Metallographic Approach to Hirbine Blade Life Time Prediction

An economically optimized and safe utilization of turbine components is of vital importance to both manufacturers and operators of aero and industrial engines. Calculations of design life must take into consideration variations in several factors, such as material properties, manufacturing processes and operational conditions. Adding safety margins into the calculation results, with necessity, in a conservative figure.

The calculated life can be confirmed, or unconfirmed, by examination and testing of randomly selected components during maintenance and overhaul. Techniques for these examinations and for evaluation of the results, in terms of life predictions are not yet fully developed.

Methodology and practical results are presented, with comments on prospects and limitations. Medium strength, wrought superalloys to modern, highly alloyed cast blades are covered. Thelife limiting mechanism of the blades in the program is normally creep. Life time extension by rejuvenation has proven successful, both technically and economically. This paper will describe the practical application of this proven metallographic approach to life time prediction and extension.