Metallurgical and Electrochemical Properties of Super Duplex Stainless Steel Clads on Low Carbon Steel Substrate produced with Laser Powder Bed Fusion

This study aims to improve the corrosion resistance of the low carbon steel by cladding it with super duplex stainless steel using laser powder bed fusion process. Critical process parameters such as laser power, laser scan speed, hatch spacing, and powder layer thickness were optimized to achieve the best possible metallurgical bonding between the clad and the substrate. The evaporative losses experienced during the laser melting process resulted in clad layers with lower chromium content (12–25 wt. %) as compared to 26 wt. % of the feedstock powder. A clad thickness of 65.8 µm was achieved after melting ten 50 µm thick powder layers. The higher cooling rates associated with laser powder bed fusion resulted in fine high aspect ratio columnar grain structures with predominantly ferrite grains; however, widmanstätten austenite needles were observed with increasing laser scan speeds. Increasing scan speed had a negative impact on the thickness, corrosion resistance, and the pitting potential of the clads exposed to 3.5 wt.% NaCl aqueous solution. Clads produced at the lowest scan speeds showed comparable corrosion resistance to rolled and annealed super duplex stainless steel.