A nickel-based alloy high-temperature oxidation-resistant strengthened surface layer and a method thereof

Abstract

This invention discloses a high-temperature oxidation-resistant strengthening surface layer for nickel-based alloys and its method. The layer is formed on the surface of a nickel-based alloy substrate, creating a continuous interface with the substrate through metallurgical bonding. It utilizes nanodiamond as a carbon source and is formed through vacuum heat treatment to create either a grain-refining region or a grain-refining region combined with a titanium carbide ceramic layer. The grain-refining region forms a continuous, defect-free cross-section with the nickel-based alloy substrate. The titanium carbide ceramic layer is generated in situ by the reaction of nanodiamond with a pre-formed titanium layer during vacuum heat treatment. This invention can form grain-refining regions on the surface of nickel-based alloys, or further form a uniform and dense titanium carbide ceramic layer, significantly improving the surface hardness, wear resistance, and high-temperature oxidation resistance of nickel-based alloys.

Description

Technical Field

[0001] This invention belongs to the field of nickel-based high-temperature oxidation-resistant alloy preparation technology, specifically relating to a nickel-based alloy high-temperature oxidation-resistant strengthening surface layer and its method. Background Technology

[0002] With the rapid development of my country's aerospace industry, the demand for high-temperature alloys for aviation is increasing daily. Nickel-based high-temperature alloys, with their excellent high-temperature strength, structural stability, and resistance to oxidation and corrosion, have long held a core position as materials for hot-end components in aero-engines, gas turbines, aerospace propulsion, and energy equipment. In addition, nickel-based alloys possess numerous advantages such as high strength, high elasticity, excellent fatigue resistance, corrosion resistance, ease of forming, easy welding, and easy machining, making them promising candidates for applications in the petroleum industry, chemical industry, thermal power, high-end equipment, and nuclear energy. Therefore, nickel-based alloys are one of the high-performance metallic materials we are focusing on developing, possessing very broad application prospects and economic value.

[0003] However, even under aging conditions, nickel-based alloys still exhibit relatively low hardness, with Rockwell hardness typically ranging from 30-40 HRC. Their wear resistance is also poor. Furthermore, with the development of aerospace technology, the operating temperature requirements for nickel-based alloys are increasing, placing higher demands on their high-temperature oxidation resistance. Current methods for improving the hardness of nickel-based alloys primarily involve alloying to enhance the overall hardness of the substrate. Surface modification typically employs surface coatings to provide surface wear resistance and high-temperature oxidation resistance. Currently, domestic research on nickel-based high-temperature alloys has spanned decades, with numerous studies reporting on optimized composition design and achieving promising applications. However, further research is needed on their preparation processes. Surface strengthening technology is crucial for the reliable operation of nickel-based alloys in high-temperature environments.

[0004] Currently, both domestically and internationally, the main technologies for strengthening the surface of nickel-based alloys include ceramic thermal barrier layers, CVD / PVD hard coatings, high-speed flame spraying, laser cladding, and plasma metal infiltration. However, these technologies generally suffer from problems such as expensive equipment, complex processes, poor coating bonding strength, and numerous interface defects. Significant shortcomings remain in areas such as the localization of high-end coating equipment, long-term interface bonding mechanisms, wide-temperature-range service reliability, batch production consistency, and quantitative assessment of service life.

[0005] Specifically, CN 108914054A discloses a method for preparing an anti-oxidation and heat-corrosion Cr-Si-BY coating on the surface of a nickel-based alloy using ball milling and embedding; CN 117947375A discloses a process for infiltrating boron into a nickel-based alloy using ball milling and powder mixing and embedding; CN110144578A discloses a method for preparing a Ni-Nb amorphous coating by combining mechanical coating and high-current pulsed electron beam; CN120023345A discloses a method for forming a high-temperature corrosion resistant coating on the surface of a nickel-based alloy by combining printing and heat treatment; CN112962065A discloses a process for preparing a load-bearing structure coating on the surface of a nickel-based alloy by combining dual-glow plasma surface metallurgy and multi-arc ion plating; CN 114318202A discloses a method for preparing a wear-resistant coating on the surface of a nickel-based alloy by dip coating, constant-current micro-arc oxidation, etc. Patent 111893418A discloses a method for improving the high-temperature oxidation resistance of nickel-based alloys by combining thermal spraying and electron beam cladding. While these existing technologies have improved the surface properties of nickel-based alloys to some extent, they still cannot simultaneously meet the comprehensive requirements of simple processing, low cost, high bonding strength of the reinforcing layer, and stable performance, and are difficult to adapt to the large-scale production needs of complex components.

[0006] Therefore, there is an urgent need to develop a nickel-based alloy surface modification technology that is simple to process, low in cost, has high bonding strength between the reinforcing layer and the substrate, stable in performance, and is environmentally friendly, so as to break through the bottleneck of existing technologies and better meet the urgent needs of high-end equipment fields such as aerospace for nickel-based alloy surface performance. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a nickel-based alloy surface layer that is resistant to high-temperature oxidation and strengthened.

[0008] Another object of the present invention is to provide a method for forming a high-temperature oxidation-resistant and strengthening surface layer on the surface of a nickel-based alloy.

