Microstructure and property of laser transformation hardening on sheet steel with high carbon content Available to Purchase

AISI 1065 sheet steel was selected as experimental material in this paper. A CO₂ laser was used to irradiate material surface and phase transformation occured. Because of thin thickness, sheet steel has low thermal conductivity and cooling occurs slower by quenching from bulk of material during laser transformation hardening (LTH). Therefore, the microstructure and property of LTH on sheet steel are different from that of LTH on general steel. A scanning electron microscope (SEM) and a transmission electron microscope (TEM) were used to observe the microstructure. Electron diffraction analysis and X-ray diffraction analysis were used to determine fine structure and austenite content of samples. The microhardness was measured in the direction of sample depth. The results show that the microstructure of LTH on sheet steel is troostite besides martensite and retained austenite. The fine structure of martensite is twins which have different angles and the twin plane of martensite is { 121 }. The microhardness of sheet steel is lower than that of thick sample after LTH.