Implementation of an experimental setup to qualitatively detect hydrogen permeation along grain boundaries in nickel using Scanning Kelvin Probe Force Microscopy under varying atmospheres
Patrick Gruenewald, Niclas Hautz, Christian Motz
Abstract
The full understanding of the mechanisms of hydrogen embrittlement requires the knowledge of the local hydrogen distribution. One of the microstructural features where hydrogen segregates are grain boundaries, which is then responsible for the transition from transgranular to intergranular fracture. Furthermore, the type of grain boundary influences the segregated hydrogen and its diffusion rates. A tool to measure local hydrogen contents qualitatively, and maybe quantitatively in the future, is Scanning Kelvin Probe Force Microscopy (SKPFM). In this work, we use SKPFM to detect hydrogen at grain boundaries in situ in a permeation setup. The influence of the operation mode as well as the atmosphere on the Contact Potential Difference VCPD is investigated in an in house atmosphere chamber. The atmosphere has a strong influence on VCPD, especially the relative humidity, which is important if the method is to be used quantitatively in the future. We propose to use low oxygen contents and high relative humidities for these SKPFM measurements.