[0009] The technical solution of the present invention is as follows:

[0010] A high-temperature oxidation-resistant strengthening surface layer for nickel-based alloys is formed on the surface of a nickel-based alloy substrate, creating a continuous interface with the substrate through metallurgical bonding. This layer comprises a grain-refining region formed by vacuum heat treatment using nanodiamond as the carbon source, or a grain-refining region combined with a titanium carbide ceramic layer.

[0011] The grain-refined region forms a continuous, defect-free cross-section with the nickel-based alloy matrix.

[0012] The titanium carbide ceramic layer is generated by the in-situ reaction of nanodiamonds with a pre-formed titanium layer during vacuum heat treatment.

[0013] In a preferred embodiment of the present invention, the grain refinement region is formed by a penetration aid infiltrating into the lattice of the nickel-based alloy, the penetration layer thickness is 50 µm, and the penetration aid is at least one of Dy powder, Gd powder, Ce powder and Y powder.

[0014] A method for forming a high-temperature oxidation-resistant and strengthened surface layer on a nickel-based alloy surface includes the following steps:

[0015] (1) Prepare a slurry containing nanodiamonds, the slurry being composed of 15-50 wt% nanodiamonds, 1-5 wt% surfactant, 3-15 wt% penetration enhancer, 13-17 wt% film-forming agent and organic solvent as the balance, wherein the penetration enhancer is at least one of Dy powder, Gd powder, Ce powder and Y powder;

[0016] (2) The slurry containing nanodiamonds is coated on the surface of a nickel-based alloy;

[0017] (3) Place the coated nickel-based alloy in an oven at 150-250 ℃ for 5-10 min to dry and cure.

[0018] (4) Place the dried and cured nickel-based alloy in a vacuum furnace and evacuate it to 1×10⁻⁶. -2 Below Pa, while maintaining a vacuum, heat to 600-700 ℃ and hold for 1-3 h; then heat to 950-1050 ℃ and hold for 1-3 h, finally cool with the furnace to obtain the product.

[0019] Because nanodiamonds have excellent nano-effects, they can easily interdiffuse with various metal elements in nickel-based alloys at high temperatures. In addition, the elements in the diffusion aid are all rare earth elements, which can play a synergistic diffusion role in the interdiffusion process between nanodiamonds and the matrix, allowing them to enter the surface layer of the nickel-based alloy. Since rare earth elements have low solid solubility in nickel-based alloys, and rare earth elements are commonly used grain refining elements in metal alloy materials, they can pin grain boundaries on the surface layer of the nickel-based alloy, inhibit grain growth, form a grain refining layer, and play the roles of grain refining and precipitation strengthening.

[0020] In a preferred embodiment of the present invention, the nanodiamond has a particle size of 100-500 nm.

[0021] In a preferred embodiment of the present invention, the organic solvent is diethylene glycol butyl ether acetate or ethyl acetate.

[0022] In a preferred embodiment of the present invention, the surfactant is tributyl phosphate.

[0023] In a preferred embodiment of the present invention, the penetration enhancer is at least one of Dy powder with a particle size of 500 nm-2 μm, Gd powder with a particle size of 500 nm-2 μm, Ce powder with a particle size of 500 nm-2 μm, and Y powder with a particle size of 500 nm-2 μm.

[0024] In a preferred embodiment of the present invention, the film-forming agent is polydimethylsiloxane or polyvinyl alcohol.

[0025] In a preferred embodiment of the present invention, the coating method in step (2) is brush coating or dip coating.

[0026] In a preferred embodiment of the present invention, before step (2), a titanium plating layer with a thickness of 50-300 nm is formed on the surface of a nickel-based alloy using PVD magnetron sputtering technology. Then, the slurry containing nanodiamonds is coated onto the surface of the titanium plating layer. Since titanium is highly reactive at high temperatures, it readily reacts with nanodiamonds exhibiting nano-effects, forming a titanium carbide reinforcing layer in situ. Furthermore, rare earth elements and the substrate diffuse with the substrate at high temperatures, forming a metallurgical bonding layer at the interface between the titanium carbide reinforcing layer and the substrate. This effectively improves the metallurgical bond between the titanium carbide reinforcing layer and the substrate, enhancing the bonding strength.

[0027] More preferably, the PVD magnetron sputtering process is as follows: placing the nickel-based alloy in a magnetron sputtering furnace and evacuating to a vacuum of 10... -3 The pressure is below Pa and maintained under vacuum. Then, pure titanium target is used for sputtering with a sputtering power of 100-200 W and a sputtering time of 0.5-3 h.

[0028] The beneficial effects of this invention are:

[0029] 1. The present invention can form a grain-refining region on the surface of nickel-based alloys, or further form a uniform and dense titanium carbide ceramic layer, which significantly improves the surface hardness, wear resistance and high-temperature oxidation resistance of nickel-based alloys.

[0030] 2. This invention utilizes the synergistic effect of nanodiamond as a carbon source and penetration aid to form a continuous cross-section and metallurgical bond between the reinforcing layer and the substrate, ensuring high bonding strength of the reinforcing layer and avoiding the problem of easy peeling of traditional coatings.

[0031] 3. The process of this invention is simple, requiring only conventional slurry coating, oven drying and vacuum furnace heat treatment (conventional PVD magnetron sputtering is optional), without the need for expensive large-scale special equipment, which greatly reduces the production threshold and manufacturing cost.

