Austenite Formation in the Oxidized Layer of Ultra-High-Strength 13Ni15Co10Mo Maraging Steel

Maraging steels are precipitation hardening alloys that can achieve an ultra-high yield strength (~3 GPa), however associated with low toughness. During exposure to high temperatures, oxidation process occurs on the surface of these steels, generally, oxides formed hematite and/or magnetite. The aim this study was investigate a maraging 13Ni15Co10Mo at annealing temperature 900 °C. bulk microstructure investigated by several complementary techniques and oxidized characterized Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) Diffraction (XRD). results showed microstructure, annealed condition, consists lath martensite hardness round 400 HV. most external contains hematite, magnetite kamiokite. Finally, presence austenite detected in first 2 μm below surface. Chemical microanalysis indicated is stable room region due composition gradient makes rich nickel cobalt. atom diffusion during formation. Austenite near very convenient as it could avoid crack initiation propagation, improving