Thermal Stability and Strengthening Mechanism of BNNT Reinforced 316L Stainless Steel Composites

Austenitic 316L stainless steel (SS) has been widely used as a structural material in light water reactors due to its good mechanical strength, corrosion resistance, and cost-effectiveness. However, advanced nuclear power concepts designed for high efficiency impose remarkably harsh operating conditions, including evaluated temperatures, irradiation, corrosive environments, complex stress, and frequent thermal cycling. These conditions pose critical challenges to the applicability of 316L SS in next-generation nuclear reactors. In this study, a novel approach to enhance the high-temperature mechanical strength, corrosion, and radiation resistance of 316L SS was developed by doping the boron nitride nanotubes (BNNTs) to form BNNT/316L SS metal matrix composite (MMC). The material was fabricated by spark plasma sintering (SPS) using functional powder to achieve a homogeneous BNNT distribution and rapid material synthesis. The thermal stability of BNNT/316L SS was investigated by conducting thermal treatment under various temperatures. Mechanical performance was assessed through tensile testing at both room and evaluated temperatures. With a particular focus on the strengthening mechanism of BNNT, the study characterized the BNNT/SS interface via multiple advanced techniques. Besides, insights into the SPS fabrication of MMC and pathways for further refinement will be discussed.