High-pressure hot-pressing die oxidation-resistant coating and preparation method thereof

Abstract

The application relates to the technical field of alloy coating materials, and particularly discloses a high-pressure hot-pressing die oxidation-resistant coating and a preparation method thereof. The high-pressure hot-pressing die oxidation-resistant coating comprises a transition layer and a functional layer arranged outward from a die base body, the transition layer is a TiN-SiC gradient composite layer, the functional layer takes Al2O3-NiCrAlY as a base body, and is compounded and doped with double-modified nano ZrB2 and rare earth CeO2; the double-modified nano ZrB2 is ZrB2 particles coated with a silane coupling agent KH-560 and a NiCr alloy. The high-pressure hot-pressing die oxidation-resistant coating has oxidation resistance and wear resistance, and effectively enhances the high-temperature hardness stability and wear resistance of the oxidation-resistant coating.

Description

Technical Field

[0001] This application belongs to the technical field of alloy coating materials, and relates to an anti-oxidation coating for high-pressure hot pressing molds and its preparation method. This coating is widely used in industrial fields requiring high-pressure hot pressing processes, such as powder metallurgy, advanced ceramic sintering, and high-performance composite material molding. It is suitable for the surface protection needs of various high-pressure hot pressing molds and can effectively solve the surface protection problem of high-pressure hot pressing molds under long-term high-temperature and high-pressure conditions. Background Technology

[0002] High-pressure hot pressing technology, a core process in high-end manufacturing fields such as aerospace, precision machinery, and new energy, is widely used in the preparation of key components such as special alloys, ceramic matrix composites, and semiconductor packaging devices due to its advantages in achieving material densification and improving workpiece precision and performance under high temperature and high pressure environments. The high-pressure hot pressing mold, as the core load-bearing component of this technology, must withstand high temperatures of 400-1200℃, high pressures of 10-100MPa, and cyclical hot and cold shocks for extended periods. Its surface is highly susceptible to oxidation, corrosion, and wear, which not only shortens the mold's lifespan and increases production costs but may also contaminate the workpiece surface due to oxide layer shedding, affecting product quality stability. Therefore, preparing a high-performance anti-oxidation coating on the surface of high-pressure hot pressing molds is a key means to improve mold weather resistance, extend service life, and ensure the reliability of the molding process, which has significant practical implications for promoting technological upgrading and quality improvement in high-end manufacturing.

[0003] Currently, various technical approaches have been developed for the composition systems and preparation processes of anti-oxidation coatings for high-pressure hot-pressing molds. In terms of composition, these mainly include ceramic-based coatings (such as Al2O3, ZrO2, Cr2O3 and their composite systems), cermet coatings (such as NiCrAlY and CoCrAlY-based cermets), and silicide coatings (such as MoSi2 and TiSi2 coatings). These components, due to their excellent high-temperature chemical stability, can form a dense oxide barrier layer on the mold surface, resisting high-temperature oxidation corrosion. Regarding preparation processes, mainstream technologies include plasma spraying, physical vapor deposition (PVD), chemical vapor deposition (CVD), and laser cladding. Among these, plasma spraying is widely used for coating preparation of large high-pressure hot-pressing molds due to its high preparation efficiency and strong controllability of coating thickness, while PVD and CVD processes are suitable for preparing thin coatings on the surface of precision small molds, ensuring the bonding accuracy between the coating and the substrate.

[0004] Several existing patents disclose technical solutions for anti-oxidation coatings for molds, but all have certain shortcomings and are difficult to fully adapt to the harsh service conditions of high-pressure hot pressing molds. For example, patent application CN116789466A discloses a high-temperature resistant PVD coating for molds and its preparation method. The technical solution involves using a PVD process, with a C / C composite material as the base layer, setting a thick metal nitride transition layer and a carbon-containing thermosetting resin protective layer, and preparing a dense SiC ceramic coating through a SiC industrial synthesis furnace. The SiO2 layer formed at high temperature is used to improve the anti-oxidation performance. However, this patent has obvious defects: the carbon-containing component of its protective layer is prone to oxidative degradation under the high-temperature environment of high-pressure hot pressing, resulting in a loose coating structure, severe attenuation of high-temperature hardness, and no targeted optimization of the coating's wear resistance. It is difficult to resist the high-pressure friction and impact between the mold and the workpiece, and its adaptability to high-pressure hot pressing molds is limited.

[0005] Patent document CN113981397B discloses a Cr2O3 / Al2O3 gradient anti-oxidation coating for titanium alloys and its preparation method. The method involves magnetron sputtering to deposit a Cr metal layer onto the surface of a titanium alloy substrate, followed by the deposition of aluminum foil, high-temperature melting, and air oxidation to obtain a dense Cr2O3 / Al2O3 gradient coating to enhance oxidation resistance. However, this technology has drawbacks. The coating design is specifically tailored to the titanium alloy substrate, resulting in poor adhesion to the mold steel substrates commonly used in high-pressure hot pressing dies. Furthermore, the high-temperature melting process easily leads to grain growth in the coating, resulting in insufficient high-temperature mechanical property stability, significant hardness reduction, and unresolved issues with wear resistance. Therefore, it cannot meet the service requirements of high-pressure hot pressing dies under long-term high-temperature and high-pressure friction.

[0006] Patent application CN104762583A discloses a method for preparing nano-ceramic materials for thermal spraying mold surfaces. The method involves mixing nano-Cr2O3, Al2O3-MgO, and Al2O3-SiO2 in a specific ratio, granulating and sintering them, and then applying a thermal spray coating to the mold surface. NiCrAlY is used as a spraying aid to enhance the adhesion between the coating and the substrate. However, its drawbacks include the fact that the thermal spraying process itself easily creates micropores in the coating. At high temperatures, these pores become channels for oxygen permeation, reducing the coating's antioxidant durability. Furthermore, uneven dispersion during nanoparticle mixing leads to an inhomogeneous internal structure in the coating, exacerbating atomic diffusion at high temperatures and further accelerating hardness reduction. Simultaneously, the coating's wear resistance is not effectively enhanced, making it unable to withstand abrasive wear during high-pressure hot pressing, resulting in surface scratches and peeling.

