Carbon / carbon composite material surface dense superhard ultrahigh temperature ceramic coating and preparation method thereof

Abstract

The application provides a carbon / carbon composite material surface dense superhard ultrahigh-temperature ceramic coating and a preparation method thereof. 1 / 4 Zr 1 / 2 Ti 1 / 4 )C solid solution powder is prepared through a carbothermal reduction reaction, then an ultrahigh-temperature ceramic coating of (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C is prepared on the surface of the C / C composite material coated with an inner SiC coating by using a supersonic atmospheric plasma spraying method, and finally, the surface of the coating is subjected to high-temperature heat treatment by using an oxyacetylene flame. The preparation method combines the supersonic atmospheric plasma spraying method and the oxyacetylene high-temperature heat treatment, densifies the surface of the coating by means of high-temperature oxidation sintering, improves the problems of the coating surface prepared by the supersonic atmospheric plasma spraying method, such as non-densification and low hardness caused by a large amount of molten phase, and synergistically improves the hardness and the density of the ultrahigh-temperature ceramic coating on the surface of the C / C composite material, so that the Ti-doped (Hf, Zr)O2 oxide coating with excellent comprehensive performance is obtained.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of ultra-high temperature ablation-resistant coating, and particularly relates to a dense and super-hard ultra-high temperature ceramic 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 hot end structural components due to its low density, good thermal shock resistance, and high mechanical properties in inert atmosphere at ultra-high temperature (above 2000℃). However, the oxidation sensitivity of C / C composite material in ultra-high temperature oxygen environment will cause a sharp decline in its mechanical properties, and thus a thermal protection oxygen barrier coating needs to be prepared on the surface of C / C composite material. Ultra-high temperature ceramic is considered as a promising coating protective material for the surface of C / C composite material due to its high hardness, high melting point, and excellent oxidation / ablation resistance. Supersonic atmospheric plasma spraying technology is often used to prepare ultra-high temperature ceramic coating on the surface of C / C composite material due to its high temperature, high enthalpy, and high deposition efficiency. This technology can efficiently melt ultra-high temperature ceramic particles during spraying process, and then form a well-bonded coating on the substrate. However, the coating prepared by supersonic atmospheric plasma spraying has problems of non-dense surface and low hardness, which results in its poor resistance to gas particle erosion and limits the further application of ultra-high temperature ceramic coating on the surface of C / C composite material.

[0003] The ZrC-SiC and ZrB2-SiC coatings were prepared by supersonic atmospheric plasma spraying method in documents 1 “Guanghui Feng, Yulan Yu, Xiyuan Yao, et al. Ablation behavior of single and alternate multilayered ZrC-SiC coatings under oxyacetylene torch. Journal of the European Ceramic Society, 2022, 42: 830-840.” and 2 “Yu Lei Zhang, Zhixiong Hu, Boxing Yang, et al. Effect of pre-oxidation on the ablation resistance of ZrB2-SiC coating for SiC-coated carbon / carbon composites. Ceramics International, 2015, 41: 2582-2589.” respectively. The non-dense accumulation of powder particles during spraying process causes the formation of part of holes on the surface of the coating, showing a loose structure. The TiB2-SiC coating was prepared by supersonic atmospheric plasma spraying method in document 3 “Preparation and properties of supersonic atmospheric plasma sprayed TiB2-SiC coating. Transactions of Nonferrous Metals Society of China, 2021, 31: 243-254.”. The coating after spraying is not dense. In addition, the large amount of molten phase formed after spraying reduces the hardness of the coating, so the coatings prepared by different powers all show low hardness, less than 4 GPa.