[0032] 4. The raw materials of this invention are readily available, the operating parameters are easy to control, and there are no harmful residues. It has green and environmentally friendly characteristics and is suitable for large-scale application of various nickel-based alloy complex components.

[0033] 5. This invention has wide applicability and can be extended to different nickel-based alloy systems, providing a reliable and economical solution for surface strengthening of high-temperature components in aerospace, energy equipment and other fields. Attached Figure Description

[0034] Figure 1 The macroscopic surfaces of the 718 alloy (original state) without the high-temperature oxidation-resistant surface layer of the present invention, the 718 alloy modified by Example 1 (Technical Solution 1) of the present invention, and the 718 alloy modified by Example 6 (Technical Solution 2) are shown.

[0035] Figure 2 The cross-sectional metallographic structure (left) and cross-sectional microhardness (middle, HRC) of the 718 alloy modified according to Example 4 (Technical Solution 1) of the present invention, as well as the cross-sectional metallographic structure of the 718 alloy modified according to Example 9 (Technical Solution 2) of the present invention are shown.

[0036] Figure 3 This shows a cross-sectional compositional scan of the 718 alloy modified according to Example 1 (Technical Solution 1) of the present invention.

[0037] Figure 4 The diagrams shown are binary phase diagrams of Ni-Ce (top left), Ni-Dy (top right), Ni-Gd (bottom left), and Ni-Y (bottom right).

[0038] Figure 5 The images show the cross-sectional scanning topography (top left), the corresponding C (top right), Ti (bottom left) compositional surface scans, and the corresponding line composition diagrams (bottom right) of the 718 alloy modified according to Example 9 (Technical Solution 2) of the present invention.

[0039] Figure 6 shows scanning electron microscope (SEM) surface morphology images of 718 alloy (original state) without surface modification according to the present invention, 718 alloy modified according to Example 4 (Technical Solution 1) of the present invention, and 718 alloy modified according to Example 9 (Technical Solution 2) of the present invention.

[0040] In Figure 7, the upper image shows the 718 alloy without surface modification according to this invention (original state), the 718 alloy modified according to Example 4 (Technical Solution 1) of this invention, and the 718 alloy modified according to Example 9 (Technical Solution 2) of this invention at 1100°C. ℃ Macroscopic morphology of air atmosphere insulation for 15 h; and corresponding scanning electron microscope surface morphology (the left image in the lower image is the original surface morphology after peeling, the middle image is the morphology after modification by technical solution one, and the right image is the morphology after modification by technical solution two).

[0041] Figure 8 shows the scratch test on the surface of the modified 718 nickel-based alloy in Example 9 of the present invention.

[0042] Figure 9 shows the nanoindentation test on the surface of the modified 718 nickel-based alloy in Example 9 of the present invention.

[0043] Figure 10 shows the friction coefficient test of the 718 nickel-based alloy surface in Example 4 of the present invention.

[0044] Figure 11 shows the friction coefficient test of the TC6718 nickel-based alloy surface in Example 9 of the present invention. Detailed Implementation

[0045] The technical solution of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.

[0046] Example 1

[0047] The slurry containing nanodiamonds in this embodiment, by weight percentage, comprises: 15% nanodiamond powder with an average particle size of 500 nm, 50% diethylene glycol butyl ether acetate, 5% tributyl phosphate, 5% Dy powder with an average particle size of 2 μm, 2% Gd powder with an average particle size of 2 μm, 5% Ce powder with an average particle size of 2 μm, 3% Y powder with an average particle size of 2 μm, and 15% polydimethylsiloxane.

[0048] The preparation method of the slurry containing nanodiamonds is as follows: First, diethylene glycol butyl ether acetate, tributyl phosphate, and polydimethylsiloxane are stirred evenly to form a transparent solution. Then, Dy powder, Gd powder, Ce powder, and Y powder are added sequentially at a speed of 500 rpm using a dispersing mixer. The speed is increased to 1400 rpm and the mixture is stirred rapidly for 30 min. Then, the speed is reduced to 500 rpm and nanodiamond powder is slowly added. After the nanodiamond powder is completely added, the speed is increased to 1400 rpm and the mixture is stirred rapidly for 30 min to obtain the final product.

[0049] A slurry containing nanodiamonds was uniformly brushed onto the surface of a 718 nickel-based alloy, then dried and cured at 150 °C for 10 min. The cured 718 nickel-based alloy was then placed in a vacuum furnace and evacuated to a vacuum level of 7 × 10⁻⁶. -3 Pa, maintain vacuum, heat to 700 ℃ at a heating rate of 20 ℃ / min and hold for 1 h, then heat to 1050 ℃ at a heating rate of 20 ℃ / min and hold for 1 h, finally cool with the furnace to obtain a 718 nickel-based alloy with a surface-modified anti-high temperature oxidation strengthening layer.

[0050] Example 2

[0051] The slurry containing nanodiamonds in this embodiment, by weight percentage, comprises: 50% nanodiamond powder with an average particle size of 100 nm, 15% ethyl acetate, 5% tributyl phosphate, 5% Dy powder with an average particle size of 500 nm, 2% Gd powder with an average particle size of 500 nm, 5% Ce powder with an average particle size of 500 nm, 3% Y powder with an average particle size of 500 nm, and 15% polyvinyl alcohol.

