Pt modified AlCoCrFeNi system high-entropy alloy and preparation method and application thereof

Abstract

The invention relates to a Pt modified AlCoCrFeNi system high-entropy alloy as well as a preparation method and application thereof. The high-entropy alloy comprises five elements, namely Al, Co, Cr, Fe and Ni, and modified elements, the modified element comprises Pt; according to the atomic percentage content, 10 at% < = Al < = 20 at%, 10 at% < = Co < = 20 at%, 10 at% < = Cr < = 20 at%, 10 at% < = Fe < = 20 at%, 20 at% < = Ni < = 40 at%, and 1 at% < = Pt < = 5 at%. According to the high-entropy alloy material and the preparation method thereof, the AlCoCrFeNi alloy is modified through Pt, all the elements are compounded and synergistically play a role by regulating and controlling the content ratio of all the elements, and the prepared high-entropy alloy material has excellent mechanical performance and more excellent oxidation resistance in a high-temperature environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermal barrier coating materials, in particular to a preparation method and application of an alloy material for a thermal barrier coating metal bond layer material, and especially to a Pt modified AlCoCrFeNi system high-entropy alloy and a preparation method and application thereof. BACKGROUND

[0002] Aero-engines and gas turbines (referred to as "two machines") are important components of aerospace technology, are strategic industries related to national energy and national defense security, and are known as the "crown jewel of manufacturing industry". The "two machine" technology is also an important embodiment of the industrial technology level of a country. With the development of advanced aero-engine propulsion engines towards high thrust and long service life, the service temperature of the engine is increased, which means that the surface of the engine blade needs to withstand higher temperature. The currently known high-temperature alloy is a nickel-based alloy with a melting point of about 1100℃, which is widely used in aero-engine and gas turbine blades. In recent years, with the continuous development of new fighter aircraft and high-Mach number aircraft, the service temperature of the hot end components of the engine has exceeded the use limit of the nickel-based high-temperature alloy. By spraying a thermal barrier coating (TBCs) on the hot end metal components of the engine, the high-temperature gas can be greatly reduced when reaching the metal components, which not only protects the alloy substrate but also increases the upper limit of the gas temperature, thereby improving the thermal efficiency of the engine.

[0003] Thermal barrier coatings (TBCs) are an important heat-insulating and protective coating, which is deposited on the surface of a high-temperature resistant metal or superalloy, so that the high-temperature gas can be greatly reduced when reaching the metal components, thereby reducing the temperature of the substrate material and improving the working temperature and service life of the hot end components of the aero-engine and the thermal efficiency of the power system (engine, etc.).

[0004] The metal bond layer is considered to be a crucial layer in the thermal barrier coating system, which has a bridging effect and even determines the thermal stability and service life of the entire coating system. The metal bond layer mainly has the following effects: (1) during high-temperature oxidation, a continuous and dense α-Al2O3 oxygen barrier layer (TGO) is formed on the surface of the bond layer, thereby protecting the high-temperature alloy substrate from oxidation; (2) relieving the thermal mismatch phenomenon between the high-temperature alloy substrate and the ceramic top layer; (3) α-Al2O3 has excellent high-temperature thermal stability and will not react with the ceramic top layer, thereby ensuring good interfacial bonding strength. Pt-NiAl and MCrAlY are the two most commonly used bond layer materials, but they cannot protect the high-temperature alloy substrate well at temperatures above 1200℃.

[0005] Currently, Pt-NiAl bond coat is formed by electroplating Pt layer (≤10 pm) on the surface of nickel-based superalloy, followed by high-temperature diffusion and aluminizing process, and mainly divided into two types: inward diffusion type, which is formed by low-temperature high-activity aluminizing (700-850 °C), has unstable structure and contains brittle PtAl2 phase, and is prone to cracking and wrinkling; outward diffusion type, which is formed by high-temperature low-activity aluminizing (>1000 °C), has a single β-(Ni, Pt)Al phase structure, uniform composition and improved toughness, and is widely used in turbine blades of aero-engine. The addition of Pt significantly improves the performance of the coating, improves the oxidation resistance, promotes the growth of dense a-Al2O3 film, reduces the Al activity, inhibits the segregation of S element, reduces the interface cavity. It improves the high-temperature phase stability, stabilizes the β-NiAl phase, slows down the β→γ' phase transition rate, and delays the formation of surface wrinkles. It is beneficial to the co-doping of active elements, and the co-doping of Hf / Zr or Hf / Dy further reduces the oxidation rate and improves the thermal cycle life. However, there are still serious problems of element interdiffusion and oxidation layer wrinkling failure. Al diffuses to the substrate at high temperature, forming a secondary reaction zone (SRZ) and a brittle topological close-packed phase (TCP) on the substrate side, which seriously damages the mechanical properties of the substrate. Interface deformation: β→γ' phase transition accompanied by volume shrinkage, causing "wrinkles" on the surface of the coating, leading to the shedding of the ceramic layer. The limitation of Pt-NiAl (γ+γ') alloy avoids SRZ, but the low Al content (~20at.%) makes the oxidation film prone to generate harmful spinel phase, and is negatively affected by W / Mo / Ta elements in the substrate.

