Ductility Loss in Aluminized CoCrAlY Coatings Exposed to In-Service Environment

2001 ◽  
Author(s):  
N. Shinohara ◽  
A. Ito ◽  
K. Sugiyama ◽  
Y. Sugita ◽  
J. Kameda ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Degradation Mechanism ◽  
Turbine Blades ◽  
Leading Edge ◽  
Testing Temperature ◽  
Thermal Ageing ◽  
Near Surface ◽  
Ductility Loss ◽  
Service Operation ◽  
Service Degradation

By applying a small punch testing technique, it has been previously shown that near-surface aluminized CoCrAlY coatings of unused advanced gas turbine blades had very low ductility due to the formation of Al and Cr rich phases, compared to internal and near-interface regions. Thus, it is important to examine how in-service operation affects the mechanical properties of the internal, near-interface coatings and substrates to maintain the integrity of gas turbines. This study attempts to compare the effects of in-service operation for 20,000 h under combustion of liquefied natural gas and thermal ageing in air. The in-service operation led to a larger ductility loss in concave coatings near the tailing edge, although the ductility slightly improved above testing temperature at 950 °C. Substrate used in-service had lower ductility at 950 °C than the used concave coatings. The ductility of used internal coatings depended on the blade location. In convex coatings near the leading edge, in-service degradation was not significant and the ductility was about two-fold greater than in the thermally aged blade. The in-service degradation mechanism of the aluminized CoCrAlY coatings is discussed in light of the operating temperature distribution and microstructural evolution.

In-Service Mechanical Property Degradation of Cocraiy Coatings in Land-Based Gas Turbine Blades

1998 ◽  
Author(s):  
J. Kameda ◽  
T.E. Bloomer ◽  
S. Sakurai
Keyword(s):  
Gas Turbine ◽  
Degradation Mechanism ◽  
Turbine Blades ◽  
Significant Loss ◽  
Nickel Titanium ◽  
Near Surface ◽  
Gas Turbine Blades ◽  
Surface And Interface ◽  
Service Degradation ◽  
Plasma Sprayed

Abstract This paper describes variations in the microstructure/composition and mechanical properties in plasma sprayed CoCrAlY coatings and a modified Rene 80 substrate of gas turbine blades operated for 21000 h under liquefied natural gas fuels. Substantial oxidation/carbonization occurred in near surface coatings of concave blades but not in convex coatings. Aluminum and nickel/titanium rich nitrides formed in concave coatings and substrates adjacent to the interface, respectively. Small punch (SP) specimens were prepared in order that the specimen surface would be located in the near surface and interface regions of the concave and convex coatings. In SP tests, brittle cracks in the near surface and interface coatings of the concave blade initiated at low strains up to 950 °C. The convex coatings had higher ductility than the concave coatings and substrate and showed a rapid increase in the ductility above 800 °C. Thus it is apparent that the oxidation/carbonization and nitridation in the concave coatings produced a significant loss of the ductility. The in-service degradation mechanism of the CoCrAlY coatings is discussed in light of the operating temperature distribution and compared to that of CoNiCrAIY coatings induced by grain boundary sulfidation/oxidation.

Microstructure/Composition Evolution and Ductility Variation in Thermally Aged Aluminized CoCrAlY Coatings

1998 ◽  
Author(s):  
J. Kameda ◽  
T. E. Bloomer ◽  
Y. Sugita ◽  
A. Ito ◽  
S. Sakurai
Keyword(s):  
Elevated Temperatures ◽  
Low Cycle Fatigue ◽  
Turbine Blades ◽  
Surface Region ◽  
Thermal Ageing ◽  
Mechanical Degradation ◽  
Near Surface ◽  
Gas Turbine Blades ◽  
Al Content ◽  
Region I

