Characterization of Additively Manufactured 18Ni Maraging 300 Steel and the Effect of Heat Treatment on the Microstructure and Mechanical Property

Abstract

Abstract Direct Metal Laser Sintering (DMLS) is one of the leading-edge additive manufacturing processes used to date, characterized by layer-by-layer deposition of powder metal, which is sintered by laser power. Maraging steel powder is one of the metal powders broadly used in metal AM processes for various applications. It is a strong, tough, low-carbon martensitic steel, and the rare combination of high strength and toughness makes it well-suited and preferable for high-performance components in the aerospace industry. Aerospace products must be produced with high quality and precision. The purpose of this research is to investigate the quality of the output product as it is manufactured, comparing it with different heat treatment methods. This can be addressed by mechanical and microstructure tests. Specimens were manufactured with MS118NI-300 Maraging steel powder using an EOS M280 metal printer. Fourteen compression and tensile test pieces were made and designed to abide by ASTM standards. Two control group pieces were set aside while the other 12 pieces underwent various heat treatment (HT) processes to alter mechanical and microstructure properties. The heat treatment processes considered for this research work are normalizing, annealing, carburizing, age hardening, and cryogenic treatments. All HT’s but carburizing impacted the steel with positive results. It was found that cryogenic treatment slightly increased the toughness, while age hardening significantly increased both toughness and ultimate tensile strength (UTS). Normalizing and annealing were found to reduce the UTS but increase the ductility with a very small reduction in toughness when compared to the control group.