A self-lubricating coating for dual-phase reinforced nickel-based superalloys and its preparation method

Abstract

This invention provides a dual-phase reinforced nickel-based superalloy self-lubricating coating and its preparation method, belonging to the field of nickel-based alloy coating preparation technology. A dual-phase reinforced nickel-based superalloy self-lubricating coating is prepared on a nickel-based superalloy substrate using laser cladding technology with a mixed powder as the cladding material. The mixed powder comprises nickel powder, aluminum powder, titanium powder, boron carbide powder, and zirconium diboride powder. The prepared dual-phase reinforced nickel-based superalloy self-lubricating coating exhibits a friction coefficient that is more than 30% lower than that of traditional NiCrAlY coatings at 800℃, a wear rate that is more than 50% lower, and after static oxidation at 1000℃ for 100 hours, the oxidation weight gain is reduced by 80% compared to the base alloy. After high-temperature treatment at 1100℃ followed by 50 water-cooled thermal shock cycles, no peeling occurs. The coating can be applied to components such as engine turbine blades, gas turbine combustion chamber bushings, and high-temperature valve sealing surfaces, significantly improving their service life under extreme environments and reducing maintenance costs.

Description

Technical Field

[0001] This invention relates to the field of nickel-based alloy coating preparation, and more particularly to a dual-phase reinforced nickel-based high-temperature alloy self-lubricating coating and its preparation method. Background Technology

[0002] High-temperature solid lubricant coatings are an effective solution to friction and wear problems under extreme operating conditions. Their advantage lies in reducing friction and wear by directly coating the substrate surface without altering the substrate material. These coatings are designed to maintain a stable low coefficient of friction in high-temperature environments. Their performance largely depends on the appropriate selection of solid lubricants. The solid lubricants used in high-temperature lubrication coatings provide protection to reduce wear during friction. Developing solid lubricant surface coatings that can withstand high temperatures, possess excellent wear resistance, and maintain a low coefficient of friction is of great significance for improving mechanical reliability and energy efficiency in extreme environments.

[0003] Nickel-based superalloys are widely used in critical components of gas turbines due to their high-temperature resistance and stable microstructure. However, when operating in extreme high-temperature, high-stress, and corrosive environments, their surfaces are prone to oxidation, hot corrosion, and wear failure. While traditional protective coatings (such as MCrAlY coatings) can provide some protection, they suffer from insufficient high-temperature hardness, the risk of peeling due to thermal expansion mismatch with the substrate, and difficulty in simultaneously achieving both wear resistance and high-temperature oxidation resistance. Summary of the Invention

[0004] The purpose of this invention is to provide a dual-phase reinforced nickel-based superalloy self-lubricating coating and its preparation method, so as to solve the problem that nickel-based superalloys are prone to oxidation, hot corrosion and wear failure when they are used in extreme high temperature, high stress and corrosive environments.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a self-lubricating coating of a biphase reinforced nickel-based superalloy, comprising the following steps: using a mixed powder as a cladding material, and using laser cladding technology to prepare a biphase reinforced nickel-based superalloy self-lubricating coating on a nickel-based superalloy substrate; The mixed powder comprises nickel powder, aluminum powder, titanium powder, boron carbide powder, and zirconium diboride powder.

[0006] Preferably, the molar ratio of nickel powder, aluminum powder, titanium powder, boron carbide powder and zirconium diboride powder is 3~4:1:2~3:1:1~2.

[0007] Preferably, the particle size of the nickel powder, aluminum powder, titanium powder, and boron carbide powder is 40~50μm.

[0008] Preferably, the zirconium diboride powder has a particle size of 5~10μm.

[0009] Preferably, the mixed powder is ball-milled before laser cladding.

[0010] Preferably, Al2O3 grinding balls with a diameter of 5-7 mm are used in the ball milling process.

[0011] Preferably, the ball milling process is performed at a speed of 100-300 rpm for 3-5 hours.

[0012] Preferably, the laser cladding power is 3000~4000W, the scanning speed is 300~400mm / min, the spot diameter is 3~5mm, and the overlap rate is 30~50%.

[0013] The present invention also provides a method for preparing a self-lubricating coating of a biphase reinforced nickel-based superalloy as described above.

