الفهرس 
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Abstract
Improving the mechanical properties of austenitic stainless steel by adding
hard ceramic powder using rapid prototyping technology is a recent interest
of researchers. In this research, SS304L powder is mixed with different
percentages of SiC powder; 5, 10, and 15 wt. %, and deposited on a mild
steel substrate using Nd: YAG laser machine.
The quality of deposited layers is analyzed by measuring geometrical
dimensions and microscopic examination of defects. The influence of
processing parameters on metallurgical characterization; microstructure,
dissolution of SiC, phases, and distribution of elements, and mechanical
properties; hardness and wear resistance, are studied.
The results show that high bonding of metal-ceramic layers is achieved by
increasing the laser energy density. As increasing the heat input, the track
characteristics; width, height, depth of penetration, and dilution, are
increased, while the aspect ratio is decreased. Slight effects on the
geometry of deposited layers are noticed at adding 5, 10, and 15 wt. % SiC.
The overlap ratios of tracks are increased at high laser energy density
leading to enhancing the effective coating height and reducing the final
post-processing cost. The percentages of defects; un-melted powder
particles and pores are reduced at higher laser energy density. The optimum
processing parameters are identified at laser power 800 w and scan speed
25 cm/min.
The main structure of both SS304L and its composites with SiC is an
austenite dendrite structure. For composites, the SiC is partially dissolved
and form a synthetic metal matrix composite with SS304L and secondary
precipitations of Fe
2
Si and Cr
7
C
3
. The distribution of alloying elements in
the deposited area indicates homogeneity.
The dilution of alloying elements can be noticed between the substrate and
the mixing area. While the measurements of hardness for substrate and
SS304L track record 160 and 210 Hv respectively, adding 5, 10, and 15
wt.% SiC reflects in a continuous increase of hardness to 320, 400, and 650
Hv successively, at a laser energy density of 82 J/mm2. Wear rate
measurements proved the realizing of the major goal of this work, which is
the improvement of wear resistance.