[0007] However, existing anti-oxidation coatings for high-pressure hot pressing molds generally suffer from core technical defects during actual service, such as significant high-temperature hardness decay and insufficient wear resistance, making it difficult to withstand the frictional impact between the mold and the workpiece during high-pressure hot pressing. The causes of this defect are relatively clear: on the one hand, the high-temperature mechanical properties of most coating components are unstable. Within the mold's operating temperature range, intensified atomic diffusion leads to a loose internal structure and grain growth in the coating, resulting in a significant decrease in hardness; on the other hand, the contact stress during high-pressure hot pressing causes intense friction between the softened coating surface and the workpiece, making the coating prone to plastic deformation and abrasive wear, gradually leading to surface scratches and peeling. This not only results in the loss of anti-oxidation protection for the mold substrate but also may cause wear debris to contaminate the workpiece, affecting the precision and surface quality of the molded product. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art, solve the technical problem of poor wear resistance of the anti-oxidation coating of high-pressure hot pressing mold, and minimize the hardness decay of the anti-oxidation coating at high temperature, and provide an anti-oxidation coating for high-pressure hot pressing mold and its preparation method.

[0009] To achieve the above-mentioned objectives, this application provides an anti-oxidation coating for high-pressure hot-pressing molds and its preparation method, employing the following technical solution:

[0010] An anti-oxidation coating for a high-pressure hot-pressing mold includes a transition layer and a functional layer arranged sequentially from the mold substrate outwards. The transition layer is a TiN-SiC gradient composite layer, and the functional layer is based on Al2O3-NiCrAlY and is composite-doped with double-modified nano-ZrB2 and rare earth CeO2.

[0011] The functional layer is made from the following raw materials in parts by weight: 64-72 parts Al2O3, 18-24 parts NiCrAlY, 6-12 parts double-modified nano ZrB2, and 0.8-2.2 parts CeO2; the double-modified nano ZrB2 is ZrB2 particles coated with silane coupling agent KH-560 and NiCr alloy.

[0012] By adopting the above technical solution, using a double-modified nano-ZrB2 and rare-earth CeO2 composite doped Al2O3-NiCrAlY as the functional layer and a TiN-SiC gradient composite layer as the transition layer, the core defects of existing coatings, such as significant high-temperature hardness decay and insufficient wear resistance, are specifically addressed, thereby improving the overall service performance and stability of the coating. In the functional layer, the double-modified nano-ZrB2 is modified by dual coating with silane coupling agent KH-560 and NiCr alloy, effectively overcoming the bottleneck of poor interfacial compatibility between traditional single ZrB2 and the Al2O3 matrix. This avoids ZrB2 particle agglomeration and interfacial delamination at high temperatures, while leveraging the strong interfacial bonding force to exert the excellent high-temperature mechanical stability of ZrB2, forming a reliable intracrystalline dispersion strengthening effect. This hinders high-temperature atomic diffusion and dislocation movement, fundamentally suppressing the loose structure and hardness decay of the coating.

[0013] The introduction of rare earth CeO2 is not a simple doping process, but rather a synergistic effect with the Al2O3-NiCrAlY matrix. It can directionally agglomerate at the grain boundaries of the functional layer, constructing a composite structure of "intragranular strengthening + grain boundary locking". Ce elements at the grain boundaries can fill vacancies, purify impurities, reduce grain boundary migration energy, inhibit grain boundary diffusion and grain growth at high temperatures, and further block the hardness decay path. At the same time, CeO2 can regulate oxygen vacancies through valence state transformation, promoting the formation of a dense Al2O3-CeO2 composite oxide film on the coating surface. This not only retains the original antioxidant properties, but also reduces the coefficient of friction between the coating and the workpiece, helping to improve wear resistance and preventing scratches and peeling of the coating due to abrasive wear.

[0014] The TiN-SiC gradient composite transition layer design provides structural support for the functional layer's performance. The gradient distribution of components achieves a smooth transition in the coefficient of thermal expansion from the mold substrate to the functional layer, effectively mitigating stress concentration caused by abrupt changes in the coefficient of thermal expansion under high-temperature conditions and preventing stress cracking from exacerbating wear. The high hardness of TiN and the high wear resistance of SiC complement each other, and the strong interfacial bonding force of the gradient structure ensures a stable bond between the functional layer and the substrate. This allows the synergistic strengthening effect of the dual-modified ZrB2 and CeO2 to be fully realized, ultimately achieving a synergistic improvement in the coating's high-temperature hardness stability and wear resistance, while retaining excellent high-temperature oxidation resistance, making it suitable for the harsh service environment of high-pressure hot-pressing molds.

[0015] In the transition layer described in this invention, the TiN mass percentage decreases linearly from 80%-85% to 30%-35% from the side near the mold substrate to the side near the functional layer, while the SiC mass percentage increases linearly from 15%-20% to 65%-70%.

[0016] By adopting the above technical solution, the design of decreasing TiN content and increasing SiC content from the substrate side to the functional layer side can precisely match the difference in thermal expansion coefficients between the substrate and the functional layer, avoiding interfacial stress concentration caused by abrupt gradient changes. Compared with coatings without a clear gradient range, this design can more effectively suppress interfacial delamination between the transition layer and the substrate / functional layer at high temperatures, reducing coating cracking and wear caused by stress. Simultaneously, increasing SiC content towards the functional layer side improves the interfacial compatibility between the transition layer and the Al2O3-based functional layer, while increasing TiN content towards the substrate side strengthens the bonding strength between the transition layer and the mold substrate. This provides a more reliable structural guarantee for the functional layer to resist high-pressure frictional impact, indirectly improving the overall wear resistance and high-temperature hardness stability of the coating.

