Superhard SiC compact protective layer on surface of refractory high-entropy alloy for hot-end component and preparation method of superhard SiC compact protective layer

Abstract

The invention discloses a superhard SiC compact protective layer on the surface of a refractory high-entropy alloy for a hot end component and a preparation method of the superhard SiC compact protective layer. The chemical expression of a refractory high-entropy alloy matrix is NBaHfbTicAldSie, and the chemical expression of the protective layer on the surface is (NBaHfbTicAldSie) x-(SiC) y, the method comprises the following steps: 1, smelting; 2, surface treatment after machining and cutting; 3, burying and pre-pressing by adopting the carbon powder subjected to flaky treatment; and 4, high-temperature thermal activation heating. According to the method, carbon powder burying and vacuum high-temperature thermal activation heating are combined, and a superhard SiC compact protective layer is grown in situ through carburization, so that the binding force between the protective layer and a refractory high-entropy alloy matrix is improved, and the hardness value of the refractory high-entropy alloy matrix is remarkably improved; the protective layer can protect the alloy in various extreme environments such as high-temperature gas scouring and corrosion, and the preparation process is simple, high in efficiency, low in cost and suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of heat-protective refractory metal materials, and in particular to a superhard SiC dense protective layer on the surface of a refractory high-entropy alloy for a hot end component and a preparation method thereof. Background Art

[0002] With the rapid development of technologies in aerospace, nuclear energy and other fields, the service conditions of hot end components are becoming increasingly harsh, such as ultra-high temperature and high pressure, oxidation, particle scouring, etc. Traditional refractory materials can no longer meet the performance requirements, which to a certain extent restricts the development of the aerospace field. As an emerging type of material, refractory high-entropy alloys have various characteristics of traditional alloys and refractory metals, such as high melting point and excellent processing performance. Therefore, they are considered to be a new type of material with great service potential under complex conditions of high temperature and high pressure. However, most refractory metal elements are not resistant to oxidation. Especially in high-temperature atmospheric environments, refractory high-entropy alloys often fail and become unstable due to harsh conditions such as oxidation and particle scouring, which greatly affects the safety and reliability of component service. Therefore, it is crucial to improve the surface hardness and oxidation resistance of refractory high-entropy alloys.

[0003] As a commonly used high-temperature coating protective material, SiC has excellent physical and chemical properties, such as high melting point, superhardness, corrosion resistance, and oxidation resistance. It has good anti-ablation performance in the temperature range of 1800℃~2000℃, so it has been widely used in aerospace and other fields. However, traditional SiC coating preparation methods generally include chemical vapor deposition, plasma spraying, chemical vapor reaction, etc. (such as patents CN114525495A, CN116003164B, CN117604490A, etc.). Most of these methods rely on special equipment, which is not only complex in process and high in cost, but also has disadvantages such as poor bonding strength and non-dense coating. It is difficult to combine with refractory high-entropy alloys under high temperature and high pressure complex working conditions. Therefore, there is an urgent need for a superhard SiC dense protective layer on the surface of a refractory high-entropy alloy for hot end components and a preparation method thereof. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a superhard SiC dense protective layer on the surface of a refractory high entropy alloy for hot end components in view of the deficiencies of the above-mentioned prior art. The method combines a process of non-consumable arc melting, machining, surface treatment, carbon powder burying, and vacuum high-temperature thermal activation heating carburizing to prepare a superhard SiC dense protective layer by in-situ carburization growth on the surface of a refractory high entropy alloy substrate for hot end components, thereby improving the bonding strength between the protective layer and the refractory high entropy alloy substrate, significantly improving its hardness value, and solving the problems of complex SiC coating process, high cost, poor bonding strength, non-dense coating, and difficulty in industrial production.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a superhard SiC dense protective layer on the surface of a refractory high entropy alloy for a hot end component, characterized in that the chemical expression of the refractory high entropy alloy matrix is ​​Nb a Hf b Ti c Al d Si e The chemical expression of the surface protective layer is (Nb a Hf b Ti c Al d Si e ) x -(SiC) y , where a, b, c, d, and e represent the atomic molar ratios of the corresponding elements, and a:b:c:d:e=1.2~1.6:0.2~0.5:1.8~2.8:3~4:1.8~2.8, and x+y=1.

[0006] The above-mentioned superhard SiC dense protective layer on the surface of a refractory high entropy alloy for a hot end component is characterized in that the surface protective layer is located within a thickness range of 50 μm on the surface of the refractory high entropy alloy substrate, and x=0.1~0.3, y=0.7~0.9.

