). It is effective in reducing the diffusion between the two layers.

Next, the preferred composition of the alloy film in the case of the Si alloy coating will be described. In the case of S i alloy coating, the alloy film 3 of the second layer, in substantially the general formula X! _ _F S i _f (wherein, X is selected from the group consisting of M 0, W and N b At least one element, f is the atomic ratio of Si) is preferably used. In this case, Si is an element that forms a dense oxide layer, and X is an element that forms a stable phase at high temperature with Si, ensuring the heat resistance and durability of the second layer coating. Is essential in doing so.

In addition, the first alloy film 2 of the Si alloy coating substantially has the general formula R e or _de T _d R _e (where T is one or more elements of Cr and Si, R is one or more elements selected from the group consisting of Ni, Mo, W, Hf, Zr, and C (Where d and e are the atomic ratios of T and R, respectively)).

 In both cases of A1 alloy coating and Si alloy coating, the reason why the first layer alloy film is composed of a ternary or higher composition is not only the element in the second layer film but also the This is because the elements are also contained in the first layer and the film in advance, and the chemical potential in each phase is made equal for each component, thereby preventing diffusion. As a result, decomposition and alteration of the oxidation-resistant coating can be suppressed, and the durability of the coating can be greatly improved.

 Further, the elements M and R in the A1 alloy coating and the elements T and R in the Si alloy coating are each preferably an element which forms a high-temperature stable phase with Re. It is effective in suppressing decomposition and alteration of a single layer film. For example, an intermetallic compound phase such as a Re—Cr—Ni system sigma phase, a Re— (Nb, Mo, W) system sigma phase or a chi phase is preferable. Since these phases have a high melting point, they can prevent the first-layer film from decomposing or diffusing and disappearing. Further, since the diffusion coefficients of other elements are small, they can prevent diffusion. Demonstrate function.

 In both cases of A1 alloy coating and Si alloy coating (hereinafter, the description of alloy coating is common to both A1 alloy coating and Si alloy coating unless otherwise specified. The alloy films of the first and second layers only need to have substantially the above composition, and may contain unavoidable impurity elements.

FIG. 2 is a schematic cross-sectional view showing a change in a film after exposing the heat-resistant member of the present invention to a high-temperature atmosphere. As can be seen in the figure, a dense oxide layer 4a is formed on the surface of the second alloy film 3. The oxide layer 4 a mainly A 1 ₂ 0 ₃ or 8 i O _2, such a Tsuteori, layer thickness smaller without having, the greater ability to block elements. When used continuously in this state, the first layer 2 It is a phase that is extremely stable at high temperatures, and has a large effect of suppressing swarf and diffusion. As a result, decomposition and alteration of the second layer film 3 can be prevented, and an oxide layer is formed again on the surface of the second layer film 3 even if a crack or peeling occurs in the outermost oxide layer 4a. Is self-healing. Thus, the durability of the oxidation resistant coating is ensured.

In the case of the A1 alloy coating, it is preferable that the atomic ratio a of the element M in the first alloy film is 0.01 or more. Below this, the diffusion of element Q from the second-layer coating to the first-layer coating increases. Further, the atomic ratio b of the elemental scale is preferably in the range of 0.01 to 0.50. If b is less than 0.01, the purpose of suppressing the diffusion of the element R from the base material to the first layer film cannot be achieved, and if b exceeds 0.50, the first layer film relatively cannot be obtained. This is because the contents of Re and M in the composition are undesirably small. Furthermore, it is preferable that a + b is 0.95 or less. If it exceeds this, the amount of Re will be too small and the diffusion prevention function will be insufficient. Further, it is preferable that the atomic ratio c of the element A 1 in the alloy film of the second layer is 0.05 to 0.95. If it is less than 0.05, the function of forming a dense oxide film will be insufficient.If it exceeds 0.95, the amount of element Q will be relatively small, and a phase stable at high temperatures will be obtained. Is not formed. Similarly, in the case of the Si alloy coating, the atomic ratio d of the element T in the first alloy film is preferably 0.1 or more. If it is less than this, diffusion of the element X from the second layer coating to the first layer coating increases. Further, the atomic ratio e of the element R is preferably from 0.01 to 0.50. If e is less than 0 or 01, the purpose of suppressing the diffusion of the element R from the base material to the first layer coating cannot be achieved, and if e exceeds 0.50, the relative content in the first layer coating is relatively small. This is because the contents of Re and T are reduced, which is not preferable. Further, d + e is preferably 0.95 or less. Beyond this, the amount of Re Too little, and the diffusion prevention function is insufficient. Further, the atomic ratio f of the element Si in the alloy coating of the second layer is preferably in the range of 0.05 to 0.95. If it is less than 0.05, the function of forming a dense oxide film will be insufficient, and if it exceeds 0.95, the amount of element X will be relatively small, and a phase stable at high temperatures will be obtained. This makes it impossible to form

