Long-life anti-erosion coating on carbon / carbon composite surface against ultra-high temperature and its preparation method

Abstract

The application provides a long-life anti-ultra-high-temperature cycle ablation coating on the surface of carbon / carbon composite material and a preparation method thereof, and solves the problems of a narrow ablation-resistant temperature range, poor anti-cycle thermal shock performance and difficulty in reuse of the coating. The coating is (Hf, Zr)C-La2O3, wherein the addition of La2O3 can inhibit the transformation of HfO2, ZrO2 and (Hf, Zr)O2 oxides from tetragonal phase to monoclinic phase, retain part of the tetragonal phase, weaken the cracks caused by phase transformation or even shedding, and thus improve the ablation resistance of the (Hf, Zr)C coating. In addition, the melting point of La2O3 is lower than the ablation temperature, and the phase is in a molten state during the ablation process. An appropriate amount of La2O3 can not only serve as a molten phase to heal the cracks and pores in the coating, but also can form a La-doped (Hf, Zr)O2 oxide film with a dense structure through solid solution reaction with (Hf, Zr)O2, further densify the surface of the coating, effectively block the penetration of oxygen during the ablation process, and inhibit the phase transformation of the oxide film.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of ultra-high temperature ablation-resistant coating, and particularly relates to a long-life ultra-high temperature cycle ablation-resistant coating on the surface of carbon / carbon composite material and a preparation method thereof. BACKGROUND

[0002] Carbon / carbon (C / C) composite material is widely used in aerospace field due to its low density, high thermal conductivity and high mechanical retention in inert atmosphere. However, when the C / C composite material is used in high-temperature oxygen-containing environment (above 2000℃), the carbon fiber will be damaged due to oxidation and ablation, which will greatly reduce the mechanical properties of the material and limit the application of the material in the ultra-high temperature field. In order to improve the ultra-high temperature ablation resistance of the C / C composite material, preparing an ablation-resistant coating on the surface of the C / C composite material is an effective means to protect the C / C composite material for a long time. However, the existing HfC and ZrC coatings have a narrow ablation-resistant temperature range and poor cycle thermal shock resistance, which are difficult to be reused and cannot meet the actual use requirements. However, the demand for reusable thermal protection components of modern spacecraft is becoming more and more urgent, so it is necessary to seek new coating materials to improve the cycle ablation resistance of the C / C composite material in a wide temperature range and ensure its long-term stable service in ultra-high temperature extreme environment.

[0003] Document 1 "Ren Jincui, Zhang Yulei, Zhang Jian, et al. Effects of HfC nanowire amount on the microstructure and ablation resistance of CVD-HfC coating. Ceramics International, 2018, 44: 11340-11349." and Document 2 "Feng Guanghui, Li Hejun, Yao Xiyuan, et al. Ablation resistance of TaC-modified HfC coating prepared by supersonic plasma spraying for SiC-coated carbon / carbon composites, Ceramics International, 2019, 45: 17936-17945." respectively prepared HfC coatings on the surface of C / C composite material by chemical vapor deposition and supersonic plasma spraying, and the ablation-resistant temperature ranges of these coatings were 2.4MW / m 2 and 4.2MW / m 2The HfC coating failed after 120 s and 40 s of continuous ablation. This is because the HfO2 formed by oxidation of HfC is loose and porous after long time ablation, and oxygen penetrates through these loose structures during ablation, diffuses to the inner SiC layer and even the C / C substrate, and aggravates the damage of the C / C composite. In addition, the volume expansion of the coating caused by the transformation of HfO2 from tetragonal phase to monoclinic phase leads to the serious delamination and peeling of the outer HfO2 oxide layer, resulting in failure. Therefore, the ablation performance of the coating is poor, and the cyclic ablation protection cannot be achieved.

[0004] Document 3 “Jia Yujun, Li Hejun, Sun Jiajia, et al. Ablation resistance of SiC-modified ZrC coating prepared by SAPS for SiC-coated carbon / carbon composites, International Journal of Applied Ceramic Technology, 2017, 14:331-343.” uses supersonic atmospheric plasma spraying technology to prepare a ZrC coating, and the coating fails after 120 s of continuous ablation at an oxygen-acetylene heat flux density of 2.4 MW / m 2 The ZrO2 formed by ZrC ablation has similar characteristics to HfO2, and the ZrO2 oxide film is still loose and porous after long time ablation, which cannot effectively inhibit the diffusion of oxygen. Moreover, the phase change of ZrO2 also causes the volume expansion of the coating and peeling, resulting in the failure of ZrC to achieve cyclic ablation protection.

[0005] After the above-mentioned HfC and ZrC coatings are ablated for a certain period of time, the coating surface is loose and porous, providing a channel for oxygen to diffuse inward and aggravating the damage of the coating. In addition, the phase change of the oxidation products HfO2 and ZrO2 of HfC and ZrC from tetragonal phase to monoclinic phase causes the volume expansion of the coating, resulting in defects such as peeling, delamination and cracking on the surface of the outer coating, poor ablation resistance, and the inability to achieve cyclic ablation protection. Therefore, the above-mentioned coatings cannot resist super-high temperature cyclic ablation for a long time, and it is difficult to meet the requirements of recyclable and reusable. In order to ensure that the coating can be stably and repeatedly used in super-high temperature cyclic ablation, the coating needs to have excellent thermal shock resistance and ablation resistance, which requires the coating to form a dense oxide film on the surface during ablation and the oxide film to be stable without phase change. SUMMARY

[0006] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a long-life super-high temperature cyclic ablation resistant coating for the surface of carbon / carbon composite materials and a preparation method thereof, in order to solve the problems of narrow ablation resistant temperature range, poor cyclic thermal shock resistance and difficulty in repeated use in the prior art.

