Kinetics and Mechanism of Hot Corrosion of γ‐Y 2 Si 2 O 7 in Thin‐Film Na 2 SO 4 Molten Salt

γ‐Y 2 Si 2 O 7 is a promising candidate material both for high‐temperature structural applications and as an environmental/thermal barrier coating material due to its unique properties such as high melting point, machinability, thermal stability, low linear thermal expansion coefficient (3.9 × 10 −6 /K, 200°–1300°C), and low thermal conductivity (<3.0 W/m·K above 300°C). The hot corrosion behavior of γ‐Y 2 Si 2 O 7 in thin‐film molten Na 2 SO 4 at 850°–1000°C for 20 h in flowing air was investigated using a thermogravimetric analyzer (TGA) and a mass spectrometer (MS). γ‐Y 2 Si 2 O 7 exhibited good resistance against Na 2 SO 4 molten salt. The kinetic curves were well fitted by a paralinear equation: the linear part was caused by the evaporation of Na 2 SO 4 and the parabolic part came from gas products evolved from the hotcorrosion reaction. A thin silica film formed under the corrosion scale was the key factor for retarding the hot corrosion. The apparent activation energy for the corrosion of γ‐Y 2 Si 2 O 7 in Na 2 SO 4 molten salt with flowing air was evaluated to be 255 kJ/mol.