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Direct Laser Deposition (DLD) of Ceramic Metal Matrix Composite (MMC) Powder onto the Surface of Mild Steel
H.A. Sabour, M.A. Taha, K.A. Gany, A.F.A.G. Youssef and Y.H. Elbashar

Nd:YAG laser direct laser deposition (DLD) of a ceramic metal matrix composite (MMC) of 304L stainless steel and SiC particles has been used for improving the surface mechanical properties of a mild steel. The layer formations and defects were studied along with the effects of adding SiC to the 304L stainless steel powder and processing parameters on the layer quality. The deposited layers were analysed by measuring the geometrical dimensions, and microscopic examination of pores and cracks. A high quality bonding of the ceramic MMC clad tracks was achieved with increasing the laser energy density. The overlap ratio of the ceramic MMC clad tracks increased the waviness but decreased the effective coating height. The heat input directly increased proportionally with the width, height, depth of penetration, root angle of contact, dilution and deposition rates; however, it was inversely proportional with the aspect ratio. Slight effects on the geometry of the ceramic MMC clad layer were noticed when adding 5, 10 and 15 wt.% SiC to the 304L stainless steel powder. The percentages of fine and coarse pores increased with lower heat input or increased SiC additions to the 304L stainless steel powder; however, these inter-run pores were eliminated by adding 0, 5, 10 and 15 wt.% SiC. Samples free from cracks were formed under different processing parameters with the optimization processing parameters being 800 W laser power and 25 cm/min scan speed.

Keywords: Nd:YAG laser, mild steel, 304L stainless steel, silicon carbide, SiC, metal matrix composite (MMC), direct laser deposition (DLD), laser cladding, bond, pores, cracks

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