Hydrocarbon Lubricants Can Control Hydrogen Embrittlement.

Hydrogen embrittlement is a known risk in steel components exposed to hydrogen-rich environments, such as fuel cells. Atomic hydrogen can diffuse into metal lattices, leading to structural failure. Rolling contact fatigue (RCF) tests have shown that tribochemical reactions can generate atomic hydrogen on wear tracks. However, the role of the hydrogen environment in lubricant hydrocracking and tribofilm formation remains unexplored. Prior research has focused on hydrogen generation from wear but not on its suppression via tribofilms. This gap motivated the current study to assess how tribofilms might limit hydrogen embrittlement. Existing studies lack direct comparisons between hydrogen, argon, and air environments in RCF. The need to evaluate non-destructive methods like micro-CT for subsurface damage is also unmet. This work addresses these limitations by introducing a novel approach to tribofilm and hydrogen interaction analysis.

This investigation aims to determine whether a hydrogen-rich environment can induce lubricant hydrocracking and tribofilm formation during rolling contact fatigue. The study compares hydrogen with argon and air environments to assess differences in tribofilm generation and hydrogen suppression. The primary goal is to evaluate if tribofilms can act as barriers to atomic hydrogen diffusion in steel bearings. A secondary objective is to test the feasibility of high-energy micro-CT for subsurface damage analysis in RCF. The study seeks to provide insights into hydrogen embrittlement prevention through lubricant chemistry. It also aims to validate micro-CT as a non-destructive alternative to traditional sectioning methods. By focusing on tribofilm composition and hydrogen suppression, the research addresses a critical gap in hydrogen-compatible lubrication strategies. The findings could inform the design of hydrogen-compatible lubricants for high-pressure applications.

The study uses rolling contact fatigue (RCF) tests to simulate high-pressure rolling contacts in steel bearings. Three environments—hydrogen, argon, and air—are compared to assess tribofilm formation and hydrogen suppression. Lubricant hydrocracking is analyzed using surface and subsurface characterization techniques. High-energy micro-computed tomography (micro-CT) is employed as a non-destructive method to evaluate subsurface damage in RCF. Traditional sectioning methods are used alongside micro-CT for comparative validation. The tribofilm composition is analyzed to determine its role in hydrogen embrittlement prevention. Atomic hydrogen levels are measured to assess the effectiveness of tribofilm barriers. The study integrates mechanical testing with advanced imaging to provide a comprehensive analysis of tribochemical interactions.

The hydrogen environment generates a significantly larger amount of atomic hydrogen compared to argon and air. However, the chemical tribofilm formed under hydrogen conditions suppresses hydrogen diffusion into steel. Tribofilm formation is most pronounced in hydrogen-rich environments, suggesting a direct link to lubricant hydrocracking. Micro-CT imaging reveals subsurface damage patterns consistent with tribofilm formation. The tribofilm acts as a barrier, reducing hydrogen embrittlement risk in rolling element bearings. Traditional sectioning methods confirm micro-CT findings, validating its use as a non-destructive technique. The tribofilm composition includes hydrocarbon-derived species, indicating lubricant breakdown. These results suggest that tribofilm formation can be leveraged to control hydrogen embrittlement in hydrogen technology applications.

The study demonstrates that tribofilms formed in hydrogen environments can significantly suppress atomic hydrogen diffusion into steel. This finding suggests a potential strategy for mitigating hydrogen embrittlement in high-pressure rolling contacts. The tribofilm acts as a barrier, reducing the risk of structural failure in hydrogen technology applications. The comparison between hydrogen, argon, and air environments highlights the unique role of hydrogen in tribofilm formation. Micro-CT emerges as a viable non-destructive method for subsurface damage characterization in RCF. The results support the use of tribochemical strategies to enhance lubricant performance in hydrogen-rich environments. The findings align with the authors' hypothesis that tribofilm formation can control hydrogen embrittlement. These conclusions provide a foundation for developing hydrogen-compatible lubrication strategies.