A ta, w modified nichiayhfsi coating target and a method of making the same

Abstract

The application belongs to the technical field of coating material preparation, and particularly relates to a Ta and W modified NiCrAlYHfSi coating target material and a preparation method thereof. The target material has the following chemical components in percentage by mass: Cr: 11-15wt%, Al: 5-10wt%, Y: 0.1-1wt%, W: 1-6wt%, Ta: 2-5wt%, Hf: 1-2wt%, Si: 0.3-0.8wt%, Fe: ≤0.5wt%, and Ni: the balance. Raw materials are weighed according to the component range, a mother alloy is prepared by one-time vacuum induction smelting, and the surface is polished to remove the oxide skin. Then, a wax mold is pressed according to the required size of the target material, the wax molds are combined and a shell is prepared, the mother alloy is cut according to the required weight, and then is poured into the shell in a vacuum induction smelting furnace by two-time vacuum induction smelting. After solidification and cooling, the shell is cleaned, and is cut and processed into the required size to obtain the Ta and W modified NiCrAlYHfSi coating target material.

Description

Technical Field

[0001] This invention belongs to the field of coating material preparation technology, specifically relating to a Ta and W modified NiCrAlYHfSi coating target and its preparation method. The coating prepared by this target is suitable for high-temperature protection of hot-end components (such as single-crystal high-temperature alloy blades) such as aero-engines and gas turbines. Background Technology

[0002] With the continuous development of aero-engine and gas turbine technology, the performance requirements for blades are gradually increasing, making single-crystal superalloy blades the preferred choice for hot-end components of engines. Since blades operate not only at high temperatures but also endure high stress and high-temperature corrosion environments such as sulfur dioxide and oxygen, single-crystal superalloys must possess not only excellent mechanical properties but also good resistance to high-temperature corrosion. However, the mechanical properties and high-temperature corrosion resistance of alloys are contradictory. To resolve this contradiction, simply improving the superalloy matrix is ​​insufficient to meet the performance requirements of aero-engines and gas turbines. Preparing a high-temperature protective coating on the alloy matrix surface is an effective approach.

[0003] Common high-temperature protective coatings are mainly classified into simple aluminide coatings, modified aluminide coatings, MCrAlY coatings, and thermal barrier coatings. Among them, MCrAlY coatings have good corrosion resistance and high-temperature oxidation resistance, as well as good adhesion and uniformity, and low surface roughness, making them one of the preferred protective coatings for hot-end components of high-temperature alloys. However, because the main constituent phases of MCrAlY coatings are NiAl(β) and Cr(α), which differ significantly from the γ or γ′ phase matrix structure of high-temperature alloys, they are prone to cracking at high temperatures.

[0004] Patent CN115652266A discloses a machinable CoCrAlY target alloy and its preparation method, with Co as the main component, primarily addressing the difficulty of machining, but it does not match the microstructure of the Ni-based superalloy matrix. Patent CN117733157A discloses a NiCrAlY alloy target and its preparation method, but its microstructure contains only β-NiAl and α-Cr, failing to reduce the phase difference with the superalloy matrix. Furthermore, it employs powder metallurgy, where compositional uniformity depends on powder mixing, resulting in weaker stability than smelting processes. Patent CN117702104A discloses an Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating and its preparation method. The matrix is ​​a tantalum alloy, and the coating is a silicide multilayer structure. Ta / W is used to form silicides rather than to regulate the γ / γ' phase, completely irrelevant to the protective requirements of Ni-based superalloys.

[0005] The target material is the main material for preparing MCrAlY coatings, directly determining the coating's microstructure and performance. It is generally believed that higher purity and density of the target material, and more uniform structure and composition, result in better uniformity and performance of the coating. Furthermore, the target material's composition directly affects the coating's performance and adhesion. Therefore, modifying the composition of NiCrAlYHfSi targets to make their microstructure more similar to that of high-temperature alloy matrices, while simultaneously exploring a preparation process that achieves uniform target material composition, has significant application value. Summary of the Invention

[0006] The purpose of this invention is to provide a target material for NiCrAlYHfSi coating modified with Ta and W and its preparation method, which can solve the problems of coating cracking and poor coating composition uniformity of hot-end components caused by the mismatch between the coating and the substrate structure in the prior art.

