(MoSi2-HfSi2) SHS-HfB2 high-oxygen-resistance layer for carbon-carbon surface gradient coating and preparation method of (MoSi2-HfSi2) SHS-HfB2 high-oxygen-resistance layer

Abstract

The invention relates to the field of gradient coatings, in particular to a (MoSi2-HfSi2) SHS-HfB2 high-oxygen-resistance layer for a carbon-carbon surface gradient coating and a preparation method of the high-oxygen-resistance layer. According to the invention, a common silicon connection mode of dissimilar transition metal elements is Mo-Si-Hf. According to the method, Hf-Si-O glass is generated in situ through oxidation of HfSi2, and in-situ modification of SiO2 rapidly generated through oxidation of MoSi2 on the surface of the carbon-based composite material is achieved. The problems that in the prior art, in the initial stage of inert oxidation, low-viscosity SiO2 is poor in stability and prone to volatilization, and a stable sealing glass layer cannot be formed to achieve efficient protection on a coating and an internal base body are solved, and the method has the advantages that SiO2 sealing oxygen resistance is enhanced, and the service life of the coating is prolonged.

Description

Technical Field

[0001] The present invention relates to the field of gradient coatings, and in particular to a carbon-carbon surface gradient coating (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer and its preparation method. Background Art

[0002] Carbon-based structural materials have excellent properties such as low thermal expansion coefficient, resistance to thermal shock, and creep resistance, and are widely used as candidate materials for spacecraft thermal protection systems and high-performance aircraft engine hot end components that are urgently needed in the national aviation strategy. However, when the temperature exceeds 400°C, the oxidation sensitivity in the air reduces the service life, greatly limiting the development of carbon structural materials. So far, oxygen barrier coating on its surface has been proven to be the most reliable way to extend the service life of carbon-based structural materials in air.

[0003] In recent years, HfB2-silicon-based coatings have attracted much attention for their high-temperature stability and integrity, and have become an important candidate material for ultra-high temperature ceramic coatings. During the high-temperature oxidation process, the coating surface can be oxidized to form an in-situ glass layer, which can adhere to the coating surface and fill the surface oxidation cavities to form a dense and compact in-situ sealing layer, forming a gradient structure with the original coating to resist the erosion of oxygen to the internal matrix. At the same time, the B2O3 generated by borides makes up for the oxidation protection weakness of SiC coatings below 1200°C. Hf oxide is embedded in the SiO2 glass layer in the form of a pinning phase, which improves the thermal stability of SiO2 and inhibits the extension of microcracks, thereby reducing the erosion of oxygen on carbon / carbon. However, with the increasingly stringent use requirements of high-performance aircraft engine hot end components, the working environment of oxygen barrier coatings urgently needs to develop towards ultra-high temperature environments.

[0004] Due to problems such as active oxidation of SiC and inert oxidation film-forming cycle, conventional HfB2-SiC based coatings can no longer meet the current application status.

[0005] Yang Qingqing et al. (Yang Qingqing. Research on the Antioxidation Mechanism of MoSi2-HfB2-SiC Coating [D]. China University of Mining and Technology, 2022.) introduced MoSi2 into the HfB2-SiC-based component, aiming to improve the oxygen barrier capacity of the coating system at ultra-high temperature of 1700°C. However, in the early stage of inert oxidation, although SiO2 rapidly generated by high-temperature oxidation of MoSi2 can provide an oxygen barrier and can slow down the oxygen erosion caused by the inert oxidation film-forming cycle of the HfB2-SiC system to a certain extent, the SiO2 produced by it has low viscosity and poor stability in ultra-high temperature environments. It is easy to volatilize and cannot form a stable sealing glass layer to achieve efficient protection of the coating and the internal substrate, resulting in further increase in coating oxidation loss, deterioration of the coating protection effect, and reduction of service life. Based on this, a feasible optimization design scheme is urgently needed to solve the above problems. Summary of the invention

[0006] The technical problem to be solved by the present invention is: in view of the shortcomings of the prior art, a carbon-carbon surface gradient coating (MoSi2-HfSi2) is provided. SHS -HfB2 high oxygen barrier layer and its preparation method, through Mo-Si-Hf bridging, form a stable sealing glass layer, so as to achieve the purpose of efficient protection of the coating and the internal substrate.

