A kind of Al-containing oxidation-resistant refractory high-entropy alloy powder and its preparation method and application in plasma spraying bonding layer

Abstract

The invention discloses an Al-containing anti-oxidation refractory high-entropy alloy powder, a preparation method thereof, and an application in a plasma spraying bonding layer, and belongs to the technical field of high-temperature metal materials. For AlCrTaMoTi (M) series refractory high-entropy alloys, the powder is prepared by adopting a process of arc alloying melting-hydrogenation treatment-mechanical crushing-dehydrogenation treatment-screening-plasma spheroidization, and the powder particle size is 18-150μm, with ultra-high sphericity, melting point ≥1900℃, and the obtained powder maintains a single-phase BCC structure, and can maintain element stability in a high-temperature oxidation environment of 1300℃. Then, a bonding layer and an overall thermal barrier coating are prepared by plasma spraying. The bonding layer has a thickness of 100-200μm, a porosity of <1%, and is well bonded to the substrate and the ceramic layer. It can prevent the diffusion of O elements during high-temperature oxidation at 1300℃, and has excellent anti-oxidation properties.

Description

Technical Field

[0001] The invention relates to the technical field of high-temperature protective materials, and in particular to an Al-containing oxidation-resistant refractory high-entropy alloy powder, a preparation method thereof, and an application thereof in a plasma spraying bonding layer. Background Art

[0002] Thermal barrier coatings (TBC) have been widely used on the surfaces of high-temperature components in high-temperature fields such as aerospace to protect high-temperature metal components (reducing the actual working temperature of high-temperature alloys and preventing alloy oxidation). The thermal barrier coating structure is a complex multilayer coating structure, which includes a ceramic top layer with low thermal conductivity (mainly for thermal insulation), a metal bonding layer for anti-oxidation (the bonding layer must have a suitable thermal expansion coefficient and good oxidation resistance, the purpose is to effectively alleviate the thermal mismatch problem between the ceramic layer and the metal substrate and protect the metal substrate from oxidation) and an oxide layer (TGO) grown between the ceramic layer and the bonding layer. At present, the most common thermal barrier coating is 6%-8% by mass yttria partially stabilized zirconia (6-8YSZ), and the most commonly used and most typical metal bonding layers are MCrAIY (M can be Co, Ni or Co+Ni) and (Pt,Ni)-Al. These two materials have good oxidation resistance and corrosion resistance and can better protect high-temperature alloys. However, the traditional MCrAlY bonding layer can guarantee excellent oxidation resistance below 1050℃, but at 1100℃ or higher, there will be three key problems: poor oxidation resistance, fast interdiffusion between bonding layer and substrate, and insufficient high temperature strength. Therefore, finding a new high temperature resistant metal bonding layer has become a problem that must be solved.

[0003] Refractory high entropy alloys are mainly composed of elements such as Hf, Nb, Ta, Ti, Zr, V, Cr, Mo, and W, which makes refractory high entropy alloys essentially have high melting points and excellent high-temperature strength characteristics, becoming a potential new type of high-temperature protective bonding layer material. However, the oxidation resistance of refractory high entropy alloys is poor. Therefore, adding Al elements to the refractory high entropy alloy system to improve its oxidation resistance has become a prerequisite for its application. However, as a low-density, low-melting-point element, adding a large amount of Al to the refractory high entropy alloy system can easily cause problems such as element segregation, burning, and alloy brittleness. This makes it impossible to prepare Al-containing refractory high entropy alloys by gas atomization to obtain powder, and only the traditional ball milling method can be used, which will inevitably introduce impurities, and the sphericity is poor, the batch output is small, and it is impossible to obtain a refractory high entropy alloy bonding layer with excellent performance. Summary of the invention

