The present study, evaluates the in-situ alloying of 20 wt% copper in 316L stainless steel by laser powder bed fusion additive manufacturing (LPBF-AM). Addition of copper with low laser absorption and high thermal conductivity could increase the required energy input to ensure complete melting [1]. Hence, laser power was varied in steps of 20 W from the optimum processing parameter for 316L stainless steel, i.e., 175 W, 195 W, 215 W and 235 W with constant hatch distance (90 µm), point distance (60 µm) and exposure time (80 µs). Sometimes even with complete melting, it’s very difficult to achieve the homogeneous distribution of alloying elements [2]. Recently researchers, found laser rescanning strategy helps in homogeneous distribution of alloying elements while in-situ alloying in LPBF-AM [3]. Hence, twelve samples, with matrix of parameters; four different laser power and three melting strategies (single laser scanning (SM), double time laser scanning (DM) and three times laser scanning (TM)) were used. 

 Scanning electron microscope (a) and EDS mapping for Cu (b) at varying laser powers and rescanning strategiesThe microstructural evolution and distribution of the copper in bulk alloy was studied under scanning electron microscope equipped with energy dispersive spectroscopy (EDS). Formation of solidification cracking perpendicular to the scanning direction is unavoidable in all laser powers in SM strategy. Further, increase in laser power improves the homogeneity in the distribution of copper in bulk alloy as in Figure. However, bands of the copper rich regions along the scanning direction were obvious even at the higher laser power 235 W. DM with scan rotation of 90ᵒ resulted in more intensive solidification crack generation in both scanning direction and perpendicular to scanning direction and laser rescanning assisted in copper redistribution to the matrix of the alloy due to remelting and solidification, with less intensive copper rich bands along the scanning direction. TM with scan rotation of 67ᵒ at higher laser powers 215 W and 235 W have completely eliminated the solidification cracking with homogeneous distribution of copper. 

Eventhough, rescanning strategy improves the homogeneity in the distribution of copper, it has resulted in formation of globular Mn and Si rich oxides along the scanning direction. Further, microhardness survey across the samples shows improvement in strength and increase in power and increase in number of rescanning increases the homogeneity in hardness distribution.