As a new type of lightweight high-temperature resistant structural material, owing to its advantages of low density, high specific strength, and excellent high-temperature creep resistance, TiAl alloys stand as the sole candidate material within the temperature range between the upper service temperature limit of titanium alloys and the lower service temperature limit of superalloys (from 700 to 900 ℃ ). However, in the actual service environment of TiAl alloys, impurities such as S, Cl, and alkali metal elements from fuel or seawater can form mixed salts. These salts deposit on the surface of the TiAl alloy components, inducing hot corrosion reactions with the alloy matrix, which leads to component failure. Thus, it is necessary to construct a high-temperature corrosion environment to investigate the hot corrosion behavior of TiAl alloys, which will provide theoretical references for advancing the evaluation and optimization of their service performance. Accordingly, a systematic study on the hot corrosion behavior of TNM alloys was conducted under 850 ℃ salt spray conditions. The surface morphology was observed, the composition of the hot corrosion products was analysed, and the mechanism of hot corrosion behavior was discussed. The results indicate that the hot corrosion products on the surface of TNM alloys are dominated by flake-like TiO2 and a continuous dense Al2O3 layer at 850 ℃,and the outermost layer is dominated by TiO2.As hot corrosion continues, the morphology of TiO2 transforms from flake-like to columnar, and its distribution tends to be clustered. With increasing hot corrosion time or an increase in the number of hot corrosion cycles, the hot corrosion layer fractures and spalls under the coupling effect of corrosive medium erosion and thermal stress, which exposes the alloy matrix and leads to further hot corrosion, resulting in a cyclic process of "formation to spallation" of the hot corrosion layer. As the hot corrosion time increases, the hot corrosion behavior on the alloy surface transitions from the cyclic process of "formation-spallation" of the corrosion layer to a phase-selective corrosion process that rapidly penetrates the alloy interior along the α2 phase. This transition makes it difficult to form a continuous protective oxide layer on the surface, which severely deteriorates the corrosion resistance of the alloy.