[0052] The preparation method of the slurry containing nanodiamonds is as follows: First, the above-mentioned ethyl acetate, tributyl phosphate, and polyvinyl alcohol are stirred evenly to form a transparent solution. Then, Dy powder, Gd powder, Ce powder, and Y powder are added sequentially at a speed of 300 rpm using a dispersing mixer. The speed is increased to 1000 rpm and the mixture is stirred rapidly for 1 h. Then, the speed is reduced to 300 rpm and nanodiamond powder is slowly added. After the nanodiamond powder is completely added, the speed is increased to 1000 rpm and the mixture is stirred rapidly for 2 h to obtain the final product.

[0053] A slurry containing nanodiamonds was uniformly brushed onto the surface of a 718 nickel-based alloy, then dried and cured at 250 °C for 5 min. The cured 718 nickel-based alloy was then placed in a vacuum furnace and evacuated to a vacuum level of 5 × 10⁻⁶. -3 Pa, maintain vacuum, heat to 700 ℃ at a heating rate of 10 ℃ / min and hold for 3 h, then heat to 950 ℃ at a heating rate of 10 ℃ / min and hold for 3 h, finally cool with the furnace to obtain a 718 nickel-based alloy with a surface-modified anti-high temperature oxidation strengthening layer.

[0054] Example 3

[0055] The slurry containing nanodiamonds in this embodiment, by weight percentage, consists of: 25% nanodiamond powder with an average particle size of 250 nm, 50% ethyl acetate, 1% tributyl phosphate, 9% Dy powder with an average particle size of 1 μm, and 15% polyvinyl alcohol.

[0056] The preparation method of the slurry containing nanodiamonds is as follows: First, the above-mentioned ethyl acetate, tributyl phosphate and polyvinyl alcohol are stirred evenly to a transparent solution. Then, Dy powder is added at a speed of 400 rpm using a dispersing mixer. The speed is increased to 1200 rpm and the mixture is stirred rapidly for 1 h. Then, the speed is reduced to 400 rpm and nanodiamond powder is slowly added. After the nanodiamond powder is completely added, the speed is increased to 1200 rpm and the mixture is stirred rapidly for 1 h to obtain the final product.

[0057] A slurry containing nanodiamonds was uniformly brushed onto the surface of a 718 nickel-based alloy, then dried and cured at 200 °C for 10 min. The cured 718 nickel-based alloy was then placed in a vacuum furnace and evacuated to a vacuum level of 4 × 10⁻⁶. -3 Pa, maintain vacuum, heat to 650 ℃ at a heating rate of 15 ℃ / min and hold for 2 h, then heat to 1000 ℃ at a heating rate of 15 ℃ / min and hold for 2 h, finally cool with the furnace to obtain a 718 nickel-based alloy with a surface-modified anti-high temperature oxidation strengthening layer.

[0058] Example 4

[0059] The slurry containing nanodiamonds in this embodiment, by weight percentage, is as follows: 30% nanodiamond powder with an average particle size of 250 nm, 50% ethyl acetate, 2% tributyl phosphate, 2% Dy powder with an average particle size of 1 μm, 1% Gd powder with an average particle size of 1 μm, and 15% polyvinyl alcohol.

[0060] The preparation method of the slurry containing nanodiamonds is as follows: First, the above-mentioned ethyl acetate, tributyl phosphate and polyvinyl alcohol are stirred evenly to a transparent solution. Then, Dy powder is added at a speed of 400 rpm using a dispersing mixer. The speed is increased to 1200 rpm and the mixture is stirred rapidly for 1 h. Then, the speed is reduced to 400 rpm and nanodiamond powder is slowly added. After the nanodiamond powder is completely added, the speed is increased to 1200 rpm and the mixture is stirred rapidly for 1 h to obtain the final product.

[0061] A slurry containing nanodiamonds was uniformly brushed onto the surface of a 718 nickel-based alloy, then dried and cured at 150 °C for 10 min. The cured 718 nickel-based alloy was then placed in a vacuum furnace and evacuated to a vacuum level of 5 × 10⁻⁶. -3 Pa, maintain vacuum, heat to 600 ℃ at a heating rate of 15 ℃ / min and hold for 1 h, then heat to 1000 ℃ at a heating rate of 15 ℃ / min and hold for 2 h, finally cool with the furnace to obtain a 718 nickel-based alloy with a surface-modified anti-high temperature oxidation strengthening layer.

[0062] Example 5

[0063] The slurry containing nanodiamonds in this embodiment, by weight percentage, is as follows: 30% nanodiamond powder with an average particle size of 250 nm, 50% ethyl acetate, 2% tributyl phosphate, 2% Dy powder with an average particle size of 1 μm, 1% Gd powder with an average particle size of 1 μm, and 15% polyvinyl alcohol.