[0017] The dual-modified nano-ZrB2 of this invention is prepared by the following method:

[0018] A1. Disperse nano-ZrB2 particles in anhydrous ethanol and sonicate to obtain a suspension. Then add silane coupling agent KH-560, adjust the pH of the system to 4.5-5.5, and stir the reaction at 70-85℃ and 300-500 r / min for 2.5-3.5 h. After the reaction is completed, centrifuge and dry in a vacuum environment at 100-120℃ for 2-3 h to obtain silane-modified ZrB2.

[0019] A2. Disperse silane-modified ZrB2 in NiCr salt solution, add chromium citrate as a complexing agent, adjust the pH to 8-9, add hydrazine hydrate solution at 50-60℃, and then keep the reaction at this temperature for 1-2 hours. After the reaction is complete, centrifuge and wash until neutral, dry in a vacuum environment at 300-350℃ for 1-2 hours, and grind to obtain double-modified nano ZrB2.

[0020] By adopting the above technical solution, a two-step modification process ensures controllable modification effects, providing key technical support for solving the problems of high-temperature hardness decay and insufficient wear resistance. The silane modification step constructs an organic bonding layer on the ZrB2 surface, improving its dispersion uniformity in the functional layer matrix and preventing particle agglomeration that forms localized weak points. The NiCr alloy coating step forms a transition layer on the ZrB2 surface through chemical plating, enabling it to form a metallurgical bond with the NiCrAlY in the functional layer, completely solving the interfacial compatibility problem between ZrB2 and the ceramic matrix. The synergistic effect of the two-step modification allows ZrB2 to stably exert its high-temperature strengthening effect while resisting interfacial delamination under high-pressure friction, significantly reducing the high-temperature hardness decay of the coating and improving wear resistance. Simultaneously, the preparation steps are simple and controllable, ensuring consistent coating performance.

[0021] In step A1 of this invention, the mass ratio of nano ZrB2 particles to anhydrous ethanol is 1:(12-20), the ultrasonic power is 300-400W, and the ultrasonic time is 20-30min.

[0022] In step A1 of this invention, the amount of silane coupling agent KH-560 added is 2%-4% of the total mass of the suspension.

[0023] In step A2 of this invention, the mass ratio of the silane-modified ZrB2 to the NiCr salt solution is 1:(20-30); the NiCr salt solution is prepared by using nickel nitrate and chromium chloride, and the concentration of nickel ions in the NiCr salt solution is 0.08-0.12 mol / L and the concentration of chromium ions is 0.03-0.05 mol / L.

[0024] By employing the above technical solution, the mass ratio of silane-modified ZrB2 to NiCr salt solution and the concentration of salt solution components are limited, optimizing the NiCr alloy coating effect and strengthening the interfacial bonding between ZrB2 and the functional layer. A reasonable solid-liquid ratio ensures that the silane-modified ZrB2 particles are in full contact with NiCr ions, while the matched concentrations of nickel nitrate and chromium chloride precisely control the Ni to Cr ratio in the coating layer, ensuring perfect compatibility with NiCrAlY in the functional layer and forming a stable metallurgically miscible zone. A uniform and well-matched NiCr alloy coating layer effectively transfers stress, preventing ZrB2 from peeling off from the substrate under high temperature and pressure, ensuring the continuous performance of dispersion strengthening, and reducing hardness decay. Simultaneously, it enhances the wear resistance of ZrB2 particles, reducing coating wear caused by particle shedding during friction, and further optimizing the coating's service performance.

[0025] In step A2 of this invention, the mass concentration of the hydrazine hydrate solution is 20%-25%, and the amount of hydrazine hydrate solution added is 8%-12% of the total mass of the NiCr salt solution.

[0026] By adopting the above technical solution, the above raw material addition ratio can ensure the density and uniformity of the NiCr alloy coating, providing a guarantee for improving the coating's wear resistance and high-temperature hardness stability.

[0027] This application also provides a method for preparing an antioxidant coating for a high-pressure hot-pressing mold, using the following technical solution:

[0028] A method for preparing an antioxidant coating for a high-pressure hot-pressing mold includes the following steps:

[0029] S1. Polish the high-pressure hot-pressing mold substrate until the surface roughness Ra ≤ 0.2 μm;

[0030] S2. Using Ti and SiC targets as sputtering sources, a transition layer is sputtered and deposited on a high-pressure hot-pressing mold substrate. The substrate temperature is controlled at 320-420℃ during the deposition process, and the total deposition time is 4-8 hours.

[0031] S3. A vacuum evaporation-RF sputtering composite process is adopted, with Al2O3 and NiCrAlY targets used as the evaporation source and sputtering source, respectively. Double-modified nano ZrB2 and CeO2 are mixed into the Al2O3 evaporation material in a certain proportion. The substrate temperature is 480-580℃, the Al2O3 evaporation power is 900-1300W, the NiCrAlY sputtering power is 150-220W, the deposition rate is 0.25-0.55μm / h, and the total deposition time is 4-8h.

[0032] S4. After deposition, the high-pressure hot press mold substrate is annealed at 680-720℃ for 1-3 hours and then cooled to room temperature in the furnace to obtain the high-pressure hot press mold anti-oxidation coating.