[0007] In addition, the present invention also discloses a method for preparing a superhard SiC dense protective layer on the surface of a refractory high entropy alloy for a hot end component as described above, characterized in that the method comprises the following steps: Step 1: clean Nb, Hf, Ti, Al, Si metal single substance raw materials are batched according to the designed composition of the target product, and then the batched metal single substance raw materials are alloyed by non-consumable arc melting to obtain an alloy ingot; Step 2: Cutting the alloy ingot obtained in step 1 into a regular cubic shape, and then performing surface treatment to remove the surface oxide scale to obtain a refractory high entropy alloy matrix; Step 3: flake the carbon powder, then put the refractory high entropy alloy matrix obtained in step 2 into a mold, bury it with the flake-treated carbon powder and perform pre-pressing; Step 4: Place the pre-pressed refractory high entropy alloy substrate in step 3 together with the mold into a vacuum furnace chamber for high-temperature thermal activation heating to obtain a dense ultra-hard SiC protective layer on the surface of the refractory high entropy alloy.

[0008] The above-mentioned preparation method is characterized in that the mass purity of the Nb, Hf, Ti, Al, and Si metal single substance raw materials described in step 1 is not less than 99.9%.

[0009] The above-mentioned preparation method is characterized in that, in the alloying process described in step 1, the low-melting-point Ti, Al, Si metal single substance raw materials and the high-melting-point Nb, Hf metal single substance raw materials are first melted into two ingots, and then melted together to obtain an alloy ingot. Considering that the melting points of different element raw materials are quite different, the ingots are melted separately to reduce the melting point difference, and then melted together to form an alloy ingot, thereby ensuring the accuracy of the composition of the alloy ingot, reducing the difficulty of melting, and making the process more reasonable.

[0010] The above-mentioned preparation method is characterized in that the surface treatment in step 2 includes mechanical polishing and acetone cleaning and degreasing.

[0011] The above-mentioned preparation method is characterized in that the average particle size of the carbon powder in step three is 50 μm, and a ball mill is used for flaking. During the flaking process of the ball mill, the mass ratio of stainless steel grinding balls to carbon powder is 10:1, the diameter of the stainless steel grinding balls is 8 mm, the ball milling time is 6 hours, the ball milling speed is 400 r / min, and the ball mill stops for 5 minutes every 40 minutes of work, and the process control agent in the ball milling is anhydrous ethanol.

[0012] The above-mentioned preparation method is characterized in that in step 3, the refractory high entropy alloy matrix is ​​placed at the center of the carbon powder after the flaking treatment, and the pre-pressing pressure is 100MPa~400MPa. By controlling the placement position of the refractory high entropy alloy matrix, the subsequent carburizing uniformity is improved, and the refractory high entropy alloy matrix is ​​prevented from contacting the bottom of the mold and failing to fully contact the carbon powder, thereby failing to produce a high-temperature diffusion process of carburization.

[0013] The above-mentioned preparation method is characterized in that the vacuum degree of the vacuum furnace chamber in step 4 is 10 -4 Pa level.

[0014] The above-mentioned preparation method is characterized in that the high-temperature thermal activation heating system described in step 4 is: firstly heat up to 1800℃~2000℃ at a rate of 5℃ / min~10℃ / min and keep warm for 10min~30min, then slowly cool down to 1400℃ at a rate not higher than 2℃ / min and keep warm for 2h~6h, and cool with the furnace. By quickly raising the temperature to 1800℃~2000℃, the adhesion between the carbon powder and the surface of the refractory high entropy alloy matrix is ​​effectively improved, and then the ultra-hard SiC dense protective layer is grown in situ by carburizing and diffusion at low temperature, which is beneficial to improve the bonding between the protective layer and the refractory high entropy alloy matrix.

[0015] Compared with the prior art, the present invention has the following advantages: 1. The present invention uses clean Nb, Hf, Ti, Al, and Si metal elements as raw materials, and utilizes a process combining non-consumable arc melting, machining, surface treatment, carbon powder embedding, and vacuum high-temperature thermal activation heating carburizing to carburize the surface of a refractory high-entropy alloy substrate for hot-end components to in-situ grow and prepare a superhard SiC dense protective layer, thereby improving the bonding force between the protective layer and the refractory high-entropy alloy substrate, and the protective layer is dense and not easy to fall off, and the hardness value is significantly improved, and the refractory high-entropy alloy for hot-end components can be protected in various extreme environments such as high-temperature gas scouring and corrosion; at the same time, the preparation process is simple, efficient, and low in cost, and is suitable for industrial production, thereby solving the problems of complex process, high cost, poor bonding force, non-dense coating, and difficulty in industrial production in preparing SiC coatings using traditional methods.

