Leonardo Tognarelli

Rig and Gas Turbine Engine Testing of MI-CMC Combustor and Shroud Components

GE is continuing work on the development of Melt-Infiltrated Ceramic Matrix Composites (MI-CMC) for use in industrial gas turbine engine components. Long-term environmental degradation of test samples under realistic engine conditions is being determined using a unique high-pressure combustion rig apparatus. Rig testing is also being used to evaluate an F-class 1st stage shroud system incorporating an MI-CMC inner shroud component. While large, advanced engines, such as the F and H classes, offer the greatest benefits for using MI-CMC components, initial engine tests have been done using a GE-2 (2MW) machine to reduce costs and risk. Long term (1000 hours) engine testing results for single piece GE-2 shrouds are also described.Copyright

High Load Ratio Fatigue Strength and Mean Stress Evolution of Quenched and Tempered 42CrMo4 Steel

The fatigue strength at a high number of cycles with initial elastic–plastic behavior was experimentally investigated on quenched and tempered 42CrMo4 steel. Fatigue tests on unnotched specimens were performed both under load and strain controls, by imposing various levels of amplitude and with several high load ratios. Different ratcheting and relaxation trends, with significant effects on fatigue, are observed and discussed, and then reported in the Haigh diagram, highlighting a clear correlation with the Smith–Watson–Topper model. High load ratio tests were also conducted on notched specimens with C (blunt) and V (sharp) geometries. A Chaboche model with three parameter couples was proposed by fitting plain specimen cyclic and relaxation tests, and then finite element analyses were performed to simulate the notched specimen test results. A significant stress relaxation at the notch root became clearly evident by reporting the numerical results in the Haigh diagram, thus explaining the low mean stress sensitivity of the notched specimens.

Rig and Engine Testing of Melt Infiltrated Ceramic Composites for Combustor and Shroud Applications

GE has developed SiC fiber reinforced SiC-Si matrix composites produced by silicon melt infiltration (MI) for use in gas turbine engine applications. High temperature, high pressure combustion rig testing and engine testing has been performed on combustor liners and turbine shrouds made from such MI composites. Frame 5 sized combustor liners were rig tested under LHE diffusion flame conditions for 150 hours, including 20 thermal trip cycles, with no observed damage to the ceramic liners. Similarly, 46 cm diameter, single piece turbine shroud rings were fabricated and tested in a PGT-2 gas turbine engine. The fabrication and testing of both components are described.Copyright

Effects of Multiple Rejuvenation Cycles on Mechanical Properties and Microstructure of IN-738 Superalloy

The scope of this work is to show the effects of multiple applications of a rejuvenation treatment studied for IN-738 on both the microstructure and the mechanical properties of the creep-damaged superalloy and to check the recovery obtained after one and two rejuvenation cycles through creep and tensile tests, whose results will be compared with the performance of the virgin material. This work will show that this rejuvenation treatment is able to recover the microstructure of creep-damaged specimens after one and two applications and that the mechanical properties of the rejuvenated alloy are very similar to the virgin material even after two rejuvenation cycles.