[0014] The beneficial effects of this invention are: The dual-phase reinforced nickel-based superalloy self-lubricating coating prepared by this invention has a friction coefficient that is more than 30% lower than that of the traditional NiCrAlY coating at 800℃, and a wear rate that is more than 50% lower.

[0015] The self-lubricating coating of biphase reinforced nickel-based superalloy prepared by this invention, after static oxidation at 1000℃ for 100h, showed an 80% reduction in oxidation weight compared to the base alloy, forming a dense Al2O3+TiO2+ZrO2 composite oxide film.

[0016] The biphase reinforced nickel-based high-temperature alloy self-lubricating coating prepared by this invention showed no peeling after being subjected to a high temperature of 1100℃ and then 50 water-cooled thermal shock cycles.

[0017] The dual-phase reinforced nickel-based high-temperature alloy self-lubricating coating of the present invention is applied to components such as engine turbine blades, gas turbine combustion chamber bushings, and high-temperature valve sealing surfaces, significantly improving their service life in extreme environments and reducing maintenance costs. Attached Figure Description

[0018] Figure 1 SEM image of the dual-phase reinforced nickel-based superalloy self-lubricating coating prepared in Example 1; Figure 2 SEM image of the dual-phase reinforced nickel-based superalloy self-lubricating coating prepared in Example 2; Figure 3 SEM image of the dual-phase reinforced nickel-based superalloy self-lubricating coating prepared in Example 3; Figure 4Friction coefficient curves for conventional NiCrAlY coatings and dual-phase reinforced nickel-based superalloy self-lubricating coatings prepared in Examples 1-3; Figure 5 Comparison of wear amounts between traditional NiCrAlY coatings and dual-phase reinforced nickel-based superalloy self-lubricating coatings prepared in Examples 1-3; Figure 6 Oxidation weight gain curves of the biphase reinforced nickel-based superalloy self-lubricating coatings prepared in Examples 1-3, using the substrate as the base. Detailed Implementation

[0019] This invention provides a method for preparing a self-lubricating coating of a biphase reinforced nickel-based superalloy, comprising the following steps: using a mixed powder as a cladding material, and using laser cladding technology to prepare a biphase reinforced nickel-based superalloy self-lubricating coating on a nickel-based superalloy substrate; The mixed powder comprises nickel powder, aluminum powder, titanium powder, boron carbide powder, and zirconium diboride powder.

[0020] In this invention, the molar ratio of nickel powder, aluminum powder, titanium powder, boron carbide powder and zirconium diboride powder is 3~4:1:2~3:1:1~2, specifically 4:1:2:1:2, 4:1:3:1:1, or 3:1:3:1:2.

[0021] In this invention, the particle size of the nickel powder, aluminum powder, titanium powder, and boron carbide powder is independently 40~50μm, specifically 40μm, 41μm, 42μm, 43μm, 44μm, 45μm, 46μm, 47μm, 48μm, 49μm, and 50μm.

[0022] In this invention, the zirconium diboride powder has a particle size of 5~10μm, specifically 5μm, 6μm, 7μm, 8μm, 9μm, or 10μm.

[0023] In this invention, the purity of the nickel powder, aluminum powder, titanium powder, boron carbide powder and zirconium diboride powder is ≥99.9%.

[0024] In this invention, the nickel-based high-temperature alloy substrate is pretreated before laser cladding. The pretreatment steps are as follows: the nickel-based high-temperature alloy substrate is polished sequentially on 400#, 600# and 1000# sandpaper, then cleaned with anhydrous ethanol, and finally dried.

[0025] In this invention, the mixed powder is ball-milled before laser cladding.

[0026] In this invention, Al2O3 grinding balls are used in the ball milling process. The diameter of the grinding balls is 5-7 mm, specifically 5 mm, 6 mm, or 7 mm.

[0027] In this invention, the ball milling process is performed at a speed of 100-300 rpm, specifically 100 rpm, 120 rpm, 140 rpm, 150 rpm, 160 rpm, 180 rpm, 200 rpm, 220 rpm, 240 rpm, 250 rpm, 260 rpm, 280 rpm, or 300 rpm, for a time of 3-5 hours, specifically 3 hours, 4 hours, or 5 hours.