[0016] 2. Compared with spherical powder, the present invention controls the particle size and morphology of carbon powder through flaking treatment, increases the contact area between carbon powder and the surface of refractory high entropy alloy matrix, and thus improves the growth rate of superhard SiC dense protective layer.

[0017] 3. The thickness of the ultra-hard SiC dense protective layer prepared on the surface of the refractory high entropy alloy substrate in the present invention is about 50 μm, and the surface hardness exceeds 1000 Hv, which is more than twice the substrate hardness of 480 Hv. The dense SiC layer can not only isolate the oxidizing environment and prevent the refractory metal elements from failing due to oxidation in the high-temperature atmospheric environment, but also effectively improve the surface hardness of the refractory high entropy alloy and enhance the anti-erosion performance.

[0018] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The microscopic morphology and element distribution diagram of the ultra-hard SiC dense protective layer on the surface of the refractory high entropy alloy prepared in Example 1 of the present invention.

[0020] Figure 2 These are the morphology images, local morphology magnification images, and linear scanning results of C element distribution of the ultra-hard SiC dense protective layer on the surface of the refractory high entropy alloy prepared in Example 1 of the present invention.

[0021] Figure 3 X-ray diffraction patterns of the dense superhard SiC protective layer on the surface of the refractory high entropy alloy prepared in Example 1 of the present invention and the refractory high entropy alloy prepared in Comparative Example 1.

[0022] Figure 4 This is a graph showing the hardness results of the ultra-hard SiC dense protective layer on the surface of the refractory high entropy alloy prepared in Example 1 of the present invention and the refractory high entropy alloy prepared in Comparative Example 1. DETAILED DESCRIPTION

[0023] Example 1 The chemical expression of the refractory high entropy alloy matrix in the superhard SiC dense protective layer on the surface of the refractory high entropy alloy used for the hot end component of this embodiment is Nb 1.25 Hf 0.35 Ti 2.3 Al 3.7 Si 2.3 The chemical expression of the surface protective layer is (Nb 1.25 Hf 0.35 Ti 2.3 Al 3.7 Si 2.3 ) 0.1 -(SiC) 0.9 .

[0024] The method for preparing a superhard SiC dense protective layer on the surface of a refractory high entropy alloy for a hot end component in this embodiment comprises the following steps: Step 1: clean Nb, Hf, Ti, Al, Si metal single material raw materials with a purity of not less than 99.9% according to the designed composition of the target product Nb 1.25 Hf 0.35 Ti 2.3 Al 3.7 Si 2.3 The materials are prepared, and then the low-melting-point Ti, Al, Si metal single material raw materials and the high-melting-point Nb, Hf metal single material raw materials are melted into two ingots by non-consumable arc melting, and then the two ingots are melted together to obtain an alloy ingot; Step 2: The alloy ingot obtained in step 1 is processed and cut into a regular cubic shape, and then mechanically polished and cleaned with acetone to remove the surface oxide scale to obtain a refractory high entropy alloy matrix; Step 3: flake the carbon powder, and then put the refractory high entropy alloy matrix obtained in step 2 into a mold so that the refractory high entropy alloy matrix is ​​placed at the center of the flake-treated carbon powder, and the flake-treated carbon powder is used to bury it and pre-press it with a pressure of 400 MPa; The carbon powder has an average particle size of 50 μm and is processed into flakes by a ball mill. During the flake processing of the ball mill, the mass ratio of stainless steel grinding balls to carbon powder is 10:1, the diameter of the stainless steel grinding balls is 8 mm, the ball milling time is 6 h, the ball milling speed is 400 r / min, and the ball mill is rested for 5 min after working for 40 min. The process control agent in the ball milling is anhydrous ethanol, and the amount of anhydrous ethanol added is 40 mL; Step 4: Place the pre-pressed refractory high entropy alloy matrix and the mold in a vacuum furnace and evacuate to 10 -4Pa was subjected to high-temperature thermal activation heating, firstly the temperature was raised to 2000°C at a rate of 5°C / min and kept at this temperature for 30 min, then the temperature was slowly lowered to 1400°C at a rate not higher than 2°C / min and kept at this temperature for 6 h. Then the alloy was cooled in the furnace to obtain a dense protective layer of superhard SiC on the surface of the refractory high-entropy alloy.

[0025] The microstructure, element distribution, X-ray diffraction analysis, phase composition and hardness value of the superhard SiC dense protective layer on the surface of the refractory high entropy alloy prepared in this embodiment were tested. The results are as follows: Figure 1~Figure 4 shown.

[0026] Figure 1 The microscopic morphology and element distribution of the superhard SiC dense protective layer on the surface of the refractory high entropy alloy prepared in this embodiment are shown in FIG. Figure 1 It can be seen that after high-temperature thermal activation heating carburization, the surface of the refractory high-entropy alloy has a Si-rich protective layer with a thickness of about 50 μm, and the Si element in the surface layer is evenly and densely distributed.

