Microstructural characterization and properties of selective laser melted maraging steel with different build directions

Abstract

A nearly fully dense grade 300 maraging steel was fabricated by selective laser melting (SLM) additive manufacturing with optimum laser parameters. Different heat treatments were elaborately applied based on the detected phase transformation temperatures. Microstructures, precipitation characteristics, residual stress and properties of the as-fabricated and heat-treated SLM parts were systematically characterized and analyzed. The observed submicron grain size (0.31 μm on average) suggests an extremely high cooling rate up to 10 7 K/s. Massive needle-shaped nanoprecipitates Ni 3 X (X = Ti, Al, Mo) are clearly present in the martensitic matrix, which accounts for the age hardening. The interfacial relations between the precipitate and matrix are revealed by electron microscopy and illustrated in detail. Strengthening mechanism is explained by Orowan bowing mechanism and coherency strain hardening. Building orientation-based mechanical anisotropy, caused by 'layer-wise effect', is also investigated in as-fabricated and heat-treated specimens. The findings reveal that heat treatments not only induce strengthening, but also significantly relieve the residual stress and slightly eliminate the mechanical anisotropy. In addition, comprehensive performance in terms of Charpy impact test, tribological performance, as well as corrosion resistance of the as-fabricated and heat-treated parts are characterized and systematically investigated in comparison with traditionally produced maraging steels as guidance for industry applications.

Mechanical Properties of 3D-Printed Maraging Steel Induced by Environmental Exposure

“…In printed samples where layering is perpendicular to the direction of the applied load, failure occurs before samples printed such that layers are parallel to the loading direction (H). Tan et al found that similar to observations in this paper, the horizontally printed maraging steel exhibited higher tensile strength then vertically printed specimens [21]. within the cells and through the cell boundaries in accordance with prior studies [17,19].…”

Laser Powder Bed Fusion of Ti-rich TiNi lattice structures: Process optimisation, geometrical integrity, and phase transformations

“…The morphology of the sample produced using 44 J/mm 3 showed irregular pores with unconsolidated particles, which is characteristic of lack of fusion defects caused by insufficient heat input [14]. At E v of 267 J/mm 3 , the sample exhibited a significant number of spherical pores, which is characteristic of keyhole defects [32,33]. In contrast, the sample produced at 67 J/mm 3 showed few fine pores, which resulted in a higher relative density.…”

Selective Laser Melting and Remelting of Pure Tungsten

“…Selective laser melting (SLM) is a kind of state‐of‐the‐art processing technology that manufactures components in an incremental layer‐by‐layer means using the laser to melt, bond, and solidify powder particles on powder bed . It has been widely used in the production of a variety of alloys including titanium alloys, aluminum alloys, and stainless steel, providing the possibility for its application in producing tungsten. Tan et al .…”