An Investigation on Hydrogen Embrittlement of the Cr-Si Spring Steel Using Slow Strain Rate Test and Weibull Model

In this paper, the hydrogen embrittlement of the high strength Cr-Si spring steel with Zn-12%Ni after electroplating, have been evaluated. Slow strain rate test with 3.34 × 10-6 sec-1 strain rate was performed, and the hydrogen embrittlement index of the different samples was calculated. The effect of shot peening before plating and the baking after plating and also the effect of applying a nickel interlayer by electroless method, is examined by using the weibull statistical model. The results showed that alloying Zn with nickel considerably reduce the diffusion of hydrogen on the substrate steel structure. So that it increases the average failure time of samples from 4.9 hours for pure Zn to 8.7 hours for Zn- Ni. By applying nickel interlayer, the failure time increased to 11.15 hour. Also by shot peening process before electroplating, the average failure time increased to 12.7 hours which showed the least amount of hydrogen embrittlement among the studied samples. Baking after the electroplating of Zn-Ni samples without interlayer, leaded to an increase in the failure time to 10.15 hours. While baking in samples containing nickel interlayer, showed the opposite effect, reducing the failure time to 8.15 hours.