固態氧化物燃料電池金屬連接板與硬銲接合件潛變性質;Creep Properties for the Joint of Metallic Interconnect and Braze Sealant in Solid Oxide Fuel Cell

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Title:	固態氧化物燃料電池金屬連接板與硬銲接合件潛變性質;Creep Properties for the Joint of Metallic Interconnect and Braze Sealant in Solid Oxide Fuel Cell
Authors:	洪瑋佟;Hung, Wei-Tong
Contributors:	機械工程學系
Keywords:	金屬支撐型固態氧化物燃料電池;硬銲封裝膠;金屬連接板;潛變性質;Metal-supported solid oxide fuel cell;Braze sealant;Interconnect;Creep property
Date:	2021-08-13
Issue Date:	2021-12-07 13:28:24 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究針對金屬支撐固態氧化物燃料系統硬銲封裝材料，進行與金屬連接板接合之接合件的高溫機械特性分析，探討硬銲填料/金屬連接板接合件於高溫下之潛變性能與破壞模式。實驗結果顯示在未時效狀態及1000小時熱時效處理後，接合件於750 °C氧化環境下的張力及剪力潛變壽命皆隨著負載減少而增加。未時效張力及剪力接合件具1000小時壽命的潛變強度分別為5.48 MPa及3.56 MPa，為未時效接合件高溫張力及剪力強度的41%及35%。而時效處理之張力及剪力接合件具1000小時壽命的潛變強度分別為5.43 MPa及3.64 MPa，分別皆為時效接合件高溫張力及剪力強度的38%。在750 °C高溫且接觸到氧氣狀況下，氧化鉻層及銀基銲料層之間會形成橘色片狀的AgCrO2，此種氧化物會在時效處理階段以及潛變試驗中生成，且隨著時間增加而擴大覆蓋面積，並可在裂縫尖端產生鈍化效應提升未時效接合件在中、長斷裂時間下之壽命。因此，在應力－斷裂時間圖中可以看到，未時效張、剪力接合件若在較短時間內(tr < 10 h)未斷裂的話，則幾乎能延後至100小時以後才斷裂。對於時效接合件來說，在進行潛變試驗之前，就已經有AgCrO2的存在，因此相較於未時效接合件，能在較短斷裂時間區間，受相同應力作用下展現較高的壽命；然而隨著未時效接合件中AgCrO2的增加，在較長斷裂時間區間，未時效接合件與時效接合件之壽命則是相差無幾。根據破斷面分析得知未時效張力及剪力接合件，在較短斷裂時間下，破斷面主要發生於氧化鉻層及銀基銲料層之間，而隨著AgCrO2的增長，在較長斷裂時間下，破斷面主要介於AgCrO2層及銀基銲料層之間。而時效處理之張力及剪力接合件，在較短斷裂時間下，破斷面發生於氧化鉻層內部或AgCrO2層及銀基銲料層之介面，面積各占一半，而隨著間增加，在較長斷裂時間下，破斷面則是主要介於AgCrO2層及銀基銲料層之間。 ;The aim of this study is to investigate the high-temperature creep properties and fracture pattern of the joint between metallic interconnect and braze sealant in metal-supported solid oxide fuel cell system. Experimental results indicate that the creep rupture time of both unaged and aged joints is increased with a decrease in the applied constant shear and tensile loadings at 750 °C. The tensile and shear creep strengths of unaged joints at 1000 h are of 5.48 MPa and 3.56 MPa, respectively, which are about 41% and 35% of the average tensile and shear strengths at 750 °C. The tensile and shear creep strengths of aged joints at 1000 h are of 5.43 MPa and 3.64 MPa, respectively, and are about 38% of the average tensile and shear strengths at 750 °C. During the thermal aging process, orange AgCrO2 is formed at the periphery of the joint specimen and is also observed at the interface between the Cr2O3 layer and the braze sealant after creep test at 750 °C in air. The formation of AgCrO2 could effectively retard the growth of crack and extend the creep rupture time of unaged specimens due to bridging effect at crack path and blunting effect at crack tip. Therefore, if the unaged joint specimens can sustain the applied stress at the first 10 h without breakage, they are likely to survive at least 100 h. Despite the fact that aged specimens exhibit a longer creep rupture time than the unaged ones in the short rupture time regime due to the pre-existence of AgCrO2, the unaged and aged specimens show a comparable creep rupture time in the long rupture time regime. For unaged tensile and shear joints, fracture occurs at the interface between Cr2O3 layer and braze sealant in the short rupture time regime while the fracture site gradually changes to the interface between the braze sealant and the AgCrO2 layer in the long rupture time regime. On the other hand, for both aged tensile and shear joints, fracture occurs at the interface between AgCrO2 layer and the braze sealant and occasionally within the Cr2O3 layer in most cases. The Cr2O3 layer covers about half of the fracture surface for a short rupture time, and the amount of coverage decreases with an increase in rupture time.
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