Hydrogen Embrittlement of Boron-Modified Supermartensitic Stainless Steel

Abstract

Supermartensitic stainless steels (SMSS) reinforced with a percolated boride network offer exceptional corrosion and wear resistance, making them well-suited for oil and gas applications. However, hydrogen embrittlement (HE) poses significant challenges in offshore environments. This study examines HE in SMSS with boron additions ranging from 0.3 to 0.7 wt%. Samples were subjected to hydrogen charging at −1.3 VSCE, 43 mA/cm2for 168 h in a 3.5 wt% NaCl solution, followed by slow strain rate tensile testing. While boron additions improved tensile strength, they severely reduced ductility. After hydrogen charging, mechanical degradation intensified, with SMSS-0.7%B experiencing >55% reduction in tensile strength and elongation. All boron-rich alloys displayed brittle intergranular fractures caused by M2B borides at the grain boundaries. HE impacted both the martensitic matrices and borides, with fractures initiating in boride-rich regions and propagating via secondary cracks. These results underscore a synergistic embrittlement mechanism and emphasize the importance of optimizing microstructures to enhance hydrogen resistance in boron-reinforced SMSS.