[0033] By adopting the above technical solution, the coating structure and performance are optimized through step-by-step coating and annealing, specifically addressing the issues of high-temperature hardness decay and insufficient wear resistance. The vacuum evaporation-RF sputtering composite process balances the density of the functional layer with the uniformity of multiple components, preventing porosity defects from becoming weak points for wear and oxidation. Reasonable control of temperature, power, and time parameters at each stage guides Ce element segregation towards grain boundaries, promoting interfacial bonding between the double-modified ZrB2 and the substrate. Subsequent annealing eliminates deposition stress, optimizes the solid solution structure, refines grains, further strengthens the intercomponent bonding force, reduces grain growth and structural loosening at high temperatures, reduces the hardness decay rate, and simultaneously improves the coating's toughness and wear resistance, ensuring stable service under long-term high-temperature and high-pressure alternating conditions.

[0034] In step S1 of the present invention, the polished high-pressure hot-press mold substrate is placed in the chamber of a multi-target composite vacuum coating machine and activated by argon ion bombardment.

[0035] By adopting the above technical solution and adding an argon ion bombardment activation step, the bonding strength between the coating and the substrate is improved by optimizing the substrate surface condition, thereby indirectly improving the coating's wear resistance and high-temperature stability. Argon ion bombardment can effectively remove oxide films, oil stains, and impurities from the substrate surface, forming a clean surface with a certain degree of roughness, increasing the contact area between the coating and the substrate, and simultaneously activating the atomic activity of the substrate surface, promoting a more stable bond between the transition layer and the substrate. The improved bonding strength between the coating and the substrate can prevent the overall peeling of the coating under high-temperature and high-pressure friction, ensuring that the synergistic effect of the transition layer and the functional layer is fully utilized, reducing hardness decay and wear caused by interface failure, and extending the service life of the coating.

[0036] The specific process parameters for the argon ion bombardment activation treatment described in this invention are: argon flow rate 22-28 sccm, bombardment voltage 900-1300V, and bombardment time 18-32min.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] 1. This application employs a functional layer design of "double-modified nano-ZrB2 + grain boundary segregated CeO2" composite doping, coupled with a TiN-SiC gradient transition layer, to specifically address the core issues of high-temperature hardness decay and insufficient wear resistance in existing coatings. Double-modified nano-ZrB2, through dual coating modification, overcomes the traditional bottleneck of interfacial compatibility between ZrB2 and the ceramic matrix, avoiding high-temperature agglomeration and interfacial delamination, while also exerting a strong intragranular dispersion strengthening effect, hindering atomic diffusion and dislocation movement, thus suppressing hardness decay at its source. CeO2 is directionally segregated at the grain boundaries, constructing a "grain boundary strengthening + grain boundary locking" structure, further blocking the grain growth path, while simultaneously promoting the formation of a dense composite oxide film, thus balancing oxidation resistance and wear resistance. The gradient transition layer achieves a smooth transition in the coefficient of thermal expansion, alleviating stress concentration and providing stable support for the performance of the functional layer, achieving a synergistic improvement in high-temperature hardness stability and wear resistance.

[0039] 2. This application preferably employs a two-step method to prepare dual-modified nano-ZrB2. By precisely controlling the modification process and component ratios, the stable performance of the strengthening phase interaction is ensured, further optimizing the high-temperature mechanical properties of the coating. The silane modification step constructs an organic bonding layer on the ZrB2 surface, improving its dispersion uniformity in the functional layer and avoiding the formation of local weak points. The NiCr alloy coating step, through component ratio control, forms a metallurgical bonding interface adapted to the functional layer, enhancing stress transmission capability and preventing interface delamination under high temperature and pressure. Simultaneously, the reasonable control of the hydrazine hydrate concentration and addition amount ensures a dense and uniform NiCr alloy coating layer, which not only improves the wear resistance of ZrB2 itself but also ensures the long-term stability of the dispersion strengthening effect, significantly reducing the high-temperature hardness decay of the coating and minimizing failure problems caused by friction and wear.

[0040] 3. The preparation method of this application, through the synergistic combination of step-by-step plating, argon ion bombardment activation, and annealing, ensures coating performance from a process perspective, effectively improving the defects of high-temperature hardness decay and insufficient wear resistance. Argon ion bombardment activation can thoroughly remove impurities and oxide films from the substrate surface, forming a clean and rough surface, improving the bonding strength between the coating and the substrate, and preventing overall coating peeling under high-temperature and high-pressure friction. The vacuum evaporation-RF sputtering composite process balances coating density and component uniformity, reducing porosity defects; the subsequent annealing treatment eliminates deposition stress, optimizes the microstructure, refines grains, and strengthens the bonding between components. The entire process can guide the directional segregation of Ce elements, promote the synergistic effect of each component, ensure that the coating maintains structural integrity under long-term high-temperature and high-pressure alternating conditions, and extend its service life. Detailed Implementation

[0041] The present application will be further described in detail below with reference to the embodiments.

[0042] Preparation example of dual-modified nano ZrB2

[0043] Preparation Example 1

[0044] The dual-modified nano-ZrB2 was prepared using the following method:

[0045] A1. 1 kg of nano ZrB2 particles were dispersed in 12 kg of anhydrous ethanol and subjected to ultrasonic treatment at a power of 300 W for 20 min. After treatment, a suspension was obtained. Then, 0.26 kg of silane coupling agent KH-560 was added to adjust the pH of the system to 4.5. The mixture was stirred at 70 °C and 300 r / min for 2.5 h. After the reaction was completed, the mixture was centrifuged and dried under vacuum at 100 °C for 2 h to obtain silane-modified ZrB2.

[0046] A2. 1 kg of silane-modified ZrB2 was dispersed in 20 kg of NiCr salt solution (the NiCr salt solution was prepared by nickel nitrate and chromium chloride, with a nickel ion concentration of 0.08 mol / L and a chromium ion concentration of 0.03 mol / L). 1.2 kg of chromium citrate was added as a complexing agent, the pH was adjusted to 8, and 1.6 kg of 20% hydrazine hydrate solution was added at 50 °C. The reaction was then kept at this temperature for 1 h. After the reaction was completed, the mixture was centrifuged and washed until neutral. It was then dried in a vacuum environment at 300 °C for 1 h and ground to obtain double-modified nano ZrB2.

