Study of Resistivity Distribution in Modified Surface Steel

This work focuses on making and studying steel conductors with inhomogeneous surface conductivity. Employing such materials (structures) for engineering the high-field pulsed magnets can provide them with enhanced durability. In this work, monotonically changing resistivity was realized by pack chromizing the medium-carbon steels, 30KhGSA and 40Kh, which were treated at 1000 °C in argon for 150 h under the Cr-load of 20 mg/cm ² to obtain a diffuse layer with minimal carbides at the surface. An approach to investigate the resistivity distribution across a diffuse layer after steel chromizing is suggested and involves a stepwise surface grinding, resistance measurement, and analytical processing of experimental data. The resistivity profile obtained by this method is well described by the complementary error function. At the near-surface layer, 30KhGSA and 40Kh steels have almost the same values of resistivity, about 110– $115 ~\mu $ Ohm $\cdot $ cm, which is 2.9–4.3 times higher than that in the bulk depending on steel. A strong correlation, almost a linear dependence, of resistivity with the depth-derived chromium concentration in the material was found. The proposed method allows one to measure the depth-varied resistivity for ferrous alloys with proper accuracy, while it does not require complex measuring equipment compared with other ones.