Atom probe field ion microscopy investigation of boron containing martensitic 9 Pct chromium steel

The chemical compositions of the ferrite matrix and various other phases in an Fe-0.17 C-9 Cr-1.55 Mo-0.27 V-0.015 N-0.01B (mass pct) steel in as-received and crept conditions were measured with atom probe field ion microscopy (APFIM). The results showed the presence of some residual boron within the ferrite matrix. Analyses showed that boron was distributed within M₂₃C₆, M₆C, MX, and Laves phases. Phosphor atoms were detected at the M₂₃C₆-ferrite interface in the crept condition. The results are compared to predictions from thermodynamic calculations. P. HOFER, formerly Graduate Student, Institute of Materials Science, Welding and Forming, Technical University Graz.