[0006] MCrAlY (M=Ni, Co, Ni / Co) is a cladding coating, independent of the substrate composition, and can be flexibly designed. The main component systems at present are: Ni-based (high-temperature oxidation resistance), Co-based (heat corrosion resistance), NiCo-based (balanced performance). High Al content is usually designed to increase Al content (>12wt.%) to promote the formation of continuous Al2O3-TGO and slow down the crack propagation at the YSZ / TGO interface. At the same time, surface modification treatment, laser treatment, sandblasting or adding "fast coating" (APS-MCrAlY layer) is used to increase the roughness and improve the adhesion of TGO. However, there are still problems. The mismatch stress of the coefficient of thermal expansion (CTE) occurs when the CTE difference between Al2O3 and MCrAlY (0.5-1.1%) causes interfacial tensile stress during cooling, which leads to TGO / MCrAlY interface cracking. And the β-NiAl→L10 martensitic transformation produces 0.7% strain, which aggravates the internal stress of the coating. And there is also the problem of SRZ. High Al coating aggravates the interdiffusion with the substrate, inducing SRZ, which requires the introduction of a sigma phase diffusion barrier layer, but increases the process complexity.

[0007] The main problems of the metal bonding layer material at present stage are: (1) Al element depletion and oxidation film failure The metal bonding layer material firstly needs to maintain sufficient Al supply. If the Al content of the metal bonding layer surface is too low, the alpha-Al2O3 layer cannot be formed, and other metal elements in the bonding layer will be oxidized to form brittle oxides without protection; (2) Interface peeling between the oxidation film and the bonding layer The thermal growth oxide (TGO) generated by the oxidation of the bonding layer is the main cause of the failure of the coating, and the accumulation of internal stress caused by the thickening of the TGO at high temperature, and the enrichment of S elements at the interface to form holes, and the thermal barrier coating is easily separated from the alpha-Al2O3 layer / bonding layer interface and fails; (3) Element interdiffusion and structure degradation The element interdiffusion between the bonding layer and the substrate is intensified at high temperature (such as Ni, Co diffusing to the substrate, Ti, Mo diffusing to the bonding layer), which further reduces the Al content in the bonding layer, and the matrix precipitates harmful phases (such as sigma phase), which weakens the mechanical properties.

[0008] In order to solve the problems of Al element depletion and oxidation film failure of the existing thermal barrier coating metal bonding layer in a long time high temperature environment, and the interface peeling between the oxidation film and the bonding layer, therefore, how to develop a new thermal barrier coating metal bonding layer material and its preparation method has become a problem to be solved at present. SUMMARY

[0009] In order to solve the above technical problems, the present application provides a Pt modified AlCoCrFeNi system high-entropy alloy and its preparation method and application. The high-entropy alloy of the present application uses Pt to modify the AlCoCrFeNi alloy, and the prepared high-entropy alloy material has excellent mechanical properties and more excellent oxidation resistance in high temperature environment, is a strong competitor of the next generation of new thermal barrier coating materials, and provides support for the development of advanced aero-engine to high thrust-to-weight ratio and long service life.

[0010] In order to achieve this purpose, the technical scheme adopted by the present application is as follows:

[0011] In a first aspect, the present application provides a Pt modified AlCoCrFeNi system high-entropy alloy, which comprises Al, Co, Cr, Fe, Ni and a modified element.

[0012] The modified element comprises Pt.

[0013] According to the atomic percentage, 10at%≤Al≤20at%, 10at%≤Co≤20at%, 10at%≤Cr≤20at%, 10at%≤Fe≤20at%, 20at%≤Ni≤40at%, and 1at%≤Pt≤5at%.

[0014] Among them, 10at%≤Al≤20at%, for example, can be 10at%, 11at%, 12at%, 13at%, 14at%, 15at%, 16at%, 17at%, 18at%, 19at%, or 20at; 10at%≤Co≤20at%, for example, can be 10at%, 11at%, 12at%, 13at%, 14at%, 15at%, 16at%, 17at%, 18at%, 19at%, or 20at; 10at%≤Cr≤20at%, for example, can be 10at%, 11at%, 12at%, 13at%, 14at%, 15at%, 16at%, 17at%, 18at%, or 19at%. Or 20at%, 10at%≤Fe≤20at%, for example, it can be 10at%, 11at%, 12at%, 13at%, 14at%, 15at%, 16at%, 17at%, 18at%, 19at% or 20at%, 20at%≤Ni≤40at%, for example, it can be 20at%, 22at%, 24at%, 26at%, 28at%, 30at%, 32at%, 34at%, 36at%, 38at% or 40at%, 1at%≤Pt≤5at%, for example, it can be 1at%, 1at%, 1at%, 1at% or 1at%, but it is not limited to the listed values. Other unlisted values ​​within the above range also apply.

[0015] In this invention, the high-entropy alloy uses five elements—Al, Co, Cr, Fe, and Ni—as the main elements, and Pt as the modifying element. When Pt is added to the AlCoCrFeNi high-entropy alloy system, Pt gradually replaces Ni in β-NiAl and γ-Ni3Al to form β′-(Ni,Pt)Al and γ′-(Ni,Pt)3Al, refining the Al-rich phase, promoting Al distribution, which is beneficial for the protective Al2O3 oxide layer and improving the oxidation resistance of the high-entropy alloy. In this invention, Pt modification of the high-entropy alloy can promote continuous and dense α-Al... The formation of the L2O3 film significantly improves the adhesion of the oxide film. The Pt-modified high-entropy alloy has a two-phase layered structure (B2 / Laves or BCC / FCC) that remains stable at high temperatures. Pt solid solution strengthening inhibits phase decomposition, and the multi-principal element design of the high-entropy alloy slows down the element diffusion rate and inhibits the interdiffusion of elements between the high-entropy alloy binder and the substrate. By controlling the content ratio of each element, the elements work synergistically to solve the problems of Al element depletion and oxide film failure in existing thermal barrier coating metal binders under long-term high-temperature conditions, as well as the interface peeling between the oxide film and the binder.