[0047] Preparation Example 2

[0048] The dual-modified nano-ZrB2 was prepared using the following method:

[0049] A1. 1 kg of nano ZrB2 particles were dispersed in 16 kg of anhydrous ethanol and subjected to ultrasonic treatment at a power of 350 W for 25 min. After treatment, a suspension was obtained. Then, 0.51 kg of silane coupling agent KH-560 was added to adjust the pH of the system to 5.0. The mixture was stirred at 78 °C and 400 r / min for 3.0 h. After the reaction was completed, the mixture was centrifuged and dried under vacuum at 110 °C for 2.5 h to obtain silane-modified ZrB2.

[0050] A2. 1 kg of silane-modified ZrB2 was dispersed in 25 kg of NiCr salt solution (the NiCr salt solution was prepared by nickel nitrate and chromium chloride, with a nickel ion concentration of 0.10 mol / L and a chromium ion concentration of 0.04 mol / L). 1.4 kg of chromium citrate was added as a complexing agent, and the pH was adjusted to 8.5. 2.5 kg of 22% hydrazine hydrate solution was added at 55 °C, and the reaction was kept at this temperature for 1.5 h. After the reaction was completed, the mixture was centrifuged and washed until neutral. It was then dried in a vacuum environment at 325 °C for 1.5 h and ground to obtain double-modified nano ZrB2.

[0051] Preparation Example 3

[0052] The dual-modified nano-ZrB2 was prepared using the following method:

[0053] A1. 1 kg of nano ZrB2 particles were dispersed in 20 kg of anhydrous ethanol and subjected to ultrasonic treatment at a power of 400 W for 30 min. After treatment, a suspension was obtained. Then, 0.84 kg of silane coupling agent KH-560 was added to adjust the pH of the system to 5.5. The mixture was stirred at 85 °C and 500 r / min for 3.5 h. After the reaction was completed, the mixture was centrifuged and dried under vacuum at 120 °C for 3 h to obtain silane-modified ZrB2.

[0054] A2. 1 kg of silane-modified ZrB2 was dispersed in 30 kg of NiCr salt solution (the NiCr salt solution was prepared by nickel nitrate and chromium chloride, with a nickel ion concentration of 0.12 mol / L and a chromium ion concentration of 0.05 mol / L). 1.6 kg of chromium citrate was added as a complexing agent, the pH was adjusted to 9, and 3.6 kg of 25% hydrazine hydrate solution was added at 60 °C. The reaction was then kept at this temperature for 2 h. After the reaction was completed, the mixture was centrifuged and washed until neutral. It was then dried in a vacuum environment at 350 °C for 2 h and ground to obtain double-modified nano ZrB2.

[0055] Example

[0056] Example 1

[0057] An anti-oxidation coating for a high-pressure hot-press mold includes a transition layer and a functional layer arranged sequentially from the mold substrate outwards. The transition layer is a TiN-SiC gradient composite layer. From the side closer to the mold substrate to the side closer to the functional layer, the mass percentage of TiN in the transition layer linearly decreases from 80% to 30%, and the mass percentage of SiC linearly increases from 20% to 70%.

[0058] The functional layer is based on Al2O3-NiCrAlY and is composite-doped with double-modified nano-ZrB2 and rare earth CeO2.

[0059] The functional layer is made from the following raw materials by weight: 64 kg Al2O3, 18 kg NiCrAlY, 6 kg double-modified nano ZrB2, and 0.8 kg CeO2; the double-modified nano ZrB2 is the double-modified nano ZrB2 prepared in Preparation Example 1.

[0060] A method for preparing an antioxidant coating for a high-pressure hot-pressing mold includes the following steps:

[0061] S1. Polish the high-pressure hot-pressing mold substrate until the surface roughness Ra≤0.2μm; ultrasonically clean it with acetone and anhydrous ethanol for 30min each, dry it at 80℃, and then place it in the chamber of a multi-target composite vacuum coating machine. Use argon ion bombardment activation treatment to remove the surface oxide film and impurities before use. The specific process parameters for argon ion bombardment activation treatment are: argon flow rate 22sccm, bombardment voltage 900V, and bombardment time 18min.

[0062] S2. Using Ti and SiC targets as sputtering sources, a transition layer is sputtered and deposited on a high-pressure hot-pressing mold substrate. The composition gradient distribution is achieved by adjusting the sputtering power ratio of the two targets in real time (the power of the Ti target is linearly reduced from 350W to 120W, and the power of the SiC target is linearly increased from 80W to 280W). The substrate temperature is controlled at 320℃ during the deposition process, and the total deposition time is 4h.

[0063] S3. A vacuum evaporation-RF sputtering composite process was adopted, with Al2O3 and NiCrAlY targets used as the evaporation source and sputtering source, respectively. Double-modified nano ZrB2 and CeO2 were mixed into the Al2O3 evaporation material in a certain proportion. The substrate temperature was 480℃, the Al2O3 evaporation power was 900W, the NiCrAlY sputtering power was 150W, the deposition rate was 0.25μm / h, and the total deposition time was 4h.

[0064] S4. After deposition, the high-pressure hot press mold substrate is annealed at 680℃ for 1 hour and then cooled to room temperature in the furnace to obtain the high-pressure hot press mold anti-oxidation coating.

[0065] Example 2

[0066] An anti-oxidation coating for a high-pressure hot-press mold includes a transition layer and a functional layer arranged sequentially from the mold substrate outwards. The transition layer is a TiN-SiC gradient composite layer. From the side closer to the mold substrate to the side closer to the functional layer, the mass percentage of TiN in the transition layer linearly decreases from 82% to 32%, and the mass percentage of SiC linearly increases from 18% to 68%.