[0007] In order to achieve the above technical purpose, the technical solution provided by the present invention is as follows:

[0008] A carbon-carbon surface gradient coating (MoSi2-HfSi2) SHS -HfB2 high-resistance oxygen layer, in which the heterogeneous transition metal elements in the high-resistance oxygen layer are connected in a co-silicon manner: Mo-Si-Hf.

[0009] As an improvement, the (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer system, the volume ratio of MoSi2, HfSi2 and HfB2 ranges from 38:2:60 to 32:8:60.

[0010] The present invention also discloses a carbon-carbon surface gradient coating (MoSi2-HfSi2) SHS -The preparation method of HfB2 high oxygen barrier layer comprises the following steps:

[0011] S1. Hf, Si, and Mo are configured in proportion, and MoSi2-HfSi2 composite powder is synthesized by self-propagating combustion synthesis method using them as raw materials;

[0012] S2. The MoSi2-HfSi2 composite powder obtained in S2 is mixed with HfB2 powder by grinding and mixing to prepare (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer powder source;

[0013] S3. Use (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier powder source, using low temperature hot pressing technology to densify the coating on the carbon / carbon surface to prepare (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer;

[0014] S4. After sintering is completed, take out the product and obtain the target product after polishing.

[0015] As an improvement, the molar ratio range of Hf, Si and Mo in step S1 is: Mo:Hf:Si=100:4:209~100:21:242.

[0016] As an improvement, the volume ratio range of the MoSi2-HfSi2 composite powder in step S2 is: MoSi2:HfSi2=95:5~80:20.

[0017] As an improvement, the (MoSi2-HfSi2) SHS -The volume ratio range of HfB2 high oxygen barrier layer powder source is: MoSi2:HfSi2:HfB2=38:2:60~32:8:60.

[0018] The present invention has the advantages that:

[0019] The present invention is based on the co-silicon connection of heterogeneous transition metal elements, and realizes the in-situ modification of SiO2 generated rapidly by oxidation of MoSi2 on the surface of carbon-based composite materials through in-situ generation of Hf-Si-O glass by oxidation of HfSi2. The present invention overcomes the problem in the prior art that low-viscosity SiO2 has poor stability and is easy to volatilize in the initial stage of inert oxidation, and cannot form a stable sealing glass layer to achieve efficient protection of the coating and the internal matrix, and has the advantages of strengthening SiO2 sealing oxygen barrier and improving the service life of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 (MoSi2-HfSi2) obtained in Examples 1 to 4 of the present invention SHS -X-ray diffraction phase analysis results of HfB2 high oxygen barrier coating.

[0021] Figure 2 (MoSi2-HfSi2) obtained in Example 1 of the present invention SHS -Surface micromorphology of HfB2 high oxygen barrier coating.

[0022] Figure 3 (MoSi2-HfSi2) obtained in Example 2 of the present invention SHS -Surface micromorphology of HfB2 high oxygen barrier coating.

[0023] Figure 4 (MoSi2-HfSi2) obtained in Example 3 of the present invention SHS -Surface micromorphology of HfB2 high oxygen barrier coating.

[0024] Figure 5 (MoSi2-HfSi2) obtained in Example 4 of the present invention SHS -Surface micromorphology of HfB2 high oxygen barrier coating.

[0025] Figure 6 (MoSi2-HfSi2) obtained in Example 1 of the present invention SHS-Surface micromorphology of HfB2 high oxygen barrier coating after high temperature oxidation at 1700℃.

[0026] Figure 7 (MoSi2-HfSi2) obtained in Example 2 of the present invention SHS -Surface micromorphology of HfB2 high oxygen barrier coating after high temperature oxidation at 1700℃.

[0027] Figure 8 (MoSi2-HfSi2) obtained in Example 3 of the present invention SHS -Surface micromorphology of HfB2 high oxygen barrier coating after high temperature oxidation at 1700℃.

[0028] Fig. 9 (MoSi2-HfSi2) obtained in Example 4 of the present invention SHS -Surface micromorphology of HfB2 high oxygen barrier coating after high temperature oxidation at 1700℃.

[0029] Fig.10 (MoSi2-HfSi2) obtained in Examples 1 to 4 of the present invention SHS -Oxidation weight gain curve of HfB2 high oxygen barrier coating after high temperature oxidation at 1700℃.

[0030] Fig.11 These are the X-ray diffraction phase analysis results of the conventional MoSi2-HfSi2-HfB2 coatings obtained in Comparative Examples 1 to 2 of the present invention.

