FEATURES OF FORMATION MICRORELIEF AND MICROHARDNESS THERMALLY HARDENED ZONES BY SCANNING LASER BEAM
DOI:
https://doi.org/10.20535/2305-9001.2015.73.40903Keywords:
surface layer, laser heat treatment, scanning, hardening, zone overlap, tempering, microhardness, microreliefAbstract
Features of formation of microrelief and microhardness thermally hardened zones as well as width and depth of the heat affected zone overlapped tracks in the cross section of the surface layer of AISI 1045 steel are presented.
Based on theoretical and experimental studies, calculation scheme of laser heat hardening with overlapping tracks and procedure of experimental studies using of fiber laser with 2D scanner are proposed. It is established that as a result of repeated effect of scanning laser radiation microhardness, width and depth of a hardened zone of AISI 1045 steel specimens vary depending on the overlapping ratio. However, regardless of the overlapping ratio is present softening zone with reduced microhardness almost double. The values of surface microhardness in the overlapping zone with increasing overlapping ratio increases as well as decreases in the depth. The optimum values of the overlapping ratio (25%) for obtaining of uniform widths, depths hardened zone and microrelief of the surface layer are determined. A method of obtaining a uniform distribution of microhardness in the softening zone by repeated laser low temperature tempering is suggested. Parameters of roughness Ra and waviness Wa in overlapping zone of laser tracks decreased almost double in comparison with not hardening overlapping zones. Program of control for automation of the process of surface thermal hardening of large dimensional parts by scanning laser beam are developed.
The procedure and results of experimental studies of determination the optimal parameters of scanning laser beam can be used in the industrial conditions for surface thermal hardening of large dimensional parts are presented.
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