大气等离子喷涂制备SOFC连接体Cu/Mn/Co金属防护涂层

Cu/Mn/Co metallic coatings for SOFC interconnect protection prepared by atmospheric plasma spraying

摘要:

为了进一步提高固体氧化物燃料电池（SOFC）连接体防护涂层的电导率，采用大气等离子喷涂技术（APS）制备了Cu/Mn/Co金属涂层．研究了不同喷涂工艺参数对涂层性能的影响，以及涂层在800 ℃下的氧化行为．通过XRD，SEM及EDS表征涂层高温氧化过程中的相结构、表面形貌和微观结构演变，采用直流四电极法测量涂层的高温电导率．结果表明，800 ℃下氧化使金属涂层转变成了MnCo₂O₄/Cu_xMn_3-xO₄相．氧化初期，涂层表面和底部出现富Cu层；随氧化时间增加，富Cu层逐渐消失，Cu元素均匀分布在涂层中；当氧化120 h时，涂层表层的CuO层已不连续，与涂层分层且产生微裂纹．同时发现，长时间氧化后涂层截面明显致密化，形成了顶部致密、底部多孔的结构．此外，电流为550 A的涂层试样（No.2）尖晶石相最多，涂层致密度最高，其电导率也最高．800 ℃下氧化120 h后，电流为500，550和600 A的三种涂层试样（No.1~No.3）电导率分别为59.68S，93.55和85.72 S/cm，并且氧化过程中电导率保持稳定．所制备的金属涂层和尖晶石涂层均表现出较好的阻Cr扩散效果，Cr主要以Cr₂O₃的形式富集在基体和涂层的结合处．

Abstract:

To improve the conductivity of protective coatings of SOFC interconnect， the Cu/Mn/Co metallic coatings were prepared by atmospheric plasma spraying （APS）. The effect of spraying parameters on the coating performance and the oxidation behavior of prepared coatings under 800℃ were studied. XRD， SEM， EDS were used to characterize the phase structure， surface morphology and microstructure evolution of coatings. The electrical conductivity of the coatings was measured by applying four-probe method. The results showed that MnCo₂O₄/Cu_xMn_3-xO₄ phases were formed after oxidation at 800℃. At the initial stage of oxidation， a Cu-enriched layer was observed in the surficial area of the coating and the underneath section as well； as the oxidation time increased， the Cu-enriched layer was no longer visible and a homogeneous distribution of Cu in the coatings was detected. After oxidized for 120h， the surficial CuO layer was discontinuously distributed and interlay was observed between the CuO layer and the coating， and microcracks were also presented. At the same time， it was found that the cross-section of the coating was significantly densified after long-term oxidation， forming a dense top and porous bottom structure. Moreover， it was found that the coating sample （No. 2） with a current of 550A consisted of the most spinel phase， showed the best densification effect and the best highest conductivity. After oxidized at 800°C for 120h， the conductivity of three coating samples （No.1~No.3） with currents of 500A， 550A， and 600A exhibited a stable conductivity of 59.68 S/cm， 93.55 S/cm， and 85.72 S/cm， respectively. Prepared metallic coatings and spinel coatings presented excellent effects to retain the diffusion of Cr， which was found enriched between the coating and the substrate in form of Cr₂O₃.