Microstructure and Mechanical Properties of P21-STS316L Functionally Graded Material Manufactured by Direct Energy Deposition 3D Print

• Published in: Metals (Basel ) Vol. 12; no. 12; p. 2086
• Main Authors: Jo, Myeongji, Kim, Hyo-Seong, Park, Jeong Yeol, Lee, Seok Goo, Kim, Byung Jun, Kim, Hyoung Chan, Ahn, Yong-sik, Kim, Byoungkoo, Kang, Namhyn, Nam, Daegeun
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-12-2022
• Subjects: 3-D printers; additive manufacturing; Austenitic stainless steels; Chemical properties; Columnar structure; Corrosion and anti-corrosives; Corrosion effects; Corrosion resistance; Deposition; Diffraction; direct energy deposition (DED); Electron backscatter diffraction; Electron probe microanalysis; Ferritic stainless steels; ferritic steel; functionally graded materials (FGMs); Functionally gradient materials; Grain refinement; Hardness; Impact tests; Iron compounds; Manufacturing; Mechanical properties; Nickel; Nuclear energy; Nuclear power plants; Optical microscopes; Phase distribution; Position measurement; Powder metallurgy; R&D; Radiation; Research & development; Residual stress; Solid solutions; Solution strengthening; Stainless steel; Stress corrosion cracking; Three dimensional printing; Titanium alloys; Ultimate tensile strength; X-rays; South Korea; Japan; United Kingdom > UK; Germany
• ISSN: 2075-4701; 2075-4701
• DOI: 10.3390/met12122086

Functionally graded materials (FGMs) have a characteristic whereby the composition and structure are gradually changed according to the location, and the mechanical properties or chemical properties are gradually changed accordingly. In this study, using a multi-hopper direct energy deposition 3D printer, an FGM material whose composition changes gradually from P21 ferritic steel to stainless steel 316L austenitic steel was fabricated. From optical microscope, scanning electron microscope, and X-ray diffraction analysis, columnar, cell, and point type solidified micro-structure and precipitations were observed depending on the deposited compositions. Electron probe microanalysis and electron backscatter diffraction analysis confirmed the component segregation, ferrite austenite volume fraction and phase distribution behavior according to compositions. In the FGM specimen test, the ultimate tensile strength of STS316L, which was the most fragile, was measured, and the toughness was measured for the notch area, which did not represent the FGM characteristics. Hardness showed changes according to FGM position and was suitable for FGM analysis. The maximum hardness was measured in the FGM duplex area, which was caused by grain refinement, precipitate strengthening, and solid solution strengthening. In nuclear power plant welds high strength can cause adverse effects on stress corrosion cracking, and caution is needed in applying FGM.