The effect of thermal ageing at 870 °C for 8000 h in air on the microstructure/composition and mechanical properties (RT and 870 °C) has been studied in aluminized CoCrAlY coatings consisting of four layered structure (region I-IV) of advanced gas turbine blades. Thermal ageing led to a little oxidation/nitridation and a decrease in the Al content in a near surface region I. In a coating region II, coarse Cr rich σ precipitates formed during the thermal ageing. Thermally aged internal (III) and near interface (IV) coating regions showed extensive dispersion of σ and/or Al/Ni rich β/α eutectic precipitates. Small punch tests at RT and 870 °C in air have shown that the coating regions I and II of imaged and aged blades indicated easier formation of brittle cracks regardless of the composition change. The ductility of the regions III and IV at RT and 870 °C, and the low cycle fatigue life of the region III were reduced by the thermal ageing. The mechanical degradation at elevated temperatures in the aged coating regions III and IV is elucidated by taking into account the microstructure/composition evolution and environmental oxidizing effects.

Numerical Prediction of Film Cooling and Heat Transfer on the Leading Edge of a Rotating Blade in a 1-1/2 Turbine Stage

2004 ◽  
Author(s):  
Huitao Yang ◽  
Hamn-Ching Chen ◽  
Je-Chin Han ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Leading Edge ◽  
High Heat ◽  
Turbine Stage ◽  
Film Cooling Effectiveness ◽  
Rotating Blade ◽  
High Heat Transfer

In modern gas turbines, the blade leading edge region is one area that experiences high heat transfer due to the stagnation flow. Many cooling techniques have been applied to blades, so they can withstand these high heat loads; one of the common methods in cooling turbine blades is to apply film cooling. In the present study, numerical simulations were performed to predict the film cooling effectiveness and heat transfer coefficient on the leading edge of a rotating blade in a 1-1/2 turbine stage using a Reynolds stress turbulence model together with a non-equilibrium wall function. In addition, the unsteady characteristics of the film cooling and heat transfer at different time phases during a passing period were also investigated.

Analysis of Cracked Gas Turbine Blades

1992 ◽  
Vol 114 (2) ◽  
pp. 293-301 ◽  
Author(s):  
H. L. Bernstein ◽  
J. M. Allen
Keyword(s):  
Base Metal ◽  
Gas Turbines ◽  
Aluminide Coating ◽  
Turbine Blades ◽  
Leading Edge ◽  
Electric Utility ◽  
Gamma Prime ◽  
Platinum Aluminide ◽  
Cooling Hole ◽  
Number Of Cycles

Results from an analysis of cracked first-stage blades (or buckets) from two General Electric MS7001E industrial/electric utility gas turbines are presented. Numerous cracks were observed along the leading-edge and midchord regions of the pressure and suction surfaces. In one unit cracks were found after 874 start-stop cycles, which included 218 trips from load and 11,000 service hours. Buckets in the sister engine were examined after 1800 cycles, which included 218 trips from load and 24,000 service hours. In both cases, cracks initiated in the platinum aluminide coating and propagated into the IN-738LC base metal. For the 11,000-hour bucket, 20-mil (0.5-mm) deep cracks were observed, and for the 24,000-hour bucket, the leading edge cracks had grown to the leading edge cooling hole, a distance of 0.2 in. (5 mm). The number of cycles to crack initiation was in good agreement with thermal mechanical fatigue (TMF) predictions from the REMLIF computer program, which is part of the Electric Power Research Institute’s (EPRI) Life Management System. The cracking was greatly accelerated by the large number of trips experienced. The extensive crack propagation that occurred is thought to have been strongly assisted by oxygen and sulfur penetration along the grain boundaries. The coating on the leading edge degraded from the original platinum-aluminide plus beta phases to a gamma prime phase after 24,000 hours of service, but it was still protective except where it was cracked. Where the coating was cracked, environmental attack of the interdiffusion zone and base metal occurred, resulting in spallation of the coating and preferential grain boundary attack. Operating and maintenance considerations for optimizing bucket life in demanding cyclic duty environments are also discussed.