[0007] To solve the above problems, the technical solution of the present invention is:

[0008] A Ta- and W-modified NiCrAlYHfSi coating target material has the following chemical composition by mass percentage:

[0009] Cr: 11-15 wt%, Al: 5-10 wt%, Y: 0.1-1 wt%, W: 1-6 wt%, Ta: 2-5 wt%, Hf: 1-2 wt%, Si: 0.3-0.8 wt%, Fe: ≤0.5 wt%, Ni balance.

[0010] The target material for the Ta and W modified NiCrAlYHfSi coating has a microstructure composed of γ phase, γ′ phase, NiAl(β) phase, and Cr(α) phase.

[0011] The target material for the Ta and W modified NiCrAlYHfSi coating has a total volume ratio of 40-65% for the γ phase and γ′ phase.

[0012] The target material for the Ta and W modified NiCrAlYHfSi coating is cylindrical with a diameter of 50-200 mm and a thickness of 10-80 mm. The average grain size of the target material is ≤1 mm.

[0013] The method for preparing the target material for the Ta, W modified NiCrAlYHfSi coating includes the following steps:

[0014] (1) Preparation of master alloy: After the alloy raw materials are batched, the master alloy ingot is prepared by vacuum induction melting in one step;

[0015] (2) Preparation of mold shell: Prepare wax mold and mold shell for the target material for secondary melting and casting of the target material;

[0016] (3) Preparation of target material: After the master alloy ingot is vacuum induction melted twice, it is poured into the mold shell, and the target material is obtained after shell cleaning and cutting.

[0017] In the preparation method of the target material for the Ta and W modified NiCrAlYHfSi coating, in step (1), the raw materials other than Al and Al-Y alloys are placed in an alumina crucible, and vacuum induction melting is carried out once. The temperature is raised to 1500-1600℃ and refined for 2-10 minutes. Al blocks and Al-Y alloys are added, and after stirring, they are cast into a master alloy ingot with a diameter of 80-90mm.

[0018] In the preparation method of the target material for the Ta and W modified NiCrAlYHfSi coating, in step (2), a wax mold is pressed with a processing allowance of 1 to 3 mm according to the finished size of the target material. The mold is coated with EC95 slurry and sprinkled with corundum sand. After repeating 5 to 6 times, the wax is removed and the mold is fired to obtain the target shell.

[0019] In the preparation method of the target material for the Ta and W modified NiCrAlYHfSi coating, in step (3), the master alloy ingot is cut and placed in a vacuum induction melting furnace, and then vacuum induction melted to 1400-1500℃ for 3-5 minutes. The alloy liquid is then poured into the target shell in a pouring time of 5-15 seconds. After pouring, the target shell is cooled in the furnace for 10-15 minutes and then taken out of the furnace and cooled to room temperature.

[0020] The design concept of this invention is:

[0021] Existing NiCrAlY sputtering targets contain only β-NiAl (nickel-aluminum phase) and α-Cr (chromium phase), which differ significantly in structure from the γ-phase (Ni-based solid solution) and γ'-phase (Ni3Al phase) of single-crystal superalloy matrices. This leads to a mismatch in thermal expansion coefficients and susceptibility to high-temperature cracking. This invention introduces two refractory elements, Ta and W, to directionally induce the formation of γ / γ' phases consistent with the superalloy matrix, while retaining the corrosion resistance advantages of the β-NiAl and α-Cr phases, resulting in a synergistic microstructure of γ+γ'+β+α phases. In particular, Ni, as a matrix element, synergistically forms a γ' phase (Ni3Al) with 5–10 wt% Al and a γ phase (Ni-Cr solid solution) with 11–15 wt% Cr. 2–5 wt% Ta and 1–6 wt% W can be dissolved into the γ / γ' phase, which on the one hand improves the high-temperature stability of the γ / γ' phase (inhibiting phase decomposition at high temperatures), and on the other hand reduces the thermal expansion coefficient of the target material, thus narrowing the difference in thermal expansion between it and the single-crystal superalloy and reducing coating cracking caused by high-temperature thermal stress. At the same time, the addition of 1–2 wt% Hf and 0.3–0.8 wt% Si refines the target material grains (inhibiting high-temperature grain growth), and 0.1–1 wt% Y improves the adhesion between the coating and the substrate, avoiding performance defects caused by single-component modification.

