电子束沉积SiC/ZrO_2热防护层的结构优化及其抗热震性能
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摘要
高性能辐射热防护层是高超声速飞行器金属热防护系统的重要组成部分。为获得高性能的热防护层,利用L5 EB-PVD电子束物理气相沉积设备在Haynes 214镍基合金表面沉积了Si C/ZrO_2防护层,测试了其在热循环条件下的抗热震性能;通过分析其沉积温度及厚度对残余热应力的影响,确定了热防护层的沉积工艺参数。结果表明:热防护层在800℃和900℃循环80次后未出现明显的宏观裂纹; 1 000℃循环60次后,Si C表面层应力集中区出现裂纹,在交变热应力作用下,裂纹不断扩展形成网状龟裂纹,最终导致热防护层剥落;热膨胀系数不匹配导致热防护层在急冷急热热震过程中产生热应力是导致其失效的主要原因。
High performance radiant heat shield is an important part of the metal thermal protection system for hypersonic vehicle. In order to optimize the coating process and obtain the high-performance coatings,the influences of the deposition temperature and the thickness of the coating on the residual thermal stress of the coating system were analyzed and the technological parameters of the thermal protective coating were determined. SiC/ZrO_2 double layer coating was prepared on Ni-based super-alloy by electron beam physical vapor deposition,and its shock resistance was tested by one side flame heating-water cooling method. Results showed that after 80 times cycles of the thermal shock under 800 ℃and 900 ℃,macroscopic cracks were not found on the surface of Si C coating. However,after 60 times cycles under 1 000 ℃,cracks appeared on the surface stress concentration area of the Si C layer,and cracks expanded and became a tortoise-shell shape under the action of alternating thermal stress,and eventually led to the coating spalling. The mismatch of thermal expansion coefficient which led to the formation of the thermal stress of the coating during the thermal shock was the main cause of the coating failure.
High performance radiant heat shield is an important part of the metal thermal protection system for hypersonic vehicle. In order to optimize the coating process and obtain the high-performance coatings,the influences of the deposition temperature and the thickness of the coating on the residual thermal stress of the coating system were analyzed and the technological parameters of the thermal protective coating were determined. SiC/ZrO_2 double layer coating was prepared on Ni-based super-alloy by electron beam physical vapor deposition,and its shock resistance was tested by one side flame heating-water cooling method. Results showed that after 80 times cycles of the thermal shock under 800 ℃and 900 ℃,macroscopic cracks were not found on the surface of Si C coating. However,after 60 times cycles under 1 000 ℃,cracks appeared on the surface stress concentration area of the Si C layer,and cracks expanded and became a tortoise-shell shape under the action of alternating thermal stress,and eventually led to the coating spalling. The mismatch of thermal expansion coefficient which led to the formation of the thermal stress of the coating during the thermal shock was the main cause of the coating failure.
引文
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[4]BERANGER M,FIARD J M,AMMAR K,et al.A new fatigue model including thermal ageing for low copper aluminum-silicon alloys[J].Procedia Engineering,2018,213:720-729.
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[6]GODSE R V,SANTHANAM A T.Composite CVD+PVDcoatings[J].Materials Science and Engineering:A,1996,209(1/2):384-388.
[7]MARTIJN Drüsedau T P,DIEZ A,Blsing J.Deposition of nanocrystalline silicon mediated by ultrathin aluminum underlayers by PCVD and sputter-deposition at 500 K[J].Thin Solid Films,1999,337(1/2):41-44.
[8]STASZUK M,PAKUA D,CHLADEK G,et al.Investigation of the structure and properties of PVD coatings and ALD+PVD hybrid coatings deposited on sialon tool ceramics[J].Vacuum,2018,154(8):272-284.
[9]郭洪波,徐惠彬,宫声凯,等.基板温度对EB-PVD梯度热障涂层的微观结构和性能的影响[J].金属学报,2001,37(9):997-1 000.
[10]陈立强,宫声凯,徐惠彬.垂直裂纹对EB-PVD热障涂层热循环失效模式的影响[J].金属学报.2005,41(9):979-984.
[11]林峰,蒋显亮.热障涂层的研究进展[J].功能材料,2003,34(3):254-261.
[12]ZHOU Y,HASHIDA T.Coupled effects of temperature gradient and oxidation on thermal stress in thermal barrier coating system[J].International Journal of Solids and Structures,2001,38:4 253-4 264.
[13]VIRKAR AV,HUANG J L,CUTLER R A.Strength of oxide ceram by tran-induced stress[J].J Am Ceram Soc,1987,70(3):164-170.
[14]单英春.EB-PVD Ni-Cr薄板沉积的多尺度模拟[D].哈尔滨;哈尔滨工业大学,2006:35-74.
[15]徐小荣.涂层的微观结构特征及其与性能的关系[D].武汉:武汉交通科技大学,2000:69-74.
[16]VASILETS V N,HIROSE A,YANG Q,et al.Characterization of Doped Diamond-Like Carbon Films Deposited by Hot Wire Plasma Sputtering of Graphite[J].Applied Physics A-Materials Science and Processing,2004,79(8):2 079-2 084.
[17]SCARDI P,LEORI M,BERTAMINI L.Residual Stress in Plasma Sprayed Partially Stabilized Zirconia TBCs:Influence of the Deposition Temperature[J].Thin Solid Films,1996,278:96-103.