[0064] The preparation method of the slurry containing nanodiamonds is as follows: First, the above-mentioned ethyl acetate, tributyl phosphate and polyvinyl alcohol are stirred evenly to a transparent solution. Then, Dy powder is added at a speed of 400 rpm using a dispersing mixer. The speed is increased to 1200 rpm and the mixture is stirred rapidly for 1 h. Then, the speed is reduced to 400 rpm and nanodiamond powder is slowly added. After the nanodiamond powder is completely added, the speed is increased to 1200 rpm and the mixture is stirred rapidly for 1 h to obtain the final product.

[0065] A slurry containing nanodiamonds was uniformly brushed onto the surface of a 718 nickel-based alloy, then dried and cured at 150 °C for 10 min. The cured 718 nickel-based alloy was then placed in a vacuum furnace and evacuated to a vacuum level of 5 × 10⁻⁶. -3 Pa, maintaining vacuum, heating to 650 ℃ at a heating rate of 15 ℃ / min and holding for 2 h, then heating to 1050 ℃ at a heating rate of 15 ℃ / min and holding for 3 h, finally cooling with the furnace to obtain a 718 nickel-based alloy with a surface-modified anti-high temperature oxidation strengthening layer.

[0066] Example 6

[0067] A slurry containing nanodiamonds was prepared according to the process described in Example 1. A 718 nickel-based alloy was placed in a magnetron sputtering furnace, with a pure titanium target as the sputtering target, and the furnace was evacuated to a vacuum of 8 × 10⁻⁶. -4 The sputtering power was 100W, the sputtering time was 0.5 h, and finally a 718 nickel-based alloy with titanium plating was obtained.

[0068] A slurry containing nanodiamonds was uniformly brushed onto the surface of a 718 nickel-based alloy with a titanium plating layer, and then dried and cured at 150°C for 10 min. The dried and cured 718 nickel-based alloy with the titanium plating layer was then placed in a vacuum furnace and evacuated to a vacuum level of 7 × 10⁻⁶. -3 Pa, maintaining vacuum, heating to 700 ℃ at a heating rate of 20 ℃ / min and holding for 1 h, then heating to 1050 ℃ at a heating rate of 20 ℃ / min and holding for 1 h, finally cooling with the furnace to obtain a 718 nickel-based alloy with a surface-modified anti-high temperature oxidation strengthening layer.

[0069] Example 7

[0070] A slurry containing nanodiamonds was prepared according to the process described in Example 2. A 718 nickel-based alloy was placed in a magnetron sputtering furnace, with a pure titanium target as the sputtering target, and the furnace was evacuated to a vacuum of 5 × 10⁻⁶. -4 The sputtering process was carried out at Pa, with a sputtering power of 200W and a sputtering time of 3 hours, finally obtaining a 718 nickel-based alloy with titanium plating on the surface.

[0071] A slurry containing nanodiamonds was uniformly brushed onto the surface of a 718 nickel-based alloy, then dried and cured at 250 °C for 5 min. The dried and cured 718 nickel-based alloy with a titanium-plated surface was then placed in a vacuum furnace and evacuated to a vacuum level of 5 × 10⁻⁶. -3 Pa, maintain vacuum, heat to 700 ℃ at a heating rate of 10 ℃ / min and hold for 3 h, then heat to 950 ℃ at a heating rate of 10 ℃ / min and hold for 3 h, finally cool with the furnace to obtain a 718 nickel-based alloy with a surface-modified anti-high temperature oxidation strengthening layer.

[0072] Example 8

[0073] A slurry containing nanodiamonds was prepared according to the process described in Example 3. A 718 nickel-based alloy was placed in a magnetron sputtering furnace, using a pure titanium target, and the furnace was evacuated to a vacuum of 5 × 10⁻⁶. -4 The sputtering process was carried out at Pa, with a sputtering power of 200W and a sputtering time of 1 h, finally obtaining a 718 nickel-based alloy with titanium plating on the surface.

[0074] A slurry containing nanodiamonds was uniformly brushed onto the surface of a 718 nickel-based alloy, then dried and cured at 200 °C for 10 min. The dried and cured 718 nickel-based alloy with a titanium-plated surface was then placed in a vacuum furnace and evacuated to a vacuum level of 4 × 10⁻⁶. -3 Pa, maintain vacuum, heat to 650 ℃ at a heating rate of 15 ℃ / min and hold for 2 h, then heat to 1000 ℃ at a heating rate of 15 ℃ / min and hold for 2 h, finally cool with the furnace to obtain a 718 nickel-based alloy with a surface-modified anti-high temperature oxidation strengthening layer.

[0075] Example 9

[0076] A slurry containing nanodiamonds was prepared according to the process described in Example 4. A 718 nickel-based alloy was placed in a magnetron sputtering furnace, using a pure titanium target, and the furnace was evacuated to a vacuum of 5 × 10⁻⁶. -4 The sputtering power was 100W, the sputtering time was 1 h, and finally a 718 nickel-based alloy with titanium plating was obtained.

[0077] A slurry containing nanodiamonds was uniformly brushed onto the surface of a 718 nickel-based alloy, then dried and cured at 150 °C for 10 min. The dried and cured 718 nickel-based alloy with a titanium-plated surface was then placed in a vacuum furnace and evacuated to a vacuum level of 5 × 10⁻⁶. -3 Pa, maintain vacuum, heat to 600 ℃ at a heating rate of 15 ℃ / min and hold for 1 h, then heat to 1000 ℃ at a heating rate of 15 ℃ / min and hold for 2 h, finally cool with the furnace to obtain a 718 nickel-based alloy with a surface-modified anti-high temperature oxidation strengthening layer.

