SEDL / STP / STP1049-EB / STP24059S

Thermomechanical Treatments and Hydrogen Embrittlement of Ferritic Stainless Steels with Different Interstitial Contents

Iyer, RN
Research associate, The Pennsylvania State University, University Park, PA

Hehemann, RF
Late professor and professor emeritus, Case Western Reserve University, Cleveland, OH

Troiano, AR
Late professor and professor emeritus, Case Western Reserve University, Cleveland, OH

Pages: 12    Published: Jan 1990

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Abstract

Hydrogen embrittlement of 26Cr-lMo ferritic stainless steels, with low and high concentrations of interstitial elements of carbon and nitrogen and with high-temperature an nealing or prestraining treatments or both, was investigated. Tests involved cathodic charging of the specimens in sulfuric acid solution at room temperature, with simultaneous tensile loading using a uniaxial constant load fixture. The steel with high interstitial contents (26-1S) hydrogen embrittled intergranularly, when either heated to 1050°C and subsequently water quenched, or plastically prestrained by 5% elongation; but the low interstitial alloy (E-Brite) hydrogen embrittled transgranularly only when both of these treatments were given in this order. The cracks originated at the surface grain boundaries in 26-1S and at interior precipitate regions in E-Brite. Based on interrupted tests and fractography, the inferred hydrogen embrittlement mechanism has been stress-induced niobium hydride formation in E-Brite; whereas, this mechanism has been hydrogen trapping and absorption by nitrogen and faceted titanium carbo-nitrides in the vicinity of grain boundaries in 26-1S. Stress corrosion crack propagation of these alloys in boiling chloride solutions can be analyzed from these mechanisms and invoking potential drop concepts.