[0067] The functional layer is based on Al2O3-NiCrAlY and is composite-doped with double-modified nano-ZrB2 and rare earth CeO2.

[0068] The functional layer is made from the following raw materials by weight: 68 kg Al2O3, 1 kg NiCrAlY2, 9 kg double-modified nano ZrB2, and 1.5 kg CeO2; the double-modified nano ZrB2 is the double-modified nano ZrB2 prepared in Preparation Example 1.

[0069] A method for preparing an antioxidant coating for a high-pressure hot-pressing mold includes the following steps:

[0070] S1. Polish the high-pressure hot-pressing mold substrate until the surface roughness Ra≤0.2μm; then ultrasonically clean it with acetone and anhydrous ethanol for 30min each, dry it at 80℃, and place it in the chamber of a multi-target composite vacuum coating machine. Use argon ion bombardment activation treatment to remove the surface oxide film and impurities before use. The specific process parameters for argon ion bombardment activation treatment are: argon flow rate 25sccm, bombardment voltage 1100V, and bombardment time 25min.

[0071] S2. Using Ti and SiC targets as sputtering sources, a transition layer is sputtered and deposited on a high-pressure hot-pressing mold substrate. The composition gradient distribution is achieved by adjusting the sputtering power ratio of the two targets in real time (the power of the Ti target is linearly reduced from 330W to 100W, and the power of the SiC target is linearly increased from 90W to 300W). The substrate temperature is controlled at 370℃ during the deposition process, and the total deposition time is 6 hours.

[0072] S3. A vacuum evaporation-RF sputtering composite process was adopted, with Al2O3 and NiCrAlY targets used as the evaporation source and sputtering source, respectively. Double-modified nano ZrB2 and CeO2 were mixed into the Al2O3 evaporation material in a certain proportion. The substrate temperature was 530℃, the Al2O3 evaporation power was 1100W, the NiCrAlY sputtering power was 180W, the deposition rate was 0.40μm / h, and the total deposition time was 6h.

[0073] S4. After deposition, the high-pressure hot press mold substrate is annealed at 700℃ for 2 hours and then cooled to room temperature in the furnace to obtain the high-pressure hot press mold anti-oxidation coating.

[0074] Example 3

[0075] An anti-oxidation coating for a high-pressure hot-press mold includes a transition layer and a functional layer arranged sequentially from the mold substrate outwards. The transition layer is a TiN-SiC gradient composite layer. From the side closer to the mold substrate to the side closer to the functional layer, the mass percentage of TiN in the transition layer linearly decreases from 85% to 35%, and the mass percentage of SiC linearly increases from 15% to 65%.

[0076] The functional layer is based on Al2O3-NiCrAlY and is composite-doped with double-modified nano-ZrB2 and rare earth CeO2.

[0077] The functional layer is made from the following raw materials by weight: 72 kg Al2O3, 24 kg NiCrAlY, 12 kg double-modified nano ZrB2, and 2.2 kg CeO2; the double-modified nano ZrB2 is the double-modified nano ZrB2 prepared in Preparation Example 1.

[0078] A method for preparing an antioxidant coating for a high-pressure hot-pressing mold includes the following steps:

[0079] S1. Polish the high-pressure hot-pressing mold substrate until the surface roughness Ra≤0.2μm; then ultrasonically clean it with acetone and anhydrous ethanol for 30min each, dry it at 80℃, and place it in the chamber of a multi-target composite vacuum coating machine. Use argon ion bombardment activation treatment to remove the surface oxide film and impurities before use. The specific process parameters for argon ion bombardment activation treatment are: argon flow rate 28sccm, bombardment voltage 1300V, and bombardment time 32min.

[0080] S2. Using Ti and SiC targets as sputtering sources, a transition layer is sputtered and deposited on a high-pressure hot-pressing mold substrate. The composition gradient distribution is achieved by adjusting the sputtering power ratio of the two targets in real time (the power of the Ti target is linearly reduced from 320W to 90W, and the power of the SiC target is linearly increased from 100W to 320W). The substrate temperature is controlled at 420℃ during the deposition process, and the total deposition time is 8h.

[0081] S3. A vacuum evaporation-RF sputtering composite process was adopted, with Al2O3 and NiCrAlY targets used as the evaporation source and sputtering source, respectively. Double-modified nano ZrB2 and CeO2 were mixed into the Al2O3 evaporation material in a certain proportion. The substrate temperature was 580℃, the Al2O3 evaporation power was 1300W, the NiCrAlY sputtering power was 220W, the deposition rate was 0.55μm / h, and the total deposition time was 8h.

[0082] S4. After deposition, the high-pressure hot press mold substrate is annealed at 720℃ for 3 hours and then cooled to room temperature in the furnace to obtain the high-pressure hot press mold anti-oxidation coating.

[0083] Example 4

[0084] An anti-oxidation coating for a high-pressure hot-pressing mold, which differs from Example 3 in that the double-modified nano ZrB2 in this example is the double-modified nano ZrB2 prepared in Preparation Example 2.

[0085] Example 5

[0086] An anti-oxidation coating for a high-pressure hot-pressing mold, which differs from Example 3 in that the double-modified nano ZrB2 in this example is the double-modified nano ZrB2 prepared in Preparation Example 3.

[0087] Example 6

[0088] An anti-oxidation coating for a high-pressure hot-pressing mold, which differs from Example 3 in that the functional layer in this example is made from the following raw materials by weight: 72 kg of Al2O3, 24 kg of NiCrAlY, 26 kg of double-modified nano ZrB, and 2.2 kg of CeO2.

