Fatigue of 3D Printed Cobalt Alloy for Artificial Joints and Methods for its Improvement : Science of Deformation in Meta-Stable Crystals

2016 Fiscal Year Final Research Report

• Project/Area Number: 26289252
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Structural/Functional materials
• Research Institution: Tohoku University
• Principal Investigator: KOIZUMI Yuichiro 東北大学, 金属材料研究所, 准教授 (10322174)
• Co-Investigator(Kenkyū-buntansha): 千葉 晶彦 東北大学, 金属材料研究所, 教授 (00197617) ; 李 云平 東北大学, 金属材料研究所, 助教 (80546862)
• Co-Investigator(Renkei-kenkyūsha): TSUJI NOBUHIRO 京都大学, 大学院工学研究科, 教授 (30263213)
• Research Collaborator: SUN SHI-HAI ; TAKASHIMA TAIYO
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: 電子ビーム積層造形 / 3Dプリンター / 人工関節 / 疲労破壊 / 相変態 / マルテンサイト / 結晶粒微細化 / 繰り返し変形

Outline of Final Research Achievements

Co-Cr-Mo (CCM) alloy is used for artificial joints because it has excellent wear and corrosion resistances and biocompatibility. Additive manufacturing technologies such as electron beam melting (EBM) is attracting growing attention because of their ability to fabricate tailor-made artificial joints. In this study, we have investigated, (i) the inhomogeneity of the microstructure with special focus on the phase distribution, (ii) the relation between the microstructure and fatigue behavior, and (iii) the effects of post-built heat treatment on the microstructure and fatigue properties of EBM-built CCM alloys. The constituent phases and grain structure were found to depend considerably on the position of the build part in the building space. Heat treatment to form ε-hcp-phase and subsequently reverse it to γ-fcc-phase via diffusive transformation greatly homogenized the phase distribution and refined the microstructure, which resulted in the great improvement of the fatigue property.

Free Research Field

材料組織、材料プロセス、材料強度