[0078] Comparative Example 1

[0079] The nanodiamond-containing slurry from Example 4 was uniformly brushed onto the surface of the 718 nickel-based alloy, then dried and cured at 150 °C for 10 min. The dried and cured 718 nickel-based alloy was then placed in a vacuum furnace and evacuated to a vacuum level of 5 × 10⁻⁶. -3 Pa, maintain vacuum, heat to 450 ℃ at a heating rate of 15 ℃ / min and hold for 1 h, then heat to 820 ℃ at a heating rate of 15 ℃ / min and hold for 2 h, and finally cool with the furnace.

[0080] The difference between Comparative Example 1 and Example 4 is that the subsequent vacuum heat treatment temperature of the dried and cured 718 nickel-based alloy is different. In Example 4, the vacuum heat treatment temperature is 600 ℃ for 1 h and then 1000 ℃ for 2 h, while in Comparative Example 1, the vacuum heat treatment temperature is 450 ℃ for 1 h and then 820 ℃ for 2 h.

[0081] Comparative Example 2

[0082] The nanodiamond-containing slurry from Example 4 was uniformly brushed onto the surface of the 718 nickel-based alloy, then dried and cured at 150 °C for 10 min. The dried and cured 718 nickel-based alloy was then placed in a vacuum furnace and evacuated to a vacuum level of 5 × 10⁻⁶. -3 Pa, maintain vacuum, heat to 450 ℃ at a heating rate of 15 ℃ / min and hold for 1 h, then heat to 1200 ℃ at a heating rate of 15 ℃ / min and hold for 2 h, and finally cool with the furnace.

[0083] The difference between Comparative Example 2 and Example 4 is that the subsequent vacuum heat treatment temperature of the dried and cured 718 nickel-based alloy is different. In Example 4, the vacuum heat treatment temperature is 600 ℃ for 1 h and then 1000 ℃ for 2 h, while in Comparative Example 1, the vacuum heat treatment temperature is 450 ℃ for 1 h and then 820 ℃ for 2 h.

[0084] Comparative Example 3

[0085] 718 nickel-based alloy was placed in a magnetron sputtering furnace, with a pure aluminum target as the sputtering material, and the vacuum was evacuated to 5×10⁻⁶. -4 The sputtering power was 200W, the sputtering time was 1 h, and finally, a 718 nickel-based alloy with aluminum plating was obtained.

[0086] The nanodiamond-containing slurry from Example 9 was uniformly brushed onto the aluminum-plated 718 nickel-based alloy surface, then dried and cured at 150 °C for 10 min. The dried and cured 718 nickel-based alloy was then placed in a vacuum furnace and evacuated to a vacuum level of 5 × 10⁻⁶.-3 Pa, maintain vacuum, heat to 600 ℃ at a heating rate of 15 ℃ / min and hold for 1 h, then heat to 1000 ℃ at a heating rate of 15 ℃ / min and hold for 2 h, finally cool with the furnace to obtain the surface-modified 718 nickel-based alloy.

[0087] The difference between Comparative Example 3 and Example 9 is that Example 9 uses a pure titanium target to plate titanium on the surface of a 718 nickel-based alloy, while Comparative Example 3 uses a pure aluminum target to plate aluminum on the surface of a 718 nickel-based alloy.

[0088] Comparative Example 4

[0089] 718 nickel-based alloy was placed in a magnetron sputtering furnace, with a pure nickel target as the sputtering material, and the vacuum was evacuated to 5×10⁻⁶. -4 The sputtering power was 200W, the sputtering time was 1 h, and finally a 718 nickel-based alloy with nickel plating on the surface was obtained.

[0090] The nanodiamond-containing slurry from Example 9 was uniformly brushed onto the surface of the nickel-plated 718 nickel-based alloy, then dried and cured at 150 °C for 10 min. The dried and cured 718 nickel-based alloy was then placed in a vacuum furnace and evacuated to a vacuum level of 5 × 10⁻⁶. -3 Pa, maintain vacuum, heat to 600 ℃ at a heating rate of 15 ℃ / min and hold for 1 h, then heat to 1000 ℃ at a heating rate of 15 ℃ / min and hold for 2 h, finally cool with the furnace to obtain the surface-modified 718 nickel-based alloy.

[0091] The difference between Comparative Example 4 and Example 9 is that Example 9 uses a pure titanium target to plate titanium on the surface of a 718 nickel-based alloy, while Comparative Example 4 uses a pure nickel target to plate nickel on the surface of a 718 nickel-based alloy.

[0092] In this invention, the technical solution in which the nickel-based alloy surface is not preferentially treated with titanium plating is named Technical Solution 1, and the technical solution in which the nickel-based alloy surface is preferentially treated with titanium plating is named Technical Solution 2.

[0093] Figure 1 The macroscopic surfaces are those of 718 alloy (original state) without surface modification according to this invention, 718 alloy modified according to Example 1 (Technical Solution 1) of this invention, and 718 alloy modified according to Example 6 (Technical Solution 2) of this invention. From Figure 1 It can be observed that the 718 alloy surface treated by the present invention has lost its metallic luster, and instead presents a macroscopic morphology similar to ceramic glaze.

