Failure analysis of TiNbCr Multi-Principal element Alloy: Temperature-Dependent oxidation and internal degradation in oxygen atmospheres

This study presents a failure analysis of a TiNbCr multi-principal element (MPE) alloy, focusing on its temperature-dependent oxidation behavior and internal degradation mechanisms in oxygen atmospheres. Thermal gravimetric analysis (TGA) conducted at varying temperatures revealed distinct oxidation mechanism: at 700 °C, a dense oxide layer formed; at 800 °C, a complex mixture of Nb, Ti, and Cr oxides was observed; and at 900 and 1000 °C, an innermost Cr₂O₃-rich layer developed, imparting improved oxidation resistance. Despite these temperature-dependent variations, the scaling kinetics of the alloy remained linear, with extensive internal oxidation observed at all exposure temperatures. In contrast, alloy 188 exhibited parabolic scaling kinetics and lower mass gain per unit area, demonstrating better oxidation resistance. The persistent presence of an internal reaction zone (IRZ) suggests that the oxide scale fails to act as an effective diffusion barrier, promoting internal degradation and increasing the risk of structural failure in high-temperature applications. Moreover, a comparison with previous studies suggests that the presence of nitrogen accelerates oxidation kinetics while reducing IRZ depth, affecting long-term material stability. These findings provide critical insights into oxidation-induced failure mechanisms, aiding in the development and selection of high-temperature alloys for aerospace, energy, and structural applications.