[0031] Fig.12 This is a surface microscopic morphology of the conventional MoSi2-HfSi2-HfB2 coating obtained in Comparative Example 1 of the present invention.

[0032] Fig.13 This is a surface microscopic morphology of the conventional MoSi2-HfSi2-HfB2 coating obtained in Comparative Example 1 of the present invention after high-temperature oxidation at 1700°C.

[0033] Fig.14 This is the oxidation weight gain curve of the conventional MoSi2-HfSi2-HfB2 coating obtained in Comparative Examples 1 to 2 of the present invention after high-temperature oxidation at 1700°C. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0035] Embodiment 1:

[0036] This embodiment discloses a carbon-carbon surface gradient coating (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer and its preparation method.

[0037] In this embodiment, the co-silicon connection mode of the heterogeneous transition metal elements in the high-resistance oxygen layer is: Mo-Si-Hf.

[0038] (MoSi2-HfSi2) SHS -The volume ratio of the HfB2 system is: MoSi2:HfSi2:HfB2=38:2:60.

[0039] The preparation method of this embodiment comprises the following steps:

[0040] S1. Hf, Si and Mo single substances are configured in proportion, and the molar ratio of the raw materials is Mo:Hf:Si=100:4:209. Then, MoSi2-HfSi2 composite powder is synthesized by self-propagating combustion synthesis method using them as raw materials. The volume ratio of the prepared MoSi2-HfSi2 composite powder is 95:5.

[0041] The method of self-propagating combustion is: Hf, Si, and Mo are mixed evenly and compacted into blocks by molding, and then the blocks are placed in a self-propagating combustion reactor, and the molybdenum wire intervention voltage is adjusted to perform self-propagating combustion synthesis.

[0042] S2. Mix and grind the MoSi2-HfSi2 composite powder and HfB2 powder to prepare (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer powder source, the volume ratio of MoSi2-HfSi2 composite powder to HfB2 powder is 40:60, and the final preparation (MoSi2-HfSi2) SHS -In the HfB2 high-resistance oxygen layer powder source, the volume ratio of MoSi2, HfSi2, and HfB2 is 38:2:60.

[0043] S3. Obtained using S2 (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier powder source, using low temperature hot pressing technology to densify the coating on the carbon / carbon surface to prepare (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer.

[0044] The method of low temperature hot pressing technology is: sintering in an SPS sintering furnace, the sintering temperature is 1200°C, the heating rate is 5°C / min, the pressure is 5MPa, and the holding time is 30min.

[0045] S4. After sintering is completed, take out the product and obtain the target product after polishing.

[0046] This embodiment provides a carbon-carbon surface gradient coating (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer preferred ratio and preparation method thereof, wherein the phase structure, surface morphology, surface morphology after oxidation, oxidation weight gain curve are respectively as follows Figure 1 , Figure 2 , Figure 6 , Fig.10 As shown in the figure, it can be seen that the carbon-carbon surface gradient coating provided in this embodiment is (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer shows lower and better oxidation weight gain after high temperature oxidation at 1700℃.

[0047] Embodiment 2:

[0048] This embodiment discloses a carbon-carbon surface gradient coating (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer and its preparation method.

[0049] In this embodiment, the co-silicon connection mode of the heterogeneous transition metal elements in the high-resistance oxygen layer is: Mo-Si-Hf.

[0050] (MoSi2-HfSi2) SHS -The volume ratio of the HfB2 system is: MoSi2:HfSi2:HfB2=36:4:60.

[0051] The preparation method of this embodiment comprises the following steps:

[0052] S1. Hf, Si and Mo single substances are configured in proportion, and the molar ratio of the raw materials is Mo:Hf:Si=100:9:219. Then, MoSi2-HfSi2 composite powder is synthesized by self-propagating combustion synthesis method using them as raw materials. The volume ratio of the prepared MoSi2-HfSi2 composite powder is 90:10.

[0053] S2. Mix and grind the MoSi2-HfSi2 composite powder and HfB2 powder to prepare (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer powder source, the volume ratio of MoSi2-HfSi2 composite powder to HfB2 powder is 40:60, and the final preparation (MoSi2-HfSi2) SHS -In the HfB2 high-resistance oxygen layer powder source, the volume ratio of MoSi2, HfSi2, and HfB2 is 36:4:60.

[0054] S3. Obtained using S2 (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer powder source (, using low temperature hot pressing technology to densify the coating on the carbon / carbon surface to prepare (MoSi2-HfSi2)SHS -HfB2 high oxygen barrier layer.