[0004] Aiming at the problem that Al-containing oxidation-resistant refractory high-entropy alloy powder is difficult to prepare and apply, the purpose of the present invention is to provide an Al-containing oxidation-resistant refractory high-entropy alloy powder and its preparation method and application in plasma spraying bonding layer. For AlCrTaMoTi (M) series refractory high-entropy alloys, the powder is prepared by arc alloying melting-hydrogenation treatment-mechanical crushing-dehydrogenation treatment-screening-plasma spheroidization process, and the powder particle size is 18-150μm, with ultra-high sphericity, melting point ≥1900℃, the powder maintains a single-phase BCC structure, and can maintain element stability in a high-temperature oxidation environment of 1300℃. Then, the bonding layer and the overall thermal barrier coating are prepared by plasma spraying. The bonding layer has a thickness of 100-200μm, a porosity of <1%, good bonding with the substrate and the ceramic layer, and can prevent the diffusion of O elements during high-temperature oxidation at 1300℃, and has excellent oxidation resistance. The present invention solves the problems of impurity introduction and low sphericity in the preparation of refractory high entropy alloy powders containing low melting point or low density elements such as Al and Ti, and produces a refractory high entropy alloy bonding layer and an overall thermal barrier coating, providing important guidance for the high-temperature protection application of refractory high entropy alloys.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A kind of Al-containing oxidation-resistant refractory high-entropy alloy powder, characterized in that: the refractory high-entropy alloy is composed of 5 or 6 elements in equiatomic ratio, the chemical formula expressed in atomic percentage is AlCrTaMoTi or AlCrTaMoTiM, and the M element is one of Hf, Nb, Zr, W and Si.

[0007] The refractory high entropy alloy powder has a particle size of 18-150 μm, a sphericity of more than 90%, and a melting point of more than 1900° C.

[0008] The refractory high entropy alloy powder has a single-phase BCC structure and has good oxidation resistance at a high temperature of 1300°C.

[0009] The preparation method of the Al-containing oxidation-resistant refractory high-entropy alloy powder adopts a process of arc alloying smelting-hydrogenation treatment-mechanical crushing-dehydrogenation treatment-screening-plasma spheroidization, and specifically includes the following steps:

[0010] (1) raw materials are proportioned according to the chemical expression of the refractory high entropy alloy, and alloying is performed in a vacuum arc melting furnace, wherein high melting point and high density elements are first melted, low melting point and low density elements are then melted, and alloying is performed finally, thereby finally obtaining a refractory high entropy alloy master alloy ingot;

[0011] (2) hydrogenating the refractory high entropy alloy master alloy ingot obtained in step (1), performing vacuum hydrogenation treatment in a hydrogenation dehydrogenation furnace, and selecting a hydrogenation temperature of 250 to 300° C. After hydrogenation, taking out the master alloy ingot and mechanically crushing it;

[0012] (3) The primary crushed material obtained by mechanical crushing in step (2) is subjected to dehydrogenation treatment in a hydrogenation dehydrogenation furnace, and the temperature of the hydrogenation dehydrogenation furnace is set at 650-750° C. and maintained for 3 hours; then the crushed material is taken out for secondary crushing, and the crushed material after secondary crushing is sieved, and the size of the obtained polygonal irregular shaped particles after crushing should be between 18 and 150 μm;

[0013] (4) The 18-150 μm polygonal irregular shaped particles obtained in step (3) are subjected to radio frequency plasma spheroidization and powdering, and the selected power should be 50-70 kW to obtain the Al-containing oxidation-resistant refractory high entropy alloy powder.

[0014] The Al-containing oxidation-resistant refractory high-entropy alloy powder is used for preparing a bonding layer by plasma spraying.

[0015] The process of preparing the bonding layer is as follows: sieving the powder with a particle size of 18-150 μm, selecting 18-53 μm refractory high entropy alloy powder for plasma spraying, selecting the spraying distance to be 180-240 mm, the spray gun moving speed to be 1000-1500 mm / s, the voltage to be 180-200 V, the current to be 200-250 A, and the powder feeding rate to be 70-80 g / min.

[0016] The bonding layer is prepared between the substrate and the ceramic layer, and the ceramic layer is Y2O3-stabilized ZrO2 (6-8YSZ).

[0017] The bonding layer has a thickness of 100 to 200 μm and a porosity of less than 1%. It is well bonded to the substrate and the ceramic layer, and can prevent the diffusion of O elements during high-temperature oxidation at 1300° C., thereby protecting the substrate and providing the overall thermal barrier coating with excellent anti-oxidation properties.

