Analysis of a Double Aging Process in a Maraging 300 Steel Fabricated by Selective Laser Melting, Using the Design of Experiments Technique

Abstract

This study aims to optimize the aging treatment of a maraging 300 steel, without prior austenitizing, manufactured by the selective laser melting (SLM) technique. The study includes the analysis of a double aging process. In addition, the impact of the aging treatment on corrosion resistance in 3.5 wt.% NaCl solution was analyzed. The research technique followed was a factorial design of experiments with three factors and two levels, performing one replicate of each experiment. The results show that excellent mechanical properties can be achieved by omitting the solubilization treatment prior to aging. The highest hardness and tensile strength were achieved by performing a double aging at 460 °C for 8 h. Under these conditions, the maximum hardness exceeded 615 HV and the tensile strength was over 2140 MPa. Aging at 520 °C caused the formation of reverse austenite. The aging temperature was the only factor that had a significant effect on the formation of reverse austenite. It should be noted that the holding time at this temperature did not have a significant effect. The corrosion resistance, in 3.5 wt.% NaCl aqueous solution, increased in the aged samples compared to the as-printed sample. Samples overaged at 520 °C showed the best corrosion resistance. It can be concluded that the predominant cathodic reaction taking place is the reduction of oxygen dissolved in the electrolyte.

Keywords

• maraging steel
• aging
• selective laser melting
• linear polarization resistance
• reverse austenite