炭/炭复合材料耐烧蚀W涂层

采用等离子喷涂技术成功在坯体密度为1.8 g/cm~3炭/炭复合材料上面制备厚度为1.2 mm与基体结合良好的较致密的W涂层的试样。利用氧乙炔焰分别测试其在30 s、60 s、90 s和120 s下的烧蚀性能。结果表明:试样的质量烧蚀率和线烧蚀率均随时间的增加而增加。其中,最大质量烧蚀率和线烧蚀率分别为7.8μg/s和3.5μm/s。XRD、SEM分析表明:在烧蚀中心区,涂层试样的烧蚀以升华分解为主,同时,还伴有氧化烧蚀和微区机械剥蚀;在烧蚀过渡区,涂层的烧蚀机制以热氧化和燃气冲刷为主;而在烧蚀边缘区,涂层的烧蚀则主要表现为弱氧化烧蚀。     

C/C复合材料表面SiC-ZrB_(2)涂层的缺陷修复与抗烧蚀性能EI北大核心CSCD

碳/碳(C/C)复合材料表面涂层在制备与服役过程中易出现裂纹、凹坑和孔洞等缺陷,使涂层失去完整性而极易导致防护失效,目前常用的解决方法为更换整体涂层,成本高、工艺复杂、耗时长,因此快速高效的涂层轻微缺陷修复技术是解决这一难题的有效途径。通过大气等离子焰流在C/C复合材料表面SiC-ZrB_(2)(SZ)涂层表面预先构造缺陷,采用异丙醇以及高温下性能稳定的含硼聚氮硅烷胶粘剂作为修复剂,以SiC-ZrB_(2)粉末作为改性填料,Al_(2)O_(3)作为烧结助剂,对SZ涂层缺陷进行修复,研究修复前后涂层的微观结构演变与烧蚀防护性能。结果表明:经等离子焰流烧蚀后,未修复的SZ涂层试样中心出现圆形凹坑缺陷,裸露出C/C复合材料基底;而对于修复后的涂层试样,修复剂热解生成的SiBCN陶瓷和改性陶瓷填料均匀覆盖于缺陷处,使涂层保持较高完整性,且在氧乙炔烧蚀下生成致密的SiO_(2)玻璃膜可有效阻挡氧扩散,保护C/C复合材料免受机械冲蚀;修复后的涂层试样在氧乙炔焰流下烧蚀60s后线烧蚀率与质量烧蚀率分别为0.65μm/s和-0.28mg/s,相比于未修复涂层试样分别降低了83.54%和129.47%,修复后涂层的抗烧蚀性能得到显著提升。     

SiC/ZrB2-SiC-B4C涂层的抗氧化和耐烧蚀性能研究

碳/碳化硅复合材料(C/SiC)在使用时经常受到高温氧化和烧蚀作用。本文采用化学气相沉积(CVD)和浆料刷涂-烧结法制备了双层SiC/ZrB2-SiC-B4C涂层,对比研究了无涂层,单层SiC涂层和双层SiC/ZrB2-SiC-B4C涂层C/SiC复合材料在1500℃下的氧化和在4.2 MW/m2热流密度下的烧蚀性能。结果表明,制备态ZrB2-SiC-B4C涂层致密、完整,表面平均粗糙度约为1 μm,孔隙率约为4.2 %。在1500℃氧化30 h后,SiC/ZrB2-SiC-B4C涂层C/SiC复合材料的质量损失率约为10%,涂层表面氧化膜致密,无明显裂纹。高温烧蚀20 s后,SiC/ZrB2-SiC-B4C涂层的线烧蚀率和质量烧蚀率分别为1.0±0.3 μm/s和1.1±0.2 mg/s,与单层SiC涂层相比分别降低了75.0 %和50.0 %,SiC/ZrB2-SiC-B4C涂层烧蚀后形成的ZrO2-SiO2氧化膜可以减缓火焰对复合材料的机械剥蚀作用。     

