Densification Behavior and Influence of Building Direction on High Anisotropy in Selective Laser Melting of High-Strength 18Ni-Co-Mo-Ti Maraging Steel

Abstract

The mechanical properties, physical properties and electrochemical behavior of metal components produced by selective laser melting can be influenced by the relative density and building direction. To this end, the optimization of the building process was conducted by identifying the influence of process parameters on the relative density and determining the ideal combination of parameters using the Box–Behnken design response surface methodology to achieve a relative density of 99.303 pct. With the ideal process parameters, material strength, thermal, and electrochemical performance were evaluated in a series of experiments. Anisotropic characteristics were displayed due to the differences in build-direction, microstructural features, and phase composition. The 0 deg possessed the highest tensile strength measured to be 1263.03 ± 8.71 MPa, while the 45 deg demonstrated the highest ductility with an elongation of 13.21 ± 0.34 pct. Thermal expansion was governed by the heat treatment process, such that anisotropic traits were eliminated after solution treatment. Strip melt tracks on the X–Y plane differed from the strip and arcuate melt tracks observed in the X–Z and Y–Z planes, leading to significant deficiencies in electrochemical reactance with an open circuit potential of − 645.8 mV in comparison to the latter measured at − 397.7 and − 396.7 mV, respectively.