[0094] Figure 2The images show the cross-sectional metallographic structure (left) and cross-sectional microhardness (middle, HRC) of the 718 alloy modified according to Example 4 (Technical Solution 1) of the present invention, as well as the cross-sectional metallographic structure of the 718 alloy modified according to Example 9 (Technical Solution 2) of the present invention. In Technical Solution 1, a distinct grain refinement region appears on the surface coated with nanodiamond slurry (the coated surface is on the right in each image), while the surface without slurry coating does not. The middle image shows that the microhardness of the grain refinement region in Technical Solution 1 is significantly higher than that of the substrate. In Technical Solution 2, a distinct grain refinement region also appears on the surface coated with nanodiamond slurry.

[0095] Figure 3 This displays a cross-sectional compositional scan of the 718 alloy modified according to Example 1 (Technical Solution 1) of the present invention. From... Figure 3 It can be observed that the surface of the 718 alloy modified by the first technical solution of this invention has obvious areas rich in penetration aid, with a penetration layer thickness of about 50 micrometers. Among them, except for Ni, the penetration aid has the highest Dy content, Ce component diffuses the deepest, Gd component is mainly concentrated on the outermost surface of the metal, and Y component diffuses relatively quickly and has a relatively uniform composition on the metal surface.

[0096] Figure 4 The diagrams shown are binary phase diagrams for Ni-Ce (top left), Ni-Dy (top right), Ni-Gd (bottom left), and Ni-Y (bottom right). From... Figure 4 It can be seen that rare earth elements have very low solid solubility in Ni, the main element of nickel-based alloys. Therefore, during high-temperature heat treatment, when rare earth elements enter the face-centered cubic lattice of nickel-based alloys, rare earth-rich compounds will precipitate when the content exceeds the solid solubility limit. Figure 2 Small black particles, and Figure 3 (Top left image) This leads to a refinement of the surface microstructure of the nickel-based alloy, and the morphology also undergoes significant changes. Figure 2 ).

[0097] Figure 5 The images show the cross-sectional scanning morphology (top left), compositional surface scans of C (top right), Ti (bottom left), and the corresponding line composition diagrams of each component (bottom right) of the 718 alloy modified according to Embodiment 9 (Technical Solution 2) of this invention. Since the 718 nickel-based alloy surface is preferentially titanium-plated in this embodiment, during the subsequent vacuum heat treatment, nanodiamonds react with titanium to form a titanium carbide ceramic layer on the alloy surface. Therefore, cross-sectional observation using scanning electron microscopy reveals the presence of titanium-rich and carbon-rich layers on the coated surface.

[0098] Figure 6 shows the scanning electron microscope (SEM) surface morphology images of the 718 alloy without surface modification according to this invention (original state), the 718 alloy modified according to Example 4 (Technical Solution 1) of this invention, and the 718 alloy modified according to Example 9 (Technical Solution 2) of this invention. The surfaces of the 718 alloys treated by Examples 4 and 9 of this invention are smoother and denser, indicating that the strengthening layer obtained by this invention on the surface of the 718 alloy is very dense and uniform, which is very beneficial for improving the surface hardness, wear resistance, and high-temperature oxidation resistance of the alloy.

[0099] Figure 7 shows the macroscopic morphology of the 718 alloy (original state) without surface modification according to this invention, the 718 alloy modified according to Example 4 (Technical Solution 1), and the 718 alloy modified according to Example 9 (Technical Solution 2) after being heat-treated at 1100 °C in air for 15 h; and the corresponding scanning electron microscope surface morphology images (the left image in the lower figure shows the morphology of the original state after surface peeling, the middle image shows the morphology after modification according to Technical Solution 1, and the right image shows the morphology after modification according to Technical Solution 2). After heat treatment at 1100 °C in air for 15 h, it can be found that the 718 alloy without surface modification has undergone severe oxidation, and the surface layer has begun to peel off. However, the 718 alloys modified according to Technical Solutions 1 and 2 of this invention only have a blackened and darkened surface, but no peeling has occurred. Observation of the surface morphology by scanning electron microscopy shows that the unmodified 718 alloy still has powdery oxides on the surface even after peeling, indicating that severe oxidation has occurred. In contrast, the surface of the modified 718 alloy is still dense, indicating that the high-temperature oxidation resistance of the 718 nickel-based alloy modified by this invention has been greatly improved.

[0100] Figure 8 shows the scratch test results on the surface of the modified 718 nickel-based alloy in Example 9 of the present invention. The technical solution of the present invention forms a titanium carbide ceramic layer on the surface of the modified 718 nickel-based alloy. Through scratch testing, the adhesion between the layer and the substrate is shown to be approximately 25 N, corresponding to a peel strength of approximately 66 MPa.

[0101] Figure 9 shows the nanoindentation test on the surface of the modified 718 nickel-based alloy in Example 9 of the present invention. In the technical solution of the present invention, a titanium carbide ceramic layer is formed on the surface of the modified 718 nickel-based alloy. The nanohardness of the surface is about 12.5 G Pa by nanoindentation test, which is much higher than the hardness of the 718 nickel-based alloy itself (HRC is 30-40).