[0022] Existing target material preparation processes (single-stage melting, powder metallurgy) are prone to compositional segregation due to differences in elemental density / melting point (e.g., Al and Y have low melting points and are easily burned, while Ta and W have high melting points and are difficult to dissolve uniformly), leading to fluctuations in coating performance. This invention weighs raw materials according to their compositional range, prepares a master alloy using a single-stage vacuum induction melting process, and removes oxide scale from the surface by grinding. Then, a wax mold is pressed according to the required target material dimensions. The wax mold is assembled and a shell is formed. The master alloy is cut to the required weight and then subjected to a second vacuum induction melting process in a vacuum induction melting furnace, poured into the shell, and after solidification and cooling, the shell is cleaned and cut to the required dimensions to obtain a Ta and W modified NiCrAlYHfSi target material for coating. This invention employs a two-stage vacuum induction melting process—one-stage melting to prepare the master alloy and a second-stage melting for near-net-shape forming—ensuring precise and uniform target material composition through step-by-step control of homogenization followed by forming. In the first vacuum induction melting process, high-melting-point elements (Ni, Cr, W, Ta, Hf, Si) are first refined at 1500–1600℃ to remove gaseous impurities and achieve preliminary homogenization. Then, low-melting-point Al and Al-Y alloys (Y is added in the form of Al-Y alloy to avoid Y volatilization loss) are added, stirred, and cast into a master alloy ingot, controlling the deviation of element proportions. In the second vacuum induction melting process, the master alloy ingot is polished to remove oxide scale and then melted again (1400–1500℃) to ensure that the master alloy is completely remelted and the composition is further homogenized. Combined with the investment casting mold shell (EC95 slurry + corundum sand to ensure the density of the mold shell), near-net-shape forming is achieved with a precise casting time of 5–15 seconds, avoiding element segregation during the second melting process.

[0023] The Ta, W modified NiCrAlYHfSi coating target and its preparation method provided by this invention have the following advantages and beneficial effects:

[0024] 1. This invention obtains a master alloy ingot with uniform composition by performing a first vacuum induction melting of high-purity raw materials. Then, the target blank is cast by a second vacuum induction melting using a near-net-shape investment casting method. The two vacuum induction melting processes effectively ensure the uniformity of the target material's composition, thereby making the composition of the coating uniform and controllable.

[0025] 2. Furthermore, by adding matrix elements such as Ta and W of high-temperature alloys to the target material, the present invention promotes the formation of γ / γ' phases in the target material, reduces the difference in composition and microstructure between the target material and the alloy, and thus reduces the coating cracking problem caused by temperature changes. It is expected to be applied to high-temperature-resistant components such as aero-engine turbines.

[0026] 3. The synergistic effect of Hf, Si and Y in the target material of this invention makes the coating's anti-oxidation and anti-hot corrosion properties superior to those of existing NiCrAlY targets, which can meet the long-life protection requirements of hot-end components of aero-engines. Attached Figure Description

[0027] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0028] Figure 1 This is a microstructure diagram of the target material in Embodiment 1 of the present invention. In the figure, the reference numerals are: 1 for Cr (α) phase, 2 for NiAl (β) phase.

