High temperature corrosion of microturbine combustor material

Two particular types of high temperature corrosion in a microturbine Rich-bum, Quick-mix, Lean-bum (RQL) combustor are discussed and reported in this paper. One type occurred in mixing tubes, part of fuel supply into the combustor. Dense concentrations of carbon monoxide and unburned hydrocarbons in a high temperature environment carburized the mixing tube, leaving it vulnerable to corrosion. The Co-based alloy was selected for the advantage of good heat resistance was exchanged for a Ni-Cr based alloy of good carburization resistance and the life of combustor successfully extended. The second type is a pitting corrosion on the inner wall of liner in the rich-burn zone. It is inferred that the corrosion was metal dusting caused from defects of the oxide film on the inner wall surface. As a countermeasure, a preoxidation step was applied to the combustor to maintain a protective oxide film for a longer period of time. This paper discusses the mechanisms and the countermeasures for these types of corrosion, which relate to carbon from the fuel origin activated in the fuel-rich environment in the combustor.