[0102] Figure 10 shows the friction coefficient test of the 718 nickel-based alloy surface in Example 4 of the present invention. The results show that the friction coefficient of the 718 nickel-based alloy surface modified by technical solution one is about 0.25, which is much lower than the friction coefficient of the 718 nickel-based alloy itself (0.5-0.8).

[0103] Figure 11 shows the friction coefficient test of the 718 nickel-based alloy surface in Example 9 of the present invention. The results show that the friction coefficient of the 718 nickel-based alloy surface modified by technical solution 2 is about 0.19, which is much lower than the friction coefficient of the 718 nickel-based alloy itself (0.5-0.8).

[0104] Compared with Example 4, Comparative Example 1 and Comparative Example 2 have different effects. In Comparative Example 1, the vacuum heat treatment temperature was insufficient, so no dense strengthening layer was formed and the grain refinement region was too thin to be of practical value. In Comparative Example 2, the vacuum heat treatment temperature was too high, so the grain refinement region was too thick and the bonding force was significantly reduced, which also had no practical value.

[0105] Compared with Example 9, Comparative Examples 3 and 4 did not form a dense titanium carbide ceramic layer due to insufficient vacuum heat treatment temperature, and the grain refinement region was too thin and had no practical value. In Comparative Example 4, the bonding force between the titanium carbide ceramic layer and the substrate was significantly reduced due to excessively high vacuum heat treatment temperature, and it also had no practical value.

[0106] Through the embodiments of the present invention and the technical results obtained therefrom, it can be seen that the present invention provides a breakthrough in the surface strengthening technology of nickel-based alloys by using nanodiamond as a carbon source to enhance the surface properties of nickel-based alloys. The surface hardness, wear resistance and high-temperature oxidation resistance of nickel-based alloys can be significantly improved through a simple process.

[0107] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A nickel-based alloy surface layer for high-temperature oxidation resistance, characterized in that: It forms on the surface of a nickel-based alloy matrix and forms a continuous interface with the nickel-based alloy matrix through metallurgical bonding; and it has a grain-refining region or a grain-refining region + titanium carbide ceramic layer formed by vacuum heat treatment with nanodiamond as the carbon source. The grain-refined region forms a continuous, defect-free cross-section with the nickel-based alloy matrix. The titanium carbide ceramic layer is generated by the in-situ reaction of nanodiamonds with a pre-formed titanium layer during vacuum heat treatment.

2. The nickel-based alloy high-temperature oxidation-resistant reinforced surface layer as described in claim 1, characterized in that: The grain refinement region is formed by the diffusion of a diffusion aid into the crystal lattice of the nickel-based alloy. The diffusion layer thickness is 50 µm. The diffusion aid is at least one of Dy powder, Gd powder, Ce powder, and Y powder.

3. A method for forming a high-temperature oxidation-resistant and strengthened surface layer on the surface of a nickel-based alloy, characterized in that: Includes the following steps: (1) Prepare a slurry containing nanodiamonds, the slurry being composed of 15-50 wt% nanodiamonds, 1-5 wt% surfactant, 3-15 wt% penetration enhancer, 13-17 wt% film-forming agent and organic solvent as the balance, wherein the penetration enhancer is at least one of Dy powder, Gd powder, Ce powder and Y powder; (2) The slurry containing nanodiamonds is coated on the surface of a nickel-based alloy; (3) Place the coated nickel-based alloy in an oven at 150-250 ℃ for drying and curing for 5-10 min; (4) Place the dried and cured nickel-based alloy in a vacuum furnace and evacuate it to 1×10⁻⁶. -2 Below Pa, while maintaining a vacuum, heat to 600-700 ℃ and hold for 1-3 hours; then heat to 950-1050 ℃ and hold for 1-3 hours, finally cooling with the furnace to obtain the final product.

4. The method as described in claim 3, characterized in that: The nanodiamonds have a particle size of 100-500 nm.

5. The method as described in claim 3, characterized in that: The organic solvent is diethylene glycol butyl ether acetate or ethyl acetate.

6. The method as described in claim 3, characterized in that: The surfactant is tributyl phosphate.

7. The method as described in claim 3, characterized in that: The penetration enhancer is at least one of Dy powder with a particle size of 500 nm-2 μm, Gd powder with a particle size of 500 nm-2 μm, Ce powder with a particle size of 500 nm-2 μm, and Y powder with a particle size of 500 nm-2 μm.

8. The method as described in claim 3, characterized in that: The film-forming agent is polydimethylsiloxane or polyvinyl alcohol.

9. The method according to any one of claims 3 to 8, characterized in that: Before step (2), a titanium plating layer with a thickness of 50-300 nm is formed on the surface of a nickel-based alloy using PVD magnetron sputtering technology, and then the slurry containing nanodiamonds is coated on the surface of the titanium plating layer.

10. The method as described in claim 9, characterized in that: The PVD magnetron sputtering process is as follows: a nickel-based alloy is placed in a magnetron sputtering furnace, and a vacuum is drawn to 10... -3 The pressure is below Pa and maintained under vacuum. Then, pure titanium target material is used for sputtering with a sputtering power of 100-200 W and a sputtering time of 0.5-3 h.

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