Catalog of NIMS creep data sheets

Area of Science:

• Materials Science
• Mechanical Engineering
• Metallurgy

Background:

• Summarizes the NIMS Creep Data Sheet Project, including preliminary studies, facilities, material selection, and testing methods.
• Focuses on the long-term creep strength of ferritic and austenitic heat-resistant steels.

Purpose of the Study:

• To explain the outcomes of the NIMS Creep Data Sheet Project.
• To analyze long-term creep strength variations and influencing factors in heat-resistant steels.
• To propose new methods for evaluating long-term creep strength and related material properties.

Main Methods:

• Analysis of stress versus time-to-rupture curves, noting differences between short-term and long-term behavior.
• Investigation of heat-to-heat variations in creep strength for ferritic and austenitic steels.
• Examination of factors contributing to variations, including chemical composition, minor elements, and grain size.

Main Results:

• Identified material-dependent differences in the slope of creep strength curves.
• Observed significant heat-to-heat variations in creep strength, even within specified chemical compositions.
• Discovered inherent long-term creep strength in ferritic steels, influenced by minor solute elements.
• Noted an inflection point in tertiary creep for specific steels with precipitation during creep.

Conclusions:

• Heat-to-heat variations in creep strength are influenced by composition, minor elements, and grain size.
• Ferritic steels exhibit inherent long-term creep strength, affected by minor solute elements.
• Proposed a region-splitting analysis for high-chromium ferritic steels and developed supplementary materials like a metallographic atlas and T-T-P diagrams.