[0016] In a second aspect, the present invention provides a method for preparing the high-entropy alloy described in the first aspect, the method comprising the following steps:

[0017] (1) Weigh the raw materials according to the atomic ratio of the high-entropy alloy to obtain a mixture;

[0018] (2) The mixture described in step (1) is smelted or solidified in a vacuum or inert atmosphere by a metallurgical process to obtain a high-entropy alloy master alloy.

[0019] (3) Anneal the high-entropy alloy master alloy obtained in step (2) to obtain the high-entropy alloy.

[0020] The method for preparing the high-entropy alloy of the present invention involves melting or solidifying mixed raw materials under vacuum or inert atmosphere through metallurgical processes to obtain a high-entropy alloy master alloy, followed by annealing to obtain the high-entropy alloy. Under vacuum or inert atmosphere, element loss due to oxidation can be avoided, ensuring that the final alloy composition is consistent with the design ratio. Annealing removes internal stress and casting defects from the high-entropy alloy, ultimately yielding a high-entropy alloy that possesses both excellent mechanical properties and superior oxidation resistance in high-temperature environments.

[0021] As a preferred technical solution of the present invention, the raw materials in step (1) include elemental Al, Co, Cr, Fe, Ni, Pt or high-purity alloys containing at least two of the elements Al, Co, Cr, Fe, Ni, Pt, wherein typical but non-limiting combinations include: AlCo alloy, AlCr alloy, NiAl alloy, NiFe alloy.

[0022] Preferably, the purity of the raw material is ≥99.95%, for example, it can be 99.95%, 99.96%, 99.97%, 99.98%, or 99.99%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0023] Preferably, the raw material is in the form of powder, granules, or blocks.

[0024] As a preferred technical solution of the present invention, the system pressure P in the vacuum environment in step (2) is ≤1×10 -3 Pa, for example, could be 1×10 -3 Pa, 8×10 -4 Pa, 6×10 -4 Pa, 4×10 -4 Pa, 2×10 -4 Pa or 1×10 -4 Pa, etc., but not limited to the listed values; other unlisted values ​​within the above range also apply.

[0025] By further limiting the pressure inside the vacuum arc melting furnace, this invention can achieve both excellent mechanical properties and superior oxidation resistance in high-temperature environments.

[0026] Preferably, the metallurgical process in step (2) includes electrothermal metallurgy, powder metallurgy, or additive manufacturing.

[0027] Preferably, the electrothermal metallurgical process includes vacuum arc melting.

[0028] Preferably, the powder metallurgy process includes hot pressing.

[0029] Preferably, the additive manufacturing process includes 3D printing.

[0030] As a preferred technical solution of the present invention, the current of the vacuum arc melting is 280-300A, for example, it can be 280A, 285A, 290A, 295A or 300A, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0031] Preferably, the vacuum arc melting is performed 5-8 times, for example, 5, 6, 7 or 8 times.

[0032] This invention ensures high purity and high uniformity of high-entropy alloys by further limiting the number of vacuum arc melting cycles.

[0033] Preferably, the time for each vacuum arc melting is independently 2-3 minutes, for example, 2 minutes, 2.2 minutes, 2.4 minutes, 2.6 minutes, 2.8 minutes or 3 minutes, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0034] Preferably, the hot pressing temperature is 1200-1350℃, for example, it can be 1200℃, 1225℃, 1250℃, 1275℃, 1300℃, 1325℃ or 1350℃, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0035] Preferably, the pressure of the hot pressing is 20-30 MPa, for example, it can be 20 MPa, 22 MPa, 24 MPa, 26 MPa, 28 MPa or 30 MPa, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0036] Preferably, the heat preservation time for hot pressing is 30-90 minutes, for example, it can be 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes or 90 minutes, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0037] As a preferred technical solution of the present invention, the laser power of the 3D printing is 200-400W, for example, it can be 200W, 250W, 300W, 350W or 400W, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0038] Preferably, the scanning speed of the 3D printing is 600-1200 mm / s, for example, it can be 600 mm / s, 700 mm / s, 800 mm / s, 900 mm / s, 1000 mm / s, 1100 mm / s or 1200 mm / s, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0039] Preferably, the diameter of the 3D printed spot is 70-150μm, for example, it can be 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm or 150μm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0040] Preferably, the thickness of the 3D print is 20-50μm, for example, it can be 20μm, 25μm, 30μm, 35μm, 40μm, 45μm or 50μm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0041] Preferably, the oxygen content of the 3D printing is less than 100 ppm, for example, it can be 90 ppm, 80 ppm, 70 ppm, 60 ppm, 50 ppm, 40 ppm or 30 ppm, but it is not limited to the listed values, and other unlisted values ​​within the above range are also applicable. As a preferred technical solution of the present invention, the inert atmosphere in step (2) includes argon.

[0042] Preferably, the annealing temperature in step (3) is 1000-1200℃, for example, it can be 1000℃, 1050℃, 1100℃, 1150℃ or 1200℃, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0043] Preferably, the annealing time in step (3) is greater than 5 hours, for example, it can be 6 hours, 10 hours, 15 hours, 20 hours, 24 hours or 30 hours, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0044] Preferably, the annealing process in step (3) is carried out under an inert atmosphere.

[0045] As a preferred technical solution of the present invention, the preparation method further includes machining the high-entropy alloy obtained in step (3).