[0007] To achieve the above object, the present application adopts the following technical solutions to achieve the above object:

[0008] The carbon / carbon composite material surface long-life anti-ultra-high temperature cycle ablation coating is coated on the surface of the carbon / carbon composite material, and the coating comprises (Hf, Zr) C phase and La2O3 phase.

[0009] The present application is further improved in that:

[0010] Preferably, the La2O3 phase accounts for 2mol.%-3mol.% of the (Hf, Zr) C phase.

[0011] Preferably, the thickness of the coating is 100-200μm.

[0012] Preferably, the ablation protection temperature range of the coating is room temperature-2600℃.

[0013] During the ablation process, when the oxyacetylene heat flow density is 2.4MW / m 2 , 4 times can be achieved, and the total effective protection time can reach 480s; when the oxyacetylene heat flow density is 4.2MW / m 2 , the cycle ablation times can reach 3 times, and the total effective protection time can reach 90s.

[0014] The preparation method of the carbon / carbon composite material surface long-life anti-ultra-high temperature cycle ablation coating comprises the following steps:

[0015] S1, mixing HfO2 powder, ZrO2 powder and C powder, ball milling and then heat treatment to obtain (Hf, Zr) C solid solution powder;

[0016] S2, preparing (Hf, Zr) C granulated powder and La2O3 granulated powder;

[0017] S3, mixing the (Hf, Zr) C granulated powder and the La2O3 granulated powder to prepare (Hf, Zr) C-La2O3 mixed granulated powder; spraying the (Hf, Zr) C-La2O3 mixed granulated powder on the surface of the carbon / carbon composite material by supersonic atmospheric plasma spraying to prepare the long-life anti-ultra-high temperature cycle ablation coating.

[0018] Preferably, in S3, during the plasma spraying process, the spraying direct current is 390-410A, and the spraying direct voltage is 90-110V.

[0019] Preferably, in S3, the main gas flow is 70-74L / min; the auxiliary gas flow is 2-7L / min; the powder feeding rate is 50-10g / min; and the spraying distance is 80-110mm.

[0020] Preferably, in S3, the spraying times are 8-10 times.

[0021] Preferably, in S2, the particle sizes of the (Hf,Zr)C granulated powder and the La2O3 granulated powder are both 20-35 μm.

[0022] Preferably, in S2, the La2O3 granulated powder is prepared from commercial La2O3 powder with a particle size of 1-3 μm and a purity of 99.99%.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] The present application provides a long-life anti-ultra-high-temperature cyclic ablation coating on the surface of carbon / carbon (C / C) composite material, which solves the problems of narrow ablation temperature range, poor cyclic thermal shock resistance and difficulty in reuse of the coating. The coating is (Hf,Zr)C-La2O3, and the addition of La2O3 can inhibit the phase transition of HfO2, ZrO2 and (Hf,Zr)O2 oxides from tetragonal phase to monoclinic phase, retain part of the tetragonal phase, weaken the cracks caused by phase transition and even shedding, thereby improving the ablation resistance of the (Hf,Zr)C coating. In addition, the melting point of La2O3 is lower than the ablation temperature, and the phase is in a molten state during ablation. An appropriate amount of La2O3 not only can heal the cracks and pores in the coating, but also can form a La-doped (Hf,Zr)O2 oxide film with a dense structure through solid solution reaction with (Hf,Zr)O2, further densifying the surface of the coating, effectively blocking the penetration of oxygen and inhibiting the phase transition of the oxide film during ablation. The (Hf,Zr)C-La2O3 two-phase inlaid composite coating not only solves the problem of densification of the coating surface after long-time ablation of HfC and ZrC, but also inhibits the coating failure caused by the phase transition of HfO2, ZrO2 and (Hf,Zr)O2 oxides in the (Hf,Zr)C coating; in the ablation test in the oxyacetylene flame with a heat flux density of 2.4 MW / m 2 and 4.2 MW / m 2 , it effectively protects for 480 s (4 times x 120 s) and 90 s (3 times x 30 s), respectively, and the outer coating remains intact after ablation, showing excellent long-life anti-ultra-high-temperature cyclic ablation performance. The coating realizes long-life ultra-high-temperature cyclic ablation of C / C composite material at room temperature-2600℃, and improves the ablation protection temperature range and cyclic thermal shock resistance of the anti-ultra-high-temperature cyclic ablation coating on the surface of C / C composite material.

[0025] The application also discloses a preparation method of a long-life anti-ultra-high-temperature cyclic ablation coating on a carbon / carbon (C / C) composite material surface. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 Figure 4 is a long-life anti-ultra-high-temperature cyclic ablation temperature curve of the "(Hf,Zr)C-La2O3" two-phase inlaid composite coating.

[0027] Figure 2 Figure 5 is macro-morphologies of the "(Hf,Zr)C-La2O3" two-phase inlaid composite coating before and after ablation. DETAILED DESCRIPTION

[0028] The application will be further described in detail below in combination with the drawings:

[0029] The application discloses a preparation method of a long-life anti-ultra-high-temperature cyclic ablation coating on a C / C composite material surface as follows:

[0030] Step 1, HfO2 powder, ZrO2 powder and C powder are mixed as raw materials to obtain a mixed powder, the molar ratio of the HfO2 powder, the ZrO2 powder and the C powder is 1:1:6; the mixed powder is ground by a planetary ball mill for 6-8 hours, the ground mixed powder is wrapped in a graphite crucible provided with graphite paper; then, the graphite crucible is placed in a high-temperature heat treatment furnace protected by Ar gas, the furnace temperature is raised to 2000-2200 DEG C at a temperature rising speed of 3-6 DEG C / min, high-temperature heat treatment is carried out for 2-4 hours, and (Hf,Zr)C solid solution powder is prepared by a carbothermal reduction reaction, the reaction occurring in the process is as follows:

[0031] HfO2(s)+ZrO2(s)+6C(s)=2(Hf,Zr)C+4CO(g)

[0032] As a preferred scheme, the molar ratio of Hf and Zr elements in the mixed powder is 1:1.

