Microstructural and Mechanical Properties of As Built, Solution treated and Aged 18Ni (300 grade) Maraging Steel Produced by Selective Laser Melting

Mechanical and microstructural properties of 18-Ni (300 grade) maraging steel processed by selective laser melting were investigat- ed to evaluate the effect of the peculiar processing conditions and of the subsequent heat treatment. No need of solution treatment prior to aging revealed necessary owing to the rapid cooling rate experienced by the material during selective laser melting. Iso- thermal aging temperature and time played a main role in promoting austenite reversion. Aging also induced a dramatic increase in strength with respect to the as-built condition and a decrease in fracture elongation. It is proposed that tensile strength and ductility are mainly governed by the effects brought by the strengthening precipitates, whereas the concurrent reversion of martensite into austenite is likely to play a minor role. Analysis of defects induced by selective laser melting process and on fracture behavior of the tensile specimens allowed to improve the understanding of materials performance and to draw guideline for process improvement.