Life Prediction and Metallographical Examination of SAGBO Cracking in RB211 High Pressure Turbine Blades

2012 ◽  
Author(s):  
Mitch Kibsey ◽  
Xiao Huang ◽  
Ashok Koul ◽  
Michael Hildebrand
Keyword(s):  
High Pressure ◽  
Life Prediction ◽  
Turbine Blades ◽  
Leading Edge ◽  
Creep Life ◽  
High Pressure Turbine ◽  
Worst Case ◽  
Cooling Channels ◽  
Blade Root ◽  
Creep Life Prediction

In a previous study, high pressure turbine blades from an RB211-24C aero-derivative industrial gas turbine engine were sectioned and metallographically examined. The turbine blades were made of cast Mar-M002, a nickel-based superalloy. It was found that stress-assisted grain boundary oxidation (SAGBO) had occurred along the inner cooling channels near the leading edge at the turbine blade root, which accelerated crack formation and propagation through dynamic embrittlement. The cracks were characterized by the presence of large Hf, Al and O concentration. It appeared that the presence of oxygen in the inner cooling channels and the rapid oxidation of hafnium carbides aggravated the onset of failure through the action of SAGBO cracking. Following this examination, a creep life prediction analysis of the RB211-24C first stage blades was performed at Life Prediction Technologies Inc. (LPTi). According to the results from LPTi’s creep life prediction, the leading edge region near the blade root is most vulnerable to combined creep and oxidation damage accumulation due to high strain accumulation, as a result of high temperatures, stress, and limited inspection ability of the inner channels. In the present study, the LPTi prediction results are compared with the metallographic analysis of RB211-24C blades. It is confirmed that SAGBO in combination with creep leads to cracking in the predicted region and the worst case creep analysis results match favorably with the field experience.

scholarly journals Evaluation of High Pressure Turbine Blade Coatings on an LM2500 Rainbow Rotor

1995 ◽  
Author(s):  
B. Nagaraj ◽  
G. Katz ◽  
A. F. Maricocchi ◽  
M. Rosenzweig
Keyword(s):  
High Pressure ◽  
Turbine Blades ◽  
Leading Edge ◽  
Service Evaluation ◽  
High Pressure Turbine ◽  
Barrier Coating ◽  
Marine Propulsion ◽  
Corrosion Resistant Coatings ◽  
Stage 1 ◽  
Plasma Sprayed

Two LM2500 rainbow rotors with repaired stage 1 and stage 2 high pressure turbine blades are being assembled for marine propulsion service evaluation by the US Navy. The blades have seen between 5,000 and 15,000 hours of service in the Navy’s Fleets. A number of corrosion resistant coatings including plasma sprayed CoCrAlHf (bill of material), composite plated CoCrAlHf, platinum aluminide, aluminum silicide, and physical vapor deposited yttria stabilized zirconia thermal barrier coating (PVD TBC) will be evaluated in the rainbow rotor. This paper will discuss the advantages and microstructures of the various coatings. Composite plated CoCrAlHf, and PVD TBCs were recently service evaluated in an industrial LM2500 rainbow rotor for 10,500 hours. Both these coatings performed well, although the PVD TBC had local spallation at the leading edge. This paper will review the details of performance of these two coatings in the industrial LM2500 application.

Experimental Study of Leakage Flow on Flow Field and Film Cooling of High Pressure Turbine Blade Platform

2015 ◽  
Author(s):  
Kenichiro Takeishi ◽  
Yutaka Oda ◽  
Shintaro Kozono
Keyword(s):  
High Pressure ◽  
Film Cooling ◽  
Turbine Blades ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
Temperature Fields ◽  
Leakage Flow ◽  
High Pressure Turbine ◽  
Film Cooling Effectiveness ◽  
Injection Angle

An experiment has been conducted to study stator/rotor disc cavity leakage flow on the platform of a highly loaded stationary linear blade cascade. The linear cascade consists of a scaled-up model of the high-pressure turbine blades of an E3 (Energy efficient engine) and leakage slot models installed under the platform. Experiments have been conducted to investigate the effect of the slot injection angle, leakage flow rates, distance between the leading edge of the blade and the slot, and spacing of the blades. The film-cooling effectiveness was measured by pressure sensitive paint (PSP), and the temperature fields and flow fields were investigated using laser-induced fluorescence (LIF) and particle image velocimetry (PIV), respectively. It was observed from the experiments that the leakage flow covered the surface of the blade platform when the distance between the leading edge and the slot was zero; however, with increasing distance, the horseshoe vortex dominates near the junction of the blade leading edge, and the leakage flow could not cover the region. It was also found that the leakage flow has an effect that promotes the formation of the horseshoe vortex for some experimental conditions.

