Study on hydrogen embrittlement in 409 ferritic stainless steel and effect of thickness on hydrogen sensitivity for hydrogen IC engine

Hydrogen is a potential suitor for carbon-free Internal combustion engine operation. The investigation is going on to identify the material that can be used in hydrogen internal combustion engines from the conventional internal combustion engine. In the traditional IC engines, 409 ferritic stainless steels are used to make automotive exhaust tubing, catalytic converter systems and mufflers. However, hydrogen embrittlement phenomena in the steels are a major concern for the application of 409 ferritic stainless-steel in hydrogen IC Engine. So, the present study is focused on analysing the hydrogen sensitivity in SS409 with varying thicknesses of specimens through experimentation. The Specimens of the SS409 with thicknesses 0.5, 1.2 and 2 mm are prepared using wire EDM based on ASTM E8 standard and hydrogen charged from a solution containing 40 g/L NaOH and 1 g/L Thiourea, ensuring a homogeneous hydrogen distribution across the surface of specimens for 6 h and kept in the hydrogen-free environment for 18 h at room temperature (25°C). XRD analysis is carried out to investigate the microstructural changes after the hydrogen exposure of specimens. The effect of the thickness of the specimen on hydrogen susceptibility is studied with tensile and hardness tests performed under continuous hydrogen charging. It has been observed that hydrogen has a significant effect on the mechanical properties of the SS409: For 1.2 mm thickness of specimen, % Elongation reduces from 21.88% to 17.19% and average micro-hardness value increased due to hydrogen hardening by 17.65%. It is found that an increase in the thickness of the specimen will increase the hydrogen sensitivity (HES %) of susceptible material. The study has focused on the effort that is required to establish a relationship between hydrogen sensitivity and the thickness of susceptible material and also to predict the impact of hydrogen on 409 ferritic stainless-steel.