[0033] Step 2: The ground (Hf, Zr)C solid solution powder, PVA, alcohol and water are loaded into a horizontal ball mill in a mass ratio of 4:4:1:1 and ball-milled for 6-8 hours to obtain a mixed slurry; finally, the mixed slurry is spray-dried to obtain (Hf, Zr)C granulated powder with a particle size of 20-35 μm. The inlet temperature of the dryer during the granulation process is 310-330 °C, and the outlet temperature is 100-120 °C.

[0034] Step 3: Commercial La2O3 powder with a particle size of 1-3 μm and a purity of 99.99% is ground using a planetary ball mill, and the ground powder, PVA, alcohol and water are loaded into a horizontal ball mill in a mass ratio of 4:4:1:1 and ball-milled for 6-8 hours to obtain a mixed slurry; finally, the mixed slurry is spray-dried to obtain La2O3 granulated powder with a particle size of 20-35 μm. The inlet temperature of the dryer during the granulation process is 310-330 °C, and the outlet temperature is 100-120 °C.

[0035] Step 4: The (Hf, Zr)C and La2O3 granulated powders are mixed by hand using a grinding bowl to obtain (Hf, Zr)C-La2O3 mixed granulated powder; then the mixed granulated powder is loaded into an ultrasonic atmospheric plasma spraying powder feeder, and an ultrasonic atmospheric plasma spraying method is used to prepare a "(Hf, Zr)C-La2O3" two-phase inlaid composite coating on the surface of a C / C composite material coated with a SiC inner coating, with the (Hf, Zr)C phase and the La2O3 phase distributed in the coating in an interlaced manner.

[0036] In the specific plasma spraying process, the direct current for spraying is 390-410 A, the direct voltage for spraying is 90-110 V, the main gas flow rate is 70-74 L / min, the auxiliary gas flow rate is 2-7 L / min, the powder feeding rate is 5-10 g / min, the spraying distance is 80-110 mm, and the spraying process is 8-10 times of spraying, with Ar gas as the main gas and H2 as the auxiliary gas.

[0037] As a preferred scheme, the molar ratio of the added La2O3 powder in the (Hf, Zr)C-La2O3 mixed granulated powder is in the range of 2 mol.% to 3 mol.%.

[0038] As a preferred scheme, the thickness of the "(Hf, Zr)C-La2O3" two-phase inlaid composite coating is in the range of 100 μm to 200 μm.

[0039] The C / C composite material is provided with a "(Hf, Zr)C-La2O3" two-phase inlaid composite coating on its surface. The ablation protection temperature range is room temperature to 2600 °C; during the ablation process, when the oxyacetylene heat flux density is 2.4 MW / m 2When the oxyacetylene heat flux density is 4.2 MW / m 2 When the oxyacetylene heat flux density is 4.2 MW / m

[0040] Example 1 and Example 2

[0041] Step 1: HfO2 powder, ZrO2 powder and C powder with a molar ratio of 1:1:6 were weighed and mixed as raw materials and put into a planetary ball mill for grinding for 8 h; the ground mixed powder was wrapped in a graphite crucible with graphite paper; then it was put into a high-temperature heat treatment furnace with Ar gas protection, the furnace temperature was raised to 2000℃ at a rate of 5℃ / min, and high-temperature heat treatment was carried out for 2 h, and (Hf,Zr)C solid solution powder was prepared by carbothermal reduction reaction.

[0042] HfO2(s)+ZrO2(s)+6C(s)=2(Hf,Zr)C+4CO(g)

[0043] Step 2: The ground (Hf,Zr)C powder, PVA, alcohol and water were put into a horizontal ball mill together according to a mass ratio of 4:4:1:1 and ball milled for 6 h to obtain a mixed slurry; finally, the obtained mixed slurry was spray dried to obtain (Hf,Zr)C granulated powder with a particle size of 30 μm. The inlet temperature of the dryer was 330℃ and the outlet temperature was 100℃.

[0044] Step 4: 2.5 mol.% of rare earth oxide La2O3 granulated powder was introduced into the (Hf,Zr)C granulated powder for doping modification, and the (Hf,Zr)C and La2O3 granulated powders were manually mixed by grinding bowl to obtain (Hf,Zr)C-La2O3 mixed granulated powder; then the mixed granulated powder was put into an ultrasonic atmospheric plasma spraying powder feeder, and a thickness of 130 μm of the "(Hf,Zr)C-La2O3" two-phase inlaid composite coating was prepared on the surface of the C / C composite material coated with SiC inner coating by ultrasonic atmospheric plasma spraying.

[0045] Plasma spraying process parameters: spraying direct current: 410 A; spraying direct voltage: 100 V; main gas flow: 74 L / min; auxiliary gas flow: 7 L / min; powder feeding rate: 5 g / min; spraying distance: 100 mm; spraying process is 8 times of spraying.

[0046] The composite coating was ablated under the conditions of 2.4 MW / m 2 and 4.2 MW / m 2 , respectively, corresponding to Example 1 and Example 2.

[0047] Referring to Figure 1 , the figure is the ablation temperature curve of the "(Hf, Zr)C-La2O3" two-phase inlaid composite coating prepared in Example 1 and Example 2, respectively, under the heat flux density of 2.4 MW / m 2 and 4.2 MW / m 2 , the effective protection time reaches 480 s (4*120 s) and 90 s (3*30 s), respectively, and the effective protection temperature range is between room temperature and 2600℃.