[0028] In this invention, the power of the laser cladding is 3000~4000W, specifically 3000W, 3200W, 3400W, 3500W, 3600W, 3800W, or 4000W; the scanning speed is 300~400mm / min, specifically 300mm / min, 320mm / min, 340mm / min, 360mm / min, 380mm / min, or 400mm / min; the spot diameter is 3~5mm, specifically 3mm, 4mm, or 5mm; and the overlap rate is 30~50%, specifically 30%, 40%, or 50%.

[0029] In this invention, a Ni-Al-Ti-B4C-ZrB2 mixed powder is used as the cladding material. During the laser cladding process, Ti and B4C undergo an in-situ reaction (3Ti+B4C=2TiB2+TiC). The generated TiB2 particles are uniformly dispersed in the nickel-based superalloy matrix, and together with the ZrB2 particles, they reinforce the nickel matrix. Ni and Al react to generate NiAl compound.

[0030] The TiB2 particles generated by the in-situ reaction have a size of 5-10 μm, exhibiting equiaxed crystals or short rod shapes. Together with ZrB2, they form a "pinning effect," inhibiting grain growth at high temperatures and enhancing the coating's high-temperature creep resistance. The generated NiAl compounds act as a binder phase within the coating, enhancing its oxidation resistance. Nickel-based alloys have a relatively high coefficient of thermal expansion, while ceramic phases have a lower one. The combined use of ZrB2 and TiB2 can adjust the overall coefficient of thermal expansion of the coating, making it closer to that of the metal matrix, thereby reducing thermal stress generated during rapid heating and cooling (thermal cycling) and preventing coating peeling.

[0031] The present invention also provides a method for preparing a self-lubricating coating of a biphase reinforced nickel-based superalloy as described above.

[0032] Working principle of self-lubricating coating: Liquid lubrication (low temperature range 600~800°C): The generated B2O3 is in a viscous fluid state (glassy state) at high temperature. It spreads on the friction surface like oil, fills microcracks and pits, plays an excellent role in reducing friction, and isolates oxygen to protect the internal matrix.

[0033] Solid support (high temperature range >800°C): As the temperature rises further, B2O3 may volatilize or be lost. The TiO2 (titanium dioxide) and ZrO2 (zirconia) particles left behind will form a hard "skeleton" to prevent the coating from being worn excessively.

[0034] Auxiliary reaction: Oxidation of the nickel matrix (protective film).

[0035] The aluminum (Al) element in the coating also participates in the reaction, forming a dense oxide film. Al2O3 is an oxide with high hardness and chemical stability, which can help improve wear resistance.

[0036]

[0037] Oxidation of titanium diboride:

[0038] B2O3 has a melting point of about 450°C, so it exists as a viscous liquid above 500°C, providing excellent lubrication.

[0039] Oxidation of zirconium diboride:

[0040] Although the reactions are similar, ZrB2 typically has a slightly higher oxidation onset temperature than TiB2, which allows the coating to continuously form a lubricating film over a wider temperature range (from 500°C to 1000°C+).

[0041] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] A GH4169 alloy sample with a size of 200mm×200mm×10mm was selected as the matrix material. The sample was polished smooth on 400#, 600# and 1000# sandpaper. Then the sample was placed in anhydrous ethanol and the oil and impurities on the sample surface were removed by ultrasonic vibration. Finally, the sample was dried and ready for use.

[0044] Nickel powder, aluminum powder, titanium powder, boron carbide, and zirconium diboride were mixed in a molar ratio of 4:1:2:1:2 (the particle size of nickel powder, aluminum powder, titanium powder, and boron carbide was 45 μm, the particle size of zirconium diboride was 8 μm, and the purity of all was 99.95%). The mixture was placed in a planetary ball mill (model DQM-0.4L) using an aluminum oxide ball mill jar and grinding balls with a diameter of Φ6 mm and a ball-to-material ratio of 10:1. The mixture was ball-milled at 200 rpm for 4 hours to obtain a mixed powder.