 The present inventors studied the mechanical properties of a niobium-based alloy, and found that a binary alloy of Nb—M0 or Nb—W or a three-part alloy of Nb—M0—W has improved high-temperature strength and toughness. It was found to be excellent and suitable as a turbine member. Appropriate ranges of the contents of the alloying elements are 1 to 30 at% for M 0 and 1 to 15 at% for W.

 The present inventors have conducted various studies on the oxidation-resistant coating of these binary or ternary alloys, and have found that, in relation to the composition of the niobium-based alloy of the base material, either A1 alloy coating or Si alloy coating is used. <First, in the case of A1 alloy coating, the second layer film should be composed of Cr-A1 alloy and a small amount of Cr should be added to the base material. As a result, it was found that they exhibited extremely excellent oxidation resistance. That is, in this heat-resistant material, the base material is Nb— (one or more of Mo and W) —Cr alloys, the first layer alloy film contains Re and Cr, and the second layer Is substantially composed of Cr-Ai or Gr-Ni-A1 alloy. A more preferred alloy film of the first layer is mainly composed of Re and Cr, and a small amount of one or more of (Ni, A1) and one of (Mo, W, Nb). It contains one or more species. The substrate may contain one or more of Si, Hf, Zr, and C as necessary.

In the heat-resistant material having the A1 alloy coating described above, it is preferable that Re in the first layer film is 10 to 60 at% and Cr is 10 to 60 at%. A 1 in the second layer coating is preferably 15 to 75 at%.

 On the other hand, with regard to the Si alloy coating, when the niobium-based alloy further contains Si, the second layer coating is made of Mo, W, and Nb silicide, thereby providing extremely excellent oxidation resistance. It has been found to exhibit the property. That is, in this heat-resistant material, the base material is Nb— (one or more of Mo and W) -Si alloys, and the first layer alloy film is substantially composed of Re and Si ( At least one of Mo, W, and Nb), and the second alloy film is substantially composed of Si and (at least one of Mo, W, and Nb). It is. Among them, it is particularly preferable that the second-layer life metal film is substantially composed of Si and (at least one of Mo and W). The substrate may contain one or more of Cr, Hf, Zr, and G as needed.

 In the heat-resistant material having the Si alloy coating, Re in the first layer film is 10 to 60 at%, (Mo + W + Nb) is 10 to 60 at%, and Si is 1 to 50 at%. It is preferably at%. Further, (M 0 + W + N b) in the second layer coating is preferably 20 to 60 at%.

In the present invention, the method of forming the alloy film on the substrate surface is not particularly limited, and may be any of, for example, a PVD method, a GVD method, a thermal spraying method, an electrolytic coating method, and a combination thereof. May be used. Further, some of the components constituting the alloy film may be added by a thermal diffusion method. In this case, a gradient may occur in the concentration of the component elements in the depth direction, but in the present invention, there may be a concentration gradient applied to the alloy film. The thickness of the alloy film of the first layer and the second layer is not particularly limited, but is usually about 1 to 100 m. If the film thickness is too small, the anti-oxidation and diffusion prevention functions will be insufficient, and if the film thickness is too large, the thermal stress will be large. Good. (Evaluation of oxidation resistance characteristics)

 A high temperature oxidation test was performed on a test piece having a two-layer oxidation resistant film formed on the surface of a niobium-based alloy substrate based on the present invention and a comparative test piece having one layer based on the present invention to evaluate the oxidation resistance properties. . This test was performed on both the A1 alloy coated test piece and the Si alloy coated test piece.

