The following property is most important for material used for gas turbine blade

Correct Answer: Creep

In the context of gas turbine blades, the most important property among the given options is Creep. Creep is a time-dependent deformation that occurs under constant load and elevated temperatures. Gas turbine blades operate in high-temperature environments and are subjected to significant mechanical and thermal stresses.

Explanation for each option:

Toughness: While toughness is important for impact resistance, it is not as critical as creep in the high-temperature and constant-load conditions experienced by gas turbine blades.
Fatigue: Fatigue is relevant for cyclic loading, but the continuous and high-temperature operation of gas turbine blades makes creep a more crucial consideration.
Creep: Creep resistance is crucial as gas turbine blades are exposed to prolonged high temperatures and constant loads during operation.
Corrosion resistance: While corrosion resistance is important for durability, it is not the primary concern when compared to the high-temperature creep behavior.

Therefore, in the context of the question, the most important property for a material used for gas turbine blades is Creep.