[0089] Comparative Example

[0090] Comparative Example 1

[0091] An anti-oxidation coating for a high-pressure hot-pressing mold. The difference between this comparative example and Example 3 is that the functional layer does not use double-modified nano ZrB2, but instead uses single silane-modified ZrB2. The preparation of silane-modified ZrB2 retains only step A1 of preparation example 1 in Example 3, without the NiCr alloy coating step. The remaining components, preparation process and parameters are the same as in Example 3.

[0092] Comparative Example 2

[0093] An anti-oxidation coating for high-pressure hot-pressing molds is provided. The difference between this comparative example and Example 3 is that the CeO2 component is removed from the functional layer, the weight of Al2O3 is adjusted to 74.2 kg (keeping the total weight of the functional layer unchanged), and CeO2 is not added. The remaining components, preparation process and parameters are the same as those in Example 3.

[0094] Comparative Example 3

[0095] An anti-oxidation coating for high-pressure hot-pressing molds is disclosed. The difference between this comparative example and Example 3 is that the TiN-SiC gradient transition layer is replaced with a single TiN transition layer. During preparation, only a Ti target is used as the sputtering source, the Ti target power is fixed at 200W, and a SiC target is not used. The thickness of the transition layer is the same as in Example 3. The remaining components, preparation process and parameters are the same as in Example 3.

[0096] Comparative Example 4

[0097] An anti-oxidation coating for a high-pressure hot-pressing mold is provided. The difference between this comparative example and Example 3 is that the argon ion bombardment activation treatment step is not performed in step S1. The substrate after polishing, cleaning and drying is directly put into the coating machine chamber for transition layer deposition. The remaining components, preparation process and parameters are the same as those in Example 3.

[0098] Performance testing

[0099] Test samples: Antioxidant coatings of high-pressure hot-press molds prepared in Examples 1-6 and Comparative Examples 1-4.

[0100] Test items:

[0101] 1. High-temperature hardness decay rate test

[0102] The microhardness of each sample was tested using a Vickers hardness tester at room temperature (25℃) and at high temperature (800℃, held for 2 hours) (load 500g, held for 10s). Five different points were tested for each sample, and the average value was taken. The high-temperature hardness decay rate = (room temperature hardness - high-temperature hardness) / room temperature hardness × 100%. The smaller the value, the better the high-temperature hardness stability.

[0103] 2. Wear resistance test

[0104] A ball-and-disc friction and wear testing machine was used, with Si3N4 ceramic balls as the grinding pair. The test conditions were: load 5N, rotation speed 300r / min, wear time 60min, and dry friction environment at room temperature. The mass of the sample was weighed using an electronic balance before and after the test. The wear amount = mass before test - mass after test; the smaller the value, the better the wear resistance.

[0105] 3. Interface bonding strength test

[0106] The scratch method was used, with a diamond indenter (100 μm in diameter) on the scratch instrument, a loading rate of 10 N / min, a scratch length of 5 mm, and a scratch speed of 1 mm / s. The edges and bottom of the scratches were observed under a microscope, and the critical load at which the coating peeled off was recorded. The higher the critical load, the higher the bonding strength.

[0107] 4. High-temperature oxidation stability test

[0108] The sample was placed in a muffle furnace and oxidized at a constant temperature of 800℃ for 100 hours. The mass was measured with an electronic balance before and after oxidation. The weight gain after oxidation = (mass after oxidation - mass before oxidation) / surface area of ​​the sample coating. The smaller the value, the better the oxidation resistance.

[0109] Test results are shown in Table 1.

[0110] Table 1 Test Results

[0111]

[0112] As can be seen from the test data in Table 1, regarding the high-temperature hardness decay rate, Examples 1-6 showed a decay rate of only 8.5%-12.3%, while Comparative Examples 1-4 all exceeded 18%, with Comparative Example 1 (single silane-modified ZrB2) reaching 27.6%. The core reason lies in the synergistic effect of the dual-modified ZrB2 in this application. The silane coupling agent improves dispersibility, and the NiCr alloy coating layer constructs a metallurgical bonding interface, avoiding ZrB2 agglomeration and interface peeling at high temperatures, effectively hindering atomic diffusion and suppressing hardness decay from the root. In contrast, single silane modification lacks an alloy transition layer, has poor interface compatibility, and is prone to failure at high temperatures, leading to a sharp drop in hardness.

[0113] The wear resistance data showed significant differences. The wear amount in the examples was only 0.58-0.82 mg, far lower than the 1.32-2.15 mg in comparative examples 1-4. This is attributed to the composite strengthening system of "dual-modified ZrB2 + CeO2": the high-temperature mechanical stability of ZrB2 forms dispersion strengthening, CeO2 is oriented and agglomerated at the grain boundaries to lock the grains, and at the same time promotes the formation of a dense Al2O3-CeO2 oxide film, reducing the coefficient of friction. Comparative example 2, due to the lack of CeO2, had grains that easily grew and an oxide film that was not dense, resulting in a significant increase in wear amount, confirming the auxiliary role of CeO2 in improving wear resistance.

[0114] Regarding interfacial bonding strength, the critical load in the examples was 48-62 N, while in the comparative examples it was only 27-35 N, a significant difference. The design of the TiN-SiC gradient transition layer is crucial; its component gradient distribution achieves a smooth transition in the coefficient of thermal expansion, alleviating high-temperature stress concentration and preventing coating cracking and peeling. In contrast, Comparative Example 3 uses a single TiN transition layer, which has a mismatch in the coefficient of thermal expansion with the substrate and functional layer, resulting in high interfacial stress and low bonding strength. Furthermore, argon ion bombardment activation (used in all examples, but omitted in Comparative Example 4) removes the oxide film and increases the roughness of the substrate, further improving the coating's bonding strength.

