Possibilities of Using Impedance Spectroscopy for Indirect Measurements of Thin Layers of Al & Cr-Al Coatings on Ni-based Superalloy Inconel 713LC Applied by the "Out-of-pack" Diffusion Method

The presented work deals with the research of the super-alloy Inconel 713LC, on which an Al-based coating was applied using the "Out-of-pack" diffusion coating process, or CrAl. In this contribution, the results of measuring the thickness of thin coatings using a confocal laser microscope and the method of impedance spectroscopy are presented and discussed. This can demonstrate the possibility of being used also for researching the properties of thin layers using a VF probe, which, thanks to the use of ferrite, has a practically constant inductance in the entire frequency range, and the presence of a metal sample in the magnetic circuit of the probe was manifested as a result of eddy currents by a significant decrease in the inductance value at higher frequencies. However, the measurements require precise measurement of impedance with an accuracy of 1mΩ and phase angle with an accuracy of 0.001° with high stability of the measuring frequency. For a better assessment of the parameters of the layers, it is necessary to extend the frequency range of the measurement to the range of MHz units.