Abstract

This study investigated the influence of microstructure on the mechanical properties and fracture toughness of API X65 pipeline steel in the presence of hydrogen. In this study, electrochemical method was used for hydrogen charging and indentation technique was applied to obtain the fracture toughness. The results showed that in the presence of hydrogen, elongation (EL%), reduction of area (RA), ductile fracture percentage, and fracture toughness of all microstructures decreased. The microstructure of martensite (M) + bainite (B) + ferrite (F), had the highest hydrogen trapping and uptake (C_app) as 8.58 × 10^–6 mol cm⁻³ and the lowest apparent hydrogen diffusivity (D_app) as 5.68 × 10⁻¹⁰ m² s⁻¹; thus, the maximum decrements of 33% in fracture toughness, 40% in ductile fracture percentage, 47% in RA, and 35% in EL% were observed. However, the microstructure of ferrite (F) + degenerated perlite (DP) + martensite-austenite micro constituent (M/A), where the lowest value of 5.85 × 10^–6 mol cm⁻³ for C_app and the highest value of 8.5 × 10^–10 m² s⁻¹ for D_app had the minimum decrements as 2% in fracture toughness, 10% in ductile fracture percentage, 4% in RA, and 7% in El%. According to the obtained results, depending on the type of microstructures, hydrogen-induced work softening or hardening were observed by decreasing or increasing the yield stress respectively.

Graphic Abstract

中文翻译：

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氢存在下组织对API X65管线钢力学性能和断裂韧性的影响

摘要

本研究研究了在氢气存在下，微观组织对API X65管线钢的力学性能和断裂韧性的影响。在这项研究中，电化学方法用于充氢，并采用压痕技术获得断裂韧性。结果表明，在存在氢的情况下，所有显微组织的伸长率（EL％），面积减小率（RA），延性断裂率和断裂韧性均降低。马氏体（M）+贝氏体（B）+铁氧体（F）的微观结构具有最高的氢俘获和吸收（C _app）为8.58×10 ^-6  mol cm ^-3。最低的表观氢扩散率（D _app）为5.68×10 ^-10  m ²  s ^-1 ; 因此，观察到断裂韧性最大降低33％，韧性断裂百分比降低40％，RA降低47％，EL％降低35％。但是，铁素体（F）+变性珍珠岩（DP）+马氏体-奥氏体微观成分（M / A）的微观结构，其中C _app的最低值为5.85×10 ^–6  mol cm ^-3，最高值为8.5 D_应用程序×10 ^–10  m ²  s ^-1的最小减量为：断裂韧性2％，延性断裂百分数10％，RA 4％和El％7％。根据得到的结果，根据显微组织的类型，通过减小或增大屈服应力分别观察到氢诱导的工件软化或硬化。

图形摘要