Creep life prediction of service-exposed turbine blades

2006 ◽  
Vol 433 (1-2) ◽  
pp. 305-309 ◽  
Author(s):  
G. Marahleh ◽  
A.R.I. Kheder ◽  
H.F. Hamad
Keyword(s):  
Life Prediction ◽  
Turbine Blades ◽  
Creep Life ◽  
Creep Life Prediction

Creep-life prediction of service-exposed turbine blades

2006 ◽  
Vol 42 (4) ◽  
pp. 476-481 ◽  
Author(s):  
G. Marahleh ◽  
A. R. I. Kheder ◽  
H. F. Hamad
Keyword(s):  
Life Prediction ◽  
Turbine Blades ◽  
Creep Life ◽  
Creep Life Prediction

Investigation of Stress Assisted Grain Boundary Oxidization (SAGBO) Cracking in Mar-M002 High Pressure Turbine Blades

2010 ◽  
Author(s):  
Austin Selvig ◽  
Xiao Huang ◽  
Mike Hildebrand ◽  
David Stek
Keyword(s):  
High Pressure ◽  
Grain Boundary ◽  
Hafnium Oxide ◽  
Turbine Blades ◽  
High Stress ◽  
Material Surface ◽  
Hafnium Carbide ◽  
High Pressure Turbine ◽  
Cooling Channels ◽  
Oxidation Resistant

Modern superalloys have enabled High Pressure Turbine (HPT) blades in Gas Turbine Engines (GTE) to operate at higher temperatures. Unfortunately the complexity of these materials can make it difficult to understand the failure mechanisms of these blades. HPT blades made of the nickel based superalloy Mar-M002 have been found to suffer from Stress Assisted Grain Boundary Oxidation (SAGBO) cracking. HPT blades removed from an RB211-24C aero-derivative industrial GTE were sectioned and the cracks and microstructure were studied using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). No cracks were found on the external surface of the blade which had been coated with an oxidation resistant material. Surface irregularities were found along the walls of the inner cooling channels throughout the entire blade. Larger SAGBO cracks were observed to be near the lower 25% span of the blade and had initiated from the surfaces of the cooling channels. SEM/EDS analysis showed that these cracks had large amounts of alumina and Hafnium-rich particles within them. It is evident that these cracks occurred in locations where the combination of high stress and high temperature led to higher rates of oxygen diffusion and subsequent oxidation of grain boundary carbides. Hafnium Carbide precipitates along the grain boundaries expanded as they converted into Hafnium Oxide, thus further increasing the stress. It is envisaged that this increase in stress along the grain boundary has caused the cracks to initiate and coalesce. Based on this observation, it is believed that the inner cooling channels of these HPT blades could benefit from the application of an oxidation resistant coating in order to prevent or delay the formation of these cracks.

Investigation of Stress Assisted Grain Boundary Oxidation Cracking in MAR-M002 High Pressure Turbine Blades

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Austin Selvig ◽  
Xiao Huang ◽  
Mike Hildebrand ◽  
David Stek
Keyword(s):  
High Pressure ◽  
Grain Boundary ◽  
Hafnium Oxide ◽  
Turbine Blades ◽  
High Stress ◽  
Material Surface ◽  
Hafnium Carbide ◽  
High Pressure Turbine ◽  
Cooling Channels ◽  
Oxidation Resistant

Modern superalloys have enabled high pressure turbine (HPT) blades in gas turbine engines (GTE) to operate at higher temperatures. Unfortunately, the complexity of these materials can make it difficult to understand the failure mechanisms of these blades. HPT blades made of the nickel-based superalloy Mar-M002 have been found to suffer from stress assisted grain boundary oxidation (SAGBO) cracking. HPT blades removed from an RB211-24C aeroderivative industrial GTE were sectioned, and the cracks and microstructure were studied using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). No cracks were found on the external surface of the blade, which had been coated with an oxidation resistant material. Surface irregularities were found along the walls of the inner cooling channels throughout the entire blade. Larger SAGBO cracks were observed to be near the lower 25% span of the blade and had initiated from the surfaces of the cooling channels. SEM/EDS analyses showed that these cracks had large amounts of alumina and hafnium-rich particles within them. It is evident that these cracks occurred in locations where the combination of high stress and high temperature led to higher rates of oxygen diffusion and subsequent oxidation of grain boundary carbides. Hafnium carbide precipitates along the grain boundaries expanded as they converted into hafnium oxide, thus further increasing the stress. It is envisaged that this increase in stress along the grain boundary has caused the cracks to initiate and coalesce. Based on this observation, it is believed that the inner cooling channels of these HPT blades could benefit from the application of an oxidation resistant coating in order to prevent or delay the formation of these cracks.

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