[0048] Referring to Figure 2 , the figure is the morphology of the "(Hf, Zr)C-La2O3" two-phase inlaid composite coating prepared in Example 1 and Example 2 before and after ablation, the coating prepared by supersonic atmospheric plasma spraying before ablation is complete and dense, and the coating still maintains the complete structure after ablation under the heat flux density of 2.4 MW / m 2 and 4.2 MW / m 2 , and can effectively protect the C / C composite material.

[0049] Table 1 is a comparison of the long-life anti-ultra-high-temperature cyclic ablation performance of different examples.

[0050] Comparative Examples 1 and 2:

[0051] Step 1: grind HfC powder for 6 h with a planetary ball mill, mix the ground HfC powder with PVA, alcohol and water according to the mass ratio of 4:4:1:1 and load them into a horizontal ball mill for 6 h to obtain a mixed slurry; finally, the obtained mixed slurry is spray dried to obtain HfC granulated powder with a particle size of 25 μm. The inlet temperature of the dryer is 320℃, and the outlet temperature is 100℃.

[0052] Step 2: The HfC granulated powder was loaded into the supersonic atmospheric plasma spraying powder feeder, and a HfC coating with a thickness of 120 μm was prepared on the surface of the C / C composite material coated with a SiC inner coating by supersonic atmospheric plasma spraying. The plasma spraying process parameters were as follows: spraying direct current: 410 A; spraying direct voltage: 110 V; main gas flow rate: 74 L / min; auxiliary gas flow rate: 6 L / min; powder feeding rate: 5 g / min; spraying distance: 100 mm; and spraying process: 8 times of spraying.

[0053] The coating was subjected to ablation under the conditions of 2.4 MW / m2and 4.2 MW / m2, corresponding to Comparative Example 1 and Comparative Example 2, respectively. 2 and 4.2 MW / m 2 , respectively.

[0054] Comparative Example 3:

[0055] Step 1: The ZrC powder was ground by a planetary ball mill for 6 h, and the ground ZrC powder, PVA, alcohol and water were loaded into a horizontal ball mill in a mass ratio of 4:4:1:1 for ball milling for 8 h to obtain a mixed slurry, and the obtained mixed slurry was finally spray dried to obtain ZrC granulated powder with a particle size of 35 μm. The inlet temperature of the dryer was 330 ℃, and the outlet temperature was 100 ℃.

[0056] Step 2: The ZrC granulated powder was loaded into the supersonic atmospheric plasma spraying powder feeder, and a ZrC coating with a thickness of 200 μm was prepared on the surface of the C / C composite material coated with a SiC inner coating by supersonic atmospheric plasma spraying. The plasma spraying process parameters were as follows: spraying direct current: 410 A; spraying direct voltage: 110 V; main gas flow rate: 74 L / min; auxiliary gas flow rate: 6 L / min; powder feeding rate: 5 g / min; spraying distance: 100 mm; and spraying process: 8 times of spraying.

[0057] Comparative Example 4:

[0058] Step 1: The HfC-ZrC powder was ground by a planetary ball mill for 7 h, and the ground mixed powder, PVA, alcohol and water were loaded into a horizontal ball mill in a mass ratio of 4:4:1:1 for ball milling for 8 h to obtain a mixed slurry, and the obtained mixed slurry was finally spray dried to obtain HfC-ZrC granulated powder with a particle size of 30 μm. The inlet temperature of the dryer was 330 ℃, and the outlet temperature was 120 ℃.

[0059] Step 2: The HfC-ZrC granulated powder was loaded into a supersonic atmospheric plasma spraying powder feeder, and a HfC-ZrC coating with a thickness of 130 μm was prepared on the surface of the C / C composite material coated with a SiC inner coating by supersonic atmospheric plasma spraying. The plasma spraying process parameters were as follows: spraying direct current: 410 A; spraying direct voltage: 110 V; main gas flow rate: 74 L / min; auxiliary gas flow rate: 6 L / min; powder feeding rate: 5 g / min; spraying distance: 100 mm; and spraying process: 9 times of spraying.

[0060] Comparative Examples 5 and 6:

[0061] Step 1: HfO2 powder, ZrO2 powder and C powder with a molar ratio of 1:1:6 were weighed and mixed as raw materials and placed into a planetary ball mill for grinding for 7 h; the ground mixed powder was wrapped in a graphite crucible provided with a graphite paper; and then placed into a high-temperature heat treatment furnace provided with Ar gas protection, and the furnace temperature was raised to 2200 ℃ at a temperature rising speed of 3 ℃ / min, and high-temperature heat treatment was carried out for 4 h to prepare (Hf, Zr)C solid solution powder by carbothermic reduction reaction.

[0062] Step 2: The ground (Hf, Zr)C powder, PVA, alcohol and water were loaded into a horizontal ball mill together according to a mass ratio of 4:4:1:1 for ball milling for 6 h to obtain a mixed slurry; and finally, the obtained mixed slurry was subjected to spray drying to obtain (Hf, Zr)C granulated powder with a particle size of 35 μm. The inlet temperature of the dryer was 310 ℃, and the outlet temperature was 100 ℃.

[0063] Step 3: The (Hf, Zr)C granulated powder was loaded into a supersonic atmospheric plasma spraying powder feeder, and a (Hf, Zr)C coating with a thickness of 135 μm was prepared on the surface of the C / C composite material coated with a SiC inner coating by supersonic atmospheric plasma spraying. The plasma spraying process parameters were as follows: spraying direct current: 400 A; spraying direct voltage: 110 V; main gas flow rate: 74 L / min; auxiliary gas flow rate: 8 L / min; powder feeding rate: 5 g / min; spraying distance: 100 mm; and spraying process: 8 times of spraying.