[0004] However, modern spacecraft puts forward higher use requirements for thermal protection components, which requires thermal protection components not only to have a dense structure, but also to have higher hardness, strength, oxidation / ablation resistance and high temperature stability and other comprehensive properties. Therefore, how to prepare a coating with high hardness and density on the surface of C / C composite material has become a focus of the research of thermal protection components at present. However, the coatings prepared by the above supersonic atmospheric plasma spraying method have the problems of non-dense surface and low hardness, which limits the further application of the superhigh-temperature ceramic coating on the surface of C / C composite material in thermal protection components. SUMMARY

[0005] The present application aims at overcoming the above-mentioned defects of the prior art, and provides a carbon / carbon composite material surface dense superhard ultrahigh temperature ceramic coating and a preparation method thereof, so as to solve the problems of low coating hardness caused by the non-dense surface of the coating prepared by the ultrasonic atmospheric plasma spraying method in the prior art.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] The preparation method of the carbon / carbon composite material surface dense superhard ultrahigh temperature ceramic coating comprises the following steps:

[0008] S1, HfO2 powder, ZrO2 powder, TiO2 powder and C powder are mixed and ball milled, and then a (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C solid solution powder is prepared after heat treatment;

[0009] S2, the (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C solid solution powder is prepared to obtain (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C granulated powder;

[0010] S3, the (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C granulated powder is sprayed on the surface of the C / C composite material coated with the SiC inner coating by the ultrasonic atmospheric plasma spraying method, and a process product is prepared;

[0011] S4, the process product is treated by the oxyacetylene high-temperature heat treatment, and a (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C ultrahigh temperature ceramic coating is prepared on the surface of the C / C composite material coated with the SiC inner coating.

[0012] Further improvement of the present application is that:

[0013] Preferably, in S4, the oxyacetylene heat flow density is 2.4 MW / m 2 .

[0014] Preferably, in S4, the acetylene gas flow in the oxyacetylene gas flow is 0.18 L / s, and the oxygen gas flow is 0.24 L / s.

[0015] Preferably, in S4, the acetylene pressure in the oxyacetylene gas flow is 0.095 MPa, and the oxygen pressure is 0.4 MPa.

[0016] Preferably, in S4, the distance between the oxyacetylene torch and the sample surface is 10-15mm during the oxyacetylene high-temperature treatment process; the oxyacetylene treatment time is between 150s and 360s.

[0017] Preferably, in S4, the coating surface temperature is 1900℃-2200℃ during the oxyacetylene high-temperature treatment process.

[0018] Preferably, in S3, the spraying direct current is 390-410A; the spraying direct voltage is 90-110V; the main gas flow is 70-74L / min; the auxiliary gas flow is 2-7L / min; the powder feeding rate is 5-10g / min; the spraying distance is 80-110mm; and the spraying times are 8-10.

[0019] A carbon / carbon composite material surface dense superhard ultrahigh-temperature ceramic coating prepared by the above preparation method, wherein the coating is a (Hf, Zr)O2 oxide doped with Ti.

[0020] Preferably, the thickness of the coating is 150-300μm.

[0021] Preferably, the average hardness of the coating is greater than or equal to 15GPa.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] The present application provides a carbon / carbon (C / C) composite material surface dense superhard ultrahigh-temperature ceramic coating preparation method, which comprises the following steps: first, preparing (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C solid solution powder through a carbothermal reduction reaction; then, preparing a (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C ultrahigh-temperature ceramic coating on the surface of a C / C composite material coated with a SiC inner coating by using a supersonic atmospheric plasma spraying method; and finally, performing high-temperature heat treatment on the coating surface by using an oxyacetylene flame.

[0024] The present application also discloses a carbon / carbon (C / C) composite material surface dense superhard ultrahigh-temperature ceramic coating. 1 / 4 Zr 1 / 2 Ti 1 / 4)C coating after heat treatment, with the help of appropriate amount of Ti element can be in the process of heat treatment of ultrasonic atmospheric plasma spraying left loose area and rely on the formation of low melting point molten phase and high melting point solid phase sintering advantage, so as to densify the coating surface. In addition, the coating surface after heat treatment of Ti doped (Hf, Zr) O2 oxide, due to the effect of entropy increase, has larger lattice distortion, shows higher hardness, so as to improve the hardness of the coating, and the average hardness value reaches 20 GPa, showing excellent comprehensive performance, which lays a theoretical foundation for subsequent use as C / C composite surface impact and wear resistant coating. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 Morphology diagram of (Hf DETAILED DESCRIPTION

[0026] The application will be further described in detail below in combination with the drawings and specific examples:

[0027] The application discloses a preparation method of a dense superhard ultrahigh-temperature ceramic coating on a C / C composite material surface.

