Effect of Density, La and Si Content on the Mechanical and Electrical Properties, High-Temperature Oxidation of Sintering Ferritic Stainless Steel

Abstract

Solid oxide fuel cells (SOFCs) are considered a high-efficiency technology for energy conversion. Ferritic stainless steel has become the preferred material for interconnects due to its proper coefficient of thermal expansion, ease of processing, and economy. This study aims to investigate the effects of density, La, and Si content on the mechanical, high-temperature oxidation, and electrical properties of powder metallurgy ferritic stainless steel used for SOFCs interconnects. Ferritic stainless steel water atomized powders with varying contents of La and Si were pressed at 600 and 700 MPa, and then sintered at 1380°C for 3 h in a hydrogen atmosphere. The properties were evaluated in this study through metallographic observations, tensile tests, high-temperature oxidation tests, and area-specific resistance (ASR) measurements. The phases and microstructures were characterized using X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results indicate that high density leads to improved oxidation resistance and electrical performance, with higher-density specimens exhibiting better oxidation mass gain and ASR values than lower-density specimens. The addition of La element improves the mechanical properties, antioxidant properties, and electrical properties of the material, and the addition of La element reduces the ASR of the specimen from 44.16 to 31.18 mΩ ∙ cm². The mechanical properties and oxidative mass gain of the specimen with low Si content are better than those of the specimen with high Si content. When the Si content is reduced from 0.7 to 0.1%, the ASR of the specimen decreases from 57.471 to 44.161 mΩ ∙ cm².