Session: MF-11-01 Small-Scale and Miniature Mechanical Testing (Joint with CS-19)

Paper Number: 106298

106298 - Mechanical Behavior of 316l-In718 Interface Produced by Directed Energy Deposition Investigated Using Miniaturized Specimens 

Functionally graded composites (FGCs) are materials distinguished by gradual variation in structure and composition within their volume. They can offer improved strength, high corrosion resistance and extension of component service life. Thanks to these characteristics, FGCs found an application in power, aerospace and medical sectors. Nowadays, the development of FGCs is also accelerated by development and expansion of additive manufacturing (AM) technology, which represents a tool for their relatively easy and precise production. Mechanical performance and reliability of FGCs are strongly dependent on the compatibility of the main materials, which are combined. In the case of stainless steel 316L (SS 316L) and nickel-based alloy Inconel 718 (IN718), a great agreement of their lattice parameters and crystal structure, and no phase transformation during temperature changes are reported. Therefore, these materials very often are combined by conventional welding processes. On the other hand, their properties such as melting point, thermal conductivity and specific heat capacity considerably differ, which potentially leads to the formation of defects and detrimental structural phases (carbides, Laves phase). Thus, great attention has to be paid to overcome above-mentioned potential issues. AM technology brings new possibilities for the components that are built based on SS 316L and IN718. Complex geometry of the product as well as precise control of the character and position of this two-material interface are beneficial. The interface of these two materials is still frequently discussed by other researchers in various studies. This contribution is focused on the characterization of mechanical performance of SS 316L-IN718 interface in terms of local tensile behavior that was investigated using miniaturized tensile test (MTT). MTT specimen geometry developed by COMTES FHT, which was recently standardized in a document ISO/ASTM 52909:2022, was used in the study. The tensile behavior of single material zones (SS 316L and IN718) as well as two-material interface zones were examined in parallel and perpendicular orientations with respect to the direction of deposition. The aim was to evaluate the dependence of the mechanical performance of the interface on the load direction. Furthermore, the deformation and failure process were monitored using Digital Image Correlation system Mercury RT. The strain maps of MTT specimens were compared and used as a tool for failure process evaluation. The relation between failure process and structural features of SS316L-IN718 interface were also evaluated in this study. Beside the sharp two-material interface observed using light microscope macrographs, a diffusion zone of certain elements was detected via wavelength-dispersive spectroscopy (WDS) line scan. The fractographic analysis of MTT specimen machined in vertical orientation showed that the fracture process was observed preferably in the 316L zone. Contrary to that, in the case of the specimen oriented horizontally, the failure process was initiated in the zone of IN718, which was characterized by higher strength but the plastic capacity was depleted earlier. In the end, all new unique tensile data were compared to the summarized literature data for the AM-processed combination of the experimental materials.

Presenting Author: Sylwia Rzepa COMTES FHT a.s.

Presenting Author Biography: She is a student of doctoral study programme in Applied Sciences in Mechanical Engineering (specialization: Biomechanics) at the Faculty of Mechanical Engineering of the Czech Technical University in Prague. The topic of her doctoral thesis is devoted to the design of additively manufactured orthopaedic implants and optimization of the deposition parameters to obtain high mechanical performance and compatibility with human tissues. The aim of the study is to comprehend the effect of manufacturing techniques on a broadly understood performance of medical devices, which is one of the factors deciding about the patients' quality of life. She is also a full-time employee of the company COMTES FHT on the position of research scientist, where cooperation in research projects (Horizon 2020, TAČR, EFRR), writing scientific articles and technical reports, mechanical testing and evaluation of mechanical characteristics of steel and non-ferrous materials are her main activities. Until now, she is a co-author of 21 scientific articles (H-index 5 according to Scopus). She regularly participates scientific conferences and events including representing Czech side on ISO meeting in Lund, Sweden (Implants for surgery, 2019).

Authors:

Sylwia Rzepa COMTES FHT a.s.
Matouš Uhlík COMTES FHT a.s.
Daniel Melzer COMTES FHT a.s.
Martina Koukolíková COMTES FHT a.s.
Pavel Konopík COMTES FHT a.s.
Ján Džugan COMTES FHT a.s.