[0028] Step 1: HfO2 powder, ZrO2 powder, TiO2 powder and C powder are mixed as raw materials to obtain mixed powder, the molar ratio of the HfO2 powder, ZrO2 powder, TiO2 powder and C powder is 1:2:1:12; the mixed powder is ground for 4-8h by using a planetary ball mill, and 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℃ at a temperature rising speed of 3-6℃ / min, and high-temperature heat treatment is carried out for 2-4h, so that (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C solid solution powder is prepared through a carbothermic reduction reaction.

[0029] HfO2 (s) + 2ZrO2 (s) + TiO2 (s) + 12C (s) = 4 (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C + 8CO (g)

[0030] Step 2: the (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C powder is mixed with PVA, alcohol and water according to a mass ratio of 4:4:1:1, and then the mixture is loaded into a horizontal ball mill for ball milling for 6-8h to obtain a mixed slurry; finally, the mixed slurry is subjected to spray drying to obtain (Hf 1 / 4Zr 1 / 2 Ti 1 / 4 )C coating. Plasma spraying process parameters: spraying direct current: 390-410 A; spraying direct voltage: 90-110 V; main gas flow: 70-74 L / min; auxiliary gas flow: 2-7 L / min; powder feeding rate: 5-10 g / min; spraying distance: 80-110 mm; spraying process is 8-10 times of spraying. The main gas is Ar gas, and the auxiliary gas is H2.

[0031] Step 3: The granulated powder after granulation is loaded into the supersonic atmospheric plasma spraying powder feeder, and a (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C coating is prepared on the surface of the C / C composite material coated with the SiC inner coating by supersonic atmospheric plasma spraying. Plasma spraying process parameters: spraying direct current: 390-410 A; spraying direct voltage: 90-110 V; main gas flow: 70-74 L / min; auxiliary gas flow: 2-7 L / min; powder feeding rate: 5-10 g / min; spraying distance: 80-110 mm; spraying process is 8-10 times of spraying. The main gas is Ar gas, and the auxiliary gas is H2.

[0032] Step 4: The (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C coating prepared is subjected to oxygen-acetylene high-temperature heat treatment.

[0033] The preparation method combines supersonic atmospheric plasma spraying with oxygen-acetylene high-temperature heat treatment. The oxygen-acetylene high-temperature heat treatment is essentially to densify the coating surface by high-temperature oxidation sintering. The oxygen-acetylene heat flow density is 2.4 MW / m 2 , wherein the acetylene gas flow is 0.18 L / s, the oxygen gas flow is 0.24 L / s, the acetylene pressure is 0.095 MPa, and the oxygen pressure is 0.4 MPa.

[0034] The distance between the oxygen-acetylene torch and the sample surface is 10-15 mm.

[0035] The coating is subjected to oxygen-acetylene heat treatment for 150 s-360 s.

[0036] The coating is prepared, and the Hf:Zr:Ti molar ratio of the coating before heat treatment is 1:2:1, and the coating thickness is between 100 μm and 220 μm; the coating surface temperature during heat treatment is between 1900°C and 2200°C; the coating thickness after heat treatment is between 100 μm and 300 μm, and the average hardness of the coating is ≥15 GPa (the method for obtaining the average hardness is to punch 5-10 points by using nanoindentation, and then to average the values); during the heat treatment process, if the surface temperature is higher than the temperature, the coating may be damaged, and if it is lower, the liquid state cannot be formed, and a dense structure cannot be formed.

