Effect of hydrogen charging on the mechanical characteristics and coating layer of CrN-coated aluminum alloy for light-weight FCEVs

Abstract

To commercialize the fuel cell electric vehicles(FCEVs), it is essential to reduce the weights of the components and lower the manufacturing cost. In this research, the effect of hydrogen charging on the mechanical characteristics of aluminum alloys and CrN coating was also investigated through cathodic hydrogen charging, indentation, and scratch experiments. The delamination of the CrN coating by hydrogen charging was observed through the experiments. In addition, as the hydrogen charging time increased, the hardness of the aluminum alloy increased about 29.7%, whereas the hardness of the CrN coating decreased about 42.8%. In particular, in the scratch experiment, it was found that hydrogen embrittlement and hydrogen blistering occurred at the interface between the CrN coating layer and the aluminum alloy due to hydrogen permeation and diffusion. Therefore the adhesion strength of the CrN coating decreased significantly. However, the CrN coating was presented to suppress hydrogen permeation into the aluminum alloy.

Effect of hydrogen embrittlement on the adhesion strength and wear resistance of DLC-coated 316L stainless steel for application in hydrogen valves of FCEVs

“…This represents a practical method that can be used to evaluate the adhesion strength of a coating by analyzing the acquired data (e.g., tip penetration depth, acoustic emission signal) and the shape of cracks formed on the coating surface by the scratches using an optical microscope [29]. In particular, the adhesion strength is closely related to the durability of the coating [30][31][32]. Therefore, in this research, the adhesion strength of the DLC coating according to the hydrogen charging was measured and evaluated quantitatively.…”

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

“…However, the Vickers hardness measurement demonstrates that the hardness of electroless nickel plating decreased from 719 HV to a maximum of 466 HV as the hydrogen permeation time increased. This is attributed to surface damage as a result of hydrogen permeation and to the formation of voids in the nickel plating layer, which reduces the bonding strength and compressive residual stress of the plating layer, resulting in a decrease in hardness [ 63 , 64 ]. However, all electroless nickel plating samples exhibited significantly higher hardness than 199 HV—the Vickers hardness of the free-cutting steel used as the substrate—and an increase of up to three times or more.…”