Research of features of structure formation in case of surface steel hardening

The geometric characteristics, microhardness and features of structure formation were studied in the heat-affected zone during the surface hardening of 09Г2, 20ФЛ, 45XHM, 65Г steels with direct current electric arc in argon. It is shown that the depth of zone with thermally modified structure is 0.7-1.2 mm with a tendency to decrease at maximum values of arc speed. Reheating of previously formed local hardening zone is accompanied by certain decrease in surface hardness, however, by changing the overlapping, the hardness of treated surface can be optimized with achieving of formation of regular structure. A regular gradient structure with periodically changing phase composition and microhardness is formed in the surface layer of steel that has been thermally treated with an electric arc. By changing the parameters of the processing conditions (electric arc current, speed of its movement, overlap of local hardening zones), it is possible to purposefully form a certain structural-phase state of the steel surface with properties that meet the operating conditions. © Published under licence by IOP Publishing Ltd