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Title: Preliminary Characterization and Mechanical Performance of Additively Manufactured HT9

Abstract

Laser-blown powder deposition of HT9 was performed to evaluate the feasibility of using advanced manufacturing to fabricate creep strength enhanced ferritic steels. The as-printed materials were tensile tested at room temperature, 330°C, and 550°C to provide a baseline value for the strength levels. The as-fabricated strengths are then compared with wrought materials in the published literature. The strength parameters for the as-fabricated HT9 was found to be significantly higher than that of wrought HT9 without sacrifice in ductility. Two different heat treatment cycles, deemed ACO3 and FCRD, involving two different austentizing temperatures (1065°C and 1040°C) and tempering temperatures (750°C and 760°C) were then evaluated. The heat-treated samples were also tensile tested and were found to show strength and ductility parameters which closely mimicked that of the wrought HT9 literature data. Detailed multi-scale characterization was performed at various length scales. The as-fabricated structure showed a refined martensitic structure with a significant fraction of δ-ferrite present. Closer examination using TEM showed a refined distribution of carbides (predominantly M 23C 6 and MX or M2X), which would have precipitated during the deposition process. Upon heat treatment, it was seen that the precipitates were more homogenous and refined in the case of the specimensmore » heat treated according to the ACO 3 cycle although there was no significant difference in the strength or the hardness results. However, the specimens heat-treated per the FCRD cycle showed significantly smaller prior austenite grains (measure and give quantitative numbers), which could result in better Charpy toughness. However, the toughness was not evaluated and will be performed in the future. In addition, possible thermos-mechanical treatments (TMT) to refine the grain structure and improve the toughness without compromising the ductility will also be evaluated in the future.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1492186
Report Number(s):
ORNL/SPR-2018/780
DOE Contract Number:  
AC05-00OR22725
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Niyanth S, Niyanth, and Field, Kevin G. Preliminary Characterization and Mechanical Performance of Additively Manufactured HT9. United States: N. p., 2018. Web. doi:10.2172/1492186.
Niyanth S, Niyanth, & Field, Kevin G. Preliminary Characterization and Mechanical Performance of Additively Manufactured HT9. United States. doi:10.2172/1492186.
Niyanth S, Niyanth, and Field, Kevin G. Thu . "Preliminary Characterization and Mechanical Performance of Additively Manufactured HT9". United States. doi:10.2172/1492186. https://www.osti.gov/servlets/purl/1492186.
@article{osti_1492186,
title = {Preliminary Characterization and Mechanical Performance of Additively Manufactured HT9},
author = {Niyanth S, Niyanth and Field, Kevin G.},
abstractNote = {Laser-blown powder deposition of HT9 was performed to evaluate the feasibility of using advanced manufacturing to fabricate creep strength enhanced ferritic steels. The as-printed materials were tensile tested at room temperature, 330°C, and 550°C to provide a baseline value for the strength levels. The as-fabricated strengths are then compared with wrought materials in the published literature. The strength parameters for the as-fabricated HT9 was found to be significantly higher than that of wrought HT9 without sacrifice in ductility. Two different heat treatment cycles, deemed ACO3 and FCRD, involving two different austentizing temperatures (1065°C and 1040°C) and tempering temperatures (750°C and 760°C) were then evaluated. The heat-treated samples were also tensile tested and were found to show strength and ductility parameters which closely mimicked that of the wrought HT9 literature data. Detailed multi-scale characterization was performed at various length scales. The as-fabricated structure showed a refined martensitic structure with a significant fraction of δ-ferrite present. Closer examination using TEM showed a refined distribution of carbides (predominantly M23C6 and MX or M2X), which would have precipitated during the deposition process. Upon heat treatment, it was seen that the precipitates were more homogenous and refined in the case of the specimens heat treated according to the ACO3 cycle although there was no significant difference in the strength or the hardness results. However, the specimens heat-treated per the FCRD cycle showed significantly smaller prior austenite grains (measure and give quantitative numbers), which could result in better Charpy toughness. However, the toughness was not evaluated and will be performed in the future. In addition, possible thermos-mechanical treatments (TMT) to refine the grain structure and improve the toughness without compromising the ductility will also be evaluated in the future.},
doi = {10.2172/1492186},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2018},
month = {2}
}

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