[0064] The coating was subjected to ablation under conditions of 2.4 MW / m2and 4.2 MW / m2, respectively, corresponding to Comparative Example 5 and Comparative Example 6. 2 2 Comparative Examples 7 and 8:

[0065] Comparative Examples 7 and 8:

[0066] ​Step 1: Hf02powder, Zr02powder and C powder were mixed as raw materials in a molar ratio of 1:1:6 and put into a planetary ball mill for 8 h; the mixed powder after grinding was wrapped in a graphite crucible with graphite paper; then it was put into a high-temperature heat treatment furnace with Ar gas protection, the furnace temperature was raised to 2000℃ at a rate of 4℃ / min, and high-temperature heat treatment was carried out for 2 h, and (Hf, Zr)C solid solution powder was prepared by carbothermal reduction reaction.

[0067] Step 2: The (Hf, Zr)C powder after grinding was mixed with PVA, alcohol and water in a mass ratio of 4:4:1:1 and put into a horizontal ball mill for 8 h to obtain a mixed slurry; finally, the mixed slurry was spray dried to obtain (Hf, Zr)C granulated powder with a particle size of 20 μm. The inlet temperature of the dryer was 320℃, and the outlet temperature was 120℃.

[0068] Step 3: Commercial La203powder was ground by a planetary ball mill, and the ground powder was mixed with PVA, alcohol and water in a mass ratio of 4:4:1:1 and put into a horizontal ball mill for 8 h to obtain a mixed slurry; finally, the mixed slurry was spray dried to obtain La203granulated powder with a particle size of 20 μm. The inlet temperature of the dryer was 320℃, and the outlet temperature was 120℃.

[0069] Step 4: 5 mol.% of rare earth oxide La203granulated powder was introduced into the (Hf, Zr)C granulated powder for doping modification, and the (Hf, Zr)C and La203granulated powders were mixed by hand in a grinding bowl to obtain (Hf, Zr)C-La203mixed granulated powder; then the mixed granulated powder was put into an ultrasonic atmospheric plasma spraying powder feeder, and an ultrasonic atmospheric plasma spraying method was used to prepare a "(Hf, Zr)C-La203" two-phase inlaid composite coating with a thickness of 120 μm on the surface of a C / C composite material coated with a SiC inner coating. The plasma spraying process parameters were: spraying direct current: 400 A; spraying direct voltage: 110 V; main gas flow: 74 L / min; auxiliary gas flow: 8 L / min; powder feeding rate: 5 g / min; spraying distance: 100 mm; spraying process: 8 times of spraying.

[0070] The coating was ablated under the conditions of 2.4 MW / m2 2 and 4.2 MW / m2 2 , corresponding to Comparative Examples 7 and 8, respectively.

[0071] The results of the above examples and comparative examples are shown in Table 1, and the corresponding results and analysis are as follows:

[0072] (1), Comparative Examples 1-3 (HfC and ZrC coatings): The traditional HfC and ZrC coatings were prepared in the comparative examples, the HfC coating was ablated under the conditions of a heat flux density of 2.4 MW / m22 and 4.2 MW / m 2 failed after ablation for 90 s and 30 s, while ZrC coating failed after ablation for 90 s at heat flux of 2.4 MW / m 2 and could not realize long time ablation resistance under ultra-high temperature.

[0073] (2), Comparative Example 4 (HfC-ZrC coating): HfC-ZrC coating was prepared in this comparative example. Although part of HfO2 and ZrO2 occurred solid solution sintering reaction to form (Hf,Zr)O2 during ablation process, the compactness of the coating surface in local area was improved and the ablation resistance was improved. However, due to the macroscopic uneven distribution of each component of HfC-ZrC coating, a large number of loose areas caused by the oxidation of HfC and ZrC to form HfO2 and ZrO2 still existed on the surface of the coating during ablation process, which led to the failure of the coating after ablation for 180 s at heat flux of 2.4 MW / m 2 .

[0074] (3), Comparative Examples 5 and 6 ((Hf,Zr)C coating): (Hf,Zr)C coating was prepared in this comparative example without introducing rare earth oxide La2O3 for doping modification in (Hf,Zr)C powder. The coating failed after ablation for 2*120 s and 3*30 s at heat flux of 2.4 MW / m 2 and 4.2 MW / m 2 , respectively. This is because the oxide (Hf,Zr)O2 produced by the oxidation of (Hf,Zr)C during ablation process will still undergo phase change, produce obvious cracks, and then cause the coating to fall off, and the outer coating is seriously damaged, so the coating cannot realize long time ablation protection under ultra-high temperature.

[0075] (4), Examples 1 and 2 ((Hf,Zr)C coating-2.5 mol.% La2O3): 2.5 mol.% of rare earth oxide La2O3 was introduced for doping modification in (Hf,Zr)C powder in this example. The prepared coating effectively protected for 4*120 s and 3*30 s at heat flux of 2.4 MW / m 2 and 4.2 MW / m 2 , respectively. The appropriate amount of La2O3 not only can act as a crack and pore in the molten phase healing coating, but also can react with (Hf,Zr)O2 to form La-doped (Hf,Zr)O2 oxide film with dense structure. The coating did not fail under two kinds of ablation conditions and could effectively protect the C / C matrix.

