阅读说明：本技术 一种耐高温氧化的AlCoCrFeNiSiY高熵合金及其制备方法 (AlCoCrFeNiSiY high-entropy alloy resistant to high-temperature oxidation and preparation method thereof ) 是由 古立建 李翔 *** 于 2020-06-03 设计创作，主要内容包括：本发明提出一种耐高温氧化的AlCoCrFeNiSiY高熵合金及其制备方法,本发明的AlCoCrFeNiSiY高熵合金对于传统NiCoCrAlY金属材料,通过使用增加合金元素种类Fe、Si,并在含量上做出显著调整,以获得一种抗氧化性强的高熵合金。相比于传统的NiCoCrAlY,本发明的AlCoCrFeNiSiY高熵合金在1150℃循环氧化条件下表现出更加优秀的抗高温氧化增重的性能。其氧化膜均匀致密,结合状态良好。因此,这种高熵合金有潜力在高温和氧化性的环境中作为结构材料应用。(The invention provides an AlCoCrFeNiSiY high-entropy alloy resistant to high-temperature oxidation and a preparation method thereof. Compared with the traditional NiCoCrAlY, the AlCoCrFeNiSiY high-entropy alloy shows more excellent high-temperature oxidation weight gain resistance under the condition of 1150 ℃ cyclic oxidation. The oxide film is uniform and compact, and the bonding state is good. Therefore, the high-entropy alloy has potential to be applied as a structural material in a high-temperature and oxidative environment.)

1. The high-entropy AlCoCrFeNiSiY alloy resistant to high-temperature oxidation is characterized in that the high-entropy AlCoCrFeNiSiY alloy is prepared by adding alloy element types Fe and Si into NiCoCrAlY.

2. The AlCoCrFeNiSiY high-entropy alloy resistant to high-temperature oxidation as claimed in claim 1, wherein the molar percentage content of each element in the AlCoCrFeNiSiY high-entropy alloy is as follows: 16.0-20.0% of Al, 12.0-18.0% of Co, 12.0-18.0% of Cr, 14.0-20.0% of Fe, 30-35% of Ni, 1.0-2.0% of Si and 0.2-0.4% of Y.

3. A method for preparing an alcocrfeniisiy high entropy alloy, which is used for preparing the alcocrfeniisiy high entropy alloy as claimed in any one of claims 1-2, and is characterized by comprising the following steps:

step 1: preparing a raw material and an intermediate alloy, and pretreating the raw material and the intermediate alloy; the raw materials comprise Al, Co, Cr, Fe and Ni; the intermediate alloy comprises FeSi and AlY;

step 2: weighing the raw materials and the intermediate alloy according to the mole percentage of the AlCoCrFeNiSiY high-entropy alloy;

and step 3: smelting the raw materials and the intermediate alloy; the method comprises the following steps:

step 3.1: sequentially placing the materials weighed in the step 2 in a water-cooled copper crucible from bottom to top according to the melting point from low to high; placing an oxygen-scavenging substance in the other crucible;

3.2, firstly, vacuumizing the water-cooled copper crucible to 5Pa by using a mechanical pump, then, starting a molecular pump, and continuously vacuumizing to 5 × 10^-3Charging inert gas under Pa to make the pressure in the furnace be 0.4-0.6 atm;

step 3.3: firstly, smelting deoxidization substances for 2-3 times, removing residual oxygen in the furnace as much as possible, then smelting a target alloy, turning over an initial melting alloy ingot after each smelting, continuing to smelt again, and repeating the smelting process for 3-5 times to ensure that the components are fully homogenized;

step 3.4: cooling the alloy along with the furnace to obtain a bowl-shaped ingot;

and 4, step 4: and carrying out heat treatment on the bowl-shaped cast ingot to further make the alloy uniform, and cooling to room temperature to obtain the AlCoCrFeNiSiY high-entropy alloy.

4. The preparation method of the AlCoCrFeNiSiY high-entropy alloy as claimed in claim 3, wherein in the step 1, the pretreatment comprises the steps of placing the raw material and the intermediate alloy in more than 99.5% of absolute ethyl alcohol for ultrasonic cleaning for 10 minutes, removing oil contamination impurities on the surface, and then soaking the surface in 20% of hydrochloric acid by mass fraction for 1min to remove surface oxides; placing pure Fe, pure Ni, pure Cr and Fe-Si and Al-Y intermediate alloy in a drying oven at 50 ℃ for drying;

the mass fractions of the elements of the FeSi intermediate alloy are as follows: 75% of Fe and 25% of Si; the mass fractions of the elements of the AlY intermediate alloy are as follows: 30% of Al and 30% of Y.

