Stress dependence of the Hall coefficient of a nickel-base superalloy

This paper reports on the Hall Effect and their stress dependence, observed experimentally on the superalloy Inconel® 718. The work is motivated by the desire to develop a nondestructive method of characterizing the near-surface protective residual stress in metals. Our approach is based on Hall Effect measurements, because it is anticipated that these measurements are less contaminated by cold work and other effects than conductivity-based measurements such as eddy current. The challenge is that, in metals, the Hall coefficient is very small. To achieve the required sensitivity, the Hall coefficient was measured with an AC injected current and an AC magnetic field. The measurements were performed on a thin film sample. The Hall coefficient was found to be positive, and varies proportionally to the applied tension. The proportionality coefficient is significantly larger than estimated from the volumetric effect in a free carrier model.