Assessment of Microstructural Evolution and Mechanical Properties of Laser Metal Deposited 316L Stainless Steel

Abstract

Laser metal deposition (LMD) method is considered as a promising additive manufacturing technique owing to its advanced features. This includes printing complex shaped structures via three-dimensional computer-aided-designs, laser cladding and rapid prototyping. In the present study, detailed microstructure-property correlation is pursued for a block of 316L stainless steel alloy, manufactured by LMD. Presence of fully austenitic phase with corresponding residual stresses in the as-built structure is observed through x-ray diffraction analysis. At the first hand, detailed microstructural analysis is done at the bottom and top sections of the block along the build direction. Presence of hatch structures, variation in the layer thickness along with non-uniformity in the grain size and morphology are noted at these sections. An enhancement in the layer thickness and residual stress along with coarsened grain size is noted to exist towards the top section. This is particularly reflected in achieving highest localized hardness at the bottom section, which progressively decreases towards the top, as characterized through nano-indentation. The LMD-manufactured 316L SS alloy however, exhibits strong indentation size effect along with higher global hardness and strengths with respect to the as-cast alloys. This is primarily related to the complex thermal history of the AM technique. Standard solution heat treatment of the LMD-manufactured 316L SS alloy although coarsens the grain size, minimizes the microstructural non-uniformities and residual stress. Such increment in grain size however, leads to reduction in hardness at the macro, micro-and nano-levels, in comparison to the as-built counterparts. Tensile tests of the solutionized 316L alloys reveal a reduction in yield and ultimate tensile strength along with increased ductility and toughness, thereby suggesting solution treatment as a useful measure to optimize the combination of properties. Importantly, the properties are noted to supersede those of the wrought alloys.

Evaluation of Selective Laser Melted Ti6Al4V/ST316L Composite and Selective Laser Sintered Polyamide 12 Implants for Orthopedic Applications: Finite Element Analysis, Physical and Mechanical Characterization, in Vitro and in Vivo Biocompatibility

“…Our implant surfaces possess a roughness that falls within the micrometer range. Consequently, these implants might facilitate in vitro cell adhesion, viability, and osteogenic differentiation, similar to the observations made with titanium having increased surface roughness [24]. Prior to cells sticking to biomaterial surfaces, proteins get absorbed from body fluids, controlling subsequent cell adhesion and behavior.…”

“…His XRD diffraction peak of Ti6Al4V was detected at 40°, indicating the presence of a peak corresponding to the structure of Ti6Al4V. Furthermore, the peak at 53° matched the structure of ST316L [23,24]. The XRD diffraction peak of polyamide 12 was detected at 21°, indicating the presence of a peak corresponding to the structure of polyamide 12.…”

Effects of selective laser melting process parameters on 3D-printing of Ti6Al4V/ST316L composite material and their optimization using response surface methodology

“…Ti6Al4V XRD diffraction peaks were detected at 40°, which indicates Ti6Al4V has a structure consistent with the peaks. Further, the peaks at 53° correspond to the structure of ST316L [23,24].…”

A physics-based modeling framework to assess the cost scaling of additive manufacturing, with application to laser powder bed fusion

“…layer thickness, material and powder size). Empirical studies have shown that the microstructure evolution and mechanical properties of LPBF-produced metals are strongly correlated to the printing process parameters (Nath et al , 2021; Kotadia, 2021; Yadroitsev et al , 2007; Kruth et al , 2004). Therefore, such correlations can be valuable input to models that evaluate tradeoffs between cost and component quality, via considering how process parameters influence both build rate and desired properties and/or the formation of defects during AM.…”