The Effect of MoS2 Content on the Protective Performance of Ni-MoS2 Composite Coatings against Hydrogen Embrittlement in High Strength Steel

Ni-MoS2 composite coatings are used as the protective coatings against hydrogen embrittlement (HE) in quenching & partitioning (QP) steels for the first time. The protective performances of Ni-MoS2 composite coatings electroplated in a Watts bath containing different concentrations of MoS2 nanosheets, were assessed via slow strain rate test (SSRT) accompanying with electrochemical hydrogen charging experiment and electrochemical hydrogen permeation method. Results showed that the content of MoS2 incorporated into deposits increases from 0 to 7.08 wt% with as the concentration increases from 0 to 8 g/L. Furthermore, the addition of MoS2 can refine significantly the microstructure of Ni deposits and reduce the compressive residual stresses in coatings, which are beneficial to not only retard hydrogen permeation toward substrate and to improve HE in QP steel, but also improve the adhesion strength between coatings and substrate. Finally, the MoS2 concentration of 5g/L is considered as the optimum value for fabricating Ni-MoS2 composite coating. (C) 2016 The Electrochemical Society. All rights reserved.