In-situ deposition of silica layers during the operation of a micro-gas turbine and their effect on the oxidation of superalloy blades

Silica-based oxide layers were deposited in-situ on turbine blades made from Inconel 713 during the operation of a 13 kg_f-class gas turbine, and their effect on the ex-situ oxidation behavior of the blades at 1050 °C was examined. The two turbines were driven by burning liquid petroleum gas (LPG), one turbine at a rotation speed of 35,000 rpm for 4 h (TB04), and the other at 42,000 rpm for 8 h (TB08). For deposition, tetraethylorthosilicate (TEOS) was sprayed into the fuel line immediately ahead of the combustion chamber. The TEOS-to-LPG ratio for TB04 and TB08 was maintained at 5.4 wt. % and 2.3 wt. %, respectively. Directly after operation, the turbine blades were coated with silica layers to a thickness of ∼10 μm, independent of the operating conditions. These oxide layers on the blades provided excellent protection against oxidation during both operation and the ex-situ isothermal oxidation test.