STEEL SURFACE HARDENING BY APPLICATION OF LASER SURFACE MELTING AND WATER- QUENCHING: A PRELIMINARY STUDY

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

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