[0037] Example 1

[0038] Step 1: HfO2 powder, ZrO2 powder, TiO2 powder and C powder were weighed in a molar ratio of 1:2:1:12, mixed as raw materials and put into a planetary ball mill for grinding for 6 h. The ground mixed powder was wrapped in a graphite crucible with graphite paper, and then put into a high-temperature heat treatment furnace with Ar gas protection. The furnace temperature was raised to 2100℃ at a rate of 3℃ / min, and then heat treated for 2 h to prepare (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C solid solution powder by carbothermal reduction reaction.

[0039] Step 2: (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C powder was mixed with PVA, alcohol and water in a ratio of 4:4:1:1 and put into a horizontal ball mill for grinding for 6 h. The ground mixed powder was put into a granulator for granulation. The inlet temperature of the dryer was 330℃, and the outlet temperature was 110℃.

[0040] Step 3: The granulated powder was put into a supersonic atmospheric plasma spraying powder feeder, and (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C coating was prepared on the surface of the C / C composite material coated with SiC inner coating by supersonic atmospheric plasma spraying. The plasma spraying used a spraying direct current of 400A, a spraying direct voltage of 110V, a main gas flow of 74L / min, an auxiliary gas flow of 6L / min, a powder feeding rate of 5g / min, a spraying distance of 100mm, and the spraying process was 8 times.

[0041] Step 4: The prepared (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C coating was heat treated by oxyacetylene. The distance between the oxyacetylene torch and the sample surface was 10mm, and the heat treatment was carried out at an oxyacetylene heat flux density of 2.4MW / m 2 , wherein the acetylene gas flow was 0.18L / s, the oxygen gas flow was 0.24L / s, the acetylene pressure was 0.095MPa, and the oxygen pressure was 0.4MPa.

[0042] After heat treatment of the coating, the surface was dense and complete, the coating did not fall off, the hardness reached 20.0±4.6GPa, and the hardness and density of the coating were significantly improved.

[0043] Figure 1 are the morphology diagrams of (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C coating before and after heat treatment. As can be seen from the figure, before heat treatment, (Hf 1 / 4 Zr1 / 2 Ti 1 / 4 )C coating surface is loose and porous, and the particles are obviously accumulated. After heat treatment, the coating has a dense surface.

[0044] Comparative Example 1

[0045] Step 1: HfO2 powder, ZrO2 powder, TiO2 powder and C powder with a molar ratio of 1:2:1:12 were weighed and mixed as raw materials and put into a planetary ball mill for grinding for 6 h. The ground mixed powder was wrapped in a graphite crucible with graphite paper, and then put into a high-temperature heat treatment furnace with Ar protection. The furnace temperature was raised to 2100℃ at a rate of 3℃ / min, and heat treated for 2 h. (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C solid solution powder was prepared by carbothermal reduction reaction.

[0046] Step 2: The (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C powder was mixed with PVA, alcohol and water in a ratio of 4:4:1:1 and put into a horizontal ball mill for grinding for 6 h. The ground mixed powder was put into a granulator for granulation. The inlet temperature of the dryer was 330℃, and the outlet temperature was 110℃.

[0047] Step 3: The granulated powder was put into a supersonic atmospheric plasma spraying powder feeder, and a (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C coating 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 used a spraying direct current of 400A, a spraying direct voltage of 110V, a main gas flow of 74L / min, an auxiliary gas flow of 6L / min, a powder feeding rate of 5g / min, a spraying distance of 100mm, and the spraying process was 8 times of spraying.

[0048] The coating was not subjected to high-temperature heat treatment by oxyacetylene flame, the coating was not dense, and the hardness was only 2.3±0.9GPa.

[0049] Comparative Example 2

[0050] Step 1: HfO2 powder, ZrO2 powder, TiO2 powder and C powder with a molar ratio of 2:1:1:12 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, and then put into a high-temperature heat treatment furnace with Ar protection. The furnace temperature was raised to 2100℃ at a rate of 3℃ / min, and heat treated for 2 h. (Hf 1 / 2 Zr 1 / 4Ti 1 / 4 )C solid solution powder.

