Comparison of hydrogen behavior trapped at precipitated and undissolved vanadium carbide in vanadium-bearing high strength steels

Abstract

Vanadium carbide (VC) in high strength steels is divided into two types, i.e., finely formed precipitated VC and coarsely formed undissolved VC. The behavior of hydrogen trapped at the two types has been investigated using thermal desorption analysis (TDA). Specimens containing different amounts of V (0, 0.10 and 0.15 %) were prepared. Specimens with 0 % V (QT) and 0.10 % V (QT) were quenched at 900 and tempered at 600 . Some specimens with 0.15 % V were quenched at 900 and are denoted here as 0.15 % V (Q). Hydrogen was charged into specimens by immersion in a NH 4 SCN aqueous solution and analyzed by TDA. The end temperatures of hydrogen release for 0 % V (QT) and 0.15 % V (Q) specimens were in a range from 76 to 79 , and that of the 0.10 % V (QT) specimen was 104 . The amounts of hydrogen were 0.10 ppm in the 0 % V (QT) specimen, 0.28 ppm in the 0.15 % V (Q) specimen and 0.54 ppm in the 0.10 % V (QT) specimen. The specimens containing precipitated VC had a higher end temperature of hydrogen release and larger amounts of hydrogen than those containing undissolved VC and matrix. These findings suggest that precipitated VC in high strength steels has a higher hydrogen trapping capacity than undissolved VC.