Effect of nickel on hydrogen embrittlement behavior of medium-carbon high strength steels

The present study was attempted to explore the influence of Ni up to 1% on hydrogen embrittlement (HE) behavior of medium-carbon high strength steel by using both constant load test (CLT) and slow strain rate test (SSRT). The results show that HE index (HEI) decreases notably with the addition of 0.55% Ni, and this decreasing tendency tends to slow down with the addition of 1.02% Ni. HEI of SSRT is comparatively higher than that of CLT. The faction of brittle crack initiation area decreases with increasing Ni content. There is a decreasing tendency of both absorbed hydrogen content in Walpole solution and pre-charged hydrogen content with the addition of Ni. Both corrosion rate and pit depth of specimens after immersed in Walpole solution tend to decrease with increasing Ni content. Further electrochemical polarization test reveals that adding Ni could enhance pitting corrosion resistance. It is concluded that the addition of Ni could further lower the HE susceptibility of the tested steels mainly owing to enhanced corrosion resistance and decreased hydrogen absorption. (C) 2016 Elsevier B.V. All rights reserved.