[0076] (5), Comparative Examples 7 and 8 ((Hf,Zr)C coating - 5 mol.% La2O3): This case introduces 5 mol.% of rare earth oxide La2O3 into the (Hf,Zr)C powder for doping modification, and the prepared coating is ablated for 4*120s and 3*30s at a heat flux of 2.4 MW / m2and 4.2 MW / m2, respectively, and fails. This is because excess La2O3 reacts with (Hf,Zr)O2 to form a low-melting-point La-rich phase (La2(Hf,Zr)2O7), which is extremely easy to be mechanically ablated during the ablation process, and the outer coating is seriously peeled off, so that long-time super-high-temperature cyclic ablation protection cannot be achieved. 2 and 4.2 MW / m 2 When the heat flux is 2.4 MW / m

[0077] Table 1 Parameters and test results of examples and comparative examples

[0078]

[0079]

[0080] From Comparative Example 1, Comparative Example 2 and Comparative Example 3, it can be seen that the traditional HfC and ZrC coatings are loose and porous after a certain time of ablation due to the large volume expansion caused by the oxidation of carbides, and cannot effectively inhibit the inward diffusion of oxygen. In addition, the damage of the coating caused by the phase change of HfO2 / ZrO2 limits the long-time cyclic ablation resistance of the coating. In the early stage of ablation of the HfC-ZrC coating, HfC and ZrC are first oxidized to form HfO2 and ZrO2, and with the increase of ablation time, part of HfO2 and ZrO2 undergoes solid solution sintering reaction to form (Hf,Zr)O2, and the local area of the coating surface is improved in density. However, due to the macroscopic uneven distribution of each component of the HfC-ZrC coating, there are still a large number of loose areas on the surface of the coating during the ablation process caused by the oxidation of HfC and ZrC to form HfO2 and ZrO2, which is difficult to resist long-time cyclic ablation (Comparative Example 4). Compared with the (Hf,Zr)C solid solution powder, the uniform distribution of Hf and Zr elements in the (Hf,Zr)C solid solution facilitates the solid solution sintering reaction of HfO2 and ZrO2 during the ablation process, so that a more uniform and dense (Hf,Zr)O2 oxide film is formed. This process ensures the uniformity of the composition and the high density of the structure of the protective layer, and improves the ablation resistance of the coating. The preparation of the (Hf,Zr)C coating improves the problem of coating density during ablation, but the problem of oxide phase change has not been solved. The oxide (Hf,Zr)O2 produced by the oxidation of (Hf,Zr)C during the cooling process of the coating still undergoes phase change from tetragonal phase to monoclinic phase, cracks are generated on the surface of the coating, and the long-life super-high-temperature cyclic ablation performance is limited (Comparative Examples 4 and 5).

[0081] As can be seen from Comparative Example 1, Example 2, Comparative Example 6 and Comparative Example 7, the introduction of 2.5 mol.% of La2O3 to modify the (Hf, Zr)C coating (Examples 1 and 2) can inhibit the transformation of HfO2, ZrO2 and (Hf, Zr)O2 oxides from tetragonal phase to monoclinic phase, retain part of the tetragonal phase, weaken the cracks caused by phase transformation and even shedding, thereby improving the ablation resistance of the (Hf, Zr)C coating; when 5 mol.% of La2O3 is introduced (Comparative Examples 6 and 7), the excess La2O3 reacts with (Hf, Zr)O2 to form a low-melting-point La-rich phase (La2(Hf, Zr)2O7), which is extremely easy to form ablation pits due to mechanical erosion during ablation, and the outer coating is seriously peeled off, thereby resulting in a decrease in the ablation resistance of the coating, and thus the long-life super-high-temperature cyclic ablation cannot be achieved.

[0082] Example 3

[0083] Step 1: HfO2 powder, ZrO2 powder and C powder with a molar ratio of 1:1:6 were weighed and mixed as raw materials and put into a planetary ball mill for grinding for 8 h; the ground mixed powder was wrapped in a graphite crucible provided with graphite paper; then it was put into a high-temperature heat treatment furnace protected by Ar gas, the furnace temperature was raised to 2000℃ at a temperature rising rate of 5℃ / min, and high-temperature heat treatment was performed for 2 h, and a (Hf, Zr)C solid solution powder was prepared by carbothermal reduction reaction.

[0084] Step 2: the ground (Hf, Zr)C powder, PVA, alcohol and water were put into a horizontal ball mill together according to a mass ratio of 4:4:1:1 and ball-milled for 6 h to obtain a mixed slurry; finally, the obtained mixed slurry was spray dried to obtain (Hf, Zr)C granulated powder with a particle size of 35 μm. The inlet temperature of the dryer was 310℃, and the outlet temperature was 110℃. Step 3: commercial La2O3 powder with a particle size of 1-3 μm and a purity of 99.99% was ground by a planetary ball mill, and the ground powder, PVA, alcohol and water were put into a horizontal ball mill together according to a mass ratio of 4:4:1:1 to obtain a mixed slurry; finally, the obtained mixed slurry was spray dried to obtain La2O3 granulated powder with a particle size of 35 μm. The inlet temperature of the dryer was 310℃, and the outlet temperature was 110℃.

[0085] Step 4: 2 mol.% of rare earth oxide La2O3 granulated powder was introduced into the (Hf, Zr)C granulated powder for doping modification, the (Hf, Zr)C and La2O3 granulated powder was mixed uniformly by hand using a grinding bowl, and a (Hf, Zr)C-La2O3 mixed granulated powder was prepared; then the mixed granulated powder was loaded into an ultrasonic atmospheric plasma spraying powder feeder, and a "(Hf, Zr)C-La2O3" two-phase inlaid composite coating with a thickness of 130 μm was prepared on the surface of the C / C composite material coated with a SiC inner coating by using the ultrasonic atmospheric plasma spraying method.

