本研究目的為探討固態氧化物燃料電池在使用條件下，其硬銲封裝填料與金屬連接板接合件的熱機疲勞性質與破裂模式，所使用之封裝填料為核能研究所所開發的銀基合金，金屬連接板使用型號為Crofer 22 H的商用肥粒鐵系不銹鋼。藉由對接合件施加不同組合的張、剪力週期性負載，進行室溫至750 °C熱循環的異相熱機疲勞實驗，並討論1000小時熱時效處理的影響。 研究結果顯示未時效及熱時效處理接合件的熱機疲勞壽命會隨著在室溫或高溫區段所施加的端應力增加而下降，顯示兩者皆為影響壽命的重要因素，且在高溫區段施加的應力影響較為顯著。另外與先前研究接合件在750 °C下的潛變壽命比較，試片在745-750 °C頂溫區段的累積時間較短，顯示熱機疲勞效應確實存在於未時效及熱時效處理二種接合件。 在接觸空氣及高溫的環境下，AgCrO2鉻酸銀會在銲料層及Cr2O3層之間隨熱時效處理及熱機疲勞試驗時間增長生成。在相同的端應力比條件下，大部分經熱時效處理試片的壽命會較未經時效處理試片長，推測AgCrO2能提升接合件阻擋裂縫成長的能力，乃是在裂縫產生架橋及尖端鈍化效應所致，導致時效試片有較長的壽命。 根據破斷面分析，未時效張力試片皆破裂在銲料層與Cr2O3層之間，時效張力試片則是破裂在Crofer 22 H側的再生銲料層與Cr2O3層之間，部分會破裂於AgCrO2層與銲料層之間；對於剪力模式，中短壽命的未時效試片破斷位置亦發生在銲料層與Cr2O3層之間，而隨著AgCrO2的增長，長壽命試片的破斷面會轉往AgCrO2層及銲料層之間，時效剪力試片破斷位置大多位於AgCrO2層及銲料層之間。 ;The purpose of this study was to investigate thermo-mechanical fatigue (TMF) properties and fracture mode of a joint between braze sealant and metallic interconnect in solid oxide fuel cell. The materials used were a silver-based braze sealant developed at the Institute of Nuclear Energy Research and a commercial ferrite stainless steel (Crofer 22 H) for interconnect. Out-of-phase TMF tests under various combinations of cyclic mechanical loadings were conducted in tensile and shear modes at a cyclic temperature range of room temperature (RT) to 750 °C. The effects of 1000-h thermal aging were also investigated. Experimental results indicated that the TMF life was increased with a decrease in applied end stresses at RT and at high temperature, for both unaged and thermally aged joint specimens. Both end stresses applied at RT and 750 °C played an important role in the TMF life which was more sensitive to the stress applied at high temperature. In addition, compared to the estimated creep rupture time, the accumulated time at 745-750 °C was much shorter, indicating the existence of a true TMF mechanism for both unaged and aged joints. AgCrO2 at the interface between braze sealant and Cr2O3 layer was formed during thermal aging at high temperature in air. The thermally aged joint specimens generally exhibited longer TMF lives than the unaged ones, given a combination of applied end stress ratios at RT and 750 °C. It was attributed to that the ability to resist cracking was enhanced by the existence of AgCrO2. The formation of AgCrO2 induced a bridging effect on the crack path and a blunting effect at the crack tip. It was beneficial to the increase of TMF life. For tensile loading mode, the fracture sites of the unaged specimens were only found at the interface between Cr2O3 layer and braze sealant. For the thermally aged specimens, cracks mainly propagated along the interface of Cr2O3/reformed braze sealant and occasionally along the interface of AgCrO2/braze sealant. As for shear loading mode, the interface between Cr2O3 and braze sealant also acted as the main fracture site for unaged joints with short and medium TMF lives. Additional cracking path at the interface between AgCrO2 and braze sealant was also observed for a longer TMF life. For the aged ones, cracks tended to propagate along the interface of AgCrO2/braze sealant and partly within Cr2O3 layer.