[0029] Figure 2 This is an X-ray diffraction (XRD) analysis diagram of the phase composition of the target material in Embodiment 1 of the present invention. Detailed Implementation

[0030] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0031] According to embodiments of the present invention, a method for preparing a target material for a Ta, W modified NiCrAlYHfSi coating is provided, comprising the following steps:

[0032] Preparation of master alloy: The master alloy is prepared by vacuum induction melting after the alloy raw materials are batched.

[0033] Preparation of mold shell: Prepare wax mold and mold shell for the target material for secondary melting and casting of the target material;

[0034] Target preparation: The master alloy is melted twice under vacuum and then poured into a mold shell. After shell cleaning and cutting, the target material is obtained.

[0035] The chemical composition of the target material, by mass percentage, is as follows:

[0036] Cr: 11-15 wt%, Al: 5-10 wt%, Y: 0.1-1 wt%, W: 1-6 wt%, Ta: 2-5 wt%, Hf: 1-2 wt%, Si: 0.3-0.8 wt%, Fe: ≤0.5 wt%, Ni balance.

[0037] In some embodiments, the step of preparing the target material further includes: preparing a master alloy ingot;

[0038] Preferably, the step of preparing the master alloy ingot includes: melting the alloy raw materials, refining them after melting, and then casting them to obtain the master alloy ingot.

[0039] In some embodiments, both the master alloy ingot and the target material are smelted using vacuum induction melting.

[0040] In some implementations, the secondary vacuum induction melting temperature is 1400–1500°C, and the casting time is 5–15 seconds.

[0041] In some embodiments, the target material is cylindrical.

[0042] On the other hand, the present invention provides a target material whose microstructure comprises a γ phase, a γ′ phase, and NiAl(β) and Cr(α).

[0043] The present invention will now be further described with reference to specific embodiments and comparative examples.

[0044] Example 1 (W 5wt%, Ta 4wt%):

[0045] In this embodiment, a method for preparing a target material for a Ta, W modified NiCrAlYHfSi coating includes the following steps:

[0046] Preparation of master alloy ingot: The raw materials are batched according to the alloy raw material ratio. The chemical composition of the alloy raw materials by mass percentage is Cr: 14wt%, Al: 8wt%, Y: 0.5wt%, W: 5wt%, Ta: 4wt%, Hf: 1.2wt%, Si: 0.5wt%, Fe: 0.1wt%, Ni balance.

[0047] The raw materials, except Al and Al-Y, are placed in an alumina crucible for vacuum induction melting. The refining temperature is 1550℃. After refining for 5 minutes, Al and Al-Y (the mass percentage of Y in the Al-Y alloy is 80wt%) are added. After stirring, the mixture is cast into a master alloy ingot with a diameter of 80-90mm.

[0048] Preparation of target shell: Prepare wax molds with a machining allowance of 1-3mm according to the target material of the required size. After assembling the wax molds into a module, make the shell. Coat the surface of the module with EC95 slurry, then sprinkle corundum sand. After drying, repeat the process of coating slurry and sprinkling sand 5 times. After it is completely dry, dewax and fire to obtain the target shell.

[0049] In this embodiment, the composition of the EC95 slurry by mass percentage is as follows: 80% alumina powder (EC95 powder, average particle size 30-50μm) and 20% silica sol binder.

[0050] Target preparation: After removing the oxide scale by surface grinding of the master alloy ingot, it is placed in an alumina crucible for a second vacuum induction melting at 1500℃. After melting for 3 minutes, the molten alloy is poured into the target mold shell for 10 seconds. After pouring, it is cooled in the furnace for 10 minutes before being removed and cooled. After cooling, the mold shell is cleaned, and the finished target material is machined according to the dimensions shown in the drawings. In this embodiment, the target material is cylindrical with a diameter of 100 mm and a thickness of 20 mm. The average grain size of the target material is approximately 0.6 mm.

[0051] like Figure 1 As shown in the microstructure of the target material prepared in this embodiment, in addition to NiAl(β) and Cr(α) phases, the target material also contains γ and γ′ phases, which are similar to those in the target material. Figure 2 The XRD phase composition results are consistent. The matrix consists of γ and γ′ phases, the white dot-like phase (indicated by arrow 1) is Cr(α) phase 1, the matrix phase of Cr(α) phase 1 (indicated by arrow 2) is NiAl(β)2, and the total volume ratio of the γ and γ′ phases is approximately 50%.