[0115] In the high-temperature oxidation weight gain data, the examples (0.025-0.032 cm) 2 It is far superior to the comparative ratio (0.041-0.068 mg / cm³). 2 This demonstrates the coating's excellent antioxidant stability. The valence state transformation of CeO2 can regulate oxygen vacancies and inhibit oxidation diffusion. The synergistic effect of the dual-modified ZrB2 and the NiCrAlY matrix also enhances oxidation resistance. In Comparative Example 1, due to the failure of the ZrB2 interface, oxidation easily penetrates along the interface, resulting in significant weight gain. In Comparative Example 2, without CeO2 regulation, the oxide film lacks density, leading to a decrease in antioxidant capacity.

[0116] In summary, Example 3 exhibits the best performance. Its optimized dual-modification process, complete CeO2 synergistic system, reasonable gradient transition layer, and standardized pretreatment process create a synergistic effect, resulting in the lowest high-temperature hardness decay rate, minimal wear, and highest bonding strength. Examples 4-6, due to slight adjustments in the preparation parameters of the dual-modified ZrB2 or the functional layer ratio, show minor performance fluctuations but are still far superior to the comparative examples, confirming the stability and superiority of the technical solution presented in this application and specifically addressing the core defects of existing coatings.

Claims

1. An anti-oxidation coating for high-pressure hot-pressing molds, characterized in that, It includes a transition layer and a functional layer arranged sequentially from the mold substrate outwards. The transition layer is a TiN-SiC gradient composite layer, and the functional layer is based on Al2O3-NiCrAlY and is composite doped with nano-ZrB2 and rare earth CeO2 that have undergone double modification treatment. The functional layer is made from the following raw materials in parts by weight: 64-72 parts Al2O3, 18-24 parts NiCrAlY, 6-12 parts double-modified nano ZrB2, and 0.8-2.2 parts CeO2; the double-modified nano ZrB2 is ZrB2 particles coated with silane coupling agent KH-560 and NiCr alloy. From the side closer to the mold substrate to the side closer to the functional layer, the mass percentage of TiN linearly decreases from 80%-85% to 30%-35%, while the mass percentage of SiC linearly increases from 15%-20% to 65%-70%. The dual-modified nano-ZrB2 was prepared by the following methods: A1. Nano-ZrB2 particles were dispersed in anhydrous ethanol and ultrasonically treated to obtain a suspension. Then, silane coupling agent KH-560 was added, and the pH of the system was adjusted to 4.5-5.

5. The mixture was stirred at 70-85℃ and 300-500 r / min for 2.5-3.5 h. After the reaction, the mixture was centrifuged and dried under vacuum at 100-120℃ for 2-3 h to obtain silane-modified ZrB2. A2. Silane-modified ZrB2 was dispersed in NiCr salt solution, and chromium citrate was added as a complexing agent. The pH was adjusted to 8-9, and hydrazine hydrate solution was added at 50-60℃. The mixture was then kept at this temperature for 1-2 h. After the reaction, the mixture was centrifuged and washed until neutral. It was dried under vacuum at 300-350℃ for 1-2 h and then ground to obtain dual-modified nano-ZrB2.

2. The anti-oxidation coating for high-pressure hot-pressing molds according to claim 1, characterized in that: In step A1, the mass ratio of nano ZrB2 particles to anhydrous ethanol is 1:(12-20), and the ultrasonic power is 300-400W and the ultrasonic time is 20-30min.

3. The anti-oxidation coating for high-pressure hot-pressing molds according to claim 2, characterized in that: In step A1, the amount of silane coupling agent KH-560 added is 2%-4% of the total mass of the suspension.

4. The anti-oxidation coating for high-pressure hot-pressing molds according to claim 3, characterized in that: In step A2, the mass ratio of the silane-modified ZrB2 to the NiCr salt solution is 1:(20-30); the NiCr salt solution is prepared by using nickel nitrate and chromium chloride, and the concentration of nickel ions in the NiCr salt solution is 0.08-0.12 mol / L and the concentration of chromium ions is 0.03-0.05 mol / L.

5. The anti-oxidation coating for high-pressure hot-pressing molds according to claim 4, characterized in that: In step A2, the mass concentration of the hydrazine hydrate solution is 20%-25%, and the amount of hydrazine hydrate solution added is 8%-12% of the total mass of the NiCr salt solution.

6. A method for preparing an anti-oxidation coating for a high-pressure hot-pressing mold according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Polish the high-pressure hot-pressing mold substrate until the surface roughness Ra ≤ 0.2 μm; S2. Using Ti and SiC targets as sputtering sources, a transition layer is sputtered and deposited on a high-pressure hot-pressing mold substrate. The substrate temperature is controlled at 320-420℃ during the deposition process, and the total deposition time is 4-8 hours. S3. A vacuum evaporation-RF sputtering composite process is adopted, with Al2O3 and NiCrAlY targets used as the evaporation source and sputtering source, respectively. Double-modified nano ZrB2 and CeO2 are mixed into the Al2O3 evaporation material in a certain proportion. The substrate temperature is 480-580℃, the Al2O3 evaporation power is 900-1300W, the NiCrAlY sputtering power is 150-220W, the deposition rate is 0.25-0.55μm / h, and the total deposition time is 4-8h. S4. After deposition, the high-pressure hot press mold substrate is annealed at 680-720℃ for 1-3 hours and then cooled to room temperature in the furnace to obtain the high-pressure hot press mold anti-oxidation coating.

7. The method for preparing an anti-oxidation coating for a high-pressure hot-pressing mold according to claim 6, characterized in that: In step S1, the polished high-pressure hot-press mold substrate is placed in the chamber of a multi-target composite vacuum coating machine and activated by argon ion bombardment.

8. The method for preparing an anti-oxidation coating for a high-pressure hot-pressing mold according to claim 7, characterized in that: The specific process parameters for argon ion bombardment activation treatment are: argon flow rate 22-28 sccm, bombardment voltage 900-1300V, and bombardment time 18-32min.

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