Determination of the hydrogen content in surface layers of U8A steel using high frequency currents

Abstract

An increase in the strength of steels is associated with a decrease in the content of impurities, which have a negative effect on the mechanical properties of steels. One of those impurities is hydrogen. It is known that at ultrahigh frequencies, due to the peculiarities of the distribution of alternating current over the cross section of a metal conductor, the conductivity is carried out by a thin surface layer (skin-effect). We present the results of using high-frequency currents for determination of the hydrogen content in a metal. The absorption of hydrogen by thin subsurface layers of steel is determined proceeding from a change in the voltage drop across the samples which depends on the resistance of the layers. The voltage drop as a function of the alternating current frequency is measured using a high-frequency generator, an HF-voltmeter, and an HF-galvanometer. Wire samples made of high-quality U8A carbon steel were used during testing procedure. At the same time, the amount of hydrogen absorbed by the steel was determined by the method of anodic dissolution. It is shown that the cathode-introduced hydrogen is unevenly distributed over the cross section of the sample. During the aging of cathodic hydrogenated steels of a U8A type, hydrogen diffusion from steels into the air takes place with an insignificant penetration of hydrogen into the deeper metal layers. Moreover, the hydrogen content and the resistance of the subsurface layers of the material increase with an increase in the current density during cathodic polarization. The results obtained can be used in nondestructive testing of the degree of hydrogenation of ferromagnetic products.