ZrC-SiC-MoSi2涂覆C/C-SiC-ZrC陶瓷基复合材料在氧乙炔焰下的烧蚀行为及机理(英文)

为进一步提高C/C复合材料在不同烧蚀环境下的烧蚀性能,采用浆料刷涂法在C/C-SiC-ZrC陶瓷基复合材料上制备Zr含量分别为34%和60%(质量分数)的ZrC-SiC-MoSi₂涂层,并且利用氧乙炔焰研究涂层C/C-SiC-ZrC复合材料在3种不同氧气及乙炔流量下的烧蚀行为。结果表明：随着Zr含量的增加,涂层内部的ZrC和SiC颗粒尺寸明显减小,且颗粒分布更加均匀。Zr含量为60%的涂层线烧蚀率随氧气和乙炔流量的增加而增加,而Zr含量为34%的涂层线烧蚀率随氧气和乙炔流量的增加,先增加后降低。此外,详细讨论ZrC-SiC-MoSi₂涂层在不同条件下的烧蚀机理。随着氧气和乙炔流量的增加,主要的烧蚀机制由氧化变为氧化和蒸发的结合作用,最后变为氧化、蒸发及剥蚀的结合作用。     

等离子喷涂ZrC涂层耐烧蚀性能与机理研究

采用等离子喷涂工艺在C/SiC基体材料表面制备了较为致密的W粘结层和ZrC耐烧蚀涂层,利用氧乙炔火焰测试其抗烧蚀性能。结果表明:涂层具有良好的抗烧蚀性能。经烧蚀距离30 mm的氧乙炔烧蚀300 s后,涂层的质量烧蚀率为1.7×10~(-3)g·s~(-1),仅为无涂层试样的68%;线烧蚀率为4.0×10~(-4)mm·s~(-1),仅为无涂层试样的30%。随着烧蚀距离的减小,涂层的质量烧蚀率不断增大,线烧蚀率不断减小。试样表面温度梯度导致涂层存在3种典型烧蚀形貌,中心致密区,过渡区以及边缘疏松区。温度较高的中心区氧化产物为WO_3,其发生熔融并填充涂层内部孔隙和裂纹,形成致密层,且与ZrO_2所产生的协同效应有效降低了机械剥蚀几率,烧蚀以热化学烧蚀为主;温度较低的边缘区烧蚀产物未发生熔融且呈现疏松状,烧蚀主要表现为热化学烧蚀和机械剥蚀。     

C／C复合材料ZrB2-SiC基陶瓷涂层制备及烧蚀性能研究

为提高C／C复合材料的抗烧蚀性能,采用两步刷涂一烧结法制备了ZrB2-SiC基陶瓷涂层。首先利用反应烧结制备ZrB2-SiC—ZrC过渡层,并在此基础上制备了ZrB2-20％SiC-5％Si3N4、ZrB2．15％SIC-20％MoSi2、ZrB2．15％SiC-20％TaC3种外涂层。利用XRD和扫描电镜研究了涂层的相组成和显微形貌,并采用氧乙炔焰烧蚀仪测试了涂层在2500℃、60S的抗烧蚀性能,探讨了涂层的高温烧蚀机理。结果表明：利用反应烧结制备的过渡层与基体结合紧密,且与外涂层无明显分层现象,起到了良好的过渡作用;由于Si,N4及MoSi2起到了烧结助剂作用,使ZrB2—20％SiC-5％Si,N4、ZrB2．15％SiC．20％MoSi2外涂层结构较为致密;ZrB2—20％SiC-5％si3N4、ZrB2—15％SiC～20％MoSi2涂层表现出了较好的抗烧蚀性能,其中ZrB2-20％SiC-5％Si3N4涂层线烧蚀率及质量烧蚀率分别为0．075mm/s、0．0081/s,ZrB2—15％SIC-20％MoSi2涂层线烧蚀率及质量烧蚀率分别为0．018mm／s、0．0064g／s,而ZrB2-15％SIC-20％TaC涂层由于结构较为松散,未能起到有效的氧化防护,导致涂层被烧穿。     

