Electroless Amorphous NiP Coatings Over API X70 Steel: Resistance to Wear and Hydrogen Embrittlement

Abstract

The present work discusses very good resistance to hydrogen embrittlement as well as wear resistance of NiP coated API (American Petroleum Institute) X70 steel as compared to the bare steel and electrolytic crystalline Ni coated steel. The NiP coatings with three compositions (hypo, hyper and near-eutectic compositions), prepared by an electroless technique, were predominantly amorphous. The relative wear behavior of the coatings was studied using ball-on disc tests in air. The hydrogen embrittlement susceptibility (HES) was assessed using slow strain rate tensile (SSRT) tests after cathodic hydrogen charging of the coated as well as bare steel. The superior wear resistance of the NiP coated steels showed abrasive wear, whereas the Ni-coated steel showed adhesive wear. Hyper and hypo-eutectic NiP coated steels showed a comparatively lower H-induced embrittlement than the uncoated and Ni-electroplated steels and these could be attributed to the excellent hydrogen barrier property of the NiP coatings.

Effects of hydrogen permeation on the mechanical characteristics of electroless nickel-plated free-cutting steel for application to the hydrogen valves of hydrogen fuel cell electric vehicles

“…Hillier et al showed that the nickel plating layer acts as a barrier to hydrogen permeation because of the low hydrogen diffusion coefficient of nickel [ 30 ]. Furthermore, Samanta et al found that the electroless nickel plating layer exhibits lower hydrogen-induced embrittlement than the electrolytic nickel plating layer does [ 31 ]. This may be attributed to the excellent hydrogen barrier characteristics of the electroless nickel plating layer.…”