Analyzing Boron in 9-12% Chromium Steels Using Atom Probe Tomography.

Area of Science:

• Materials Science
• Metallurgy
• Physical Chemistry

Background:

• Boron additions improve long-term creep resistance in 9-12% Cr steels.
• Mechanisms of boron segregation to grain boundaries and precipitates are not fully understood.
• Atom probe tomography (APT) is crucial for analyzing boron distribution but faces challenges.

Purpose of the Study:

• To develop and validate a site-specific APT specimen preparation method for 9-12% Cr steels.
• To investigate boron distribution at grain boundaries and in precipitates using APT.
• To address challenges in quantitative boron analysis in 9-12% Cr steels.

Main Methods:

• Developed a novel site-specific APT specimen preparation technique.
• Utilized APT to analyze boron segregation at grain boundaries and within precipitates.
• Investigated boron distribution profiles and evaporation field effects.
• Applied a 10B correction method for quantitative analysis of borides.

Main Results:

• Successfully prepared APT specimens with targeted grain boundaries.
• Observed a widening of boron distribution profiles at boundaries and in carbides/borides.
• Analyzed the influence of evaporation fields on boron signal.
• Achieved good quantification of boron in metal borides using 10B correction.

Conclusions:

• The developed method facilitates site-specific APT analysis of boron in 9-12% Cr steels.
• Understanding boron distribution is key to optimizing creep resistance.
• Addressed key challenges in APT analysis of boron, improving quantification accuracy.