Laser beam hardening of carbon and low alloyed steels: discussion of increased quantity of retained austenite

摘要

It was shown that mainly three effects areresponsible for the increased quantity of retained austenite incarbon and low alloyed steels after laser transformation hardening.At low peak temperatures a high dislocation density appears in theinitial austenite phase during the reversed polymorphictransformation which is preserved till the martensitetransformation begins and retards this reaction. At high peaktemperatures this is more complete carbides dissolution than afterstandard furnace hardening. Both effects are overlapped by a thirdone. This is the carbon up-hill diffusion resulting in surfaceenrichment of carbon and a decrease of the martensite start temperature.