Microhardness of armco iron samples with different initial structures after rolling in a helium or nitrogen medium

Abstract

We have analyzed the dependences of microhardness H on load P for the surface layers of Armco iron samples with different initial structures, i.e., annealed and after equal-channel angular pressing (ECAP). The microhardness was measured in air after rolling of the sample in helium or nitrogen medium. It has been found that these mediums produce different effects on the H(P) dependences for preliminarily annealed samples compared to those subjected to ECAP. This is due to the differences in their initial defects structures and in the types of binding forces of helium atoms and nitrogen molecules with dislocations, which determine the intensity of their penetration into the surface layer of the samples under investigation. We have obtained curves that describe the release of helium from samples rolled in different mediums and have measured the amount of helium.