(1) Preparation of test piece

As the niobium-based alloy of the base material, Nb-5M0-5W-5Cr (mol%) alloy (A alloy) for A1 alloy coating, Nb-5 for Si alloy coating M 0 - 5 W- 5 C r - 1 6 S i ( mol _^0/0) of alloy (B alloy) _c any alloy used also, purity 9 9.9 to 9 9.9 9% N b , Mo, W, Cr and Si powders or granular raw materials were blended into a predetermined composition, and the raw materials were melted by arc melting in an Ar atmosphere to produce ingots. The ingot is subjected to a homogenization heat treatment of 1700 to 180 ° C for 24 hours in an Ar gas stream of 1 atm, and then a test specimen substrate of 30 x 20 x 2 (thickness) mm Was cut out and subjected to a coating treatment.

The test piece (two-layer coating) of the present invention coated with an A1 alloy was prepared by first depositing a 5-meter-thick metal Re on the surface of the base A alloy from a molten chloride bath containing rhenium chloride. Then embedded in an alumina crucible with Hue port chromium powder, it was more diffuse process C r vapor to 1 0 hr held at 1 3 0 0 ° C in a vacuum of 1 X 1 0- ³ P a. The test piece was taken out from the crucible, again embedded in an alumina crucible together with F e-A 1 alloy powder followed Pull, and 6 hr held at 1 0 0 0 ° C in a vacuum of 1 X 1 0- ³ P a , And A1 vapor diffusion treatment.

In addition, a comparative test piece (single-layer coating) coated with A1 alloy was prepared by subjecting the A alloy base material prepared by the same method as described above to the electrodeposition treatment of metal Vapor diffusion treatment, A 1 A vapor diffusion treatment performed under the same conditions as above Prepared.

 As a preliminary treatment, a diffusion / oxidation treatment of heating in a still air at 110 ° C. for 9 hours was applied to the test pieces of the present invention and the comparative test pieces subjected to the coating treatment according to the above steps. As a result, in the test piece of the present invention, as shown in FIG. 2, the first layer film 2 and the second layer film 3 were laminated on the surface of the substrate 1, and the oxide layer (A1, 0) was formed on the outermost surface. A heat-resistant material on which 4a was formed was obtained. Table 1 shows the thickness and composition of each layer of the coating on this test piece. Table 1 In the test piece of the present invention coated with A1 alloy

 Thickness and composition of each layer after pretreatment

第 1表の結果から知れるように、 基材表面に形成した R eの電析層に,

As can be seen from the results in Table 1, the electrodeposited layer of Re formed on the substrate surface

Gr penetrated by the vapor diffusion treatment of Cr and Nb diffused from the base material, and the Re electrodeposition layer was the first layer consisting mainly of the ternary system of Re—Cr—Nb. It changed to film 2. Further, the second layer coating 3 mainly composed of Cr—A 1 is formed by the A 1 vapor diffusion treatment, and the oxide layer 4 a is formed by the oxidation treatment.

In addition, as shown in Fig. 3 (a), in the comparative test piece after the pretreatment, the oxide layer (Al, 0) 4a having a thickness of about 5 m and a thickness of about 5 m in order from the surface. A 2 μm oxide layer (Cr, b) 4 b was formed, followed by a layer of about 8 ^ m, consisting mainly of Cr and Nb. The Cr-Nb layer had a two-layer structure consisting of the upper G rich layer 5b and the lower N rich layer 5a. Table 2 shows the thickness and composition of each layer in this test piece. Table 2 shows the results of the comparative test pieces coated with the A1 alloy.