[0051] Step 2: (Hf 1 / 2 Zr 1 / 4 Ti 1 / 4 )C powder, PVA, alcohol and water were put into a horizontal ball mill at a ratio of 4:4:1:1 and ground for 6h; the ground mixed powder was put into a granulator for granulation. The inlet temperature of the dryer was 320℃ and the outlet temperature was 110℃.

[0052] Step 3: The granulated powder was put into a supersonic atmospheric plasma spraying powder feeder, and (Hf 1 / 2 Zr 1 / 4 Ti 1 / 4 )C coating was prepared on the surface of the C / C composite material coated with SiC inner coating by supersonic atmospheric plasma spraying. The plasma spraying used a spraying direct current of 400A, a spraying direct voltage of 100V, a main gas flow of 74L / min, an auxiliary gas flow of 8L / min, a powder feeding rate of 5g / min, a spraying distance of 100mm, and the spraying process was 8 times of spraying.

[0053] The coating was not subjected to high-temperature heat treatment by oxyacetylene flame, the coating was not dense, and the hardness was only 2.4±0.6GPa.

[0054] Comparative Example 3:

[0055] Step 1: HfO2 powder, ZrO2 powder, TiO2 powder and C powder with a molar ratio of 2:1:1:12 were weighed and mixed as raw materials and put into a planetary ball mill for grinding for 8h; the ground mixed powder was wrapped in a graphite crucible with graphite paper, and then put into a high-temperature heat treatment furnace protected by Ar gas, the furnace temperature was raised to 2100℃ at a heating rate of 3℃ / min, and high-temperature heat treatment was carried out for 2h, (Hf 1 / 2 Zr 1 / 4 Ti 1 / 4 )C solid solution powder was prepared by carbothermic reduction reaction.

[0056] Step 2: (Hf 1 / 2 Zr 1 / 4 Ti 1 / 4 )C powder, PVA, alcohol and water were put into a horizontal ball mill at a ratio of 4:4:1:1 and ground for 6h; the ground mixed powder was put into a granulator for granulation. The inlet temperature of the dryer was 320℃ and the outlet temperature was 110℃.

[0057] Step 3: The granulated powder was put into a supersonic atmospheric plasma spraying powder feeder, and (Hf 1 / 2 Zr1 / 4 Ti 1 / 4 )C coating. Plasma spraying was performed with a spraying direct current of 400 A, a spraying direct voltage of 100 V, a primary gas flow of 74 L / min, a secondary gas flow of 8 L / min, a powder feeding rate of 5 g / min, a spraying distance of 100 mm, and 8 spraying processes.

[0058] Step 4: The prepared (Hf 1 / 2 Zr 1 / 4 Ti 1 / 4 )C coating was subjected to oxyacetylene high-temperature heat treatment. The distance between the oxyacetylene torch and the sample surface was 10 mm, and the oxyacetylene heat flow density was 2.4 MW / m 2 , wherein the acetylene gas flow was 0.18 L / s, the oxygen gas flow was 0.24 L / s, the acetylene pressure was 0.095 MPa, and the oxygen pressure was 0.4 MPa.

[0059] After the heat treatment of the coating, the coating was destroyed, and the hardness of the coating was only 4.5±1.9 GPa, and the heat treatment failed.

[0060] Comparative Example 4:

[0061] Step 1: HfO2 powder, ZrO2 powder, TiO2 powder and C powder with a molar ratio of 1:1:2:12 were weighed and mixed as raw materials and put into a planetary ball mill for grinding for 6 h. The ground mixed powder was wrapped in a graphite crucible containing graphite paper, and then was put into a high-temperature heat treatment furnace protected by Ar gas. The furnace temperature was raised to 2100°C at a heating rate of 3°C / min, and was kept for 4 h for high-temperature heat treatment to prepare (Hf 1 / 4 Zr 1 / 4 Ti 1 / 2 )C solid solution powder by carbothermal reduction reaction.

[0062] Step 2: The (Hf 1 / 4 Zr 1 / 4 Ti 1 / 2 )C powder was mixed with PVA, alcohol and water according to the ratio of 4:4:1:1 and was put into a horizontal ball mill for grinding for 6 h. The ground mixed powder was put into a granulator for granulation. The inlet temperature of the dryer was 330°C, and the outlet temperature was 100°C.

