How the Marangoni Effect Influences Fluid Flow of Fe-based Powder Laser Clad onto 304 Stainless Steel and 7075 Al Alloy Substrates

Laser beam welding (LBW), laser cladding and selective laser melting (SLM) with metals without active substances such as O-2 or S present poor processability. The most important reason for this is the negative surface tension coefficient leading to outward fluid flow inside the meltpool. In this work JG-3 Fe-based powder was clad onto 304 stainless steel and 7075 Al alloy substrates using a fibre laser. The fluid flow fields inside the meltpools of two materials with opposite surface tension coefficient were studied and a two-dimensional (2-D) axisymmetric numerical model was proposed. The Marangoni effect on fluid flow greatly influences the processing parameters and cladding effectiveness. The opposite surface tension coefficients of the 304 stainless steel and 7075 Al alloy brought about different fluid flow field inside the meltpool. The inward and outward fluid flow mode result in different meltpool morphology. The fluid flow mode affected by Marangoni effect and the process of the free surface motion.