 Thickness and composition of each layer after pretreatment

On the other hand, in the test piece of the present invention coated with a Si alloy, a metal Re having a thickness of 5 μπι was electrodeposited from a molten chloride bath containing dimethyl chloride on the surface of the base material of the B alloy. Subsequently, after being immersed in a molten metal Si bath in an Ar atmosphere, it was pulled up and subjected to Si plating. The Si deposition amount at this time was about 60 g / m ² (equivalent to a thickness of about 25 m) from the weight change before and after plating. Then embedded in an alumina crucible together with alumina powder was subjected to diffusion treatment by maintaining 6 hours 1 4 0 0 ° C to have you in a vacuum of 1 X 1 0- ³ P a. In addition, as a comparative test piece, Si plating and diffusion treatment were performed on the B alloy base material prepared by the same method without depositing metal Re under the same conditions as above. I prepared something.

 As a preliminary treatment, a diffusion / oxidation treatment in which heating was performed in a still air at 110 ° C. for 9 hours was performed on the test pieces of the present invention and the comparative test pieces subjected to the coating treatment according to the above steps. As a result, in the test piece of the present invention, as shown in FIG. 2, the first layer film 2 and the second layer film 3 were laminated on the surface of the substrate 1, and the oxide layer (S i, O) was formed on the outermost surface. A heat-resistant material on which 4a was formed was obtained. Table 3 shows the thickness and composition of each layer of the coating on this test piece.

As can be seen from the results in Table 3, the deposited layer of Re formed on the substrate surface. Due to the infiltration of Si by the hot-dip Si plating and the subsequent diffusion treatment in vacuum, and the diffusion of Nb from the base metal, the Re electrodeposited layer was mainly composed of Re—Si—Nb It was changed to the first layer coating 2 consisting of a ternary system. Further, excess Si dissolved Nb that passed through the Re electrodeposited layer to form a Si—Nb alloy layer, and the second layer film 3 was formed. Moreover, Te cowpea to the oxidation process, S i - only the surface layer of the N b layer is oxidized, an oxide layer consisting of _{S i 0 2 (S i,} 0) 4 a is formed. Table 3 Test pieces of the present invention coated with Si alloy

 Thickness and composition of each layer after pretreatment

また、 予備処理後の比較用試験片では、 第 3図（b)に示すように、 表 面から順に、 厚さ約 1 . 5 111の酸化物層（8 i , N b， 0) 4 b、 その 内側に厚さ約 4 5 μπιの主に S i と N bからなる層 （ S i — N b層 5 ) が形成されていた。 この試験片における各層の厚さや組成を第 4表に示 す。 第 4表 S i合金被覆した比較用試験片における

In addition, in the comparative test piece after the pretreatment, as shown in FIG. 3 (b), in order from the surface, an oxide layer (8i, Nb, 0) 4b having a thickness of about 1.5111 was formed. A layer consisting mainly of S i and N b (S i —N b layer 5) with a thickness of about 45 μπι was formed inside. Table 4 shows the thickness and composition of each layer in this test piece. Table 4 Comparative test specimens coated with Si alloy

 Thickness and composition of each layer after pretreatment

 Layer symbol Layer thickness Composition (mol%) Remarks

 (131 (b)) (μm) Nb Mo W Cr Si

 4 b 1.5 Oxide layer (Si, Nb, 0)

5 45 33 2 1 1 63 (2) High temperature oxidation test results of specimen coated with A1 alloy

 The A1 alloy-coated test pieces prepared as described above and the comparative test pieces were subjected to a high-temperature oxidation test of isothermal continuous heating in a still air at 110 ° C. to compare oxidation resistance properties. The heating time of the test piece of the present invention was 168 hours. Since the appearance of the test specimen for comparison was significantly changed, the time was set to 12 hours. The results are shown in Tables 5 and 6. Table 5 A1 For the test piece of the present invention coated with alloy

 Layer before and after high temperature oxidation test

 Comparison of A1 concentration of thickness and second layer coating

第 6表 A 1合金被覆した比較用試験片における

Table 6 A1 alloy-coated comparative specimens

 Comparison of oxide layer thickness before and after high-temperature oxidation test

