The VAT46 alloy was developed to be an option to the alloys commonly used in internal combustion engines, VAT80A and VAT751. The microstructure of the VAT46 alloy, after undergoing heat treatment, is formed by the phases y [Ni3(Al,Ti)], y (Ni3Nb), niobium carbides (NbC) and δ [Ni3(Al,Ti,Nb)]. The δ phase contributes to alloy optimization, but may be a pathway for hydrogen to cause embrittlement. The oxidation mechanism studies for this alloy did not analyze the influence and consequences of water vapor and the δ phase in the initial stages of the oxidation process. Due to insufficient data, generating unpublished information on the influence of water vapor and the δ phase in the initial moments of oxidation makes this type of study relevant. Two types of samples of the VAT46 alloy were submitted to the oxidation experiment, one with the precipitation of the δ phase, and were used as a parameter the temperature of 800ºC for 10 hours and divided into two stages, one with the presence of water vapor and the other in a dry environment. Only the sample without the δ phase was oxidized in both environments. The oxidized samples were analyzed using an optical microscope, a scanning electron microscope (SEM) and an EDS technique. The microstructural analyses of the samples as received show the formation of phase δ with needle morphology and adjacent regions poor in metals such as niobium and nickel, which may mean the formation of this phase by the dissolution of phase y. The results showed that the nucleation of oxides at the surface is related to the carbides and not to the δ phase and that the presence of water vapour increased the lateral growth speed of the oxide nuclei initially formed in carbides.