[0052] Example 2 (W 5wt%, Ta 3wt%):

[0053] In this embodiment, a method for preparing a target material for a Ta, W modified NiCrAlYHfSi coating includes the following steps:

[0054] Preparation of master alloy ingot: The raw materials are batched according to the alloy raw material ratio. The chemical composition of the alloy raw materials by mass percentage is Cr: 13wt%, Al: 8wt%, Y: 0.5wt%, W: 5wt%, Ta: 3wt%, Hf: 1.6wt%, Si: 0.6wt%, Fe: 0.3wt%, Ni balance.

[0055] The raw materials, except Al and Al-Y, are placed in an alumina crucible for vacuum induction melting. The refining temperature is 1550℃. After refining for 5 minutes, Al and Al-Y (the mass percentage of Y in the Al-Y alloy is 80wt%) are added. After stirring, the mixture is cast into a master alloy ingot with a diameter of 80-90mm.

[0056] Preparation of target shell: Prepare wax molds with a machining allowance of 1-3mm according to the target material of the required size. After assembling the wax molds into a module, make the shell. Coat the surface of the module with EC95 slurry, then sprinkle corundum sand. After drying, repeat the process of coating slurry and sprinkling sand 5 times. After it is completely dry, dewax and fire to obtain the target shell.

[0057] In this embodiment, the composition of the EC95 slurry by mass percentage is as follows: 80% alumina powder (EC95 powder, average particle size 30-50μm) and 20% silica sol binder.

[0058] Target preparation: After removing the oxide scale by surface grinding of the master alloy ingot, it is placed in an alumina crucible for a second vacuum induction melting at a temperature of 1480℃. After melting for 3 minutes, the molten alloy is poured into the target mold shell for 6 seconds. After pouring, it is cooled in the furnace for 10 minutes before being removed and cooled. After cooling, the mold shell is cleaned, and the finished target material is machined according to the dimensions in the drawing.

[0059] In this embodiment, the target material is cylindrical with a diameter of 80 mm and a thickness of 100 mm. The average grain size of the target material is approximately 0.8 mm. The microstructure of the target material consists of γ phase, γ′ phase, NiAl(β) phase, and Cr(α) phase, with the total volume percentage of the γ phase and γ′ phase being approximately 45%.

[0060] Example 3 (W 3wt%, Ta 3wt%):

[0061] In this embodiment, a method for preparing a target material for a Ta, W modified NiCrAlYHfSi coating includes the following steps:

[0062] Preparation of master alloy ingot: The raw materials are batched according to the alloy raw material ratio. The chemical composition of the alloy raw materials by mass percentage is Cr: 11.5wt%, Al: 9wt%, Y: 0.8wt%, W: 3wt%, Ta: 3wt%, Hf: 1.2wt%, Si: 0.5wt%, Fe: 0.4wt%, Ni balance.

[0063] The raw materials, except Al and Al-Y, are placed in an alumina crucible for vacuum induction melting. The refining temperature is 1550℃. After refining for 5 minutes, Al and Al-Y (the mass percentage of Y in the Al-Y alloy is 80wt%) are added. After stirring, the mixture is cast into a master alloy ingot with a diameter of 80-90mm.

[0064] Preparation of target shell: Prepare wax molds with a machining allowance of 1-3mm according to the target material of the required size. After assembling the wax molds into a module, make the shell. Coat the surface of the module with EC95 slurry, then sprinkle corundum sand. After drying, repeat the process of coating slurry and sprinkling sand 5 times. After it is completely dry, dewax and fire to obtain the target shell.

[0065] In this embodiment, the composition of the EC95 slurry by mass percentage is as follows: 80% alumina powder (EC95 powder, average particle size 30-50μm) and 20% silica sol binder.

