Influences of Al concentration and Nb addition on oxidation behavior of Ti₂AlC ceramics at high temperatures

Figures & data

Table 1. Sample symbols and categories.

Ti:Al:C:Nb	Symbols	Category name
2:1:0.9:0	Al1	Al-poor
2:1.2:0.9:0	Al1.2	Al-rich
2:1.5:0.9:0	Al1.5
1.9:1:0.9:0.1	Al1Nb	Nb-doped
1.9:1.2:0.9:0.1	Al1.2Nb

Figure 1. X-ray diffraction patterns recorded for bulk samples: Al1, Al1.2, Al1.5, Al1Nb and Al1.2Nb.

Figure 2. Magnified images of Ti₂AlC and Nb-doped Ti₂AlC samples with various Al molar ratios after 2 − 14 d of isothermal oxidation in laboratory air at 800°C.

Figure 3. X-ray diffraction patterns recorded for samples Al1, Al1.2, Al1.5, Al1Nb and Al1.2Nb after 14 d of isothermal oxidation in laboratory air at 800°C.

Figure 4. SEM and EDS images of the cross-sections of samples Al1.2, Al1Nb and Al1.2Nb after 14 d of isothermal oxidation in laboratory air at 800°C.

Figure 5. SEM and EDS images of the surface of Al1.2Nb after 14 d of isothermal oxidation in laboratory air at 800°C.

Figure 6. SEM and EDS images of the cross-sections of Al1 after 14 d of isothermal oxidation in laboratory air at 800°C.

Figure 7. Oxide scale thickness (x) versus time (t) for Al1 oxidized at 800°C for 14 d.

Figure 8. Oxidation kinetics for all investigated samples over 150 h of isothermal oxidation in laboratory air at 800°C, presented in a linear plot.

Table 2. Parabolic rate constants of oxidation (k_p) of all samples determined after 150 h of isothermal oxidation in laboratory air at 800°C.

Sample	kp/g^2cm^−4s^−1	Category name
Al1	1.6 × 10^−12	Al-poor
Al1.2	3.1 × 10^−13	Al-rich
Al1.5	1.0 × 10^−13
Al1Nb	6.4 × 10^−14	Nb-doped
Al1.2Nb	2.7 × 10^−14

Figure 9. Arrhenius plot showing the parabolic rate constants determined for the oxidation of Ni₅₀AI₅₀ [19] and the k_p values determined in the present experiment (Table 2).

Brumm M, Grabke H. The oxidation behaviour of NiAl-I. Phase transformations in the alumina scale during oxidation of NiAl and NiAl-Cr alloys. Corros Sci. 1992;33(11):1677–1690.

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