[0018] The advantages and beneficial effects of the present invention are as follows:

[0019] 1. The present invention aims at Al-containing oxidation-resistant refractory high-entropy alloys, and adopts an appropriate preparation method to obtain a powder material with good performance. The powder particle size is 18 to 150 μm, has ultra-high sphericity, and a melting point of ≥1900°C. The obtained powder maintains a single-phase BCC structure and can maintain element stability in a high-temperature oxidation environment of 1300°C.

[0020] 2. The Al-containing oxidation-resistant refractory high-entropy alloy powder prepared by the method of the present invention obtains a refractory high-entropy alloy bonding layer through a plasma spraying method. The thickness is 100-200 μm, the porosity is less than 1%, and it is well bonded with the substrate and the ceramic layer. It can hinder the diffusion of O elements during high-temperature oxidation at 1300°C, protect the substrate, and enable the overall thermal barrier coating to have excellent oxidation resistance.

[0021] 3. The present invention solves the problems of impurity introduction and low sphericity in the preparation of refractory high entropy alloy powders containing low melting point or low density elements such as Al and Ti, and produces a refractory high entropy alloy bonding layer and an overall thermal barrier coating, providing important guidance for the high-temperature protection application of refractory high entropy alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Surface morphology of the Al-containing refractory high-entropy master alloy ingot prepared by arc alloying in Example 1 of the present invention; in the figure, (a) is the plane of the alloy ingot; (b) is the arc surface of the alloy ingot.

[0023] Figure 2 The polygonal irregular shaped particles are obtained by mechanical crushing after hydrogenation and dehydrogenation treatment in Example 1 of the present invention. After screening, the particle size range is 18 to 150 μm. In the figure, (a) is the particle morphology; (b) is a high-magnification image of (a).

[0024] Figure 3 It is a spherical powder of Al-containing refractory high entropy alloy obtained by plasma spheroidization in Example 1 of the present invention; in the figure: (a) is the morphology observation of the powder; (b) is a high-magnification image of (a); (c) is a high-magnification image of (b); (d) is a high-magnification image of (c).

[0025] Figure 4 This is the XRD analysis spectrum of the Al-containing refractory high entropy alloy powder prepared in Example 1 of the present invention.

[0026] Figure 5 This is an EDS analysis spectrum of element distribution and diffusion of the Al-containing refractory high entropy alloy powder prepared in Example 1 of the present invention in a high-temperature oxidation environment of 1300°C.

[0027] Figure 6 This is the EDS analysis spectrum of the oxide film elements of the Al-containing refractory high entropy alloy powder prepared in Example 1 of the present invention in a high-temperature oxidation environment of 1300°C.

[0028] Figure 7 The surface morphology of the Al-containing refractory high entropy alloy bonding layer and the overall thermal barrier coating prepared in Example 1 of the present invention; in the figure: No. 1 and No. 2 are plasma sprayed single-layer Al-containing refractory high entropy alloy samples; No. 3 and No. 4 are plasma sprayed overall thermal barrier coating samples (containing Al refractory high entropy alloy as bonding layer).

[0029] Figure 8 The cross-sectional morphology and interface of the Al-containing refractory high entropy alloy bonding layer and the overall thermal barrier coating prepared in Example 1 of the present invention; in the figure: (a) is the cross-sectional morphology of a plasma-sprayed single-layer Al-containing refractory high entropy alloy; (b) is the cross-sectional morphology of the plasma-sprayed overall thermal barrier coating; (c) is the interface observation between the Al-containing refractory high entropy alloy bonding layer and the outermost layer of the ceramic.

[0030] Fig. 9 This is a microscopic morphology and pore observation diagram of the Al-containing refractory high entropy alloy bonding layer prepared in Example 1 of the present invention.

[0031] Fig.10 This is the EDS distribution spectrum of the element distribution of the integral thermal barrier coating prepared in Example 1 of the present invention after high-temperature oxidation at 1300°C.

