Laser surface cladding of mild steel with 316L stainless steel for anti-corrosion applications

Abstract

Fiber YAG (Yttrium-Aluminum-Garnet) Laser cladding is used to generate a thin layer of 316L stainless steel over low carbon steel substrate alloy to enhance corrosion resistance. In this work, the cladding technique was used at the laser powers of 2800, 2400 and 2000 W with a fixed travelling speed of 6 mm/s. The work aims to investigate the optimal heat-input for the thin clad in terms of microstructure and bonding quality. The microstructure of both formed layers by cladding and substrate was investigated. On the clad cross-section of the specimens, the micro-Vickers hardness was measured. At laser powers of 2800 and 2400 W, the produced layers were well bonded to the substrate without visually noticeable macro-defects. Some defects associated with cracks appeared at a laser power of 2000 W. The stainless steel clad layer consisted mainly from highly refined mixed columnar and cellular dendritic austenite structure elongated perpendicularly to the substrate surface in the direction of heat flow. At higher powers, the structure showed organized parallel columnar dendrites while at lower powers, it shows fine cellular dendrites in random directions. A narrow dilution zone (less than 10 µm) was obtained where the carbon and chromium elements can stay together and form harmful carbides. The depth of the fused part in carbon steel side has a direct relationship with the laser power, and it consisted mainly from feathery bainite inside large ferrite grains. The hardness of the produced layers was improved than the base metal. Sudden hardness increment at the limited area around the interface was obtained after all the laser powers. Decreasing laser power led to hardness increment at the clad and fusion zone.