[0027] Figure 2 The morphology of the superhard SiC dense protective layer on the surface of the refractory high entropy alloy prepared in this embodiment, the local morphology magnification and the linear scanning result of the C element distribution are shown in FIG. Figure 2 It can be seen that the C element is enriched within the 50 μm thickness range of the surface layer of the refractory high-entropy alloy, which corresponds to the enrichment of the Si element in the surface protective layer.

[0028] Will Figure 1 and Figure 2 It can be seen from the above that in this embodiment, a dense ultra-hard SiC protective layer is prepared on the surface of the refractory high entropy alloy.

[0029] Comparative Example 1 The difference between this comparative example and Example 1 is that the processes in step three and step four are not carried out, and the refractory high entropy alloy is prepared only through step one and step two.

[0030] Figure 3 The X-ray diffraction patterns of the dense superhard SiC protective layer on the surface of the refractory high entropy alloy prepared in Example 1 of the present invention and the refractory high entropy alloy prepared in Comparative Example 1 are shown in FIG. Figure 3 It can be seen that the main phase of the superhard SiC dense protective layer on the surface of the refractory high entropy alloy prepared in Example 1 is SiC, with a content of about 90%, and the chemical expression can be defined as (Nb 1.25 Hf 0.35 Ti 2.3 Al 3.7 Si 2.3 ) 0.1 -(SiC) 0.9 , while the refractory high entropy alloy prepared without carburization in Comparative Example 1 has a complex phase consisting of multiple phases (Ti5Si3 +Nb+Si+TiSi 2 +Al), does not contain SiC phase, which is opposite to SiC, the main phase of the surface layer in Example 1.

[0031] Figure 4 The hardness result diagram of the superhard SiC dense protective layer on the surface of the refractory high entropy alloy prepared in Example 1 of the present invention and the refractory high entropy alloy prepared in Comparative Example 1 is shown in FIG. Figure 4 It can be seen that the hardness of the refractory high entropy alloy prepared without carburization in Comparative Example 1 is only 480Hv~600Hv, while the hardness of the superhard SiC dense protective layer on the surface of the refractory high entropy alloy prepared in Example 1 exceeds 1000Hv, that is, (Nb 1.25 Hf 0.35 Ti 2.3 Al 3.7 Si 2.3 ) 0.1 -(SiC) 0.9 The hardness value is about Nb 1.25 Hf 0.35 Ti 2.3 Al 3.7 Si 2.3 Twice the base.

[0032] Example 2 The chemical expression of the refractory high entropy alloy matrix in the superhard SiC dense protective layer on the surface of the refractory high entropy alloy used for the hot end component of this embodiment is Nb 1.2 Hf 0.2 Ti 1.8 Al 3.0 Si 1.8 The chemical expression of the surface protective layer is (Nb 1.2 Hf 0.2 Ti 1.8 Al 3.0 Si 1.8 ) 0.15 -(SiC) 0.85 .

[0033] The method for preparing a superhard SiC dense protective layer on the surface of a refractory high entropy alloy for a hot end component in this embodiment comprises the following steps: Step 1: clean Nb, Hf, Ti, Al, Si metal single material raw materials with a purity of not less than 99.9% according to the designed composition of the target product Nb 1.2 Hf 0.2 Ti 1.8 Al 3.0 Si 1.8The materials are prepared, and then the low-melting-point Ti, Al, Si metal single material raw materials and the high-melting-point Nb, Hf metal single material raw materials are melted into two ingots by non-consumable arc melting, and then the two ingots are melted together to obtain an alloy ingot; Step 2: The alloy ingot obtained in step 1 is processed and cut into a regular cubic shape, and then mechanically polished and cleaned with acetone to remove the surface oxide scale to obtain a refractory high entropy alloy matrix; Step 3: flake the carbon powder, and then put the refractory high entropy alloy matrix obtained in step 2 into a mold so that the refractory high entropy alloy matrix is ​​placed at the center of the flake-treated carbon powder, and the flake-treated carbon powder is used to bury it and pre-press it with a pressure of 100 MPa; The carbon powder has an average particle size of 50 μm and is subjected to flaking treatment by a ball mill. During the flaking treatment by the ball mill, the mass ratio of stainless steel grinding balls to carbon powder is 10:1, the diameter of the stainless steel grinding balls is 8 mm, the ball milling time is 6 h, the ball milling speed is 400 r / min, and the ball mill is stopped for 5 min after working for 40 min. The process control agent in the ball milling is anhydrous ethanol, and the amount of anhydrous ethanol added is 40 mL; Step 4: Place the pre-pressed refractory high entropy alloy matrix and the mold in a vacuum furnace and evacuate to 10 -4 Pa was subjected to high-temperature thermal activation heating, firstly the temperature was raised to 2000°C at a rate of 10°C / min and kept for 10 min, then the temperature was slowly lowered to 1400°C at a rate not higher than 2°C / min and kept for 2 h. Then the furnace was cooled to obtain a superhard SiC dense protective layer on the surface of the refractory high entropy alloy.