5. The method for preparing the AlCoCrFeNiSiY high-entropy alloy according to claim 3, wherein in the step 3, alloy smelting is performed by using a non-consumable vacuum tungsten electrode arc furnace;

the deoxidizing substance is a titanium block; the inert gas is argon.

6. The method for preparing the AlCoCrFeNiSiY high-entropy alloy as claimed in claim 3, wherein in the step 4, the heat treatment is homogenizing heat treatment of the bowl-shaped ingot at 1200 +/-30 ℃ for 6 hours.

Technical Field

The invention relates to the technical field of high-entropy alloys, in particular to a high-entropy alloy of AlCoCrFeNiSiY with high temperature oxidation resistance and a preparation method thereof.

Background

The thermal protection material has important application in the aspect of prolonging the service life of high-temperature components of industrial equipment. Taking the example of a thermal barrier coating, it is generally a two-layer coating consisting of a metallic bond coat and a ceramic layer deposited on a superalloy. The thermal barrier coating can block the heat transfer of high-temperature gas, slow down the oxidation and corrosion to the substrate and improve the service temperature of high-temperature alloy in the gas turbine. With increasing production requirements and technological advances, gas turbine pre-turbine temperatures continue to rise. The MCrAlY (M is Ni, Co) and (Ni, Pt) Al bonding layers applied to the thermal barrier coating have insufficient performance under a severe service environment, for example, the growth rate of the metal bonding layer oxide is accelerated to cause the thickness of the metal bonding layer to increase rapidly, the bonding of the metal layer and the ceramic layer interface is poor, and the spalling failure of the coating is caused. In addition, there are problems with aluminum depletion and degradation of the coating structure. Therefore, reasonable alloy components are adopted, and on the premise of keeping better mechanical property, the oxidation resistance of the alloy is improved, such as reduction of oxidation weight gain rate, and improvement of oxide flatness and bonding force, so that the method has very important significance. After the alloy composition is adjusted, the alloy can be used for protecting other types of high-temperature resistant materials.

Unlike conventional single element based alloys, multi-principal element high entropy alloys contain several high (often greater than 5% atomic fraction) levels of major alloying elements. The high entropy of mixing facilitates the generation of solid solutions rather than brittle intermetallics, expanding the range of choice and content of alloying elements. The atoms in the high-entropy alloy are often in disordered arrangement, and the structure of the high-entropy alloy is a simple face-centered cubic (FCC) or body-centered cubic (BCC) structure. The high-entropy alloy has strong solid solution strengthening and obvious grain refinement phenomena, has the characteristics of high strength, corrosion resistance, diffusion retardation and the like, and provides a new idea for improving the oxidation resistance of the alloy.

Disclosure of Invention

The invention aims to provide a high-entropy alloy of AlCoCrFeNiSiY with high-temperature oxidation resistance and a preparation method thereof, so that the high-entropy alloy of the invention has more excellent high-temperature oxidation weight gain resistance.

In order to achieve the purpose, the invention provides an AlCoCrFeNiSiY high-entropy alloy resistant to high-temperature oxidation, which is prepared by NiCoCrAlY interplanetary alloy element species Fe and Si.

Further, the AlCoCrFeNiSiY high-entropy alloy comprises the following elements in percentage by mole: 16.0-20.0% of Al16, 12.0-18.0% of Co12, 12.0-18.0% of Cr12, 14.0-20.0% of Fe14, 78-35% of Ni30, 1.0-2.0% of Si and 0.2-0.4% of Y.