[0086] Plasma spraying process parameters: spraying direct current: 400 A; spraying direct voltage: 90 V; main gas flow rate: 70 L / min; auxiliary gas flow rate: 2 L / min; powder feeding rate: 10 g / min; spraying distance: 90 mm; spraying process: 9 times of spraying.

[0087] Case 4

[0088] Step 1: HfO2 powder, ZrO2 powder and C powder with a molar ratio of 1:1:6 were weighed and mixed as raw materials and put into a planetary ball mill for grinding for 8 h; the ground mixed powder was wrapped in a graphite crucible with graphite paper; then it was put into a high-temperature heat treatment furnace with Ar gas protection, the furnace temperature was raised to 2000℃ at a rate of 5℃ / min, and heat treatment was carried out for 2 h, and (Hf, Zr)C solid solution powder was prepared by carbothermal reduction reaction.

[0089] Step 2: The ground (Hf, Zr)C powder, PVA, alcohol and water were mixed together according to a mass ratio of 4:4:1:1 and loaded into a horizontal ball mill for ball milling for 6 h to obtain a mixed slurry; finally, the obtained mixed slurry was spray dried to obtain (Hf, Zr)C granulated powder with a particle size of 20 μm. The inlet temperature of the dryer was 320℃, and the outlet temperature was 120℃.

[0090] Step 3: Commercial La2O3 powder with a particle size of 1-3 μm and a purity of 99.99% was ground using a planetary ball mill, and the ground powder was mixed with PVA, alcohol and water according to a mass ratio of 4:4:1:1 and loaded into a horizontal ball mill to obtain a mixed slurry; finally, the obtained mixed slurry was spray dried to obtain La2O3 granulated powder with a particle size of 20 μm. The inlet temperature of the dryer was 320℃, and the outlet temperature was 120℃.

[0091] Step 4: 3 mol.% of rare earth oxide La2O3 granulated powder was introduced into the (Hf, Zr)C granulated powder for doping modification, the (Hf, Zr)C and La2O3 granulated powder was mixed uniformly by hand using a grinding bowl, and a (Hf, Zr)C-La2O3 mixed granulated powder was prepared; then the mixed granulated powder was loaded into a supersonic atmospheric plasma spraying powder feeder, and a "(Hf, Zr)C-La2O3" two-phase inlaid composite coating with a thickness of 130 μm was prepared on the surface of the C / C composite material coated with a SiC inner coating by supersonic atmospheric plasma spraying.

[0092] Plasma spraying process parameters: spraying direct current: 390 A; spraying direct voltage: 110 V; main gas flow rate: 72 L / min; auxiliary gas flow rate: 5 L / min; powder feeding rate: 8 g / min; spraying distance: 100 mm; spraying process: 10 times of spraying.

[0093] Case 5

[0094] Step 1: HfO2 powder, ZrO2 powder and C powder with a molar ratio of 1:1:6 were weighed and mixed as raw materials and put into a planetary ball mill for grinding for 8 h; the ground mixed powder was wrapped in a graphite crucible with graphite paper; then it was put into a high-temperature heat treatment furnace with Ar gas protection, the furnace temperature was raised to 2000℃ at a heating rate of 5℃ / min, and high-temperature heat treatment was carried out for 2 h, and (Hf, Zr)C solid solution powder was prepared by carbothermal reduction reaction.

[0095] Step 2: The ground (Hf, Zr)C powder, PVA, alcohol and water were loaded into a horizontal ball mill together according to a mass ratio of 4:4:1:1 and ball milled for 6 h to obtain a mixed slurry; finally, the obtained mixed slurry was spray dried to obtain (Hf, Zr)C granulated powder with a particle size of 25 μm. The inlet temperature of the dryer was 315℃, and the outlet temperature was 105℃.

[0096] Step 3: Commercial La2O3 powder with a particle size of 1-3 μm and a purity of 99.99% was ground by a planetary ball mill, and the ground powder, PVA, alcohol and water were loaded into a horizontal ball mill together according to a mass ratio of 4:4:1:1 to obtain a mixed slurry; finally, the obtained mixed slurry was spray dried to obtain La2O3 granulated powder with a particle size of 25 μm. The inlet temperature of the dryer was 315℃, and the outlet temperature was 105℃.

[0097] Step 4: 2.2 mol.% of rare earth oxide La2O3 granulated powder was introduced into the (Hf, Zr)C granulated powder for doping modification, the (Hf, Zr)C and La2O3 granulated powder was mixed uniformly by hand using a grinding bowl, and a (Hf, Zr)C-La2O3 mixed granulated powder was prepared; then the mixed granulated powder was loaded into an ultrasonic atmospheric plasma spraying powder feeder, and a "(Hf, Zr)C-La2O3" two-phase inlaid composite coating with a thickness of 130 μm was prepared on the surface of the C / C composite material coated with a SiC inner coating by using the ultrasonic atmospheric plasma spraying method.

[0098] Plasma spraying process parameters: spraying direct current: 395 A; spraying direct voltage: 95 V; main gas flow rate: 74 L / min; auxiliary gas flow rate: 7 L / min; powder feeding rate: 7 g / min; spraying distance: 110 mm; spraying process: 9 times of spraying.

[0099] Case 6

[0100] Step 1: HfO2 powder, ZrO2 powder and C powder with a molar ratio of 1:1:6 were weighed and mixed as raw materials and put into a planetary ball mill for grinding for 8 h; the ground mixed powder was wrapped in a graphite crucible with graphite paper; then it was put into a high-temperature heat treatment furnace protected by Ar gas, the furnace temperature was raised to 2000℃ at a rate of 5℃ / min, and high-temperature heat treatment was carried out for 2 h, and (Hf, Zr)C solid solution powder was prepared by carbothermal reduction reaction.