[0032] Fig.11 The figure shows the morphology of the Al-containing refractory high entropy alloy powder prepared in the comparative example of the present invention. DETAILED DESCRIPTION

[0033] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0034] Embodiment 1:

[0035] The present embodiment is a method for preparing Al-containing anti-oxidation refractory high-entropy alloy powder and its application in plasma spraying bonding layer. The refractory high-entropy alloy should be composed of 5-6 elements in equiatomic proportions, and the atomic percentage formula should be AlCrTaMoTi(M). The M element can be any one of Hf, Nb, Zr, W, and Si. It is prepared by adopting the process of arc alloying melting-hydrogenation treatment-mechanical crushing-dehydrogenation treatment-screening-plasma spheroidization. First, the raw materials are proportioned according to the chemical expression of the refractory high-entropy alloy, and alloying melting is carried out in a vacuum arc melting furnace. The high melting point and high density elements and the low melting point and low density elements are melted separately, and finally alloyed to obtain an Al-containing refractory high-entropy alloy ingot, whose surface morphology is as follows Figure 1 As shown, it can be seen that the surface of the master alloy ingot has no obvious oxidation and presents a metallic luster; the obtained refractory high entropy alloy master alloy ingot is then subjected to hydrogenation and dehydrogenation and mechanical crushing to obtain polygonal irregular shaped particles, and the particles with a size ranging from 18 to 150 μm are sieved, and the size and morphology of the particles are observed as shown in FIG. Figure 2 As shown, it can be clearly seen that the maximum particle size in the field of view does not exceed 150μm; then the polygonal irregular shaped particles in the size range of 18 to 150μm are subjected to radio frequency plasma spheroidization and powdering, and the power is selected to be 50 to 70kw. At this time, the Al-containing oxidation-resistant refractory high-entropy alloy powder obtained has excellent powder properties, a powder particle size of 18-150μm, and ultra-high sphericity, such as Figure 3As shown, and the melting point is ≥1900℃, the powder obtained maintains a single-phase BCC structure (see Figure 4 ), and has good anti-oxidation performance at 1300℃ high temperature environment, can maintain uniform distribution of elements and form a dense oxide film, such as Figure 5 and Figure 6 As shown. After obtaining the Al-containing oxidation-resistant refractory high-entropy alloy powder, the bonding layer is prepared by plasma spraying. First, the powder with a particle size of 18-150μm is screened, and the refractory high-entropy alloy powder with a particle size of 18-53μm is selected for plasma spraying preparation. The spraying distance is selected to be 180-240mm, the spray gun moving speed is 1000-1500mm / s, the voltage is 180-200V, the current is 200-250A, and the powder feeding rate is 70-80g / min. The surface of the Al-containing refractory high-entropy alloy coating obtained by this method melts evenly, as shown in FIG. Figure 7 For samples No. 1 and No. 2, the ceramic layer was selected as Y2O3-stabilized ZrO2 (6-8YSZ) and the overall thermal barrier coating was prepared. Figure 7 Samples No. 3 and No. 4 are integral thermal barrier coatings, and it can be clearly seen that the surface of the ceramic layer is melted evenly without obvious defects. Figure 8 The cross-sectional morphology and interface observation of the Al-containing refractory high entropy alloy bonding layer and the overall thermal barrier coating prepared in this embodiment are as follows: Figure 8 (a) is the cross-sectional morphology of a plasma sprayed single-layer Al-containing refractory high-entropy alloy. It can be seen that the interface between the substrate and the refractory high-entropy alloy coating is well bonded, with only a small amount of pores. Figure 8 (b) is the cross-sectional morphology of the plasma sprayed overall thermal barrier coating, from which it can be seen that the interface between the ceramic layer and the Al-containing refractory high entropy alloy bonding layer is well bonded; 8(c) is the interface observation between the Al-containing refractory high entropy alloy bonding layer and the ceramic outermost layer, from which it can be seen that there is no obvious mutual diffusion between the two. Fig. 9 The microscopic morphology analysis of the Al-containing refractory high entropy alloy bonding layer shows that the bonding layer has no obvious pores. The porosity of the coating calculated by image analysis is 0.6%, which is less than 1%. In order to verify the oxidation resistance of the Al-containing refractory high entropy alloy bonding layer and the overall thermal barrier coating, a high-temperature oxidation test of 1300°C was carried out on the coating. The element distribution results after oxidation are shown in the figure below. Fig.10 As shown in the figure, it can be clearly seen that under the hysteretic diffusion mechanism and antioxidant properties of the Al-containing refractory high entropy alloy coating, the O element is enriched in large quantities outside the bonding layer, and a very small amount enters the bonding layer. In addition, a Cr-rich area can be found at the interface between the bonding layer and the ceramic layer, which proves the antioxidant properties of the Al-containing refractory high entropy alloy bonding layer and its application potential as a high-temperature protective material.

