文献类型：期刊文献

中文题名：W,Re过渡层对碳基体表面Al_(2)O_(3)涂层高温热匹配性和层间扩散的影响

英文题名：Alleviating High Temperature Thermal Mismatch and Element Diffusion of Al2O3 Coating on Carbon Substrate by Introducing W/Re Interlayer

作者：李东鹏[1];王卫泽[1];黄继波[1];朱含[1];付鑫[2];孙杰[2]

机构：[1]华东理工大学机械与动力工程学院承压系统与安全教育部重点实验室,上海200237;[2]上海卫星工程研究所,上海201109

年份：2022

卷号：46

期号：9

起止页码：1181

中文期刊名：稀有金属

外文期刊名：Chinese Journal of Rare Metals

收录：CSTPCD;;EI(收录号：20224413017736);Scopus;北大核心:【北大核心2020】；CSCD:【CSCD2021_2022】；

基金：上海航天科技创新基金项目(SAST2019-056)资助。

语种：中文

中文关键词：碳基体;大气等离子喷涂(APS);射频磁控溅射(RFMS);元素扩散;钨;铼

外文关键词：carbon substrate;atmospheric plasma spraying(APS);radio frequency magnetron sputtering(RFMS);element diffusion;W;Re

摘要：在含碳材料表面沉积氧化铝(Al_(2)O_(3))涂层是目前常用的一种高温防护手段,但其在高温下长期使用,易产生涂层开裂、层间元素扩散等现象,进而导致防护失效。本文以大气等离子喷涂(APS)结合射频磁控溅射(RFMS)沉积铼(Re)涂层和钨(W)涂层作为过渡层,研究过渡层对碳基体表面沉积Al_(2)O_(3)涂层的高温下的热匹配性和层间扩散的影响。通过比较不同试样加热后的界面形貌发现,1100℃保温3 h后无W层的涂层试样表面开裂剥落,而添加过渡层的试样表面完好,截面微观结构分析也未发现明显开裂。对界面两侧元素扩散分析发现,添加过渡层W后Al元素扩散现象减弱,添加Re/W层后,元素扩散进一步降低。可见W层、Re/W层加入到含碳材料和氧化铝层间后,可提高涂层抗开裂剥落能力,且涂层层间元素扩散明显减弱。
Alumina(Al_(2)O_(3))coating deposited on carbon-containing materials was a common high temperature protection method.However,when it was used at high temperature for a long time,it was easy to develop coating cracking caused by mismatch of thermal expansion coefficient and interlayer element diffusion caused by concentration difference,which leaded to protection failure.The re-fractory metal tungsten(W)had good stability at high temperature,and the thermal expansion coefficient was between the substrate and the alumina coating,which could improve the thermal matching of the coating.The low diffusivity of W could be used as the diffu-sion barrier between layers,and rhenium(Re)could reduce the formation of tungsten carbide(WC)in W layer and improve the pro-tective temperature of the coating.In this paper,Re and W were deposited by atmospheric plasma spraying(APS)combined with ra-dio frequency magnetron sputtering(RFMS)as transition layers to study the effect of transition layer on the thermal matching and interlayer diffusion of Al_(2)O_(3)coating deposited on the carbon substrate at high temperature.The tungsten coating was prepared by spherical tungsten powder with a purity of 99%and an average particle size of less than 45μm.The magnetron sputtering target with a purity of more than 99.9%was used for the deposition of Re and W films.The substrate of the sample was graphite with a carbon content of more than 99.5%.In order to study the thermal matching and diffusion resistance of the transition layer,three different coating samples were prepared in the experiment(Sample 1:Al_(2)O_(3)-C,Sample 2:Al_(2)O_(3)-W-C,Sample 3:Al_(2)O_(3)-W-Re/W-C).Before the coating was deposit-ed,the substrate surface should be coarsened by sand blasting and cleaned by anhydrous ethanol.The thickness of Re/W layer deposit-ed by magnetron sputtering was 2~3μm,the thickness of W layer deposited by plasma spraying was 80~100μm,and the thickness of Al_(2)O_(3)coating was 160~200μm.By comparing the structure of samples with different structures after heating,it was found that the sur-face of the coating sample without W layer cracked and fell off after holding at 1100℃for 3 h,while the surface of the sample with transition layer was intact.By observing the microstructure of each coating,obvious penetrating cracks were found in the coating of Sample1,and the samples with transition layer had better thermal matching and less thermal stress at high temperature,so the coating structure was still intact.In diffusion experiments,the coating was heated by high power laser.The laser power was 1000 W,and scanned 15 times along the sample diameter direction.By analyzing the element distribution on both sides of the alumina coating inter-face after heating,it was found that the diffusion flux of Al element outside the ceramic coating was significantly reduced after adding the transition layer W,and the diffusion phenomenon between the layers of the sample was weakened.The results showed that the addi-tion of W transition layer could reduce the loss of Al in the Al_(2)O_(3)coating and prolong the protection time of the coating at high tempera-ture.The element distributions on both sides of W layer in Sample 2 and Sample 3 samples were analyzed by the same method.It could be found that Re/W layer reduced the diffusion of W and C elements at W/C interface,and reduced the contact between W and C,which was beneficial to the formation of brittle WC at high temperature(1400℃),and it was beneficial to maintain the bonding strength of the coating and improve the protection temperature of the coating.The change of diffusion coefficient of Al element in the coating after adding W transition layer was calculated by Boltzman-Matona method.The calculation results showed that the diffusion co-efficient of Al in alumina coating in carbon matrix was 4.66×10^(-14)m^(2)·s^(-1),while the diffusion coefficient of Al decreased to 9.81×10^(-15)m^(2)·s^(-1)after W transition layer was added.The same method was used to calculate the influence of Re/W layer on the diffu-sion coefficient of W element.The diffusion coefficient of W element decreased from 6.95×10^(-14)to 4.97×10^(-15)m^(2)·s^(-1)after adding Re/W layer.Through the above experiments and calculations,the following conclusions were obtained:(1)The thermal expansion rate of W layer was close to that of carbon matrix.As a transition layer,it could alleviate the cracking of Al_(2)O_(3)coating and prolong the service life of coating.(2)The existence of W layer reduced the diffusion of Al element in Al_(2)O_(3)coating to the substrate at high temperature,which could avoid the loss of main components of the coating,maintain the protective effect of the coating,and reduce the pollution of the diffusion of coating elements to the substrate.(3)The existence of Re reduced the diffusion amount at the interface between W lay-er and matrix,which helped to reduce the generation of brittle carbides at the interface.