Investigation of Intergranular Corrosion in 2nd stage gas turbine blades of an aircraft engine

•Intergranular Corrosion in the top and middle portion of turbine blades was investigated.•2nd stage turbine blades made of Udimet 500 materials were analyzed.•Blades were subjected to high temperature exposure and alkaline media exposure.•At high temperature precipitation of Cr carbide was observed.•On exposure to alkaline media, Cr and Mo carbide precipitation and pitting was observed.

Intergranular corrosion is one of the decisive tools for the life of turbine blade for its continuous use. The study was to ascertain the occurrence of Intergranular Corrosion (IGC) in the turbine blades of an aircraft. For this purpose 2nd stage turbine blades made up of Nickel Based Superalloy Udimet 500 were used to find out attack of IGC in the top & middle portion of blades as the same was detected during Eddy Current Testing. The turbine blades having different flying hours (700, 1700 & 2700) were selected for specimen while simulating actual conditions which the turbine blades encounter during flight & maintenance/overhaul. High temperature exposure (at 900 °C for 1min & 950 °C for 1min) and alkaline media exposure (at normal and aggressive condition) were introduced to find out the damaging results. It was found that Cr carbide is precipitated at GBs on exposure to 900 °C and an excessive Cr carbide precipitation at GBs on exposure to 950 °C due to Intergranular Corrosion. On exposure to alkaline media, pitting was observed within grains and at grain boundaries on the specimen of blades.