Abstract The hydrogen embrittlement (HE) and H trapping sites of pearlitic steel specimens with various lamellar spacings (λ) were evaluated through slow strain rate tensile testing and thermal desorption analysis.… Click to show full abstract
Abstract The hydrogen embrittlement (HE) and H trapping sites of pearlitic steel specimens with various lamellar spacings (λ) were evaluated through slow strain rate tensile testing and thermal desorption analysis. When λ decreases, both tensile strength and resistance to HE were unusually improved. This is because tearing, which is the initiation of H cracking, was delayed in the specimen with fine λ and short cementite (θ) platelets. Undeformed H-charged specimens showed a peak (peak 1), which is separable into two sub-peaks (peak 1-1 and peak 1–2) in their H desorption rate curves, regardless of λ. Peak 1-1 and peak 1–2 were generated by H atoms detrapped from FP/θ interfaces and from dislocations inside FP, respectively. The Ea values of H desorption for peak 1-1 and peak 1–2 were 23.2 kJ/mol, and 26.1 kJ/mol, respectively. Meanwhile, deformed H-charged specimens exhibited the second peak (peak 2) with peak temperature (TP) of ∼600 K, as well as peak 1 with TP of ∼375 K. When tensile strain increased, peak 2 increased at the expense of peak 1. Primary H trapping sites for peak 2 are strained FP/θ interfaces with interfacial dislocations.
               
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