Effect of Scan Space and Post-Deposition Heat Treatment at Different Aging Temperatures on Structure–Property Evolution of L-PBFed Maraging Steel 300 Part
摘要
In the present work, laser-powder bed fusion (L-PBF) is carried out to additively fabricate maraging steel 300 parts at different values of scan spacing (0.05 and 0.10 mm). The effect of scan space on microstructure and mechanical properties (including tensile properties and microhardness) of the as built specimens is studied. Between the two scan spacing values tested, wider scan space causes better part strength. The setting of lower scan space causes excessive energy density and consequently material loss which may possibly be due to overheating. Therefore, the part fabricated at a lower scan space corresponds to a higher level of porosity. The as built parts are then subjected to a STA (solution treatment followed by aging) schedule. Solution treatment (ST) is performed at 840 °C, 2 h + oil quenching. Afterward, the solution-annealed specimens are subjected to aging treatment (AT) at 492 °C, 2 h + oil quenching. Aging treatment promotes precipitation of secondary intermetallic phases which contribute toward imparting improved strength and hardness to the alloy. However, response of the post-heat treatment depends on the initial microstructure of the specimen (in the as built condition) as influenced by the setting of fabrication parameters. Attempt is also made to understand the effect of aging temperature (450, 490 and 550 °C) on microhardness (temperature and time for ST being constant) of the post-heat-treated specimens. It is experienced that the presence of reverted austenite lowers microhardness of the STAed specimen. The highest microhardness value (~618.2 ± 20.1 HV0.05) is obtained upon aging at 490 °C as the corresponding specimen does not contain reverted austenite.