[0063] Step 3: The granulated powder was put into a supersonic atmospheric plasma spraying powder feeder, and a (Hf 1 / 4 Zr 1 / 4 Ti 1 / 2)C coating. Plasma spraying was performed with a spraying direct current of 400 A, a spraying direct voltage of 110 V, a primary gas flow of 74 L / min, a secondary gas flow of 6 L / min, a powder feeding rate of 6 g / min, a spraying distance of 100 mm, and 8 spraying processes.

[0064] The coating was not subjected to oxyacetylene flame high temperature heat treatment, the coating was not dense, and the hardness was only 5.8±2.0 GPa.

[0065] Comparative Example 5:

[0066] Step 1: HfO2 powder, ZrO2 powder, TiO2 powder and C powder with a molar ratio of 1:1:2:12 were weighed and mixed as raw materials and put into a planetary ball mill for grinding for 6 h. The ground mixed powder was wrapped in a graphite crucible with graphite paper, and then put into a high temperature heat treatment furnace with Ar gas protection. The furnace temperature was raised to 2100°C at a temperature rising speed of 3°C / min, and high temperature heat treatment was performed for 4 h. (Hf 1 / 4 Zr 1 / 4 Ti 1 / 2 )C solid solution powder was prepared by carbothermal reduction reaction.

[0067] Step 2: The (Hf 1 / 4 Zr 1 / 4 Ti 1 / 2 )C powder was mixed with PVA, alcohol and water in a ratio of 4:4:1:1 and put into a horizontal ball mill for grinding for 6 h. The ground mixed powder was put into a granulator for granulation. The inlet temperature of the dryer was 330°C, and the outlet temperature was 100°C.

[0068] Step 3: The granulated powder was put into a supersonic atmospheric plasma spraying powder feeder, and a (Hf 1 / 4 Zr 1 / 4 Ti 1 / 2 )C coating was prepared on the surface of the C / C composite material coated with a SiC inner coating by supersonic atmospheric plasma spraying. Plasma spraying was performed with a spraying direct current of 400 A, a spraying direct voltage of 110 V, a primary gas flow of 74 L / min, a secondary gas flow of 6 L / min, a powder feeding rate of 6 g / min, a spraying distance of 100 mm, and 8 spraying processes.

[0069] Step 5: The (Hf 1 / 4 Zr 1 / 4 Ti 1 / 2 )C coating was subjected to oxyacetylene high temperature heat treatment. The distance between the oxyacetylene torch and the sample surface was 10 mm, and the oxyacetylene heat flow density was 2.4 MW / m 2wherein the acetylene gas flow is 0.18 L / s, the oxygen gas flow is 0.24 L / s, the acetylene pressure is 0.095 MPa, and the oxygen pressure is 0.4 MPa.

[0070] After the heat treatment, the coating is damaged, and the hardness of the coating is only 6.8±0.9 GPa, and the heat treatment fails.

[0071] Table 1 Comparison of different examples before and after heat treatment

[0072]

[0073]

[0074] As can be seen from the table, in Example 1, the (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C coating after heat treatment, the appropriate proportion of Ti element can densify the coating surface at high temperature; the (Hf,Zr)O2 oxide doped with Ti has a large lattice distortion due to the entropy effect, so the hardness of the coating is improved. The (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C coating prepared by high-velocity atmospheric plasma spraying in Comparative Example 1, the (Hf 1 / 2 Zr 1 / 4 Ti 1 / 4 )C in Comparative Example 2 and the (Hf 1 / 4 Zr 1 / 4 Ti 1 / 2 )C coating in Comparative Example 4 is not dense, showing typical particle accumulation characteristics, and because a large amount of molten phase is formed during the spraying process, the hardness of the coating is low. The (Hf 1 / 2 Zr 1 / 4 Ti 1 / 4 )C coating in Comparative Example 3 has a high Hf element, and the volume expansion caused by the phase transition of the (Hf,Zr)O2 doped with Ti is large, resulting in cracks and shedding to form and fail. At this time, the Si element in the SiC inner coating diffuses outward and reacts with the outer coating to form a low-hardness silicate molten phase, resulting in no obvious improvement in the hardness of the coating. The (Hf 1 / 4 Zr 1 / 4 Ti 1 / 2 )C coating in Comparative Example 5 is damaged by mechanical ablation due to the formation of a low-melting-point Ti-rich phase ((Hf,Zr)TiO4) during heat treatment. The formation of a low-hardness silicate molten phase results in no obvious improvement in the hardness of the coating.

