Laser Rescanning for Enhancing Mechanical Properties of Laser-Directed Energy-Deposited High-Manganese Steels

This study investigates the effects of laser deposition and laser rescanning (LR) on the microstructure and mechanical properties of high-manganese steel (HMnS) deposited by laser-directed energy deposition (L-DED) comprising 24 wt.% Mn. Four types of laser deposition and LR strategies were investigated: unidirectional L-DED scanning without laser rescanning, L-DED scanning with 90° alterations in the laser scanning path on each layer without laser rescanning, unidirectional L-DED with laser rescanning in the same direction, and L-DED with laser rescanning with 90° alterations in the laser scanning path. The L-DED-processed HMnS had only a few small pores and exhibited a microstructure without any serious defects such as cracks. Additionally, a strong fibrous texture along the <101>/building direction of the fully austenite phase was found. The mechanical properties (microhardness and tensile strength) of HMnS were improved by the LR with a grain refinement effect and fine solidification cell size due to the significantly faster solidification rate in LR than that in L-DED.