Improving the ductility of laser directed energy deposited borated stainless steel by increasing laser power

Borated stainless steels (BSSs) are extensively applied in the nuclear energy industry due to boron's excellent thermal neutron absorption capacity, but large and brittle borides formed during casting result in a low ductility. Here, a BSS was produced by laser directed energy deposition, and an investigation was conducted to analyze the impact of laser power on both the microstructure and mechanical properties of the deposited material. Fibrous borides with relatively low volume fraction in the overlapping zone resulted in higher ductility, while lamellar borides with relatively large volume fraction in the non-overlapping zone led to higher strength. As the laser power increased from 180 W to 330 W, the size of fibrous and lamellar eutectic borides and austenite increased significantly, the width of the soft overlapping zone increased by 2.27 times, and the elongation increased by 2.03 times, although yield strength and ultimate tensile strength decreased by 46.3 % and 31.7 %, respectively. As a result, these findings confirmed the feasibility of significantly improving the ductility of the as-deposited BSS by increasing the laser power. The work here provides a way to tailoring the mechanical properties of BSS produced by laser additive manufacturing.