[0034] After testing, it was found that the main phase of the ultra-hard SiC dense protective layer on the surface of the refractory high entropy alloy prepared in this embodiment was SiC, the Si element was evenly and densely distributed, and the hardness value of the protective layer was 1010Hv.

[0035] Example 3 The chemical expression of the refractory high entropy alloy matrix in the superhard SiC dense protective layer on the surface of the refractory high entropy alloy used for the hot end component of this embodiment is Nb 1.5 Hf 0.35 Ti 2.0 Al 3.5 Si 2.0 The chemical expression of the surface protective layer is (Nb 1.5 Hf 0.35 Ti 2.0 Al 3.5 Si 2.0 ) 0.2 -(SiC) 0.8 .

[0036] The method for preparing a superhard SiC dense protective layer on the surface of a refractory high entropy alloy for a hot end component in this embodiment comprises the following steps: Step 1: clean Nb, Hf, Ti, Al, Si metal single material raw materials with a purity of not less than 99.9% according to the designed composition of the target product Nb 1.5 Hf 0.35 Ti 2.0 Al 3.5 Si 2.0 The materials are prepared, and then the low-melting-point Ti, Al, Si metal single material raw materials and the high-melting-point Nb, Hf metal single material raw materials are melted into two ingots by non-consumable arc melting, and then the two ingots are melted together to obtain an alloy ingot; Step 2: The alloy ingot obtained in step 1 is processed and cut into a regular cubic shape, and then mechanically polished and cleaned with acetone to remove the surface oxide scale to obtain a refractory high entropy alloy matrix; Step 3: flake the carbon powder, and then put the refractory high entropy alloy matrix obtained in step 2 into a mold so that the refractory high entropy alloy matrix is ​​placed at the center of the flake-treated carbon powder, and the flake-treated carbon powder is used to bury it and pre-press it with a pressure of 100 MPa; The carbon powder has an average particle size of 50 μm and is processed into flakes by a ball mill. During the flake processing of the ball mill, the mass ratio of stainless steel grinding balls to carbon powder is 10:1, the diameter of the stainless steel grinding balls is 8 mm, the ball milling time is 6 h, the ball milling speed is 400 r / min, and the ball mill is rested for 5 min after working for 40 min. The process control agent in the ball milling is anhydrous ethanol, and the amount of anhydrous ethanol added is 40 mL; Step 4: Place the pre-pressed refractory high entropy alloy matrix and the mold in a vacuum furnace and evacuate to 10 -4 Pa was subjected to high-temperature thermal activation heating, firstly the temperature was raised to 1800°C at a rate of 7°C / min and kept for 15 min, then the temperature was slowly lowered to 1400°C at a rate not higher than 2°C / min and kept for 3 h. After cooling with the furnace, a superhard SiC dense protective layer was obtained on the surface of the refractory high entropy alloy.

[0037] After testing, it was found that the main phase of the ultra-hard SiC dense protective layer on the surface of the refractory high entropy alloy prepared in this embodiment was SiC, the Si element was evenly and densely distributed, and the hardness value of the protective layer was 1000Hv.

[0038] Example 4 The chemical expression of the refractory high entropy alloy matrix in the superhard SiC dense protective layer on the surface of the refractory high entropy alloy used for the hot end component of this embodiment is Nb 1.4 Hf 0.4 Ti 2.0 Al 3.5 Si2.1 The chemical expression of the surface protective layer is (Nb 1.4 Hf 0.4 Ti 2.0 Al 3.5 Si 2.1 ) 0.1 -(SiC) 0.9 .

