Suppression of hydrogen-induced damage in 22MnB5 hot stamping steel by microalloying

A comparative study was conducted to reveal the effects of microalloying with Ti + Nb + V on the hydrogen permeation and damage behaviors of the 22MnB5 hot stamping steel. For 22MnB5, the hydrogen-induced blisters preferentially originated from grain boundaries and further propagated into cracks, which can be greatly suppressed by adding Ti + Nb + V. This can be attributed to the microalloying-induced increasing of binding energy and irreversible traps including nano-sized carbides, fined grains, as well as low angle grain boundaries, as confirmed by high resolution transmission electron microscopy and electron back-scattered diffraction determinations. The hydrogen diffusion coefficient of 1.67 x 10(-5) cm s(-1) was thus obtained for the Ti + Nb + V added microalloyed 22MnB5, which is approximately four times lower than that for 22MnB5. Furthermore, a reasonable model was proposed to illustrate the improvements of hydrogen diffusion and hydrogen damage in the hot stamping steels.