Metal dusting in combustor basket

Combustor basket is a component inside a combustion chamber of a gas turbine in a power plant, functioning as a container for combustion process. An unexpected shutdown was conducted on a gas turbine power plant, operating on high speed diesel fuel, due to high spread temperature after being operated for 2,723 operating hours. Following the shutdown, a hole (seen from the outer surface) was found in the combustor basket material. The material used in the combustor basket is nickel-based superalloy. A visual macrograph investigation revealed the effect of severe heat exposure around the hole area. On the inner surface of the combustor basket, the protective coating has deteriorated and eventually exfoliated, exposing the material to combustion gas environment. The surface of material exposed to the combustion gas environment has a phase with the color of black. A chemical composition and SEM-EDX test revealed that the carbon content of the material from the material neighboring to the hole until the material which is nearest to the hole has increased, indicating metal dusting process has occured.