[0045] The mixed powder was pre-placed (laid) on the surface of the sample with a pre-placed thickness of 0.8 mm. Then, the sample was placed on a fixed step in a semi-enclosed container for laser cladding (TJ-HL-5000 transverse multimode CO2 continuous laser complete set of equipment). The laser cladding parameters were: laser power of 3.5 kW, scanning speed of 360 mm / min, spot diameter of 4 mm, and overlap rate of 40%. During the laser cladding process, argon gas was introduced from the bottom of the semi-enclosed container upwards to obtain a biphase reinforced nickel-based high-temperature alloy self-lubricating coating, which is denoted as coating 1.

[0046] Example 2

[0047] The difference from Example 1 is that the molar ratio of nickel powder, aluminum powder, titanium powder, boron carbide and zirconium diboride in the mixed powder is 4:1:3:1:1, and all other conditions are the same, so a dual-phase reinforced nickel-based high-temperature alloy self-lubricating coating is prepared, which is referred to as coating 2.

[0048] Example 3

[0049] The difference from Example 1 is that the molar ratio of nickel powder, aluminum powder, titanium powder, boron carbide and zirconium diboride in the mixed powder is 3:1:3:1:2, and all other conditions are the same, so a dual-phase reinforced nickel-based high-temperature alloy self-lubricating coating is prepared, which is referred to as coating 3.

[0050] Comparative Example 1

[0051] A thermal barrier coating NiCrAlY was prepared on a 15 mm × 15 mm × 3 mm nickel-based superalloy substrate using an atmospheric plasma spraying system (APS) equipped with a spray gun (6 mm nozzle diameter). NiCrAlY powder was used for spraying. Before spraying, the substrate underwent the following pretreatments: first, it was sanded sequentially with 240-grit and 600-grit sandpaper to remove surface deposits and oxides; then, it was roughened by sandblasting with #24 brown corundum abrasive to enhance its surface roughness; finally, it was ultrasonically cleaned in anhydrous ethanol to remove residual abrasive. The spraying process parameters were as follows: spraying power 33 kW, spraying current 460 A, powder feed rate 32 g / min, spraying distance 120 mm, hydrogen flow rate 8.2 L / min, spray gun movement speed 800 mm / s, and overlap step 4 mm, resulting in a conventional NiCrAlY coating.

[0052] Performance verification: (1) Antioxidant test: The test was conducted using the intermittent oxidation method in a box-type resistance furnace of type SX2-12-10. The temperature was measured by thermocouples. The test environment was air and the test temperature was 1000℃.

[0053] Sample preparation

[0054] Before the test, all samples were polished with diamond abrasive paste on a pre-grinding machine, and then the surface roughness of the samples was polished to below 1.0 μm with diamond polishing agent. The polished samples were then cleaned with acetone in an ultrasonic bath for 20 minutes and dried for later use. The crucibles used in the test were calcined at 900℃ to remove moisture and impurities.

[0055] Test methods

[0056] First, the box-type resistance furnace was heated to the predetermined test temperature, and then the sample placed in the crucible was placed into the furnace chamber. The oxidation weighing method was used in the experiment. Before oxidation, the weight of the sample and the crucible was weighed and recorded. During the oxidation process, the crucible was removed every 2 hours, and the weight of the sample and the crucible was weighed again. The total oxidation time was 100 hours, and the oxidation kinetic curve was plotted based on the results. The oxidation morphology of the sample surface and cross-section was observed using SEM, and the phase structure was analyzed using X-ray diffraction (XRD).

[0057] (2) High-temperature abrasion resistance test: The wear test was conducted using an HT-1000 reciprocating high-temperature friction and wear testing machine. The sample was placed in a high-temperature furnace and heated to a predetermined temperature. The required load was then applied to the loading device, driving the rod containing the friction balls to reciprocate, thus rubbing the surface of the test material. Data such as the friction coefficient were detected and recorded by a computer. The test temperature was 800℃, and the friction balls were made of SiC. The wear rate was measured using the volumetric method. The wear amount was calculated using the following formula: (1) Wherein, V is the wear amount; A is the cross-sectional area of ​​the wear mark, which is measured at four different locations using a probe profilometer, the data is imported into CurveSnap software, the cross-sectional shape is drawn, the cross-sectional area at each location is calculated, and the average value of the wear mark cross-sectional area is taken; L is the length of the scratch.

[0058] The formula for calculating the wear rate is: (2) Where S is the total sliding distance and P is the applied load.

