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Korean Journal of Metals and Materials > Volume 55(8); 2017 > Article
Korean Journal of Metals and Materials 2017;55(8): 550-558. doi: https://doi.org/10.3365/KJMM.2017.55.8.550
Direct Laser Deposition of 14Cr Oxide Dispersion Strengthened Steel Powders Using Y2O3 and HfO2 Dispersoids
Barton Mensah Arkhurst1, Jin-Ju Park2, Chang-Hoon Lee3, Jeoung Han Kim1
1Department of Advanced Materials Engineering, Hanbat National University, Daejeon 34158, Republic of Korea
2Nuclear Materials Development Division, Korea Atomic Energy Research Institute, Daejeon 34057, Republic of Korea
3Ferrous Alloy Department, Advanced Metallic Materials Division, Korea Institute of Materials Science, Changwon 51508, Republic of Korea
Correspondence  Jeoung Han Kim ,Tel: +82-42-821-1240, Email: jh.kim@hanbat.ac.kr
Received: 8 February 2017;  Accepted: 27 March 2017.  Published online: 1 August 2017.
ABSTRACT
This study investigated the feasibility of using HfO2 as a dispersoid in the additive manufacturing process, compared to Y2O3. The effect of pre-annealing treatment was investigated too. Scanning electron microscopy (SEM) analyses revealed unusually coarse deposition layers for both the HfO2 and Y2O3 dispersed oxide dispersion strengthed (ODS) steels, in both the as-milled and the pre-annealed conditions. The deposited layer of the HfO2 dispersed ODS steel had relatively coarser grains than the deposited layer of the Y2O3 dispersed ODS steel in both the as-milled and the pre-annealed conditions. Moreover, the SEM results also revealed the presence of nanometer sized particles in all the deposition layers of both Y2O3 and HfO2 dispersed ODS steels, and their number densities were far lower than those in conventional bulk ODS steels. However, transmission electron microscopy analyses revealed that the dispersion and retention of nanoparticles within the melt were not achieved, even with HfO2 as a dispersoid, in contrast to the results from the SEM analyses. Furthermore, the deposition layers of both the as-milled Y2O3 and HfO2 ODS steels also exhibited an unusual nano-grained structure. The microhardnesses of the HfO2 and the Y2O3 dispersed ODS steels in both the as-milled and the pre-annealed conditions were higher than the substrate. Furthermore, the Y2O3 dispersed ODS steel had a higher microhardness than the HfO2 dispersed ODS steel in both the as-milled and the pre-annealed conditions.
Keywords: oxide dispersion strengthened steel, direct laser deposition, mechanical alloying, ultra fine grain, nano-particle.
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