Metal combustion is one of the main issues threatening service safety in oxygen-enriched atmospheres, leading to unexpected explosions in rocket engines. This paper reviews the recent development of metals combustion in oxygen-enriched atmospheres. Test methods under three typical conditions and combustion behaviors of three typical metals are mainly discussed. The microstructures of the combustion areas of tested samples in stainless steels, nickel superalloys, and titanium alloys are similar, containing an oxide zone, a melting zone, and a heat-affected zone. The development trend of metal combustion in oxygen-enriched atmospheres in the future is also forecasted.

The combustion velocity and the mechanism for a series of Ti-Cr-V alloys with different chemical compositions are studied by a promoted ignition combustion test corresponding to different oxygen pressures to investigate the influence of alloying elements, such as Cr and V, on combustion behavior. The microstructures and composition distributions of the alloying elements in the reaction and oxide areas are observed and analyzed. The thermogravimetry analysis results show that the oxidation mass gain decreases with the increasing Cr content, and the oxidation resistance obviously increases from 10 Cr to 20 Cr. The combustion velocity decreases with increasing Cr content, and it is concluded that elevated Cr content can effectively retard the flame propagation velocity. Importantly, for the Ti-Cr-V alloys, the Cr and V elements accumulate in the melting zone and reduce the heat created by combustion.

The oxidation of 3Cr3Mo2NiW and 3CrNi3Mo steels was studied at 600 °C in air, and the test results suggest that the parabolic rate law fitted the oxidation kinetics of both steels. The microstructure, morphology, structure, and phase composition of the oxide film cross-sectional layers of the two Cr-Ni-Mo hot-work die steels were analyzed using scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and X-ray diffraction (XRD). The influences of Cr, Ni, and Mo on the high-temperature oxidation resistance of the two Cr-Ni-Mo hot-work die steels are discussed, and the oxidation mechanism is summarized. Heat-treated samples were analyzed using electron backscattered diffraction (EBSD) to obtain inverse pole figures (IPFs) and average sample grain sizes, and the percentages of twin grain boundaries (TGBs) (θ = 60°) were also measured. After heat treatment, recrystallization was observed in both steels with a large portion of twin grain boundaries. After 10 h of oxidation, the dense chromium-rich oxide layer that formed in the inner oxide layer of 3Cr3Mo2NiW steel effectively prevented the continuation of oxidation. The inner oxide layer in 3CrNi3Mo steel formed an adhesion layer with a network structure composed mainly of Ni- and Cr-rich spinel oxide, without forming a barrier to prevent oxidation.