[0036] Comparative Example 1:

[0037] Different from Example 1, the present comparative example selected polygonal irregular shaped particles with a size of <18 μm. After plasma spheroidization using the same process as Example 1, it was found that a large amount of powder agglomeration occurred, such as Fig.11 shown.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An Al-containing oxidation-resistant refractory high-entropy alloy powder, characterized in that: The refractory high entropy alloy is composed of six elements in equal atomic proportions, and the chemical formula expressed in atomic percentage is AlCrTaMoTiM, where the M element is one of Hf, Nb, Zr, W and Si; The refractory high entropy alloy powder has a particle size of 18-150 μm, a sphericity of more than 90%, and a melting point of ≥1900°C; The refractory high entropy alloy powder has a single-phase BCC structure and has good oxidation resistance at a high temperature of 1300°C.

2. The method for preparing the Al-containing oxidation-resistant refractory high entropy alloy powder according to claim 1, characterized in that: The method adopts the process of arc alloying melting-hydrogenation treatment-mechanical crushing-dehydrogenation treatment-screening-plasma spheroidization, which specifically includes the following steps: (1) The raw materials are proportioned according to the chemical expression of the refractory high entropy alloy, and alloying is performed in a vacuum arc melting furnace, wherein the high melting point and high density elements are first melted, and then the low melting point and low density elements are melted, and finally alloying is performed to finally obtain a refractory high entropy alloy master alloy ingot; (2) hydrogenating the refractory high entropy alloy master alloy ingot obtained in step (1), performing vacuum hydrogenation treatment in a hydrogenation dehydrogenation furnace, and selecting a hydrogenation temperature of 250-300° C. After hydrogenation, taking out the master alloy ingot and mechanically crushing it; (3) The primary crushed material obtained by mechanical crushing in step (2) is subjected to dehydrogenation treatment in a hydrogenation dehydrogenation furnace, and the temperature of the hydrogenation dehydrogenation furnace is set to 650-750°C and maintained for 3 hours; then the crushed material is taken out for secondary crushing, and the crushed material after secondary crushing is sieved, and the size of the obtained polygonal irregular shaped particles after crushing should be between 18 and 150 μm; (4) The 18-150 μm polygonal irregular shaped particles obtained in step (3) are subjected to radio frequency plasma spheroidization and powdering, and the selected power should be 50-70 kW, so as to obtain the Al-containing oxidation-resistant refractory high entropy alloy powder.

3. The use of the Al-containing oxidation-resistant refractory high entropy alloy powder in a plasma spraying bonding layer according to claim 1, characterized in that: The Al-containing oxidation-resistant refractory high-entropy alloy powder is used for preparing a bonding layer by plasma spraying.

4. The use of the Al-containing oxidation-resistant refractory high entropy alloy powder in a plasma spraying bonding layer according to claim 3, characterized in that: The process of preparing the bonding layer is as follows: sieving the powder with a particle size of 18-150 μm, selecting 18-53 μm refractory high entropy alloy powder for plasma spraying, selecting the spraying distance to be 180-240 mm, the spray gun moving speed to be 1000-1500 mm / s, the voltage to be 180-200 V, the current to be 200-250 A, and the powder feeding rate to be 70-80 g / min.

5. The use of the Al-containing oxidation-resistant refractory high entropy alloy powder in a plasma spraying bonding layer according to claim 3, characterized in that: The bonding layer is prepared between the substrate and the ceramic layer, and the ceramic layer is Y2O3-stabilized ZrO2 (6-8YSZ).

6. The use of the Al-containing oxidation-resistant refractory high entropy alloy powder in a plasma spraying bonding layer according to claim 3, characterized in that: The bonding layer has a thickness of 100-200 μm and a porosity of less than 1%. It is well bonded to the substrate and the ceramic layer, and can prevent the diffusion of O elements during high-temperature oxidation at 1300° C., thereby protecting the substrate and enabling the overall thermal barrier coating to have excellent anti-oxidation properties.

Images