[0075] These coatings, when heat treated at high temperature, have high melting point of Hf and Zr rich oxide (Hf,Zr)02, which often acts as the high melting point oxide skeleton on the surface of the coating. However, this structure is loose and porous, and Ti element forms low melting point Ti rich phase during heat treatment, which is in molten state during heat treatment. Appropriate amount of Ti element (25 mol%) not only heals the loose area left by supersonic atmospheric plasma spraying method, but also reacts with (Hf,Zr)02 to form Ti doped (Hf,Zr)02 oxide film with dense structure during heat treatment. Therefore, the case 1 (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C coating and the comparative example 3 (Hf 1 / 2 Zr 1 / 4 Ti 1 / 4 )C coating, the appropriate amount of Ti element in the coating can densify the surface of the coating during high temperature heat treatment. In addition, the Ti doped (Hf,Zr)02 oxide has larger lattice distortion due to the entropy effect, so it has higher hardness.

[0076] The phase transition of Ti doped (Hf,Zr)02 oxide from tetragonal phase to monoclinic phase will cause volume expansion, and the volume expansion caused by Hf02 is greater than that of Zr02. Therefore, the volume expansion caused by phase transition of the case 2 (Hf 1 / 2 Zr 1 / 4 Ti 1 / 4 )C coating is more serious than that of the case 1 (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C coating. Therefore, the case 2 (Hf 1 / 2 Zr 1 / 4 Ti 1 / 4 )C coating is more prone to crack and fall off during heat treatment, which leads to the damage of the case 2 (Hf 1 / 2 Zr 1 / 4 Ti 1 / 4 )C coating after heat treatment for 240 s. The damage of the outer coating leads to the diffusion of oxygen to the internal SiC coating, and the oxidation of SiC and the reaction with the outer coating to form a low hardness silicate molten phase, so the case 2 (Hf 1 / 2 Zr 1 / 4Ti 1 / 4 )C coating has no obvious hardness improvement after heat treatment. The case 3 (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C coating has less Hf element ratio, which weakens the volume expansion caused by phase transition, so the coating is complete and dense after heat treatment. However, with the increase of the ratio of Ti element, the comparative example 5 (Hf 1 / 4 Zr 1 / 4 Ti 1 / 2)The excessive Ti element ratio (50 mol%) in the C coating leads to the formation of a low-melting-point Ti-rich phase ((Hf,Zr)TiO4) during heat treatment, which is extremely susceptible to mechanical denudation and damages the coating, resulting in the destruction of the coating after heat treatment for 240 s. In addition, the formation of a Si-rich phase also leads to an insignificant increase in the hardness of the coating. Therefore, the coating does not achieve the desired effect after heat treatment.

[0077] Example 2

[0078] In this embodiment, in step 3, the plasma spraying adopts a spraying direct current of 390 A; a spraying direct voltage of 90 V; a main gas flow rate of 72 L / min; an auxiliary gas flow rate of 7 L / min; a powder feeding rate of 8 g / min; a spraying distance of 90 mm; and the spraying process is performed for 9 times.

[0079] In step 4, the distance between the oxyacetylene torch and the sample surface is 12 mm, and the oxyacetylene heat treatment time is 300 s.

[0080] In this embodiment, the parts not involved are the same as those in Example 1.

