Session: MF-02-01 Materials for hydrogen service I (Joint with C&S)

Paper Number: 61919

Start Time: Tuesday, July 13, 2021, 09:00 AM

61919 - Role of Pearlite in Ductility Loss of Carbon Steels Under High-Pressure Hydrogen Gas 

Toward widely-spread commercialization of hydrogen energy systems, there is a need in industry to enable low-cost, ferritic steels, e.g. carbon steels, to be used for high-pressure hydrogen environment. However, these materials are categorized as “severely embrittled”, and therefore, the use of them tends to be avoided in existing regulations and standards. In this study, as a part of the comprehensive investigations on the hydrogen compatibility of carbon steels, we focused on the hydrogen-induced ductility loss.

Four, hot-rolled, carbon steels with varying carbon content were subjected to slow strain-rate tensile (SSRT) tests in 95-MPa hydrogen gas at ambient temperature. The influence of pearlite volume fraction on the magnitude of hydrogen-induced degradation of the materials’ ductility was thereby determined. The hydrogen gas environment was seen to significantly affect strain-to-failure and reduction-in-area in all the four materials, wherein such a loss of tensile ductility was ascribed to the premature initiation and subsequent propagation of surface micro-cracks as revealed by the quantitative damage evolution analyses on the post-fractured specimens. The pearlite grains on specimen surface manifestly served as the preferential origins of hydrogen-induced micro-cracks, resulting in more considerable embrittlement in materials possessing a higher percentage of pearlite, due to the rapid coalescence of discrete embryonic damage during tensile straining.

Presenting Author: Hisao Matsunaga Kyushu University

Authors:

Yuhei Ogawa Kyushu University
Masaki Hino JFE Steel Corporation
Masami Nakamura Kyushu University
Hisao Matsunaga Kyushu University