X-ray Photoelectron characterization of the chemical states and the natural oxidation behavior of TiC ceramics reinforced steel matrix composite after stabilizing heat treatments

Abstract

In the present work, the microstructure and chemical behavior of TiC ceramic reinforced steel matrix composite material after stabilizing heat treatments have been studied. The composition of the naturally formed oxide layer on the surface of the composite and the potential natural oxidation mechanisms are also elucidated. The results showed that the naturally formed oxide layer contained mainly O, C, Fe and Ti, with small amounts of Cr and Mo. In the multi-metallic oxide layer, Fe3+, Mo6+, and Ti4+ species are enriched on the free external surface of the composite, the protective Fe2+ oxides were distributed in the relative inner part of the oxide layer, and Mo4+ was more uniformly distributed throughout the natural oxide film. The Cr oxides formed near the substrate acted as a diffusion barrier for iron and chromium ions, and the preferential oxidation of chromium formed a passivation film, which effectively improved the corrosion resistance of the material. Due to the interfacial evolution and complex stress changes in the composite during the stabilizing heat treatments, the XPS spectral peaks were shifted towards lower binding energies than in the annealed sample. The core level spectra of Mo 3d, Ti 2p, and Fe 2p were all shifted to lower binding energies due to the combination of ligand and strain effects after quenching, and there was no significant difference in the spectra of the tempered and thermal cooling cycling (TCC) treated composites, which suggested that the chemical state was relatively stable during the subsequent stabilizing heat treatments.