[0039] The method for preparing a superhard SiC dense protective layer on the surface of a refractory high entropy alloy for a hot end component in this embodiment comprises the following steps: Step 1: clean Nb, Hf, Ti, Al, Si metal single material raw materials with a purity of not less than 99.9% according to the designed composition of the target product Nb 1.4 Hf 0.4 Ti 2.0 Al 3.5 Si 2.1 The materials are prepared, and then the low-melting-point Ti, Al, Si metal single material raw materials and the high-melting-point Nb, Hf metal single material raw materials are melted into two ingots by non-consumable arc melting, and then the two ingots are melted together to obtain an alloy ingot; Step 2: The alloy ingot obtained in step 1 is processed and cut into a regular cubic shape, and then mechanically polished and cleaned with acetone to remove the surface oxide scale to obtain a refractory high entropy alloy matrix; Step 3: flake the carbon powder, and then put the refractory high entropy alloy matrix obtained in step 2 into a mold so that the refractory high entropy alloy matrix is ​​placed at the center of the flake-treated carbon powder, and the flake-treated carbon powder is used to bury it and pre-press it with a pressure of 300 MPa; The carbon powder has an average particle size of 50 μm and is processed into flakes by a ball mill. During the flake processing of the ball mill, the mass ratio of stainless steel grinding balls to carbon powder is 10:1, the diameter of the stainless steel grinding balls is 8 mm, the ball milling time is 6 h, the ball milling speed is 400 r / min, and the ball mill is rested for 5 min after working for 40 min. The process control agent in the ball milling is anhydrous ethanol, and the amount of anhydrous ethanol added is 40 mL; Step 4: Place the pre-pressed refractory high entropy alloy matrix and the mold in a vacuum furnace and evacuate to 10 -4 Pa was subjected to high-temperature thermal activation heating, firstly the temperature was raised to 1800°C at a rate of 6°C / min and kept for 12 min, then the temperature was slowly lowered to 1400°C at a rate not higher than 2°C / min and kept for 3 h. Then the furnace was cooled to obtain a superhard SiC dense protective layer on the surface of the refractory high-entropy alloy.

[0040] After testing, it was found that the main phase of the ultra-hard SiC dense protective layer on the surface of the refractory high entropy alloy prepared in this embodiment was SiC, the Si element was evenly and densely distributed, and the hardness value of the protective layer was 1005Hv.

[0041] Example 5 The chemical expression of the refractory high entropy alloy matrix in the superhard SiC dense protective layer on the surface of the refractory high entropy alloy used for the hot end component of this embodiment is Nb 1.4 Hf 0.4 Ti 2.0 Al 3.5 Si 2.6 The chemical expression of the surface protective layer is (Nb 1.4 Hf 0.4 Ti 2.0 Al 3.5 Si 2.6 ) 0.3 -(SiC) 0.7 .

[0042] The method for preparing a superhard SiC dense protective layer on the surface of a refractory high entropy alloy for a hot end component in this embodiment comprises the following steps: Step 1: clean Nb, Hf, Ti, Al, Si metal single material raw materials with a purity of not less than 99.9% according to the designed composition of the target product Nb 1.4 Hf 0.4 Ti 2.0 Al 3.5 Si 2.6 The materials are prepared, and then the low-melting-point Ti, Al, Si metal single material raw materials and the high-melting-point Nb, Hf metal single material raw materials are melted into two ingots by non-consumable arc melting, and then the two ingots are melted together to obtain an alloy ingot; Step 2: The alloy ingot obtained in step 1 is processed and cut into a regular cubic shape, and then mechanically polished and cleaned with acetone to remove the surface oxide scale to obtain a refractory high entropy alloy matrix; Step 3: flake the carbon powder, and then put the refractory high entropy alloy matrix obtained in step 2 into a mold so that the refractory high entropy alloy matrix is ​​placed at the center of the flake-treated carbon powder, and the flake-treated carbon powder is used to bury it and pre-press it with a pressure of 250 MPa; The carbon powder has an average particle size of 50 μm and is subjected to flaking treatment by a ball mill. During the flaking treatment by the ball mill, the mass ratio of stainless steel grinding balls to carbon powder is 10:1, the diameter of the stainless steel grinding balls is 8 mm, the ball milling time is 6 h, the ball milling speed is 400 r / min, and the ball mill is stopped for 5 min after working for 40 min. The process control agent in the ball milling is anhydrous ethanol, and the amount of anhydrous ethanol added is 40 mL; Step 4: Place the pre-pressed refractory high entropy alloy matrix and the mold in a vacuum furnace and evacuate to 10 -4 Pa was subjected to high-temperature thermal activation heating, firstly the temperature was raised to 1900°C at a rate of 8°C / min and kept at this temperature for 20 min, then the temperature was slowly lowered to 1400°C at a rate not higher than 2°C / min and kept at this temperature for 3.5 h. Then the alloy was cooled with the furnace to obtain a dense ultra-hard SiC protective layer on the surface of the refractory high-entropy alloy.

[0043] After testing, it was found that the main phase of the ultra-hard SiC dense protective layer on the surface of the refractory high entropy alloy prepared in this embodiment was SiC, the Si element was evenly and densely distributed, and the hardness value of the protective layer was 970Hv.