[0046] Preferably, the machining process includes preparing the high-entropy alloy obtained in step (3) into the required size by a metal cutting machine, and then performing grinding and polishing.

[0047] As a preferred technical solution of the present invention, the preparation method specifically includes the following steps:

[0048] (1) Weigh the raw materials according to the atomic ratio of the high-entropy alloy to obtain a mixture; wherein the raw materials include Al, Co, Cr, Fe, Ni, Pt elements or high-purity alloys containing at least two of Al, Co, Cr, Fe, Ni, Pt, the purity of the raw materials is ≥99.95%, and the shape of the raw materials includes powder, granules or blocks;

[0049] (2) The mixture obtained in step (1) is smelted or solidified under vacuum or inert atmosphere by metallurgical process to obtain a high-entropy alloy master alloy; wherein the system pressure P in the vacuum environment is ≤1×10 -3 Pa, the inert atmosphere includes argon, the metallurgical process includes electrothermal metallurgy, powder metallurgy, or additive manufacturing, the electrothermal metallurgy includes vacuum arc melting, the powder metallurgy includes hot pressing, the additive manufacturing process includes 3D printing, the current of the vacuum arc melting is 280-300A, the number of vacuum arc meltings is 5-8, the time of each vacuum arc melting is 2-3 minutes, the temperature of the hot pressing is 1200-1350℃, the pressure of the hot pressing is 20-30MPa, the holding time of the hot pressing is 30-90 minutes, the laser power of the 3D printing is 200-400W, the scanning speed of the 3D printing is 600-1200mm / s, the spot diameter of the 3D printing is 70-150μm, and the thickness of the 3D printing is 20-50μm;

[0050] (3) The high-entropy alloy master alloy described in step (2) is annealed at 1000-1200℃ for more than 5 hours. The annealing is carried out in an inert atmosphere. After that, it is prepared into the required size by a metal cutting machine and then polished to obtain the high-entropy alloy.

[0051] Thirdly, the present invention provides an application of the high-entropy alloy described in the first aspect, wherein the high-entropy alloy is applied in the field of thermal barrier coating materials technology.

[0052] Compared with the prior art, the present invention has at least the following beneficial effects:

[0053] (1) High temperature stability and excellent oxide film properties: The Pt modified high entropy alloy prepared by this invention has a room temperature yield strength ≥765MPa and an elongation ≥7%; it still maintains a yield strength ≥339MPa and an elongation ≥13% at 800℃. It can also maintain good phase stability after high temperature oxidation at 1200℃ and has good high temperature mechanical properties. The yield strength at 1200℃ is ≥85MPa and the elongation is ≥17%. It can generate a continuous and complete protective oxide layer. The mass change at 1200℃ is ≤3.41% and the corrosion area after 200h is ≤15.13%.

[0054] (2) Structure stability and element interdiffusion: The multi-principal element design of the high-entropy alloy slows down the element diffusion rate and inhibits the element interdiffusion between the high-entropy layer and the matrix. The coarsening rate of the matrix γ′ phase is less than 16.48%. Attached Figure Description

[0055] Figure 1 These are the XRD patterns of the samples from Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0056] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0057] Example 1

[0058] This embodiment provides a Pt-modified AlCoCrFeNi high-entropy alloy and its preparation method. The high-entropy alloy comprises the following components: Al: 16 at%, Co: 16 at%, Cr: 16 at%, Fe: 16 at%, Ni: 34 at%, and Pt: 2 at%.

[0059] The preparation method includes the following steps:

[0060] (1) Weigh out Al, Co, Cr, Fe, Ni and Pt elements with a purity of 99.99% according to the above atomic percentages to obtain a mixture;

[0061] (2) Place the mixed metal obtained in step (1) into a copper crucible in a vacuum arc melting furnace, and make the pressure inside the vacuum arc melting furnace reach 1×10 -3 Pa, then release high-purity argon into the furnace, and then prepare to start the arc to start melting the alloy. When the arc is started for the first time, the titanium ingot placed in the arc melting furnace is melted to remove the residual oxygen in the furnace. After the residual oxygen is fully absorbed, the arc is started again to melt the raw material alloy weighed and mixed in step (1) that was placed in the previous step. The selected arc melting current is 280A. After the alloy is melted and completely cooled, it is flipped over using a robotic arm. The alloy is melted 8 times to ensure the uniformity of the alloy ingot composition. Each melting time is 3 minutes. After the melting is completed, the alloy ingot is taken out to obtain the high-entropy alloy master alloy.

[0062] (3) The high-entropy alloy master alloy obtained in step (2) is placed in a vacuum tube furnace and annealed at 1200°C for 24 hours. High-purity argon is introduced throughout the process to remove oxygen. Then, it is prepared into the required size by a metal cutting machine and then polished to obtain the high-entropy alloy.

[0063] Depend on Figure 1 It can be seen that the high-entropy alloy obtained in Example 1 has a dual-phase structure with β-NiAl and γ-Ni3Al phases, i.e., BCC and FCC phases coexisting. The BCC and FCC phases reach equilibrium, which is beneficial to the balance between the strength and toughness of the high-entropy alloy and improves its high-temperature mechanical properties to a certain extent. In contrast, the alloy obtained in Comparative Example 1 shows a certain angular shift in 2θ, indicating that when Pt is added to the alloy as a modifying element, Pt will gradually replace Ni in β-NiAl and γ-Ni3Al to form β′-(Ni,Pt)Al and γ′-(Ni,Pt)3Al, which refines the Al-rich phase, promotes the distribution of Al, is beneficial to the protective Al2O3 oxide layer, and improves the oxidation resistance of the high-entropy alloy.

