Tensile Properties of 21-6-9 Austenitic Stainless Steel Built Using Laser Powder-Bed Fusion

Abstract

Alloy 21-6-9 is an austenitic stainless steel with high strength, thermal stability at high temperatures, and retained toughness at cryogenic temperatures. This type of steel has been used for aerospace applications for decades, using traditional manufacturing processes. However, limited research has been conducted on this alloy manufactured using laser powder-bed fusion (LPBF). Therefore, in this work, a design of experiment (DOE) was performed to obtain optimized process parameters with regard to low porosity. Once the optimized parameters were established, horizontal and vertical blanks were built to investigate the mechanical properties and potential anisotropic behavior. As this alloy is exposed to elevated temperatures in industrial applications, the effect of elevated temperatures (room temperature and 750 °C) on the tensile properties was investigated. In this work, it was shown that alloy 21-6-9 could be built successfully using LPBF, with good properties and a density of 99.7%, having an ultimate tensile strength of 825 MPa, with an elongation of 41%, and without any significant anisotropic behavior.

Simulation of 316L Stainless Steel Produced the Laser Powder Bed Fusion Process

“…This resulted in lower tensile strength and yield strength compared to the values obtained for standard samples. The tensile properties of austenitic stainless-steel material, specifically 21-6-9, were investigated by Neikter et al [32], who dealt with the optimisation of LPBF process parameters with respect to grain size, density, and hardness. In their experiment, they dealt with the influence of room temperature and a temperature of 1023 K, as well as the influence of the orientation of the structure during construction.…”

Microstructural Characterization and Mechanical Properties of Additively Manufactured 21-6-9 Stainless Steel for Aerospace Applications

“…L-PBF's advantages extend beyond the aerospace and medical sectors, as highlighted by Mishra et al [4], who further emphasized its ability to produce intricate and lightweight parts with exceptional precision. Neikter et al [5] specifically pointed out the shorter production times, leading to decreased manufacturing costs. While L-PBF offers numerous advantages, it is crucial to consider the resulting microstructure obtained through this manufacturing process.…”

“…While L-PBF offers numerous advantages, it is crucial to consider the resulting microstructure obtained through this manufacturing process. The unique microstructure achieved through L-PBF sets it apart from conventional processes, with distinct features such as melt pool boundaries, columnar grains, cellular solidification structures, and nano inclusions [2, 4,5]. These microstructural elements play a pivotal role in influencing local microscopic deformations, ultimately impacting the macroscopic mechanical properties [5,6].…”

“…The unique microstructure achieved through L-PBF sets it apart from conventional processes, with distinct features such as melt pool boundaries, columnar grains, cellular solidification structures, and nano inclusions [2, 4,5]. These microstructural elements play a pivotal role in influencing local microscopic deformations, ultimately impacting the macroscopic mechanical properties [5,6]. Palcheo et al [7] emphasized the importance of meticulous selection of process parameters and scan strategies in L-PBF to achieve desired microstructure and mechanical properties.…”

“…To the authors knowledge, very few studies have been conducted on alloy 21-6-9 processed with L-PBF. Neikter et al [5] studied the process parameters for L-PBF processing of alloy 21-6-9 and showed that it can be successfully manufactured with good mechanical properties and no significant anisotropic properties. Edin et al [24] evaluated the thermal stability and tensile properties of an alloy 21-6-9 through microstructural characterization and tensile testing after different annealing temperatures.…”