Production and Characterization of Oxides Formed on Grade 300 and 350 Maraging Steels Using two Oxygen/Steam Rich Atmospheres

The study investigates the production and characterization of oxide films formed on grade 300 and 350 maraging steels under two different oxygen/steam-rich atmospheres during aging heat treatment. The objective was to analyze the growth process of a spinel-like oxide film and to assess the resultant oxide's chemical, microstructural, and mechanical properties. Advanced characterization techniques were applied to examine the oxidation layers that developed at 490ºC, revealing a non-homogeneous mix of oxides including magnetite, nickel and cobalt ferrites, and MoO3. Interestingly, the presence of TiO2 and significant amounts of hematite was noted in the oxide layers. Moreover, the study highlights the formation of a nickel-rich austenite phase at the interphase, influenced by the diffusion of cobalt, molybdenum, and iron ions. The results showed that maraging 300 steels exhibited a greater susceptibility to oxidation compared to grade 350, alongside excellent adherence of the oxide films produced in air atmosphere, suggesting their potential for tribological applications under sliding contact conditions.