[0044] Example 6 The chemical expression of the refractory high entropy alloy matrix in the superhard SiC dense protective layer on the surface of the refractory high entropy alloy used for the hot end component of this embodiment is Nb 1.2 Hf 0.2 Ti 2.0 Al 3.1 Si 2.8 The chemical expression of the surface protective layer is (Nb 1.2 Hf 0.2 Ti 2.0 Al 3.1 Si 2.8 ) 0.25 -(SiC) 0.75 .

[0045] The method for preparing a superhard SiC dense protective layer on the surface of a refractory high entropy alloy for a hot end component in this embodiment comprises the following steps: Step 1: clean Nb, Hf, Ti, Al, Si metal single material raw materials with a purity of not less than 99.9% according to the designed composition of the target product Nb 1.2 Hf 0.2 Ti 2.0 Al 3.1 Si 2.8 The materials are prepared, and then the low-melting-point Ti, Al, Si metal single material raw materials and the high-melting-point Nb, Hf metal single material raw materials are melted into two ingots by non-consumable arc melting, and then the two ingots are melted together to obtain an alloy ingot; Step 2: The alloy ingot obtained in step 1 is processed and cut into a regular cubic shape, and then mechanically polished and cleaned with acetone to remove the surface oxide scale to obtain a refractory high entropy alloy matrix; Step 3: flake the carbon powder, and then put the refractory high entropy alloy matrix obtained in step 2 into a mold so that the refractory high entropy alloy matrix is ​​placed at the center of the flake-treated carbon powder, and the flake-treated carbon powder is used to bury it and pre-press it with a pressure of 350 MPa; The carbon powder has an average particle size of 50 μm and is subjected to flaking treatment by a ball mill. During the flaking treatment by the ball mill, the mass ratio of stainless steel grinding balls to carbon powder is 10:1, the diameter of the stainless steel grinding balls is 8 mm, the ball milling time is 6 h, the ball milling speed is 400 r / min, and the ball mill is stopped for 5 min after working for 40 min. The process control agent in the ball milling is anhydrous ethanol, and the amount of anhydrous ethanol added is 40 mL; Step 4: Place the pre-pressed refractory high entropy alloy matrix and the mold in a vacuum furnace and evacuate to 10 -4 Pa was subjected to high-temperature thermal activation heating, firstly the temperature was raised to 1800°C at a rate of 5°C / min and kept at this temperature for 25 min, then the temperature was slowly lowered to 1400°C at a rate not higher than 2°C / min and kept at this temperature for 6 h. Then the alloy was cooled with the furnace to obtain a dense ultra-hard SiC protective layer on the surface of the refractory high-entropy alloy.

[0046] After testing, it was found that the main phase of the ultra-hard SiC dense protective layer on the surface of the refractory high entropy alloy prepared in this embodiment was SiC, the Si element was evenly and densely distributed, and the hardness value of the protective layer was 960Hv.

[0047] Example 7 The chemical expression of the refractory high entropy alloy matrix in the superhard SiC dense protective layer on the surface of the refractory high entropy alloy used for the hot end component of this embodiment is Nb 1.6 Hf 0.5 Ti 2.8 Al 4 Si 2.8 The chemical expression of the surface protective layer is (Nb 1.6 Hf 0.5 Ti 2.8 Al 4 Si 2.8 ) 0.25 -(SiC) 0.75 .

[0048] The method for preparing a superhard SiC dense protective layer on the surface of a refractory high entropy alloy for a hot end component in this embodiment comprises the following steps: Step 1: clean Nb, Hf, Ti, Al, Si metal single material raw materials with a purity of not less than 99.9% according to the designed composition of the target product Nb 1.6 Hf 0.5 Ti 2.8 Al 4 Si 2.8 The materials are prepared, and then the low-melting-point Ti, Al, Si metal single material raw materials and the high-melting-point Nb, Hf metal single material raw materials are melted into two ingots by non-consumable arc melting, and then the two ingots are melted together to obtain an alloy ingot; Step 2: The alloy ingot obtained in step 1 is processed and cut into a regular cubic shape, and then mechanically polished and cleaned with acetone to remove the surface oxide scale to obtain a refractory high entropy alloy matrix; Step 3: flake the carbon powder, and then put the refractory high entropy alloy matrix obtained in step 2 into a mold so that the refractory high entropy alloy matrix is ​​placed at the center of the flake-treated carbon powder, and the flake-treated carbon powder is used to bury it and pre-press it with a pressure of 350 MPa; The carbon powder has an average particle size of 50 μm and is subjected to flaking treatment by a ball mill. During the flaking treatment by the ball mill, the mass ratio of stainless steel grinding balls to carbon powder is 10:1, the diameter of the stainless steel grinding balls is 8 mm, the ball milling time is 6 h, the ball milling speed is 400 r / min, and the ball mill is stopped for 5 min after working for 40 min. The process control agent in the ball milling is anhydrous ethanol, and the amount of anhydrous ethanol added is 40 mL; Step 4: Place the pre-pressed refractory high entropy alloy matrix and the mold in a vacuum furnace and evacuate to 10 -4 Pa was subjected to high-temperature thermal activation heating, firstly the temperature was raised to 1800°C at a rate of 5°C / min and kept at this temperature for 25 min, then the temperature was slowly lowered to 1400°C at a rate not higher than 2°C / min and kept at this temperature for 6 h. Then the alloy was cooled with the furnace to obtain a dense ultra-hard SiC protective layer on the surface of the refractory high-entropy alloy.

