Diffusion method of determination of the thermal pulse duration upon quenching of surface layers of steel articles

Industrial technologies that employ fast heating and cooling of surface layers of articles for their hardening are widely applied nowadays. For many steel grades, the duration of thermal pulse should be less than 1 ms. Data on the experimental determination of this technological parameter are lacking; therefore, in the work presented, a method is proposed that serves to solve this task via investigation of diffusion of light elements into steel directly in the course of surface treatment. The application of diffusion method is favored by the presence in the atmosphere of oxygen, nitrogen, carbon, and hydrogen atoms upon treatment of the article surface, their diffusion coefficients in iron and steels at high temperatures, strong temperature dependence of the diffusion coefficients, characteristic values of the critical quenching rate for steels, metrological characteristics of nuclear -reaction -based methods and secondary ion -mass spectrometry upon studying diffusion in solids, and other factors. Approbation of this method was carried out based on the data on nitrogen diffusion gained by the method of nuclear reactions. Steel specimens were modified with argon plasma; the plasma source worked in the stationary mode and pulse heating and cooling of the surface were performed by moving plasma torch across the specimen surface. Such technology provides hardening of steel specimens at a depth of about 1 mm and the duration of thermal pulse obtained by diffusion method was less than 1 ms. The diffusion method is promising for characterization of surface treatment technologies for steel items using plasma, high frequency currents, and laser irradiation.