Microstructural studies of direct-laser-deposited stainless steel 316L-Si on 316L base material

Microstructure and hardness of SS316L-Si deposited by direct laser deposition (DLD) on a conventional SS316L base material are studied. The DLD process produced a crack-free metallic part with a density of similar to 99.5%. The as-deposited samples exhibit a microstructure with millimetre-sized solidified melt pools. They consist mainly of columnar dendrites which were formed preferentially along < 001 > direction, generating solidification texture and columnar grains. Dendrites with cellular morphology were also formed in regions of higher solidification rates, mainly above the localized heat-affected zone in the layers.The deposited SS316L-Si contains a primary austenitic matrix and secondary delta-ferrite in the interdendritic regions. The average hardness measured along parallel and normal surfaces with respect to the building direction is nearly the same (similar to 185 HV), indicating homogeneity in the microstructure of the as-deposited SS316L-Si along the two orthogonal surfaces. The analysis of microstructure, defects and intermetallic phases was carried out using optical microscopy, scanning electron microscopy and transmission electron microscopy.