[0064] Example 2

[0065] This embodiment provides a Pt-modified AlCoCrFeNi high-entropy alloy and its preparation method. The high-entropy alloy comprises the following components: Al: 19.6 at%, Co: 19.6 at%, Cr: 19.6 at%, Fe: 19.6 at%, Ni: 19.6 at%, and Pt: 2 at%.

[0066] The preparation method includes the following steps:

[0067] (1) Weigh out Al, Co, Cr, Fe, Ni and Pt elements with a purity of 99.95% according to the above atomic percentages to obtain a mixture;

[0068] (2) Place the mixed metal obtained in step (1) into a copper crucible in a vacuum arc melting furnace, and make the pressure inside the vacuum arc melting furnace reach 8×10 -4 Pa, then release high-purity argon into the furnace, and then prepare to start the arc to start melting the alloy. When the arc is started for the first time, the titanium ingot placed in the arc melting furnace is melted to remove the residual oxygen in the furnace. After the residual oxygen is fully absorbed, the arc is started again to melt the raw material alloy weighed and mixed in step (1) that was placed in the previous step. The selected arc melting current is 2900A. After the alloy is melted and completely cooled, it is flipped over using a robotic arm. The alloy is melted 6 times to ensure the uniformity of the alloy ingot composition. Each melting time is 2 minutes. After the melting is completed, the alloy ingot is taken out to obtain the high-entropy alloy master alloy.

[0069] (3) The high-entropy alloy master alloy obtained in step (2) is placed in a vacuum tube furnace and annealed at 1000°C for 15 hours. High-purity argon is introduced throughout the process to remove oxygen. Then, it is prepared into the required size by a metal cutting machine and then polished to obtain the high-entropy alloy.

[0070] Example 3

[0071] This embodiment provides a Pt-modified AlCoCrFeNi high-entropy alloy and its preparation method. The high-entropy alloy comprises the following components: Al: 10 at%, Co: 10 at%, Cr: 20 at%, Fe: 15 at%, Ni: 40 at%, and Pt: 5 at%.

[0072] The preparation method includes the following steps:

[0073] (1) Weigh out Al, Co, Cr, Fe, Ni and Pt elements with a purity of 99.96% according to the above atomic percentages to obtain a mixture;

[0074] (2) Place the mixed metal obtained in step (1) into a copper crucible in a vacuum arc melting furnace, and make the pressure inside the vacuum arc melting furnace reach 6×10 -4 Pa, then release high-purity argon into the furnace, and then prepare to start the arc to start melting the alloy. When starting the arc for the first time, first melt the titanium ingot that was placed in the arc melting furnace to remove the residual oxygen in the furnace. After the residual oxygen is fully absorbed, start the arc again to melt the raw material alloy weighed and mixed in step (1) that was placed in the previous step. The selected arc melting current is 300A. After the alloy is melted and completely cooled, use a robotic arm to turn it over and repeat the alloy melting 5 times to ensure the uniformity of the alloy ingot composition. Each melting time is 3 minutes. After the melting is completed, take out the alloy ingot to obtain the high-entropy alloy master alloy.

[0075] (3) The high-entropy alloy master alloy obtained in step (2) is placed in a vacuum tube furnace and annealed at 1100°C for 6 hours. High-purity argon is introduced throughout the process to remove oxygen. Then, it is prepared into the required size by a metal cutting machine and then polished to obtain the high-entropy alloy.

[0076] Example 4

[0077] This embodiment provides a Pt-modified AlCoCrFeNi high-entropy alloy and its preparation method. The high-entropy alloy comprises the following components: Al: 20 at%, Co: 20 at%, Cr: 10 at%, Fe: 10 at%, Ni: 39 at%, and Pt: 1 at%.

[0078] The preparation method includes the following steps:

[0079] (1) Weigh out Al, Co, Cr, Fe, Ni and Pt elements with a purity of 99.97% according to the above atomic percentages to obtain a mixture;

[0080] (2) Place the mixed metal obtained in step (1) into a copper crucible in a vacuum arc melting furnace, and make the pressure inside the vacuum arc melting furnace reach 1×10 -3 Pa, then release high-purity argon into the furnace, and then prepare to start the arc to start melting the alloy. When the arc is started for the first time, the titanium ingot placed in the arc melting furnace is melted to remove the residual oxygen in the furnace. After the residual oxygen is fully absorbed, the arc is started again to melt the raw material alloy weighed and mixed in step (1) that was placed in the previous step. The selected arc melting current is 285A. After the alloy is melted and completely cooled, it is flipped over using a robotic arm. The alloy is melted 6 times to ensure the uniformity of the alloy ingot composition. Each melting time is 3 minutes. After the melting is completed, the alloy ingot is taken out to obtain the high-entropy alloy master alloy.

[0081] (3) The high-entropy alloy master alloy obtained in step (2) is placed in a vacuum tube furnace and annealed at 1000°C for 24 hours. High-purity argon is introduced throughout the process to remove oxygen. Then, it is prepared into the required size by a metal cutting machine and then polished to obtain the high-entropy alloy.

[0082] Example 5

[0083] This embodiment provides a Pt-modified AlCoCrFeNi high-entropy alloy and its preparation method. The high-entropy alloy comprises the following components: Al: 16 at%, Co: 16 at%, Cr: 16 at%, Fe: 16 at%, Ni: 34 at%, and Pt: 2 at%.

