Effect of Creep Degradation on Hardness Changes of Ni-based Alloys for A-USC Power Boiler

• Saito Nobuhiko

  Research & Innovation Center, Mitsubishi Heavy Industries, Ltd.

• Ishiyama Kazuki

  Graduate Student at Department of Materials and Engineering, Kyushu Institute of Technology.

• Yamaguchi Tomiko

  Department of Materials and Engineering, Kyushu Institute of Technology

• Masuyama Fujimitsu

  Department of Materials and Engineering, Kyushu Institute of Technology

抄録

A project to develop Advanced Ultra-Supercritical (A-USC) power plant which operate at 700°C has been under way in Japan with the intension to reduce the CO₂ emission and improve the power generation efficiency. Ni-based alloys, UNS N06674 (ASME Code Case 2826, 47Ni-23Cr-23Fe-7W, HR6W) and UNS N06617 (52Ni-22Cr-13Co-9Mo, Alloy 617) are candidate materials used in the high temperature regions of the A-USC power boilers. In this study, effect of creep degradation on the hardness change of both Ni-based alloys was investigated in order to evaluate the potential of the hardness method for creep life assessment. The investigation results showed that the scattering of hardness values in the latter stage of the creep life was increased as a result of hardening and softening of the material due to the increase of dislocation density with creep deformation and coarsening of precipitates followed by the formation of creep cavities, respectively. This tendency shows a good correlation with the creep life fraction. Therefore, it could be an useful tool for creep life evaluation. In addition, it was found that the hardness variation of the HR6W can be expressed as a function of temperature, stress and creep life fraction and thus leads to postulate a regression equation with hardness by a multivariate analysis. The creep life fraction can be calculated by substituting the values of service temperature and stress, and measured hardness into the multivariate regression equation. Those findings suggested that the hardness method was useful for the creep life assessment of Ni-based alloys.

収録刊行物

• ＩＳＩＪ　Ｉｎｔｅｒｎａｔｉｏｎａｌ

  ＩＳＩＪ　Ｉｎｔｅｒｎａｔｉｏｎａｌ 59 (9), 1695-1704, 2019-09-15

  一般社団法人 日本鉄鋼協会

キーワード

• A-USC power boiler
• Ni-based alloy
• creep life assessment
• hardness
• multivariate analysis

詳細情報

• CRID: 1390282752325903872
• NII論文ID: 130007706700
• DOI: 10.2355/isijinternational.isijint-2018-878
• ISSN: 13475460
• ISSN: 09151559
• Web Site: https://www.jstage.jst.go.jp/article/isijinternational/59/9/59_ISIJINT-2018-878/_pdf
• 本文言語コード: en
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