COMMON FAILURES IN GAS TURBINE BLADE: A CRITICAL REVIEW

Almost all commercial electrical power on earth is generated with a turbine, driven either by wind, water, steam or burning gas. Turbine blades are subjected to very strenuous environments inside a gas turbine. They face high temperatures, high stresses, and a potentially high vibration environment. All these factors can lead to blade failure, resulting in catastrophic failure of turbine. In the event of turbine blade failure, turbine does not work and this leads to shutdown of power plant from one to four weeks or longer, depending on the extent of the damage and the procedure used to make the machine operational again, which results in economic loss and service to mankind also stops. For each day of a forced outage, a utility could lose hundreds of thousands of dollars in electrical power. The external and internal surface damages include corrosion, oxidation, crack formation, erosion, foreign object damage and fretting. The internal damage of microstructure include γ' phase, CoNi3 [(Al, Ti)] phase aging (rafting), grain growth, brittle phases formation, carbides precipitation, creep and grain boundary void formation. These damages produce dimensional change which results in increase in operational stress that leads to deterioration in turbine efficiency. The deterioration of blade material is related to the high gas temperature, high steady state load levels (centrifugal load) and high thermal transient load (trips, start-ups, start downs). In this research, a review of common failures due to metallurgical defects found in gas turbine discussed is presented