Mg ₂ SiO ₄ as a novel thermal barrier coating material for gas turbine applications

Forsterite-type Mg ₂ SiO ₄ was investigated systematically for thermal barrier coating (TBC) applications. Results showed that Mg ₂ SiO ₄ synthesized by solid-state reaction possessed the good phase stability up to 1573 K. The thermal conductivity of Mg ₂ SiO ₄ at 1273 K was lower ˜20% than that of yttria stabilized zirconia (8YSZ). Mg ₂ SiO ₄ also presented moderate thermal expansion coefficients, which increased from 8.6 × 10 ⁻⁶ K ⁻¹ to 11.3 × 10 ⁻⁶ K ⁻¹ (473˜1623 K). Mechanical properties including hardness, fracture toughness, and Young's modulus of Mg ₂ SiO ₄ were comparable to those of 8YSZ. The sintering results indicated a promising low-sintering activity of Mg ₂ SiO ₄ . Mg ₂ SiO ₄ samples were subjected to water quenching test at 1573 K and showed a superior thermal shock resistance compared to 8YSZ. Mg ₂ SiO ₄ coating with stoichiometric composition was produced by atmospheric plasma spraying. The thermal cycling test result showed that Mg ₂ SiO ₄ coating had a lifetime more than 830 cycles at 1273 K, which is desirable for TBC applications.