[0055] S4. After sintering is completed, take out the product and obtain the target product after polishing.

[0056] This embodiment provides a carbon-carbon surface gradient coating (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer preferred ratio and preparation method thereof, wherein the phase structure, surface morphology, surface morphology after oxidation, oxidation weight gain curve are respectively as follows Figure 1 , Figure 3 , Figure 7 , Fig.10 As shown in the figure, it can be seen that the carbon-carbon surface gradient coating provided in this embodiment is (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer shows lower and better oxidation weight gain after high temperature oxidation at 1700℃.

[0057] Embodiment 3:

[0058] This embodiment discloses a carbon-carbon surface gradient coating (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer and its preparation method.

[0059] In this embodiment, the co-silicon connection mode of the heterogeneous transition metal elements in the high-resistance oxygen layer is: Mo-Si-Hf.

[0060] (MoSi2-HfSi2) SHS -The volume ratio of the HfB2 system is: MoSi2:HfSi2:HfB2=34:6:60.

[0061] The preparation method of this embodiment comprises the following steps:

[0062] S1. Hf, Si and Mo single substances are configured in proportion, and the molar ratio of the raw materials is Mo:Hf:Si=100:15:230. Then, MoSi2-HfSi2 composite powder is synthesized by self-propagating combustion synthesis method using them as raw materials. The volume ratio of the prepared MoSi2-HfSi2 composite powder is 85:15.

[0063] S2. Mix and grind the MoSi2-HfSi2 composite powder and HfB2 powder to prepare (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer powder source, the volume ratio of MoSi2-HfSi2 composite powder to HfB2 powder is 40:60, and the final preparation (MoSi2-HfSi2) SHS -In the HfB2 high-resistance oxygen layer powder source, the volume ratio of MoSi2, HfSi2, and HfB2 is 34:6:60.

[0064] S3. Obtained using S2 (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer powder source (, using low temperature hot pressing technology to densify the coating on the carbon / carbon surface to prepare (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer.

[0065] This embodiment provides a carbon-carbon surface gradient coating (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer preferred ratio and preparation method thereof, wherein the phase structure, surface morphology, surface morphology after oxidation, oxidation weight gain curve are respectively as follows Figure 1 , Figure 4 , Figure 8 , Fig.10 As shown in the figure, it can be seen that the carbon-carbon surface gradient coating provided in this embodiment is (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer shows lower and better oxidation weight gain after high temperature oxidation at 1700℃.

[0066] Embodiment 4:

[0067] This embodiment discloses a carbon-carbon surface gradient coating (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer and its preparation method.

[0068] In this embodiment, the co-silicon connection mode of the heterogeneous transition metal elements in the high-resistance oxygen layer is: Mo-Si-Hf.

[0069] (MoSi2-HfSi2) SHS -The volume ratio of the HfB2 system is: MoSi2:HfSi2:HfB2=32:8:60.

[0070] The preparation method of this embodiment comprises the following steps:

[0071] S1. Hf, Si and Mo single substances are configured in proportion, and the molar ratio of the raw materials is Mo:Hf:Si=100:21:242. Then, MoSi2-HfSi2 composite powder is synthesized by self-propagating combustion synthesis method using them as raw materials. The volume ratio of the prepared MoSi2-HfSi2 composite powder is 80:20.

[0072] S2. Mix and grind the MoSi2-HfSi2 composite powder and HfB2 powder to prepare (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer powder source, the volume ratio of MoSi2-HfSi2 composite powder to HfB2 powder is 40:60, and the final preparation (MoSi2-HfSi2) SHS-In the HfB2 high-barrier oxygen layer powder source, the volume ratio of MoSi2, HfSi2, and HfB2 is 32:8:60.

[0073] S3. Obtained using S2 (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier powder source, using low temperature hot pressing technology to densify the coating on the carbon / carbon surface to prepare (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer.

[0074] This embodiment provides a carbon-carbon surface gradient coating (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer preferred ratio and preparation method thereof, wherein the phase structure, surface morphology, surface morphology after oxidation, oxidation weight gain curve are respectively as follows Figure 1 , Figure 5 , Fig. 9 , Fig.10 As shown in the figure, it can be seen that the carbon-carbon surface gradient coating provided in this embodiment is (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer shows lower and better oxidation weight gain after high temperature oxidation at 1700℃.