等离子喷涂制备C/C复合材料SiC涂层的驻点烧蚀性能

目的在C/C复合材料表面制备SiC涂层,提高C/C复合材料抗烧蚀性能。方法采用真空等离子喷涂技术在C/C复合材料表面制备纯Si涂层,在惰性气氛保护下对涂层高温热处理,纯Si涂层与C元素在高温下反应,原位生成SiC涂层。利用电弧加热器在不同烧蚀温度下,分别考核涂层的驻点烧蚀性能,并采用OM、SEM、EDS和XRD等对烧蚀前后的微观形貌和物相成分进行分析。结果在C/C复合材料表面制备了致密的SiC涂层,涂层中没有明显的裂纹存在,并在涂层下方产生较深的渗透区域,深度超过涂层厚度。制备的SiC涂层在1400℃下烧蚀50 s,涂层完整,具有良好的驻点烧蚀性能;在1600℃和1650℃下烧蚀50 s,涂层部分剥落,C/C复合材料基体产生烧蚀。结论 SiC涂层在高温下氧化成Si O2玻璃态膜,并覆盖在C/C复合材料表面,对基体具有良好的保护作用。随着烧蚀温度的提高,在超音速气流的冲刷下,由于热膨胀系数不匹配和SiC主动氧化的原因,涂层在烧蚀面边缘出现剥落,且剥落现象越来越严重,涂层失去对C/C基体的保护作用,烧蚀性能下降。     

W-SiC-C/C复合材料制备及等离子烧蚀性能

目的提高C/C复合材料在超高温下的抗烧蚀性能。方法采用化学气相沉积法,在C/C复合材料表面制备SiC过渡层,然后以惰性气体保护等离子喷涂工艺在带有SiC过渡层的C/C材料表面制备W涂层,研究所制备的W-SiC-C/C复合材料的微观形貌与结构特征。以200 kW超大功率等离子焰流,考核W-SiC-C/C材料的抗烧蚀性能,并与无涂层防护的C/C材料进行对比分析。结果W涂层主要为层状的柱状晶结构。W涂层与SiC过渡层、过渡层与基体界面呈镶嵌结构,结合良好。SiC过渡层阻止了W、C元素相互迁移与反应。在驻点压力为4.5 MPa、温度约5000 K、热流密度为36 MW/m²的烧蚀条件下,当烧蚀时间小于10 s时,涂层对C/C材料起到了较好的保护作用,W涂层发生氧化烧蚀,基体未发现烧蚀,平均线烧蚀率为0.0523 mm/s;当烧蚀时间超过15 s后,涂层防护作用基本失效,基体C/C材料发生烧蚀现象。结论以W涂层、SiC过渡层为防护的C/C复合材料,能够适用于短时间超高温的烧蚀环境,如固体火箭发动机等。W涂层的熔融吸热、氧化耗氧以及SiC过渡层的氧化熔融缓解涂层热应力和氧扩散阻碍的联合作用,提高了C/C材料的抗烧蚀性能。     

C/C复合材料大气等离子喷涂mullite/ZrB_2-MoSi_2涂层抗烧蚀性能（英文）

采用大气等离子喷涂技术(APS)在C/C复合材料表面制备了mullite/ZrB_2-MoSi_2双层抗烧蚀涂层。借助XRD、SEM、EDS等分析手段对涂层的组织结构进行研究;基于氧丙烯焰烧蚀试验考察ZrB_2-MoSi_2/mullite复合涂层对C/C复合材料高温耐烧蚀性能的影响。结果表明,在1700和1800℃的氧丙烯焰下烧蚀60s,ZrB_2-MoSi_2/mullite涂层试样的质量烧蚀率分别为3.49×10~(-3)与3.77×10~(-3)g/s。其与单层ZrB_2-MoSi_2涂层试样相比,ZrB_2-MoSi_2/mullite涂层试样展现了出色的抗烧蚀性能。烧蚀过程中形成的硅酸盐玻璃可以作为热障层而减少氧气的进一步渗透,并且还具有自我封填缺陷的能力,使ZrB_2-MoSi_2/mullite涂层表现较好的抗烧蚀性。     