[0084] The preparation method is hot pressing molding, which includes the following steps: (1) weigh Al, Co, Cr, Fe, Ni and Pt elements with a purity of 99.99% according to the above atomic percentage to obtain a mixture; (2) use the hummingbird resonance mixing method to fully mix the mixture obtained in step (1);

[0085] (3) The uniformly mixed powder is loaded into a graphite mold for hot pressing. Before loading the powder, a layer of graphite paper is laid on the inner wall of the mold to prevent the powder from sticking to the mold and to facilitate subsequent demolding. The powder is filled in layers and compacted appropriately to reduce the initial porosity. After the mold is loaded, the mold is placed in a hot press furnace. The furnace atmosphere is controlled in a high-purity argon environment by repeatedly evacuating and filling the furnace with argon to effectively suppress high-temperature oxidation.

[0086] (4) During the hot pressing sintering process, the sample is heated to the predetermined sintering temperature at a rate of 5℃ / min; the sintering temperature is set to 1200℃; when the temperature approaches or reaches the target sintering temperature, unidirectional pressure is applied, the pressure range is usually 30MPa, and the sample is kept at this temperature and pressure for 90min to promote the diffusion bonding and pore closure between powder particles and achieve the densification of the alloy. The whole process is kept in a high-purity argon gas environment.

[0087] (5) After sintering, the sample is cooled in the furnace under pressure or slow pressure relief to slowly reduce the temperature to room temperature in order to avoid cracking caused by thermal stress. After the furnace temperature drops to room temperature, the sample is taken out and demolded to remove the surface graphite paper and any surface contamination that may be formed.

[0088] (6) The high-entropy alloy master alloy obtained in step (5) is placed in a vacuum tube furnace and annealed at 1200°C for 24 hours. High-purity argon is introduced throughout the process to remove oxygen. Then, it is prepared into the required size by a metal cutting machine and then polished to obtain the high-entropy alloy.

[0089] Example 6

[0090] This embodiment provides a Pt-modified AlCoCrFeNi high-entropy alloy and its preparation method. The high-entropy alloy comprises the following components: Al: 16 at%, Co: 16 at%, Cr: 16 at%, Fe: 16 at%, Ni: 34 at%, and Pt: 2 at%.

[0091] The preparation method is 3D printing, which includes the following steps:

[0092] (1) Weigh out Al, Co, Cr, Fe, Ni and Pt elements with a purity of 99.99% according to the above atomic percentages to obtain a mixture;

[0093] (2) High-purity argon gas is introduced into the forming cavity during the printing process as a protective atmosphere, and the oxygen content is strictly controlled at around 80ppm to suppress the oxidation and volatilization of Al elements in the high-temperature molten pool. The substrate is cleaned and preheated to an appropriate temperature before printing to improve forming stability and reduce residual stress.

[0094] (3) During the SLM forming process, the laser power is set to 300W, the scanning speed is controlled at 800mm / s, the spot diameter is 100μm, the layer thickness is 30μm, the island scanning strategy is adopted, and the adjacent layers are rotated 90° to reduce the heat accumulation effect and suppress the formation of cracks.

[0095] (4) After printing, the sample is cooled to room temperature in a protective atmosphere. Then, the sample is removed from the substrate by wire cutting and the support structure is removed.

[0096] (5) The high-entropy alloy master alloy obtained in step (4) is placed in a vacuum tube furnace and annealed at 1200°C for 24 hours. High-purity argon is introduced throughout the process to remove oxygen. Then, it is prepared into the required size by a metal cutting machine and then polished to obtain the high-entropy alloy.

[0097] Example 7

[0098] This embodiment provides a Pt-modified AlCoCrFeNi system high-entropy alloy and its preparation method. The only difference from Embodiment 1 is that in step (2), P=1×10⁻⁶ in the vacuum arc melting furnace. -2 Except for Pa, everything else is the same as in Example 1.

[0099] Example 8

[0100] This embodiment provides a Pt-modified AlCoCrFeNi system high-entropy alloy and its preparation method. The only difference from Example 1 is that the number of vacuum arc melting in step (2) is 4 times, and the rest are the same as in Example 1.

[0101] Comparative Example 1

[0102] This comparative example provides a high-entropy alloy of AlCoCrFeNi system and its preparation method. The only difference from Example 1 is that the high-entropy alloy does not include Pt element, and its reduction is proportionally allocated to other components of the metal salt precursor.

[0103] Comparative Example 2

[0104] This comparative example provides a high-entropy alloy of AlCoCrFeNi system and its preparation method. The only difference from Example 1 is that the atomic percentage of Pt element in the high-entropy alloy is 0.5 at, and the reduction is proportionally allocated to other components of the metal salt precursor.

[0105] Comparative Example 3

[0106] This comparative example provides a high-entropy alloy of AlCoCrFeNi system and its preparation method. The only difference from Example 1 is that Pt is replaced with Sc.

[0107] Comparative Example 4

[0108] This comparative example provides a Pt-modified AlCoCrFeNi system high-entropy alloy and its preparation method. The only difference from Example 1 is that the atomic percentage of Al in the high-entropy alloy is 5 at%, and the reduction is proportionally allocated to other components of the metal salt precursor.

[0109] Comparative Example 5

[0110] This comparative example provides a Pt-modified AlCoCrFeNi system high-entropy alloy and its preparation method. The only difference from Example 1 is that the atomic percentage of Al in the high-entropy alloy is 25 at, and the increase comes from other components of the metal salt precursor in proportion.

