Microstructural Characterization of Maraging 300 Steel Fabricated by Select Laser Melting

Abstract

3D printing of components using a layer-based deposition of materials is referred to as additive manufacturing (AM). The ability to build complex geometry components, reduce waste and avoid assembly are the main advantages of this process. AM has been used in different industries like aerospace, medical, goods and automotive. In the aerospace, materials with high performance are needed to fulfill the requirements of the industry. Maraging steels are among the materials widely used for several applications in the aerospace industry due to its high strength and toughness. These steels are hardened by the precipitation of intermetallics in a martensitic matrix. In this work, a maraging 300 steel powder was used to produce components by selective laser melting (SLM). Two heat treatments were applied to study the martensite-to-austenite reversion, HT1: 480 ℃/3 h and HT2: 980 ℃/1 h + 2 × 690 ℃/5 min + 480 ℃/6 h. The microstructural characterization was assessed by optical microscopy (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). As-built condition revealed a cellular and dendritic morphology with segregation of Ti, Ni and Mo to the grain boundaries. Direct aging treatment does not erase the typical AM morphology, but a solubilization at 980 ℃/1 h was capable of fully recrystallize the microstructure. The EBSD analysis showed the increase of reverted austenite for the HT2 and this was attributed to the cycling reversion.