C/C复合材料大气等离子喷涂mullite/ZrB2-MoSi2涂层抗烧蚀性能

采用大气等离子喷涂技术(APS)在C/C复合材料表面制备了mullite/ZrB₂-MoSi₂双层抗烧蚀涂层。借助XRD、SEM、EDS等分析手段对涂层的组织结构进行研究;基于氧丙烯焰烧蚀试验考察ZrB₂-MoSi₂/mullite复合涂层对C/C复合材料高温耐烧蚀性能的影响。结果表明,在1700 °C和1800 °C的氧丙烯焰下烧蚀60 s,ZrB₂-MoSi₂/mullite涂层试样的质量烧蚀率分别为3.49×10_-3 g/s与3.77×10_-3 g/s。其与单层ZrB₂-MoSi₂涂层试样相比,ZrB₂-MoSi₂/mullite涂层试样展现了出色的抗烧蚀性能。烧蚀过程中形成的硅酸盐玻璃可以作为热障层而减少氧气的进一步渗透,并且还具有自我封填缺陷的能力,使ZrB₂-MoSi₂/mullite涂层表现较好的抗烧蚀性。     

等离子喷涂制备ZrB2/SiC/Ta2O5涂层抗烧蚀性能研究

为了提高C/C复合材料的抗烧蚀性能,通过等离子喷涂法在C/C表面制备了SiC/Al₂O₃内层和ZrB₂/SiC/Ta₂O₅外层的双层涂层,通过XRD,SEM和EDS分析了涂层烧蚀前后的物相组成、微观结构和成分分布。烧蚀前涂层表面没有裂纹并且内层与基体、内层与外层之间结合良好。元素Zr、Si、Ta在涂层表面的分布相近,涂层表面成分分布均匀性良好。通过氧乙炔火焰在1800 ℃下对涂层的抗烧蚀性能进行考核。烧蚀过程中形成的镶嵌结构有利于阻挡氧气的渗入,Ta-Si-O玻璃层的形成封填了涂层孔隙,对基体有良好的保护效果,涂层表现出了较好的抗烧蚀性能。     

Effects of ablation at different regions in three-dimensional orthogonal C/SiC composites ablated by oxyacetylene torch at 1800 °C

C/SiC composites were prepared by polycarbosilane infiltration pyrolysis and ablated by oxyacetylene flame at 1800 °C for 180 s. Morphology and microstructure of C/SiC have been studied by scanning electron microscopy/energy dispersive spectroscopy, and X-ray diffraction analysis. Two concentric ring regions appeared on the surface of the ablated C/SiC. In the centre region of the ablated C/SiC was composed of irregular SiC particles with a lot of pores. The pores were resulted from (i) gas expansion in closed pores during ablation, and (ii) from the release of SiO gas produced by the oxidation of SiC with sufficiently low oxygen partial pressure. The results indicated the ablation was due to a combination of oxidation, mechanical erosion and recrystallization of the surface SiC.     

Microstructures and Ablation Resistance of ZrC Coating for SiC-Coated Carbon/Carbon Composites Prepared by Supersonic Plasma Spraying

To improve ablation resistance of silicon carbide (SiC)-coated carbon/carbon (C/C) composites, in this study, zirconium carbide (ZrC) coating was prepared on the surface of SiC-coated C/C composites by supersonic plasma spraying. The coating exhibits dense structure, and a good bonding with substrate. The oxyacetylene ablation results show that the ZrC coating greatly improved the ablation resistance of SiC-coated C/C composites. After ablation for 30 s in oxyacetylene flame, the linear ablation rate is only 0.9 × 10⁻³ mm/s, and the weight is increased by 2.0 × 10⁻³ g/s. The excellent ablation resistance is mainly attributed to the formation of a dense and continuous zirconia (ZrO₂) layer during the oxidation of the ZrC coating.     

