Development of TRIP/TWIP-assisted Co-Cr alloys for next generation small diameter stents

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K23580
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0401:Materials engineering, chemical engineering, and related fields
• Research Institution: Kindai University
• Principal Investigator: Ueki Kosuke 近畿大学, 理工学部, 助教 (10845928)
• Project Period (FY): 2019-08-30 – 2021-03-31
• Keywords: バルーン拡張型ステント / Co-Cr-W-Ni合金 / 機械的特性 / 微細組織制御 / 塑性変形挙動 / 析出挙動

Outline of Final Research Achievements

In order to reduce the invasiveness of stent placement, it is essential to reduce the diameter of the stent. In this study, Mn and Si-added Co-20Cr-15W-10Ni alloys (mass%, CCWN) were developed for the purpose of improving the performance of the CCWN alloy used for balloon-expandable stents.
The Mn-added CCWN alloys showed higher ductility as compared with the CCWN alloy, and showed a plastic deformation behavior in which the work-hardening rate increased during plastic deformation. Furthermore, it was suggested that the addition of Mn to the CCWN alloy is effective in reducing the yield stress of the alloy. The strength of the CCWN alloy was improved by adding Si. However, the addition of more than 1masss% of Si caused a decrease in ductility due to the formation of precipitates.
From these results, it is considered that the addition of Mn to the CCWN alloy is one of the promising methods for developing high performance alloy for next-generation small-diameter stents.

Free Research Field

金属材料工学

Academic Significance and Societal Importance of the Research Achievements

Mnを添加することでCCWN合金の積層欠陥エネルギーが上昇し、変形誘起塑性が発現したと考えられ、その結果、優れた機械的特性および加工硬化特性を示したと考えられる。Si添加CCWN合金においては、CCWN合金に関する過去の研究では確認されていない、CoWSi型laves相の形成が確認された。これらの結果は、Co-Cr系合金の析出物形成挙動や積層欠陥エネルギーと変形モードの関係といった観点から、学術的意義のあるものと言える。さらに、Mn添加CCWN合金が優れた機械的特性、加工硬化特性を示したことから、本研究の成果は、次世代小径ステントの開発につながる社会的意義のあるものと考えられる。