[0059] (3) Thermal shock resistance test: Thermal shock resistance was determined using the water quenching method. The sample was heated to 1100℃ in a muffle furnace and held for 5 minutes to ensure uniform heating. It was then rapidly cooled in water at 0℃. After cooling to room temperature, the sample was removed and dried, and the coating peeling was observed. This process was repeated multiple times until the coating peeled off completely.

[0060] The thickness of the self-lubricating coatings prepared in Examples 1-3 is between 0.6 and 0.8 mm, and they exhibit good metallurgical bonding with the substrate material without obvious defects such as cracks or fissures. Figure 1 , Figure 2 and Figure 3 The SEM images are of coatings 1, 2, and 3, respectively. The self-lubricating coating of this invention mainly consists of independent plate-like and hexagonal TiB2, granular, cross-petal-like, and dendritic TiC. 0.3 N 0.7 And the TiB2-ZrB2 syngenetic structure.

[0061] from Figure 4 It can be seen that at room temperature, the actual friction coefficient of traditional NiCrAlY coatings generally fluctuates between 0.3 and 0.35. The friction coefficient of coating 1 is between 0.1 and 0.14, the actual friction coefficient of coating 2 is between 0.13 and 0.16, and the actual friction coefficient of coating 3 is generally between 0.15 and 0.2. The friction coefficient of the self-lubricating coating prepared in this invention is much smaller than that of traditional NiCrAlY coatings.

[0062] from Figure 5 It can be seen that the volumetric wear of the traditional NiCrAlY coating is approximately 0.4804 mm. 3 The volumetric wear of coating 1 is approximately 0.057 mm. 3 The volumetric wear of coating 2 is approximately 0.060 mm. 3 The volumetric wear of coating 3 is approximately 0.054 mm. 3 .

[0063] from Figure 6 It can be seen that the substrate exhibits the most significant weight gain due to oxidation, and the oxidation rate follows a parabolic curve. The oxidation rates of coatings 1, 2, and 3 are all very slow. As the oxidation time increases, the weight gain tends to stop, and the oxidation almost ceases, indicating that the self-lubricating coating prepared in this invention has excellent resistance to high-temperature oxidation.

[0064] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing a bi-phase reinforced nickel-based superalloy self-lubricating coating, characterized in that, The process includes the following steps: using the mixed powder as a cladding material, a dual-phase reinforced nickel-based superalloy self-lubricating coating is prepared on a nickel-based superalloy substrate using laser cladding technology; The mixed powder comprises nickel powder, aluminum powder, titanium powder, boron carbide powder, and zirconium diboride powder.

2. The method of claim 1, wherein the duplex enhanced nickel-based superalloy self- lubricating coating is prepared by a process comprising: The molar ratio of nickel powder, aluminum powder, titanium powder, boron carbide powder and zirconium diboride powder is 3~4:1:2~3:1:1~2.

3. The method for preparing a self-lubricating coating for a dual-phase reinforced nickel-based superalloy according to claim 1 or 2, characterized in that, The particle size of the nickel powder, aluminum powder, titanium powder, and boron carbide powder is independently 40~50μm.

4. The method of claim 3, wherein the duplex enhanced nickel-based superalloy self- lubricating coating is prepared by a process comprising: The zirconium diboride powder has a particle size of 5~10μm.

5. The method of claim 1 or 2 or 4, wherein The mixed powder is ball-milled before being laser cladding.

6. The method of claim 5, wherein the duplex enhanced nickel-based superalloy self- lubricating coating is prepared by a process comprising: The ball milling process uses Al2O3 grinding balls with a diameter of 5-7 mm.

7. The method for preparing a self-lubricating coating for a dual-phase reinforced nickel-based superalloy according to claim 6, characterized in that, The ball milling process is performed at a speed of 100-300 rpm for 3-5 hours.

8. The method for preparing a self-lubricating coating for a dual-phase reinforced nickel-based superalloy according to claim 4, 6, or 7, characterized in that, The laser cladding has a power of 3000~4000W, a scanning speed of 300~400mm / min, a spot diameter of 3~5mm, and an overlap rate of 30~50%.

9. The self-lubricating coating of a dual-phase reinforced nickel-based superalloy obtained by the preparation method of any one of claims 1 to 8.

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