[0081] Example 3

[0082] In this embodiment, in step 3, the plasma spraying adopts a spraying direct current of 410 A; a spraying direct voltage of 100 V; a main gas flow rate of 70 L / min; an auxiliary gas flow rate of 6 L / min; a powder feeding rate of 10 g / min; a spraying distance of 80 mm; and the spraying process is performed for 10 times.

[0083] In step 4, the distance between the oxyacetylene torch and the sample surface is 15 mm, and the oxyacetylene heat treatment time is 360 s.

[0084] In this embodiment, the parts not involved are the same as those in Example 1.

[0085] Example 4

[0086] In this embodiment, in step 3, the plasma spraying adopts a spraying direct current of 395 A; a spraying direct voltage of 95 V; a main gas flow rate of 74 L / min; an auxiliary gas flow rate of 2 L / min; a powder feeding rate of 9 g / min; a spraying distance of 95 mm; and the spraying process is performed for 9 times.

[0087] In step 4, the distance between the oxyacetylene torch and the sample surface is 14 mm, and the oxyacetylene heat treatment time is 150 s.

[0088] In this embodiment, the parts not involved are the same as those in Example 1.

[0089] The above merely provides the preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for the production of a dense, superhard, ultra-high temperature ceramic coating on the surface of a carbon / carbon composite material, characterized in that, The method comprises the following steps: S1, Hf02powder, Zr02powder, Ti02powder and C powder are mixed and ball-milled, and a (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C solid solution powder is prepared after heat treatment; S2, (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C solid solution powder to obtain (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C granulated powder; S3, (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C granulated powder is sprayed on the surface of the C / C composite material coated with a SiC inner coating by supersonic atmospheric plasma spraying to obtain a process product; In S3, during the plasma spraying process, the spraying direct current is 390-410 A, the spraying direct voltage is 90-110 V, the main gas flow is 70-74 L / min, the auxiliary gas flow is 2-7 L / min, the powder feeding rate is 5-10 g / min, the spraying distance is 80-110 mm, and the spraying times are 8-10. S4, the process product is high-temperature heat treated by oxygen ethylene, and a (Hf 1 / 4 Zr 1 / 2 Ti 1 / 4 )C ultra-high temperature ceramic coating is prepared on the surface of the C / C composite material coated with a SiC inner coating. In S4, during the oxyacetylene high-temperature treatment process, the coating surface temperature is 1900-2200℃. The coating is a Ti-doped (Hf, Zr)O2 oxide.

2. The method of claim 1, wherein the carbon / carbon composite surface densification ultra-high temperature ceramic coating is prepared by the steps of: In S4, the oxyacetylene heat flux density is 2.4 MW / m 2 .

3. The method of claim 1, wherein the carbon / carbon composite surface densification ultra-high temperature ceramic coating is prepared by the steps of: In S4, the acetylene gas flow in the oxyacetylene gas flow is 0.18 L / s, and the oxygen gas flow is 0.24 L / s.

4. The method of claim 1, wherein the carbon / carbon composite surface densification ultra-high temperature ceramic coating is prepared by the steps of: In S4, the acetylene pressure in the oxyacetylene gas flow is 0.095 MPa, and the oxygen pressure is 0.4 MPa.

5. The method of claim 1, wherein the carbon / carbon composite surface densification ultra-high temperature ceramic coating is prepared by the steps of: In S4, during the oxyacetylene high-temperature treatment process, the distance between the oxyacetylene torch and the sample surface is 10-15 mm, and the oxyacetylene treatment time is 150-360 s.

6. A carbon / carbon composite material surface densified with a superhard ultrahigh-temperature ceramic coating prepared by the method of any one of claims 1-5, characterized in that, The coating is a Ti-doped (Hf, Zr)O2 oxide.

7. The carbon / carbon composite surface-densified ultra-high temperature ceramic coating of claim 6, wherein, The thickness of the coating is 150-300 μm.

8. The carbon / carbon composite surface-densified ultra-high temperature ceramic coating of claim 6, wherein, The average hardness of the coating is ≥15 GPa.

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