Cryogenic mechanical properties and tribological behaviors of AISI stainless 316L steel cooled by liquid nitrogen

The use of stainless steel instead of traditional aerospace-grade aluminum alloys and carbon fiber-reinforced polymers is promising to further reduce the launch cost of reusable rockets. In this study, the mechanical properties and tribological behaviors of AISI 316L stainless steel under cryogenic conditions were comprehensively investigated through experiments. Liquid nitrogen was employed to cool the samples and simulate the cryogenic fluid environment inside rockets for safety considerations. Tests of Rockwell hardness, tensile strength, dynamic toughness, falling-ball impact fatigue behaviors, and tribological behaviors under both room-temperature and cryogenic conditions were performed using commercial and self-developed devices. Compared with the test results at room temperature, 316L samples cooled by liquid nitrogen reveled higher hardness, greater tensile strength, enhanced impact fatigue resistance, and improved wear resistance. The improved performance of 316L under cryogenic conditions is beneficial for the application in liquid rocket. However, cryogenic dynamic toughness and impact fatigue tests demonstrates a reduction in the plasticity of 316L cooled by liquid nitrogen, which should be taken into consideration in engineering to avoid sudden failure.