Investigating the thermal oxidation behavior of Ti–6Al–7Nb alloy in dry air

Abstract

The thermal oxidation behavior of a forged Ti–6Al–7Nb (Ti67) alloy was investigated in dry air conditions. The alloy specimens were oxidized for 50 h at different temperatures (650°C, 750°C, and 850°C) and the oxidation kinetics were analyzed. The microstructure of Ti67 after oxidation and the different phases and compounds were identified. A parabolic equation based on weight gain was used to define the oxidation rate. The parabolic rate constant increased from 1.10 × 10−8 at 650°C to 2.10 × 10−8 and 1.53 × 10−7 g2/(cm4·h) at 750°C and 850°C, respectively. At 650°C, the oxidation behavior resumed the parabolic behavior until 40 h, a breakaway phenomenon. At 750°C, a linear behavior was observed in the periods of 20–50 h. This linear trend appeared also after 35–50 h at 850°C. The activation energy was found to be 238.4 kJ/mole. At the lowest oxidation temperature (650°C), a disconnected oxide layer was observed. These variations in the response of Ti67 alloy to the different thermal oxidation conditions are worthy of consideration when modifying the surfaces for biomedical applications.

Oxidation of Fe35Mn21Ni20Cr12Al12 High Entropy Alloy in Dry Air

“…where t denotes the oxidation time, K L denotes the linear rate constant, ∆W denotes the weight gain per unit area, n represents the rate exponent, and r represents the correlation coefficient. By applying the Arrhenius Equation ( 2), it could calculate the apparent activation energy of oxidation of the alloy as illustrated in Figure 3 [34,35].…”

“…Alloys 2024, 3, FOR PEER REVIEW 5 2), it could calculate the apparent activation energy of oxidation of the alloy as illustrated in Figure 3 [34,35]. R denotes the gas constant, Q represents the activation energy, T represents the oxidation temperatures in kelvin, and K L represents the linear oxidation rate.…”

“…applying the Arrhenius Equation (2), it could calculate the apparent activat energy of oxidation of the alloy as illustrated in Figure3[34,35]. KL = A exp (−Q/RT)…”