The invention also provides a preparation method of the AlCoCrFeNiSiY high-entropy alloy, which comprises the following steps:

step 1: preparing a raw material and an intermediate alloy, and pretreating the raw material and the intermediate alloy; the raw materials comprise Al, Co, Cr, Fe and Ni; the intermediate alloy comprises FeSi and AlY;

step 2: weighing the raw materials and the intermediate alloy according to the mole percentage of the AlCoCrFeNiSiY high-entropy alloy;

and step 3: smelting the raw materials and the intermediate alloy; the method comprises the following steps:

step 3.1: sequentially placing the materials weighed in the step 2 in a water-cooled copper crucible from bottom to top according to the melting point from low to high; placing an oxygen-scavenging substance in the other crucible;

3.2, firstly, vacuumizing the water-cooled copper crucible to 5Pa by using a mechanical pump, then, starting a molecular pump, and continuously vacuumizing to 5 × 10^-3Charging inert gas under Pa to make the pressure in the furnace be 0.4-0.6 atm;

step 3.3: firstly, smelting deoxidization substances for 2-3 times, removing residual oxygen in the furnace as much as possible, then smelting a target alloy, turning over an initial melting alloy ingot after each smelting, continuing to smelt again, and repeating the smelting process for 3-5 times to ensure that the components are fully homogenized;

step 3.4: cooling the alloy along with the furnace to obtain a bowl-shaped ingot;

and 4, step 4: and carrying out heat treatment on the bowl-shaped cast ingot to further make the alloy uniform, and cooling to room temperature to obtain the AlCoCrFeNiSiY high-entropy alloy.

Further, in step 1, the pretreatment comprises the steps of placing the raw material and the intermediate alloy in absolute ethyl alcohol with the concentration of 99.5% or more for carrying out an ultra-treatment for 10 minutes to remove oil contamination impurities on the surface, and then soaking the raw material and the intermediate alloy in hydrochloric acid with the mass fraction of 20% for 1min to remove surface oxides; placing pure Fe, pure Ni, pure Cr and Fe-Si and Al-Y intermediate alloy in a drying oven at 50 ℃ for drying;

the mass fractions of the elements of the FeSi intermediate alloy are as follows: 75% of Fe and 25% of Si; the mass fractions of the elements of the AlY intermediate alloy are as follows: 30% of Al and 30% of Y.

Further, in step 3, alloy smelting is carried out by using a non-consumable vacuum tungsten electrode arc furnace;

the deoxidizing substance is a titanium block; the inert gas is argon.

Further, in step 4, the heat treatment is homogenizing heat treatment of the bowl-shaped ingot at 1200 +/-30 ℃ for 6 hours.

Compared with the prior art, the invention has the advantages that: compared with the traditional NiCoCrAlY metal material, the AlCoCrFeNiSiY high-entropy alloy of the invention increases the types of alloy elements Fe and Si by using and obviously adjusts the content so as to obtain the high-entropy alloy with strong oxidation resistance. The alloy provided by the invention is an alloy with unequal atomic ratio, but the alloy components have high mixed entropy and have the basic characteristics of the high-entropy alloy. The alloy is a BCC and FCC dual-phase structure, and the BCC structure has slightly high aluminum content, oxidation resistance and better high-temperature strength; the FCC phase gives consideration to the toughness and plasticity of the alloy, and the alloy performance is relatively balanced on the whole. Si and Y can improve the oxidation resistance of NiCoCrAl series alloy. Fe can ensure that the alloy still maintains high mixed entropy when the content of Si and Y is higher, and has no obvious complex precipitated phase. Si is added in the form of Fe-Si master alloy so that Si is fully alloyed. Y is added in the form of Al-Y intermediate alloy, so that the burning loss and volatilization of Y are reduced. Compared with NiCoCrAlY, the AlCoCrFeNiSiY high-entropy alloy shows more excellent high-temperature oxidation weight gain resistance under the condition of 1150 ℃ cyclic oxidation. The oxide film is uniform and compact, and the bonding state is good. Therefore, the high-entropy alloy has potential to be applied as a structural material in a high-temperature and oxidative environment.

Drawings

FIG. 1 is an XRD pattern of a high-entropy alloy prepared by smelting in step three of example 1;

FIG. 2 is a scanning electron microscope microstructure of a high-entropy alloy prepared by melting in step three of example 1;

FIG. 3 is a graph of the rate of weight gain of the sample of example 3 under cyclic oxidation conditions.

FIG. 4 is a cross-sectional view taken by a scanning electron microscope microstructure after oxidation of the high-entropy alloy after the fourth treatment of example 3;

FIG. 5 is a surface XRD pattern of the high-entropy alloy prepared by melting in step three of example 3 after cyclic oxidation;

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be further described below.