للكاتب :
Hashem F. El-Labban
Production Engineering Dept., Alexandria University, Alexandria, Egypt
ABSTRACT
A conventional laser surface melting treatment was applied to steel specimens of two
different compositions, an alloy steel (0.76wt.% C, 0.76wt.% Si, 1.5wt.% Mn,..) and a high
speed steel ( 0.94wt.% C, 4.42wt.% Cr, 5.43wt.% Mo, 2.17wt.% V, 3.85wt.% W, 0.30wt.%
Si, .% , 0.34wt.% Mn,..), using a Nd:YAG laser. A combined treatment of the conventional
laser surface melting and water-quenching was proposed and applied to two sets of specimens
from the two types of steels. The microstructures of base metal, treated (melted and then
rapidly solidified and cooled) and heat affected zones were investigated using an optical
microscope. In the case of alloy steel, treated zone of fine microstructure was observed.
The large carbides of high speed steel (HSS) were completely melted in the treated zone and
partially dissolved in the HAZ. An appreciable increase in surface hardness was obtained by
the application of conventional laser surface melting treatment. Higher improvement in
surface hardness was achieved by application of the combined treatment. Further, the
increase of laser beam (processing) speed during the combined treatment was accompanied by
a decrease in width of the heat affected zone (HAZ) and a remarkable improvement in the
surface hardness. In case of the HSS, HAZ of high hardness was produced due to application
of the combined treatment