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Effect of Post-Heat Treatment Cooling Conditions on Microstructures and Fatigue Properties of Cobalt Chromium Molybdenum Alloy Fabricated through Selective Laser Melting

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Removable Partial Prosthodontics, Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo 113-8549, Japan
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Department of Conservative Dentistry and Prosthodontics, Faculty of Dentistry, Srinakharinwirot University, Bangkok 10110, Thailand
3
Department of Metallic Biomaterials, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo 101-0062, Japan
*
Author to whom correspondence should be addressed.
Academic Editor: Christian Mittelstedt
Metals 2021, 11(7), 1005; https://doi.org/10.3390/met11071005
Received: 25 May 2021 / Revised: 18 June 2021 / Accepted: 22 June 2021 / Published: 23 June 2021
Although post-heat treatment can improve the fatigue life of selective laser melting (SLM)-fabricated cobalt chromium molybdenum (CoCrMo) alloys, the effect of cooling conditions on the fatigue properties of such alloys remains unclear. In this study, we fabricated SLM CoCrMo alloy specimens and, after heat-treating them, cooled them either via furnace-cooling (FC) or air-cooling (AC). Subsequently, we analyzed their microstructures using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, electron backscattered diffraction, confocal laser scanning microscopy, and X-ray diffraction. Tensile and Vickers hardness (HV) tests and axial-fatigue tests were also conducted to assess their mechanical and fatigue properties, respectively. The microstructures of all samples showed homogeneous equiaxed grains, with the grains and precipitates of the AC samples (grain size: 84.9 μm) smaller than those of the FC samples (grain size: 109.7 μm). The AC samples exhibited better ductility than the FC samples. However, we observed no significant differences in the 0.2% yield strength and HV tests. The S–N curve derived from the fatigue tests showed that the AC samples had greater fatigue life than the FC samples. Therefore, a high cooling rate during post-heat treatment is effective in reducing grain and precipitate sizes, resulting in improved ductility and fatigue life. View Full-Text
Keywords: additive manufacturing; post-heat treatment cooling conditions; mechanical property; fatigue; CoCrMo alloy additive manufacturing; post-heat treatment cooling conditions; mechanical property; fatigue; CoCrMo alloy
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MDPI and ACS Style

Wai Cho, H.H.; Takaichi, A.; Kajima, Y.; Htat, H.L.; Kittikundecha, N.; Hanawa, T.; Wakabayashi, N. Effect of Post-Heat Treatment Cooling Conditions on Microstructures and Fatigue Properties of Cobalt Chromium Molybdenum Alloy Fabricated through Selective Laser Melting. Metals 2021, 11, 1005. https://doi.org/10.3390/met11071005

AMA Style

Wai Cho HH, Takaichi A, Kajima Y, Htat HL, Kittikundecha N, Hanawa T, Wakabayashi N. Effect of Post-Heat Treatment Cooling Conditions on Microstructures and Fatigue Properties of Cobalt Chromium Molybdenum Alloy Fabricated through Selective Laser Melting. Metals. 2021; 11(7):1005. https://doi.org/10.3390/met11071005

Chicago/Turabian Style

Wai Cho, Hla H., Atsushi Takaichi, Yuka Kajima, Hein L. Htat, Nuttaphon Kittikundecha, Takao Hanawa, and Noriyuki Wakabayashi. 2021. "Effect of Post-Heat Treatment Cooling Conditions on Microstructures and Fatigue Properties of Cobalt Chromium Molybdenum Alloy Fabricated through Selective Laser Melting" Metals 11, no. 7: 1005. https://doi.org/10.3390/met11071005

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