[0066] Target preparation: After removing the oxide scale by surface grinding of the master alloy ingot, it is placed in an alumina crucible for a second vacuum induction melting at a temperature of 1430℃. After melting for 3 minutes, the molten alloy is poured into the target mold shell for 6 seconds. After pouring, it is cooled in the furnace for 10 minutes before being removed and cooled. After cooling, the mold shell is cleaned, and the finished target material is machined according to the dimensions in the drawing.

[0067] In this embodiment, the target material is cylindrical with a diameter of 120 mm and a thickness of 30 mm. The average grain size of the target material is approximately 0.5 mm. The microstructure of the target material consists of γ phase, γ′ phase, NiAl(β) phase, and Cr(α) phase, with the total volume percentage of the γ phase and γ′ phase being approximately 60%.

[0068] The results show that by adding refractory elements such as Ta and W to the target material of this invention, the composition and coefficient of thermal expansion of the coating prepared using this target material are closer to those of the high-temperature alloy substrate, reducing the cracking problem caused by temperature changes. Simultaneously, this invention provides a method for preparing a modified NiCrAlYHfSi coating target material, employing a secondary vacuum induction melting method to ensure the uniformity of the target material composition, effectively avoiding compositional fluctuations in the coating prepared from the target material.

Claims

1. A target material for a Ta, W-modified NiCrAlYHfSi coating, characterized in that, Its chemical composition, by mass percentage, is as follows: Cr: 11-15 wt%, Al: 5-10 wt%, Y: 0.1-1 wt%, W: 1-6 wt%, Ta: 2-5 wt%, Hf: 1-2 wt%, Si: 0.3-0.8 wt%, Fe: ≤0.5 wt%, Ni balance; The microstructure of the target material consists of γ phase, γ′ phase, β-NiAl phase, and α-Cr phase; The total volume percentage of the γ phase and γ′ phase is 40–65%.

2. The target material for the Ta, W modified NiCrAlYHfSi coating according to claim 1, characterized in that, The target material is cylindrical, with a diameter of 50–200 mm and a thickness of 10–80 mm. The average grain size of the target material is ≤1 mm.

3. A method for preparing a target material for a Ta, W modified NiCrAlYHfSi coating as described in claim 1 or 2, characterized in that, Includes the following steps: (1) Preparation of master alloy: After the alloy raw materials are batched, the master alloy ingot is prepared by vacuum induction melting in one step; (2) Preparation of mold shell: Prepare wax mold and mold shell for the target material for secondary melting and casting of the target material; (3) Preparation of target material: After the master alloy ingot is vacuum induction melted twice, it is poured into the mold shell, and the target material is obtained after shell cleaning and cutting.

4. The method for preparing the target material for Ta, W modified NiCrAlYHfSi coating according to claim 3, characterized in that, In step (1), raw materials other than Al and Al-Y alloys are placed in an alumina crucible and subjected to vacuum induction melting. The temperature is raised to 1500-1600℃ and refined for 2-10 minutes. Al blocks and Al-Y alloys are added, stirred, and then cast into a master alloy ingot with a diameter of 80-90mm.

5. The method for preparing the target material for Ta, W modified NiCrAlYHfSi coating according to claim 3, characterized in that, In step (2), a wax mold is pressed with a processing allowance of 1-3 mm reserved according to the finished size of the target material. The mold is coated with EC95 slurry and sprinkled with corundum sand. After repeating 5-6 times, the wax is removed and the mold is fired to obtain the target material shell.

6. The method for preparing the target material for Ta, W modified NiCrAlYHfSi coating according to claim 3, characterized in that, In step (3), the master alloy ingot is cut and placed in a vacuum induction melting furnace. It is then vacuum induction melted to 1400-1500℃ and held for 3-5 minutes. The alloy liquid is then poured into the target shell in a pouring time of 5-15 seconds. After pouring, it is cooled in the furnace for 10-15 minutes and then taken out of the furnace and cooled to room temperature.

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