[0111] Comparative Example 6

[0112] This comparative example provides a Pt-modified AlCoCrFeNi system high-entropy alloy and its preparation method. The only difference from Example 1 is that annealing is not performed in step (3).

[0113] Performance testing:

[0114] (1) Phase stability test: The high-entropy alloys obtained in Example 1 and Comparative Example 1 were tested by X-ray diffractometer (XRD) to analyze their crystal structure. The diffraction angle 2θ range for crystal structure analysis was 20°-95°.

[0115] (2) Antioxidant performance test: The high-entropy alloys obtained in Examples 1-8 and Comparative Examples 1-6 were heated to 1200℃ at room temperature at 20℃ / min using a simultaneous thermal analyzer (TG-DSC) and held at 1200℃ for 10h to test the mass change.

[0116] (3) Mechanical property testing: The high-entropy alloys obtained in Examples 1-8 and Comparative Examples 1-6 were subjected to mechanical property testing using the micro tensile testing method at room temperature and other different temperatures and strain rates of 1×10⁻⁶. -4 s -1 Yield strength and elongation were tested under air atmosphere conditions;

[0117] (4) Performance stability: The performance stability of the high-entropy alloys obtained in Examples 1-8 and Comparative Examples 1-6 under high temperature long-term service conditions was tested, and the coarsening rate of the γ′ phase was obtained. The microstructure of the high-entropy alloys obtained by SEM analysis was calculated using Image J software.

[0118] (5) Corrosion resistance: The high-entropy alloys obtained in Examples 1-8 and Comparative Examples 1-6 were tested using the method in GB / T 10125-2021 "Artificial Atmosphere Corrosion Test Salt Spray Test". The alloys were corroded in neutral salt spray at 35±2℃ for 25, 50, 100 and 200 hours, and the corrosion area was tested.

[0119] The results of the antioxidant performance test are shown in Table 1.

[0120] Table 1

[0121]

[0122] The mechanical performance test results are shown in Table 2.

[0123] Table 2

[0124]

[0125] The results of the corrosion resistance test are shown in Table 3.

[0126] Table 3

[0127]

[0128] The performance stability test results are shown in Table 4.

[0129] Table 4

[0130]

[0131] The test results show that:

[0132] (1) As can be seen from Examples 1 to 6, the present invention uses five elements—Al, Co, Cr, Fe, and Ni—as the main elements, and Pt as the modifying element, and controls the content ratio of each element, as well as electrothermal metallurgy, powder metallurgy, or additive manufacturing processes, so that the high-entropy alloy has both excellent mechanical properties and superior oxidation resistance in high-temperature environments. The improvement of the performance of high-entropy alloy by Pt is mainly in the oxidation resistance. The mechanical properties and corrosion area mainly depend on the intrinsic properties of the high-entropy alloy. Due to the difference in the proportion of different elements, its properties also vary. Pt-modified high-entropy alloys exhibit a room temperature yield strength ≥765 MPa and an elongation ≥7%; at 800℃, they maintain a yield strength ≥339 MPa and an elongation ≥13%. They also maintain good phase stability even after high-temperature oxidation at 1200℃, demonstrating excellent high-temperature mechanical properties. At 1200℃, the yield strength is ≥85 MPa and the elongation is ≥17%. They can form a continuous and complete protective oxide layer, with a mass change ≤3.41% at 1200℃ and a corrosion area ≤15.13% after 200 hours.

[0133] (2) As can be seen from Examples 1 and 7, by further limiting the pressure inside the vacuum arc melting furnace, the present invention can achieve better mechanical properties and better antioxidant properties in a high-temperature environment.

[0134] (3) As can be seen from Examples 1 and 8, the present invention ensures high purity and high uniformity of high entropy alloy by further limiting the number of vacuum arc meltings. When the number of vacuum arc meltings is too low, it is easy to cause component segregation and uneven oxide film, and its high temperature oxidation resistance and high temperature mechanical properties will decrease significantly.

[0135] (4) As can be seen from Example 1 and Comparative Examples 1 and 2, when the AlCoCrFeNi alloy is not modified with Pt or the atomic percentage content of Pt is too low, the unmodified alloy structure (such as precipitates) may be more prone to coarsening, resulting in faster performance degradation, poor performance stability, lack of strong solid solution strengthening and precipitation strengthening effect brought by Pt, and the mechanical properties and oxidation resistance of the alloy at high temperature are significantly worse.

[0136] (5) As can be seen from Example 1 and Comparative Example 3, when Pt is replaced with Sc, the oxidation resistance and high-temperature mechanical properties of the alloy decrease to varying degrees. The reason is that Pt and Sc have different mechanisms of action on the alloy. Pt does not react with oxygen or the alloy, while Sc is similar to an active element. It reacts with oxygen to generate oxides, inhibits the enrichment of impurity elements or forms oxide pinning to protect the oxide film, but may also damage the oxide film.

[0137] (6) As can be seen from Example 1 and Comparative Examples 4 and 5, when the atomic percentage of Al in the high-entropy alloy is too low, the Al content is insufficient and a protective Al2O3 film cannot be formed, its anti-oxidation performance is seriously deteriorated, it is easy to form a soft FCC phase, and its mechanical properties are also significantly worse. When the Al content is too high, the alloy changes from the FCC structure to a hard and brittle BCC structure, which is prone to brittle fracture. Excessive Al may lead to an excessively thick oxide film or internal oxidation, which in turn affects the adhesion due to increased stress.

[0138] (7) As can be seen from Example 1 and Comparative Example 6, the present invention removes the internal stress of the high-entropy alloy and the defects formed during the preparation process by annealing. If annealing is not performed, the mechanical properties and oxidation resistance of the alloy at high temperature will be significantly worse.

