In situ deposition of oxide layer using fuel additive and its effect on the oxidation of SM 45C blades for micro-gas turbines

In situ deposition of a silica-based oxide layer on carbon steel (SM45C) turbine blades was tried during the operation of a 13 kgf-class gas turbine engine using fuel additive, and its effect on the durability and the static oxidation at 700 °C of the blade was studied. The gas turbine was actuated by burning kerosene as fuel, for one turbine wheel with fuel additive (0.5 wt.% PDMS), and for another without additive. The oxide scales formed on the turbine blades were characterized using SEM, EDX and XRD. The results of the test revealed that the durability of SM45C turbine was prolonged more than 10 times when operated with additive than when operated without additive at the rotation speed of 30,000 rpm and a turbine exhaust temperature of 780 °C. Combustion with 0.5 wt.% PDMS gave a white residue containing up to 16.5 at.% Si in the wüstite-based scale. The influx of silicon oxide into the growing scale suppressed the formation of hematite on the surface of the blade during the operation. As the static oxidation test gives no difference in the oxidation rate between the two kinds of operated blades, the prolonged durability was attributed to the silicon oxide continuously supplied to the surface of the blade during the operation.