[0101] Step 2: The ground (Hf, Zr)C powder, PVA, alcohol and water were loaded into a horizontal ball mill together according to a mass ratio of 4:4:1:1 and ball milled for 6 h to obtain a mixed slurry; finally, the obtained mixed slurry was spray dried to obtain (Hf, Zr)C granulated powder with a particle size of 30 μm. The inlet temperature of the dryer was 325℃, and the outlet temperature was 115℃. Step 3: Commercial La2O3 powder with a particle size of 1-3 μm and a purity of 99.99% was ground using a planetary ball mill, and the ground powder was loaded into a horizontal ball mill together with PVA, alcohol and water according to a mass ratio of 4:4:1:1 to obtain a mixed slurry; finally, the obtained mixed slurry was spray dried to obtain La2O3 granulated powder with a particle size of 25 μm. The inlet temperature of the dryer was 325℃, and the outlet temperature was 115℃.

[0102] Step 4: 2.7 mol.% of rare earth oxide La2O3 granulated powder is introduced into (Hf, Zr)C granulated powder for doping modification, the (Hf, Zr)C and La2O3 granulated powder is mixed uniformly by hand using a grinding bowl, and (Hf, Zr)C-La2O3 mixed granulated powder is prepared; then the mixed granulated powder is loaded into an ultrasonic atmospheric plasma spraying powder feeder, and a "(Hf, Zr)C-La2O3" two-phase inlaid composite coating with a thickness of 130 μm is prepared on the surface of the C / C composite material coated with a SiC inner coating by using the ultrasonic atmospheric plasma spraying method.

[0103] Plasma spraying process parameters: spraying direct current: 405 A; spraying direct voltage: 105 V; main gas flow rate: 71 L / min; auxiliary gas flow rate: 6 L / min; powder feeding rate: 10 g / min; spraying distance: 100 mm; spraying process is 8 times of spraying.

[0104] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A long-life, ultra-high temperature cyclic ablation resistant coating for carbon / carbon composite surfaces, characterized in that, The coating is coated on the surface of the carbon / carbon composite material, and the coating comprises (Hf, Zr)C phase and La2O3 phase. The La2O3 phase accounts for 2-3 mol.% of the (Hf, Zr)C phase. The ablation protection temperature range of the coating is room temperature-2600℃. When the oxyacetylene heat flow density is 2.4 MW / m 2 2 during the ablation process, the cyclic ablation times can reach 4 times, and the total effective protection time can reach 480 s; when the oxyacetylene heat flow density is 4.2 MW / m 2 2, the cyclic ablation times can reach 3 times, and the total effective protection time can reach 90 s. The preparation method of the long-life anti-ultra-high-temperature cycle ablation coating comprises the following steps: S1, mixing HfO2 powder, ZrO2 powder and C powder, ball milling and then heat treatment to obtain (Hf, Zr)C solid solution powder; S2, preparing (Hf, Zr)C granulated powder and La2O3 granulated powder; S3, mixing the (Hf, Zr)C granulated powder and the La2O3 granulated powder to obtain (Hf, Zr)C-La2O3 mixed granulated powder; and spraying the (Hf, Zr)C-La2O3 mixed granulated powder on the surface of the carbon / carbon composite material by the supersonic atmospheric plasma spraying method to obtain the long-life anti-ultra-high-temperature cycle ablation coating.

2. The long-life, ultra-high-temperature cyclic ablation-resistant coating for carbon / carbon composite surfaces of claim 1, wherein, The thickness of the coating is 100-200 μm.

3. A method for preparing the long-life, superhigh-temperature cycle ablation coating of claim 1 on the surface of carbon / carbon composite material, characterized in that, The preparation method comprises the following steps: S1, mixing HfO2 powder, ZrO2 powder and C powder, ball milling and then heat treatment to obtain (Hf, Zr)C solid solution powder; S2, preparing (Hf, Zr)C granulated powder and La2O3 granulated powder; S3, mixing the (Hf, Zr)C granulated powder and the La2O3 granulated powder to obtain (Hf, Zr)C-La2O3 mixed granulated powder; and spraying the (Hf, Zr)C-La2O3 mixed granulated powder on the surface of the carbon / carbon composite material by the supersonic atmospheric plasma spraying method to obtain the long-life anti-ultra-high-temperature cycle ablation coating.

4. The method of claim 3, wherein the carbon / carbon composite surface long- life ultrahigh-temperature cyclic ablation-resistant coating is prepared by the steps of: In S3, during the plasma spraying process, the spraying direct current is 390-410 A, and the spraying direct voltage is 90-110 V.

5. The method for preparing a long-life, ultra-high temperature cyclic ablation resistant coating on the surface of a carbon / carbon composite material according to claim 3, characterized in that, In S3, the main gas flow rate is 70-74 L / min, the auxiliary gas flow rate is 2-7 L / min, the powder feeding rate is 50-10 g / min, and the spraying distance is 80-110 mm.

6. The method of making a long-life, ultra-high-temperature cyclic ablation- resistant coating for carbon / carbon composite surfaces of claim 3, wherein, In S3, the spraying times are 8-10.

7. The method of making a long-life, ultra-high-temperature cyclic ablation- resistant coating for carbon / carbon composite surfaces of claim 3, wherein, In S2, the particle size of the (Hf, Zr)C granulated powder and the La2O3 granulated powder is 20-35 μm.

8. The method for preparing a long-life, ultra-high temperature cyclic ablation resistant coating on the surface of a carbon / carbon composite material according to claim 3, characterized in that, In S2, the La2O3 granulated powder is prepared by using commercial La2O3 powder with a particle size of 1-3 μm and a purity of 99.99%.

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