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Microstructure oxidation resistance relationship in Ti3AlC2 MAX Phase

Spark Plasma Sintering and Hot Isostatic Pressing were used to synthesize coarse-grained and fine-grained Ti3AlC2 specimens. Moreover, Spark Plasma Sintering processing parameters were modified to vary the TiC, Al2O3, and TixAly impurity and porosity in the fine-grained samples. The influence of the Ti3AlC2 microstructure on the oxidation resistance was assessed. It is demonstrated that the grain size can drastically modify the oxidation resistance. The higher density of grain boundaries in fine-grained specimens increases the number of Al diffusion paths and leads to forming a protective alumina scale. Al diffusion is the rate-limiting step of the α−Al2O3 formation in the coarse-grained samples, and TiO2 is formed simultaneously with alumina. TiC impurities and porosity are demonstrated to be detrimental to the oxidation resistance in the 800°C – 1000°C temperature range by favoring TiO2 formation. Finally, it is also shown that, for fine-grained specimens, the oxide scale grows very slowly for oxidation times in the 20-40 days range. MAX phase materials are quite recent materials developed nearly 50 years ago by Nowotny. These ternary nano-layered compounds can be described by the empirical formula Mn+1AXn, with n equal to 1, 2, or 3, where M represents an early transition metal, A represents A-group elements (i.e., from columns IIIA to VIA of the periodic table), and X represents carbon and nitrogen. The hexagonal structure (P63/MMC) of MAX phase materials is characterized by M6X octahedra separated by A atomic layers. This structure, combining strong covalent M-X bonds and weaker M-A bonds, confers to the MAX phase properties of both ceramics and metals. They are stiff, lightweight, chemically stable, and oxidation resistant, like ceramics. Like metals, they are relatively ductile at high temperatures, machinable, resistant to thermal shock, and exhibit good electric and thermal conductivity. This class of materials, specifically Cr2AlC, has also been used as a coating for Ni-based polycrystalline superalloy, taking advantage of its very good corrosion/oxidation resistance. If you are looking for high quality, high purity, and cost-effective Ti3AlC2, or if you require the latest price of Ti3AlC2, please feel free to email contact mis-asia.

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