The phase transitions in selective laser-melted 18-NI (300-grade) maraging steel

Dilatometric studies in 18-Ni steel components fabricated by selective laser melting technique were carried out to determine the influence of heating rate on transitions occurring during the heating cycle. SLM components have been examined in controlled heating and cooling cycles. For analysis, heating of the analysed materials was carried out at heating rates of 10, 15, 20, 30 and 60 degrees C min(-1). During the heating process, two solid-state reactions were identified-i.e. precipitation of intermetallic phases and the reversion of martensite to austenite. A simplified procedure based on the Kissinger equation was used to determine the activation energy of individual reactions. For precipitation of intermetallic phases, the activation energy was estimated 301 kJ mol(-1), while the martensite to austenite reversion was determined at the activation energy 478 kJ mol(-1).