Elucidation of damage mechanism of high temperature fatigue material by nano meso macro strength analysis

2016 Fiscal Year Final Research Report

• Project/Area Number: 23560110
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Materials/Mechanics of materials
• Research Institution: National Institute for Materials Science
• Principal Investigator: NAGASHIMA NOBUO 国立研究開発法人物質・材料研究機構, 構造材料研究拠点 疲労研究グループ, 主幹研究員 (30354252)
• Project Period (FY): 2011-04-28 – 2017-03-31
• Keywords: ferritic Cr-W steel / tempered martensite / coarse block / grain boundary / creep-fatigue / nano-indentation / pop-in behavior

Outline of Final Research Achievements

Nano indentation were performed for 12Cr-2W ferritic heat-resisting steels. One of the 12Cr-2W with superior creep-fatigue property showed transgranular fractures, whereas the other steel with inferior creep-fatigue property did intergranular fractures. In the inferior steel,the coares blocks neighboring the prior austenite grain boundaries were fomed during the creep-fatigue testing. Nano-scale hardness of the blocks neighboring the grain boundaries were markdely became less than those of the fine blocks inner grains after the tests. Moreover, a pop-in behavior occurred at only the coarse blocks neighring the grain boundaries. The pop-in behavior indicates that the dislocation density in the coarse blocks should be extremely lower by the recovery or rearrangement of dislocation by the creep-fatigue process at high-temperature. Therefore local deformations were assisted in the coarse blocks neighboring to grain boundaries and introduce the intergranular fractures.

Free Research Field

材料力学