Laser free-form fabrication of dual phase DP600 steel using water atomized feedstock powder

Abstract

Wrought dual-phase (DP) steels are exploited extensively within the automotive sector in the manufacture of components critical to occupant safety. Despite the widespread deployment of these alloys in wrought form, there exists an acute lack of knowledge on their performance/applicability in the context of additive manufacturing (AM). To address this knowledge gap, a preliminary study into the feasibility of utilizing laser directed energy deposition as a means to fabricate prototype structural components from a water atomized dual-phase (DP600) steel powder was completed. A statistical design of experiments approach was used to parametrically model the effects of laser power, traverse rate, hatch spacing, z-step size and powder feed rate on the density, tensile properties, microstructure, and impurity content (O-H-N) of the deposited products produced from each powder. Using optimized parameters, specimen with densities of up to 7.867 g/cm 3 (were obtained while maintaining an equiaxed ferritic microstructure. Intercritical heat treatment developed the requisite dual phase microstructure and elevated tensile properties to effectively match wrought DP600. The prototyping capability of this material and system were then demonstrated through the fabrication of large format tubular specimen coupled with quasi-static axial compression tests.