In the context of process efficiency, reducing the energy required for diffusion bonding of nickel-based alloys is of great importance for the chemical, nuclear, and aerospace industry. By employing different mechanical methods and electrochemical processing, as well as their combinations, modifications can be made to the surface of metallic nickel by changing surface geometry and introducing microstrain, residual stress, and grain refinement. This allows accelerating the diffusion behavior at the metal diffusion bonding interface. For industrial production, there is a need for rapid characterization methods to determine indirectly the diffusion activity of modified metal surfaces. Contact angle measurement and impedance spectroscopy analysis are considered to be promising methods. In this study, surface properties were changed by PECM, turning an diamond smoothing. Afterwards, the contact angles of modified metal surfaces were measured using four types of liquids containing different polar and dispersive fractions. Impedance signals of different metal surfaces from 10 Hz to 10 MHz were also measured. A comparative analysis was conducted with respect to the microstructure of the metal surfaces, surface roughness, the distribution of internal stresses, and microstrain density. Results indicate that the characteristics of metal surfaces corresponding to different processing methods and parameters can be linked to the results of contact angle measurements and the mid-to-high frequency characteristic signals in impedance spectrum.This study demonstrates that the combination of contact angle measurement and impedance spectrum has great application potential for characterizing the diffusion welding activity of metal surfaces.

Keywords: Ni and Ni based alloy, diffusion bonding, surface modifications, surface characterization, contact angles measurements, impedance spectroscopy