Post-Test Evaluation of a Prototype Composite Water-Cooled Gas Turbine Nozzle

Abstract

Water-cooled high temperature gas turbine technology has been under investigation by the Gas Turbine Division of the General Electric Company for the past 15 years. The transition from testing small scale laboratory-size hardware to full-scale gas turbine components was initiated in 1975 by General Electric and extended further under the U.S. Department of Energy’s High Temperature Turbine Technology (HTTT) Program. A key element in this transition was the identification of a composite (hybrid) design for the first-stage nozzles. This design permits efficient heat transfer to the water-cooling passage-ways, thus lowering effective strains and increasing part life. The results of GE’s extensive efforts over many years to develop a composite water-cooled first-stage nozzle were further confirmed through the successful fabrication and testing of full-scale hardware under the DOE/HTTT Program. This paper describes the post test metallurgical evaluation of two segments of the nozzle tested under the DOE/HTTT program. A brief description of the actual hot-gas path testing of the part is given. The bulk of the paper deals with a microstructural evaluation of the segments including microprobe traces and hardness surveys. Pre- and post-test non-destructive evaluations are also reviewed.