scholarly journals Analysis of Cracked Gas Turbine Blades

1991 ◽  
Author(s):  
Henry L. Bernstein ◽  
James M. Allen
Keyword(s):  
Base Metal ◽  
Gas Turbines ◽  
Aluminide Coating ◽  
Turbine Blades ◽  
Leading Edge ◽  
Electric Utility ◽  
Gamma Prime ◽  
Platinum Aluminide ◽  
Cooling Hole ◽  
Number Of Cycles

Results from an analysis of cracked first stage blades (or buckets) from two General Electric Frame 7001E industrial/electric utility gas turbines are presented. Numerous cracks were observed along the leading-edge and mid-chord regions of the pressure and suction surfaces. In one unit cracks were found after 874 start-stop cycles, which included 218 trips from load and 11,000 service hours. Buckets in the sister engine were examined after 1800 cycles, which included 218 trips from load and 24,000 service hours. In both cases, cracks initiated in the platinum aluminide coating and propagated into the IN-738LC base metal. For the 11,000-hour bucket, 20-mil (0.5-mm) deep cracks were observed, and for the 24,000-hour bucket, the leading edge cracks had grown to the leading edge cooling hole, a distance of 0.2 inches (5 mm). The number of cycles to crack initiation was in good agreement with thermal mechanical fatigue (TMF) predictions from the REMLIF computer program, which is part of the Electric Power Research Institute’s (EPRI) Life Management System. The cracking was greatly accelerated by the large number of trips experienced. The extensive crack propagation that occurred is thought to have been strongly assisted by oxygen and sulfur penetration along the grain boundaries. The coating on the leading edge degraded from the original platinum-aluminide plus beta phases to a gamma prime phase after 24,000 hours of service, but it was still protective except where it was cracked. Where the coating was cracked, environmental attack of the interdiffusion zone and base metal occurred, resulting in spallation of the coating and preferential grain boundary attack. Operating and maintenance considerations for optimizing bucket life in demanding cyclic duty environments are also discussed.

Degradation Mechanism Characterization and Remaining Life Prediction for NiCoCrAlY Coatings

2004 ◽  
Author(s):  
K. S. Chan ◽  
N. S. Cheruvu
Keyword(s):  
Gas Turbines ◽  
Cyclic Oxidation ◽  
Degradation Mechanism ◽  
Turbine Blades ◽  
Thermal Cycles ◽  
Combustion Gas ◽  
Thermal Fatigue Crack ◽  
Β Phase ◽  
Attack Type ◽  
Oxidation Behaviors

The cyclic oxidation behaviors of two NiCoCrAlY coatings, which are PWA 286 and CT102 (GT33-like), were characterized using one-hour thermal cycles between ambient temperature and a peak temperature at either 1010°C or 1066°C. Weight change curves were generated as a function of thermal cycles. During cyclic oxidation testing, selected test specimens were removed and sectioned to characterize the coating degradation processes, such as oxidation attack, type and morphology of oxides, Al depletion, β-phase exhaustion, microstructural changes, and thermal fatigue crack formation. These experimental data were utilized in conjunction with a coating lifing model, called COATLIFE, to develop coating life diagrams that depicts the useful life of the coatings as a function of cycle time. Application of the COATLIFE approach and the coating life diagrams to predicting the remaining lives of GT33-like and PWA 286 coatings are demonstrated for turbine blades in land-based combustion gas turbines.

Selection of a leading edge noise prediction method for PNoise

2018 ◽  
pp. 214-223
Author(s):  
AM Faria ◽  
MM Pimenta ◽  
JY Saab Jr. ◽  
S Rodriguez
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Prediction Method ◽  
Leading Edge ◽  
Wind Farms ◽  
Broadband Noise ◽  
Turbulence Energy ◽  
Noise Prediction ◽  
Migration Routes ◽  
Turbulent Inflow

