High-Temperature Oxidation Behavior of Stainless Steels with Protective Pulsed DC Magnetron Sputtering Coating

• Main Authors: Peng Yang, 楊朋
• Other Authors: Chia-Chi Sung
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/47601011183551283342

博士 === 國立臺灣大學 === 工程科學及海洋工程學研究所 === 101 === LaxSr1-xMnO3 (LSM) is commonly used as a protective layer on the metallic interconnects of solid oxide fuel cells (SOFCs) to prevent surface oxidation and Cr poisoning. However, the different of thermal expansion coefficient (CTE) at elevated temperatures causes the LSM coatings to crack, resulting in Cr evaporation. Therefore, this paper investigates the effects of pre-oxidation on the microstructure and electrical properties of ferritic stainless steels coated with La0.67Sr0.33MnO3. Four ferritic stainless steels were selected for use as interconnect substrates: Crofer22 APU, Crofer22 H, ss441, and G1. The candidate materials were pre-oxidised at 850oC for 25, and 50 hours, respectively. After the pre-oxidation process, the LSM films with a thickness of 3~4 μm were deposited on the surface of samples by using pulsed DC magnetron sputtering. After aging the coated specimens at elevated temperatures, the morphologies and crystalline structures were examined using SEM/EDX and XRD, respectively. The results indicated that the pre-oxidized layer, (Mn, Cr)3O4, could significantly suppress chromium penetration from the interior to the surface of the specimens. Moreover, the area specific resistance (ASR) values for the 25 hours pre-oxidized specimens were 2.24, 12.21, 2.30, and 6.77 mΩ‧cm2 for Crofer22APU, Crofer22H, ss441, and G1, respectively, at 800oC for 500 hours in an air atmosphere.