Materials Issues For Users Of Gas Turbines.

Tutorialpg. 197-214Material issues are of paramount importance for the reliable and cost effective operation of gas turbine engines. Because of the high turbine temperatures, the materials degrade over time, which requires their repair or replacement. Rapid degradation or the inability to repair these complex materials result in excessively high operating costs. This paper concentrates upon the hot section components, because this is where the majority of turbine distress occurs. Superalloys, both nickel based and cobalt based, and high temperature coatings are discussed from a user's perspective. The degradation of the hot section components--combustor hardware, blades, and vanes-is described. This degradation includes that due to creep, thermal mechanical fatigue, high temperature oxidation, and hot corrosion. Approaches to determining the remaining life of these components is discussed, including the data that the user must supply. A computer program for determining the remaining life of the first stage blades and vanes is presented. Finally, the repair and rejuvenation of the materials and components are described, including heat treatment, welding, brazing, and recoating