Wind energy expansion is worldwide followed by various limitations, i.e. land availability, the NIMBY (not in my backyard) attitude, interference on birds migration routes and so on. This undeniable expansion is pushing wind farms near populated areas throughout the years, where noise regulation is more stringent. That demands solutions for the wind turbine (WT) industry, in order to produce quieter WT units. Focusing in the subject of airfoil noise prediction, it can help the assessment and design of quieter wind turbine blades. Considering the airfoil noise as a composition of many sound sources, and in light of the fact that the main noise production mechanisms are the airfoil self-noise and the turbulent inflow (TI) noise, this work is concentrated on the latter. TI noise is classified as an interaction noise, produced by the turbulent inflow, incident on the airfoil leading edge (LE). Theoretical and semi-empirical methods for the TI noise prediction are already available, based on Amiet’s broadband noise theory. Analysis of many TI noise prediction methods is provided by this work in the literature review, as well as the turbulence energy spectrum modeling. This is then followed by comparison of the most reliable TI noise methodologies, qualitatively and quantitatively, with the error estimation, compared to the Ffowcs Williams-Hawkings solution for computational aeroacoustics. Basis for integration of airfoil inflow noise prediction into a wind turbine noise prediction code is the final goal of this work.

Improving Efficiency in Robot Assisted Belt Grinding of High Performance Materials

2014 ◽  
Vol 907 ◽  
pp. 139-149 ◽  
Author(s):  
Eckart Uhlmann ◽  
Florian Heitmüller
Keyword(s):  
Gas Turbines ◽  
High Performance ◽  
Scale Effects ◽  
Turbine Blades ◽  
Repair Process ◽  
Industrial Robots ◽  
Robot Assisted ◽  
Belt Grinding ◽  
Economy Of Scale ◽  
The Individual

In gas turbines and turbo jet engines, high performance materials such as nickel-based alloys are widely used for blades and vanes. In the case of repair, finishing of complex turbine blades made of high performance materials is carried out predominantly manually. The repair process is therefore quite time consuming. And the costs of presently available repair strategies, especially for integrated parts, are high, due to the individual process planning and great amount of manually performed work steps. Moreover, there are severe risks of partial damage during manually conducted repair. All that leads to the fact that economy of scale effects remain widely unused for repair tasks, although the piece number of components to be repaired is increasing significantly. In the future, a persistent automation of the repair process chain should be achieved by developing adaptive robot assisted finishing strategies. The goal of this research is to use the automation potential for repair tasks by developing a technology that enables industrial robots to re-contour turbine blades via force controlled belt grinding.

scholarly journals A Novel Evaluation Method For Particle Deposition Measurement

Open Physics ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 927-934
Author(s):  
Tao Song ◽  
Chao Liu ◽  
Hengxuan Zhu ◽  
Min Zeng ◽  
Jin Wang
Keyword(s):  
Layer Thickness ◽  
Dielectric Layer ◽  
Gas Turbines ◽  
Particle Deposition ◽  
Optimization Design ◽  
Turbine Blades ◽  
Simulation Software ◽  
Circuit Board ◽  
Normal Operation ◽  
Mass Detection

Abstract Normal operation of gas turbines will be affected by deposition on turbine blades from particles mixed in fuels. This research shows that it is difficult to monitor the mass of the particles deposition on the wall surface in real time. With development of electronic technology, the antenna made of printed circuit board (PCB) has been widely used in many industrial fields. Microstrip antenna is first proposed for monitoring particles deposition to analyse the deposition law of the particles accumulated on the wall. The simulation software Computer Simulation Technology Microwave Studio (CST MWS) 2015 is used to conduct the optimization design of the PCB substrate antenna. It is found that the S11 of vivaldi antenna with arc gradient groove exhibits a monotonous increase with the increase of dielectric layer thickness, and this antenna is highly sensitive to the dielectric layer thickness. Moreover, a cold-state test is carried out by using atomized wax to simulate the deposition of pollutants. A relationship as a four number of times function is found between the capacitance and the deposited mass. These results provide an important reference for the mass detection of the particle deposition on the wall, and this method is suitable for other related engineering fields.

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