[0049] After testing, it was found that the main phase of the ultra-hard SiC dense protective layer on the surface of the refractory high entropy alloy prepared in this embodiment was SiC, the Si element was evenly and densely distributed, and the hardness value of the protective layer was 1000Hv.

[0050] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A superhard SiC dense protective layer on the surface of a refractory high entropy alloy for a hot end component, characterized in that: The chemical expression of the refractory high entropy alloy matrix is ​​Nb a Hf b Ti c Al d Si e The chemical expression of the surface protective layer is (Nb a Hf b Ti c Al d Si e ) x -(SiC) y , where a, b, c, d, and e represent the atomic molar ratios of the corresponding elements, and a:b:c:d:e=1.2~1.6:0.2~0.5:1.8~2.8:3~4:1.8~2.8, and x+y=1.

2. The superhard SiC dense protective layer on the surface of a refractory high entropy alloy for a hot end component according to claim 1, characterized in that: The surface protective layer is located within a 50 μm thickness range on the surface of the refractory high entropy alloy substrate, and x=0.1-0.3, y=0.7-0.

9.

3. A method for preparing a superhard SiC dense protective layer on the surface of a refractory high entropy alloy for a hot end component as claimed in claim 1 or 2, characterized in that: The method comprises the following steps: Step 1: clean Nb, Hf, Ti, Al, Si metal single substance raw materials are batched according to the designed composition of the target product, and then the batched metal single substance raw materials are alloyed by non-consumable arc melting to obtain an alloy ingot; Step 2: Cutting the alloy ingot obtained in step 1 into a regular cubic shape, and then performing surface treatment to remove the surface oxide scale to obtain a refractory high entropy alloy matrix; Step 3: flake the carbon powder, then put the refractory high entropy alloy matrix obtained in step 2 into a mold, bury it with the flake-treated carbon powder and perform pre-pressing; Step 4: Place the pre-pressed refractory high entropy alloy substrate in step 3 together with the mold into a vacuum furnace chamber for high-temperature thermal activation heating to obtain a dense ultra-hard SiC protective layer on the surface of the refractory high entropy alloy.

4. The preparation method according to claim 2, characterized in that: The mass purity of the Nb, Hf, Ti, Al, and Si metal single substance raw materials described in step 1 is not less than 99.9%.

5. The preparation method according to claim 2, characterized in that: In the alloying process described in step 1, low melting point Ti, Al, Si metal single substance raw materials and high melting point Nb, Hf metal single substance raw materials are first melted into two ingots, and then melted together to obtain an alloy ingot.

6. The preparation method according to claim 2, characterized in that: The surface treatment in step 2 includes mechanical polishing and acetone cleaning and degreasing.

7. The preparation method according to claim 2, characterized in that: The average particle size of the carbon powder in step three is 50 μm, and a ball mill is used for flaking. During the flaking process of the ball mill, the mass ratio of stainless steel grinding balls to carbon powder is 10:1, the diameter of the stainless steel grinding balls is 8 mm, the ball milling time is 6 h, the ball milling speed is 400 r / min, and the ball mill stops for 5 min after working for 40 min. The process control agent in the ball milling is anhydrous ethanol.

8. The preparation method according to claim 2, characterized in that: In step three, a refractory high entropy alloy substrate is placed at the center of the carbon powder after the flaking treatment, and the pre-pressing pressure is 100MPa~400MPa.

9. The preparation method according to claim 2, characterized in that: The vacuum degree of the vacuum furnace chamber in step 4 is 10 -4 Pa level.

10. The preparation method according to claim 2, characterized in that: The high temperature thermal activation heating system described in step 4 is: first increase the temperature to 1800℃~2000℃ at a rate of 5℃ / min~10℃ / min and keep it for 10min~30min, then slowly cool down to 1400℃ at a rate not higher than 2℃ / min and keep it for 2h~6h, and cool with the furnace.

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