Scanning strategies for texture and anisotropy tailoring during selective laser melting of TiC/316L stainless steel nanocomposites

Abstract

Selective laser melting (SLM) is a promising additive manufacturing technique that allows fabrication of complex functional components via the selective layer-by-layer melting of powder bed particles using a high-energy laser beam. This technique can allows the production of a wide range of novel high-performance materials including metal matrix nanocomposites with unique microstructures and superior properties. In this study, the SLM process was used with various laser-scanning methods to fabricate cylindrically shaped components from 316L stainless steel reinforced with 15 vol.% TiC nanoparticles. A deep relationship between the SLM process and the microstructure and mechanical properties of the resulting components was established to understand the influence of the selected scanning strategy on the densification, solidification microstructure, texture, and anisotropy. It was found that the building strategy has a significant influence on the build densification, with the highest densification obtained using a cross-hatched scanning strategy. The resulting bimodal grain structure was related to the heat flowing from the solidifying melt pool (i.e., the developed microstructure depends on the local heat transfer conditions); the TiC content in the fabricated nanocomposite was also varied according to the applied scanning method. The relatively strong crystallographic textures along the building and scanning directions can be transformed into weak ones, and the mechanical properties of the produced components can be made nearly isotropic by rotating the scanning vector inside or between the created layers by 90° (known as alternate and cross hatched scanning strategies, respectively) using a single pass of the laser beam. The obtained results indicate that the utilized laser-scanning strategies allowed tailoring of the densification level, solidification microstructure, crystallographic texture, and anisotropy of mechanical properties the fabricated parts. Hence, SLM can be successfully used for manufacturing 316L stainless steel nanocomposite parts with a high degree of densification and controllable texture.