 *: Total thickness of layer 4a and layer 4b in Fig. 3 (a)

**: Total thickness of layers 4 c (20 (im) and 4 d (150 iim) in FIG. 4 (a). In the test piece of the present invention, there is no significant change in the coating structure even after the high-temperature oxidation test. The state was maintained as shown in Table 2. Table 5 shows the change in the thickness of the oxide layer 4a before and after the oxidation resistance test of the present invention for 16 hours, and the change in the oxide layer 4a. It shows the change in the A1 concentration in the second layer coating 3 underneath.After the oxidation for 16 hours, the A1 concentration of 14% was maintained in the second layer. Therefore, in the first layer, A 1 of the second layer diffuses inward (diffusion to the substrate side) It can be seen that there is an effect of the diffusion preventing layer. Also, 4 a oxide layer, _c also being alumina according to X-ray diffraction, the alumina is maintained without change in the extreme thickness at the substrate surface, A 1 concentration of the second layer Indicates that the concentration is equal to or higher than the concentration capable of expressing the alumina forming ability in the Cr—A1 alloy.

 On the other hand, Fig. 4 (a) schematically shows the state of the film after the 12-hour high-temperature oxidation test of the comparative test piece. Table 6 shows the change in oxide layer thickness before and after the high-temperature oxidation test. After the high-temperature oxidation test, the surface oxide layer (Cr, Nb, 0) 4c and the lower oxide layer (Nb, 0) 4d were two layers. Has a thickness of 170 m, most of which (approximately 150 μπι) is a layer 4d consisting of Nb and 0, indicating that the base Nb-based alloy has been oxidized. ing.

(3) High-temperature oxidation test results of test specimens coated with Si alloy

 The Si alloy-coated test pieces prepared as described above and the comparative test pieces were subjected to a high-temperature oxidation test in which the test pieces were isothermally continuously heated in a still air at 1200 ° C. to compare the oxidation resistance properties. The heating time of the test piece of the present invention was 168 hours. The test specimen for comparison was set to 8 hours because the appearance change was remarkable. The results are shown in Tables 7 and 8. Table 7 Test pieces of the present invention coated with Si alloy

 Layer before and after high temperature oxidation test

 Comparison of thickness and Si concentration of second layer coating

 1200 ° C oxidation test (168 fights)

 After S-test

 Oxide layer (4a) 1.5 1.5 to 3.0

 Thickness (μm)

 76 69

S level (mo) In the test piece of the present invention, there was no significant change in the coating structure even after the high-temperature oxidation test. The state as shown in FIG. 2 was maintained. Table 7 shows the change in the thickness of the oxide layer 4a before and after the high-temperature oxidation test of the test piece of the present invention for 16 hours, and the change in the thickness of the second layer film 3 under the oxide layer 4a. This shows the change in the Si concentration of FIG. After oxidation for 168 hours, the second layer maintains a Si concentration of 69%. Therefore, the first layer acts to prevent inward diffusion of Si in the second layer. It turns out that there is. Table 8 Comparative test specimens coated with Si alloy

 Comparison of oxide layer thickness before and after high-temperature oxidation test

 * 1: Total thickness of layer 4a and layer 4b in Fig. 3 (b)

 * 2: Total thickness of layer 4 b (20 | tm) and layer 4 c (100 / m) in Fig. 4 (b)

Also, 4 a oxide layer was S i 0 ₂ According to the X-ray diffraction. Furthermore, the oxides layer is maintained without change in the extreme thickness at the surface of the member, S i the concentration of the second layer S i - N b or concentration capable of expressing the S i 0 ₂ forming ability in the alloy It represents that.

