TY - JOUR
T1 - Cooling rate effect on tensile strength of laser deposited Inconel 718
AU - Bennett, Jennifer L.
AU - Kafka, Orion L.
AU - Liao, Haiguang
AU - Wolff, Sarah J.
AU - Yu, Cheng
AU - Cheng, Puikei
AU - Hyatt, Gregory
AU - Ehmann, Kornel
AU - Cao, Jian
N1 - Funding Information:
The authors would like to thank Dr. Jun-Sang Park and Dr. Xianghui Xiao at the Advanced Photon Source at Argonne National Laboratory (ANL) for providing the tensile test load frame. The authors would also like to thank the Digital Manufacturing and Design Innovation Institute (DMDII) for their support through award number 15-07 and the U.S. Department of Commence National Institute of Standards and TechnolsorgeeCyn’tfoclcrharriiaeH Materials Design (CHiMaD) under grant No. 70NANB14H012. O.L. Kafka acknowledges the support of the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1324585. This work made use of facilities at DMG MORI, Northwestern University, and ANL.
PY - 2018
Y1 - 2018
N2 - The thermal history generated by the additive manufacturing process influences the resulting material properties. Although trends exist between solidification rate and microstructure, solidification rate is not enough to predict final microstructure and thus mechanical properties. The purpose of this study is to relate the combined effects of solidification time and cooling time of the built material to its final ultimate tensile strength. Cooling time was defined as the time from when the location of interest last passes through 1,200 °C to when it reaches 400°C. Nine locations on a laser deposited IN718 thin wall were studied in detail to understand the effect of cooling rate on tensile strength. Tensile samples were machined at these locations. The thermal histories of the locations of interest were compared with build geometry and the ultimate tensile strength of that location. An inverse proportional relationship was seen between the distance of the location of interest from the substrate and the cooling time. A trend was also seen linking increased surface temperature and increased solidification time. Weighted Cooling And Solidification Time (WCAST) was defined as the sum of weighted normalized solidification time and the normalized cooling time. Ultimate tensile strength was seen to decrease as WCAST increased. Optical microscopy images of the build microstructure confirm that longer cooling and solidification times lead to coarser microstructures, which may cause the lower tensile strengths measured.
AB - The thermal history generated by the additive manufacturing process influences the resulting material properties. Although trends exist between solidification rate and microstructure, solidification rate is not enough to predict final microstructure and thus mechanical properties. The purpose of this study is to relate the combined effects of solidification time and cooling time of the built material to its final ultimate tensile strength. Cooling time was defined as the time from when the location of interest last passes through 1,200 °C to when it reaches 400°C. Nine locations on a laser deposited IN718 thin wall were studied in detail to understand the effect of cooling rate on tensile strength. Tensile samples were machined at these locations. The thermal histories of the locations of interest were compared with build geometry and the ultimate tensile strength of that location. An inverse proportional relationship was seen between the distance of the location of interest from the substrate and the cooling time. A trend was also seen linking increased surface temperature and increased solidification time. Weighted Cooling And Solidification Time (WCAST) was defined as the sum of weighted normalized solidification time and the normalized cooling time. Ultimate tensile strength was seen to decrease as WCAST increased. Optical microscopy images of the build microstructure confirm that longer cooling and solidification times lead to coarser microstructures, which may cause the lower tensile strengths measured.
KW - INCONEL 718
KW - additive manufacturing
KW - cooling rate
KW - direct energy deposition
KW - solidification
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U2 - 10.1016/j.promfg.2018.07.118
DO - 10.1016/j.promfg.2018.07.118
M3 - Conference article
AN - SCOPUS:85052876778
VL - 26
SP - 912
EP - 919
JO - Procedia Manufacturing
JF - Procedia Manufacturing
SN - 2351-9789
T2 - 46th SME North American Manufacturing Research Conference, NAMRC 2018
Y2 - 18 June 2018 through 22 June 2018
ER -