Comparison of morphology and microstructure of ablation centre of C/SiC composites by oxy-acetylene torch at 2900 and 3550 °C

High-temperature application above 1600 °C of C/SiC composites requires evaluation of the ablation properties. The C/SiC composites were prepared by low pressure chemical vapor infiltration using CH₃SiCl₃ as precursor. As-prepared C/SiC composites were ablated by oxy-acetylene flame with the temperature of 2900 and 3550 °C. Above 3550 °C, subliming of carbon fiber and silicon carbide matrix was the main ablation behaviour. At 2900 °C, thermal decomposition and oxidation of SiC matrix were the main ablation behaviour. A carbon coating resulted from the pyrolysis of the acetylene prevented the C/SiC from oxidizing dramatically.     

Effect of surface ablation products on the ablation resistance of C/C–SiC composites under oxyacetylene torch

Single and cyclic ablations under oxyacetylene torch with 2380 ± 10% kW/m² heat flux were performed to evaluate the effect of ablation products on the ablation resistance of carbon/carbon – silicon carbide (C/C–SiC) composites separately. As a result of the accumulation of noncrystalline SiO₂ enwrapped SiC, ablation resistance of prepared composites was enhanced with time prolonging under single ablation while it was improved more significantly under cyclic ablation. The ablation products played several key roles during ablation: decreasing surface temperature, acting a barrier to oxidizing species attack and conglutinating defective ablated carbon fibers.     

ZrC-HfC-TaC改性C/SiC复合材料的循环氧化烧蚀行为

难熔金属碳化物改性是提升陶瓷基复合材料抗氧化性能的有效途径。然而,ZrC-HfC-TaC改性对循环氧化烧蚀性能的影响却鲜有报道。利用前驱体浸渍裂解结合化学气相沉积工艺构筑了ZrC-HfC-TaC改性C/SiC复合材料,剖析了1600 ℃/5 h循环静态氧化后材料的力学强度、化学组成以及微观结构的变化,根据表征结果提出了改性后材料的抗氧化机理,并利用1700 ℃/4000 s循环氧乙块焰烧蚀试验验证了ZrC-HfC-TaC改性对提升循环氧化烧蚀性能的有效性。研究表明,经过ZrC-HfC-TaC改性的C/SiC复合材料具备优异的高温循环氧化烧蚀性能。     

Ablation in different heat fluxes of C/C composites modified by ZrB2–ZrC and ZrB2–ZrC–SiC particles

Carbon/carbon composites modified by ZrB₂–ZrC–SiC particles (C/C–Z–SiC), C/C–Z and C/C were ablated by oxyacetylene torch using two different heat fluxes to investigate the effect of doped ceramic particles. Results indicated that C/C–Z–SiC had the best ablation property in heat flux of 2.38 MW/m² whereas their ablation rates increased fastest when heat flux rising from 2.38 to 4.18 MW/m². C/C composites had the poorest ablation property in the lower heat flux and their ablation rates increased slowest. Thermal mismatch of Z, SiC and C and evaporation of SiO₂ induced the various ablation behavior.     

The effect of zirconium carbide on ablation of carbon/carbon composites under an oxyacetylene flame

Ablation of zirconium carbide (ZrC) modified carbon/carbon (C/C) composites was tested by an oxyacetylene torch. The formation of zirconia from the oxidation of ZrC improves the ablation resistance of the C/C composites because of the evaporation at elevated temperature, which absorbs heat from the flame and reduces the erosive attack to carbon. Zirconia also acts as an accelerator for carbon oxidation as it reacts with carbon during the ablation, increasing the mechanical breakage rate of the fibres. However, the effect of mechanical breakage is inferior in the ablation of the composites. The heterogeneous reactions control the ablation of the composites.