On the other hand, Fig. 4 (b) schematically shows the state of the film after the 8-hour high-temperature oxidation test of the comparative test piece. Table 8 shows the change in oxide layer thickness before and after the high-temperature oxidation test. After the high-temperature oxidation test, the surface oxide layer (Si, Nb, 0) 4b and the lower oxide layer (Nb, 0) 4c were two layers. The thickness of this material reached 120 m, most of which (about lOOim) was a layer 4c consisting of Nb and 0, indicating that the Nb base alloy of the substrate was oxidized. ing. Industrial applicability

 As described above, according to the present invention, it has become possible to provide a heat-resistant material in which a coating having a large effect of suppressing high-temperature oxidation is formed on a base material surface of a niobium-based alloy. This oxidation-resistant coating is a self-repairing process that regenerates oxides by oxidizing A1 or Si in the second layer coating to maintain the function of blocking non-metallic elements such as oxygen and nitrogen in the atmosphere. In addition to having the function of (1), diffusion of elements is suppressed by the first layer film, so that the film hardly deteriorates even if it is kept at a high temperature of 110 to 1200 ° C or more for a long time. Excellent in oxidation resistance and durability.

 Therefore, this heat-resistant material is suitable as a structural member for a gas turbine blade engine, a rocket engine, and the like. In addition, since these members can be used without cooling, it is possible to contribute to improvement of thermal efficiency and simplification of a device structure.

Claims

The scope of the claims 1. A first layer alloy film composed of Re and at least two other metal elements is formed on the surface of a niobium-based alloy substrate, and the surface is coated with one of A 1 and S i. A heat-resistant material of a niobium-based alloy on which a second alloy film made of at least one other metal element is formed. 2. The composition of the alloy film of the first layer is substantially formula R e _b M _a R _b (where, M is one or more source selected from the group consisting of C r N i and A 1 And R is one or more elements selected from the group consisting of Nb, Mo, W, Hf, Zr, and C, and a and b are the atomic ratios of M and R, respectively. a it shall be, and the composition of the alloy film of the second layer, _C a 1 substantially have the general formula Q. 2. The heat-resistant material according to claim 1, wherein Q is at least one element of Cr and Ni, and c is an atomic ratio of A 1.  3. The atomic ratio a is not less than 0.01, the atomic ratio b is not more than 0.95 & +1), and the atomic ratio c is not more than 0.050. 3. The heat-resistant material according to claim 2, which is 95.  The niobium-based alloy contains at least one of Mo and W and Cr at a pace of Nb, and optionally one of Si, HfZrC. An alloy containing the above, wherein the element M in the alloy film of the first layer contains at least Cr, and the element Q in the alloy film of the second layer is Cr or Cr and Ni. 4. The heat-resistant material according to claim 2 or 3.  5. The heat-resistant material according to claim 4, wherein the element M is mainly composed of Cr and contains a small amount of one or more of A 1 and Ni. 6. The niobium-based alloy is an intermetallic compound containing Nb and A1. 4. A heat-resistant material according to paragraph 2 or 3. 7. The composition of the alloy film of the first layer is substantially the general formula R e _{de de} T _d R _e (where T is one or more elements of Cr and Si, and R is N b , M o, W, H f, Z r and at least one element selected from the group consisting of C and d and e are the atomic ratios of ¹ , ¹ and R, respectively, and The composition of the alloy film of the second layer is substantially the general formula X! _{F Sif} (where X is one or more elements selected from the group consisting of Mo _: W and Nb, f The heat-resistant material according to claim 1, wherein the heat-resistant material is represented by the following formula: 8. The atomic ratio d is 0.10 or more, the atomic ratio e is 0.01 to 0 · 50, d + e force 0.95 or less, and the atomic ratio: f is 0.0. 8. The heat-resistant material according to claim 7, which has a value of 5 to 0.95.  9. The niobium-based alloy contains at least one of Mo and W and Si at a pace of Nb and, if necessary, of Cr, Hf, Zr, and G 9. The heat-resistant material according to claim 7, wherein the alloy is an alloy containing at least one element, and wherein the element T in the alloy film of the first layer is Si.  10. The heat-resistant material according to claim 9, wherein the element X in the alloy film of the second layer is one or more of M 0 and W.