[0075] Comparative Example 1:

[0076] The MoSi2-HfSi2-HfB2 oxygen barrier layer for the carbon-carbon surface gradient coating involved in this comparative example is a conventional MoSi2-HfSi2-HfB2 oxygen barrier coating without co-silicon connection of heterogeneous transition metal elements inside, and the system volume ratio is 38:2:60, which is carried out according to the following steps:

[0077] A method for preparing a conventional MoSi2-HfSi2-HfB2 oxygen barrier layer for the above-mentioned carbon-carbon surface gradient coating comprises:

[0078] (1) Commercial powders of MoSi2, HfSi2, and HfB2 were used as coating powder sources (the powder source volume ratio was 38:2:60). After the mixed materials were ground, they were placed in a graphite mold. The coating was densified and sintered on the surface of the carbon matrix using low-temperature hot pressing technology to prepare a conventional MoSi2-HfSi2-HfB2 coating.

[0079] (2) After sintering, the product is taken out and polished to obtain a conventional MoSi2-HfSi2-HfB2 coating.

[0080] This comparative example provides a comparative case of a conventional MoSi2-HfSi2-HfB2 oxygen barrier coating without co-silicon bonding of heterogeneous transition metal elements inside, that is, compared with Example 1, the system ratio is the same, but there is no co-silicon bonding of Mo-Si-Hf heterogeneous transition metal elements inside the coating. Among them, the phase structure, surface morphology, surface morphology after oxidation, and oxidation weight gain curve are shown as follows: Fig.11 , Fig.12 , Fig.13 , Fig.14 shown.

[0081] It can be seen from the figure that the sample obtained in comparative example 1 has more pores after oxidation, and there are more defects in the structural oxygen barrier, which provides a channel for oxygen diffusion. Compared with Example 1, since there is no Mo-Si-Hf heterogeneous transition metal element co-silicon connection inside the coating, although the SiO2 sealing glass layer can be formed by rapid oxidation of MoSi2, it has low viscosity, poor stability, and is easy to volatilize, and cannot play the role of stable sealing glass, and the protective effect is limited, resulting in further increase in coating oxidation loss.

[0082] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A carbon-carbon surface gradient coating (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer, characterized in that, The co-silicon connection mode of heterogeneous transition metal elements in the high-resistance oxygen layer is: Mo-Si-Hf.

2. A carbon-carbon surface gradient coating (MoSi2-HfSi2) according to claim 1 SHS -HfB2 high oxygen barrier layer, characterized in that, The (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer system, the volume ratio of MoSi2, HfSi2 and HfB2 ranges from 38:2:60 to 32:8:

60.

3. A carbon-carbon surface gradient coating (MoSi2-HfSi2) according to claim 1 SHS -A method for preparing a HfB2 high oxygen barrier layer, characterized in that: The steps include: S1. Hf, Si, and Mo are configured in proportion, and MoSi2-HfSi2 composite powder is synthesized by self-propagating combustion synthesis method using them as raw materials; S2. The MoSi2-HfSi2 composite powder obtained in S2 is mixed with HfB2 powder by grinding and mixing to prepare (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer powder source; S3. Use (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier powder source, using low temperature hot pressing technology to densify the coating on the carbon / carbon surface to prepare (MoSi2-HfSi2) SHS -HfB2 high oxygen barrier layer; S4. After sintering is completed, take out the product and obtain the target product after polishing.

4. A carbon-carbon surface gradient coating (MoSi2-HfSi2) according to claim 3 SHS -A method for preparing a HfB2 high oxygen barrier layer, characterized in that: The molar ratio of Hf, Si and Mo in step S1 is in the range of Mo:Hf:Si=100:4:209 to 100:21:

242.

5. A carbon-carbon surface gradient coating (MoSi2-HfSi2) according to claim 3 SHS -A method for preparing a HfB2 high oxygen barrier layer, characterized in that: The volume ratio range of the MoSi2-HfSi2 composite powder in step S2 is: MoSi2:HfSi2=95:5~80:

20.

6. A carbon-carbon surface gradient coating (MoSi2-HfSi2) according to claim 3 SHS -A method for preparing a HfB2 high oxygen barrier layer, characterized in that: As described in step S3 (MoSi2-HfSi2) SHS -The volume ratio range of HfB2 high oxygen barrier layer powder source is: MoSi2:HfSi2:HfB2=38:2:60~32:8:60.

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