[0139] In summary, the high-entropy alloy of the present invention utilizes Pt to modify AlCoCrFeNi alloy. By controlling the content ratio between each element, the elements work synergistically, resulting in a high-entropy alloy material that exhibits both excellent mechanical properties and superior oxidation resistance in high-temperature environments.

[0140] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A Pt-modified AlCoCrFeNi high-entropy alloy, characterized in that, The high-entropy alloy comprises five elements: Al, Co, Cr, Fe, and Ni, as well as modifying elements; The modifying element includes Pt; Based on atomic percentage, 10at%≤Al≤20at%, 10at%≤Co≤20at%, 10at%≤Cr≤20at%, 10at%≤Fe≤20at%, 20at%≤Ni≤40at%, 1at%≤Pt≤5at.

2. A high-entropy alloy according to claim 1, characterized in that, The preparation method of the high-entropy alloy includes the following steps: (1) Weigh the raw materials according to the atomic ratio of the high-entropy alloy to obtain a mixture; (2) The mixture described in step (1) is smelted or solidified in a vacuum environment or an inert atmosphere by a metallurgical process to obtain a high-entropy alloy master alloy. (3) Anneal the high-entropy alloy master alloy obtained in step (2) to obtain the high-entropy alloy.

3. The preparation method according to claim 2, characterized in that, The raw materials mentioned in step (1) include elemental Al, Co, Cr, Fe, Ni, and Pt or high-purity alloys containing at least two of the elements Al, Co, Cr, Fe, Ni, and Pt; Preferably, the purity of the raw material is ≥99.95%; Preferably, the raw material is in the form of powder, granules, or blocks.

4. The preparation method according to claim 2 or 3, characterized in that, In step (2), the system pressure P in the vacuum environment is ≤ 1 × 10⁻⁶. -3 Pa; Preferably, the metallurgical process in step (2) includes electrothermal metallurgy, powder metallurgy, or additive manufacturing, with electrothermal metallurgy being the preferred method. Preferably, the electrothermal metallurgical process includes vacuum arc melting; Preferably, the powder metallurgy process includes hot pressing; Preferably, the additive manufacturing process includes 3D printing.

5. The preparation method according to claim 4, characterized in that, The current for the vacuum arc melting is 280-300A; Preferably, the vacuum arc melting is performed 5-8 times; Preferably, the time for each vacuum arc melting is 2-3 minutes independently; Preferably, the hot pressing temperature is 1200-1350℃; Preferably, the pressure of the hot pressing is 20-30 MPa; Preferably, the heat preservation time for hot pressing is 30-90 minutes.

6. The preparation method according to claim 4 or 5, characterized in that, The laser power for 3D printing is 200-400W; Preferably, the scanning speed of the 3D printing is 600-1200 mm / s; Preferably, the diameter of the 3D printed spot is 70-150 μm; Preferably, the thickness of the 3D print is 20-50 μm; Preferably, the oxygen content of the 3D print is less than 100 ppm.

7. The preparation method according to any one of claims 2-6, characterized in that, The inert atmosphere in step (2) includes argon; Preferably, the annealing temperature in step (3) is 1000-1200℃; Preferably, the annealing process in step (3) takes longer than 5 hours; Preferably, the annealing process in step (3) is carried out under an inert atmosphere.

8. The preparation method according to any one of claims 2-7, characterized in that, The preparation method further includes machining the high-entropy alloy obtained in step (3); Preferably, the machining process includes preparing the high-entropy alloy obtained in step (3) into the required size by a metal cutting machine, and then performing grinding and polishing.

9. The preparation method according to any one of claims 2-8, characterized in that, The preparation method specifically includes the following steps: (1) Weigh the raw materials according to the atomic ratio of the high-entropy alloy to obtain a mixture; wherein the raw materials include Al, Co, Cr, Fe, Ni, Pt elements or high-purity alloys containing at least two of Al, Co, Cr, Fe, Ni, Pt, the purity of the raw materials is ≥99.95%, and the shape of the raw materials includes powder, granules or blocks; (2) The mixture obtained in step (1) is smelted or solidified under vacuum or inert atmosphere by metallurgical process to obtain a high-entropy alloy master alloy; wherein the system pressure P in the vacuum environment is ≤1×10 -3 Pa, the inert atmosphere includes argon, the metallurgical process includes electrothermal metallurgy, powder metallurgy, or additive manufacturing, the electrothermal metallurgy includes vacuum arc melting, the powder metallurgy includes hot pressing, the additive manufacturing process includes 3D printing, the current of the vacuum arc melting is 280-300A, the number of vacuum arc meltings is 5-8, the time of each vacuum arc melting is 2-3 minutes, the temperature of the hot pressing is 1200-1350℃, the pressure of the hot pressing is 20-30MPa, the holding time of the hot pressing is 30-90 minutes, the laser power of the 3D printing is 200-400W, the scanning speed of the 3D printing is 600-1200mm / s, the spot diameter of the 3D printing is 70-150μm, and the thickness of the 3D printing is 20-50μm; (3) The high-entropy alloy master alloy described in step (2) is annealed at 1000-1200℃ for more than 5 hours. The annealing is carried out in an inert atmosphere. After that, it is prepared into the required size by a metal cutting machine and then polished to obtain the high-entropy alloy.

10. An application of the high-entropy alloy according to claim 1, characterized in that, The high-entropy alloy is applied in the field of thermal barrier coating materials technology.

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