Influence of Powder Manufacturing Process on TBC Lifetime

1995 ◽  
Author(s):  
Marc J. Froning ◽  
Purush Sahoo
Keyword(s):  
Manufacturing Process ◽  
Gas Turbines ◽  
Thermal Cycle ◽  
Thermodynamic Efficiency ◽  
Air Plasma ◽  
Before And After ◽  
Coating Characteristics ◽  
Lifetime Studies ◽  
Plasma Sprayed ◽  
Powder Manufacturing

Thermal barrier coatings (TBC) have been used extensively in aircraft engines to protect the gas turbines’ hot section from mechanical and enviromental degradation as well as to improve thermodynamic efficiency. Because TBC’s enhance operating temperature and service life, they are expected to play and increasingly important role in protecting both flight and land based industrial turbine engines. This investigation examines the functionality of air plasma sprayed two-layer TBC systems with a MCrAlY bond coat and a yttria partially stabilized zirconia (YSZ) top coat. Qualitative X-ray diffraction (XRD) analyses were conducted on several commercially produced YSZ powders and the coatings produced from the powders. Thermal cycle lifetime studies were carried out at 2040°F. Phase structures of the coatings were evaluated before and after testing. An attempt was then made to correlate those results to thermal cycle life. It was found that the powder manufacturing process appears to have an influence on coating characteristics and on thermal shock lifetime.

EFFECT OF OXYACETYLENE FLAME REMELTING ON WEAR BEHAVIOUR OF SUPERSONIC AIR-PLASMA SPRAYED NiCrBSi/h-BN COMPOSITE COATINGS

2016 ◽  
Vol 24 (06) ◽  
pp. 1750083 ◽  
Author(s):  
N. N. ZHANG ◽  
D. Y. LIN ◽  
B. HE ◽  
G. W. ZHANG ◽  
Y. ZHANG ◽  
...  
Keyword(s):  
Wear Resistance ◽  
Composite Coatings ◽  
Alloy Coating ◽  
Wear Behaviour ◽  
Air Plasma ◽  
X Ray ◽  
Wear And Corrosion ◽  
Before And After ◽  
Higher Temperature ◽  
Plasma Sprayed

NiCrBSi alloy coatings are widely used in wear and corrosion protection at higher temperature. As a primary hard phase forming element, B element can effectively improve the coating hardness. In this study, the low coefficient of friction of BN with three ratios (10%, 20%, and 30%) was added in order to reduce the wear rate and provide additional B element. The NiCrBSi/h-BN composite coatings were successfully prepared on a cast-iron substrate using supersonic air-plasma spray technology. The phase constitution, microstructure characterization, and microhardness of the coatings before and after oxyacetylene flame remelting were investigated by means of scanning electron microscope (SEM), X-ray diffraction, and energy dispersive analysis of X-ray techniques, respectively. The wear resistance of composite coatings was also tested in this paper. It was found that the microstructure was well refined by remelting treatment and this was beneficial for the adherence between the coating and the substrate, which was nearly 33[Formula: see text]MPa. The wear resistance of the NiCrBSi alloy coating was also improved with the increasing component of h-BN in remelted samples. When the h-BN content reached 30%, the friction coefficient decreased to 0.38 for the remelted coating. The effect of the remelting process on the anti-abrasive property and extension of the material’s wear life was quite important.

Microstructure and Oxidation Behavior of Molybdenum Disilicide Coating Prepared by Air Plasma Sprayed

2011 ◽  
Vol 686 ◽  
pp. 583-588 ◽  
Author(s):  
Jian Hui Yan ◽  
Si Wen Tang ◽  
Jian Guang Xu
Keyword(s):  
Plasma Spraying ◽  
Gas Turbines ◽  
Hexagonal Lattice ◽  
Molybdenum Disilicide ◽  
Temperature Structure ◽  
Air Plasma ◽  
Air Plasma Spraying ◽  
Plasma Sprayed ◽  
Molybdenum Disilicide Coating ◽  
Oxidation Behaviors

Intermetallics molybdenum dislicied has a great potential as a protective coating in aircraft engines and gas turbines in the elevated temperature. The suit for plasma spraying MoSi2powders were prepared by spray drying process and vacuum sintered. The oxidation behaviors of the coating were determined at 1200 °C. The coatings as sprayed and oxidized were characterized by XRD, SEM and EDS. Results show that the flow ability and loose density of MoSi2powder by sintered treatment, were 17.1 s/50g and 2.1g/cm3, respectively, ideal for air plasma spraying. During the course of spraying, some of molybdenum disilicide with a tetragonal lattice was converted into molybdenum disilicide with a hexagonal lattice. Also, part of MoSi2 phase oxidized and transformed to Mo5Si3phase. A relative dense molybdenum disilicide coating was prepared by air plasma spraying. A protective SiO2layer, seems to be glassy, with a thickness about 10 μm was formed on the surface of MoSi2coating during MoSi2coating oxidized at 1200°C for 200 h. The results of the oxidation tests show that MoSi2coating prepared by air plasma spraying may be provide a protect layer for high temperature structure material.

Investigation of Changes in Microstructure of Remelted Air Plasma Sprayed NiCrAlY Coating after Short Thermal Exposure in Air with the Assistance of Microhardness Measurements

2013 ◽  
Vol 586 ◽  
pp. 226-229
Author(s):  
Veronika Řičánková ◽  
Ladislav Čelko ◽  
Jiří Švejcar
Keyword(s):  
Substrate Surface ◽  
Thermal Exposure ◽  
Ambient Atmosphere ◽  
Air Plasma ◽  
X Ray Diffraction ◽  
Nickel Based Superalloy ◽  
Nicraly Coating ◽  
Before And After ◽  
Coating Microstructure ◽  
Plasma Sprayed

The specimens in the present study were prepared by air plasma spraying of NiCrAlY coatings onto the INCONEL 713LC nickel-based superalloy substrate surface. Subsequently an aluminium sheet was cladded onto the coating surface by means of uniaxial cold pressing. After that the specimens were annealed at temperatures of 650, 850 and 1000°C for two hours in argon-flow atmosphere. The remelted NiCrAlY coating specimens were annealed at a temperature of 800°C for fifty hours in ambient atmosphere. A scanning electron microscope was used to record the changes in the modified coating microstructure. Chemical composition was measured by means of energy dispersive microanalysis. Qualitative and quantitative x-ray diffraction analysis was used for the final determination of phases. The microhardness of remelted air-plasma-sprayed NiCrAlY coatings before and after short thermal exposure was also measured.

3404 Thermal Cycle Damage Behavior in the Air Plasma Sprayed Thermal Barrier Coatings

2006 ◽  
Vol 2006.1 (0) ◽  
pp. 519-520
Author(s):  
Yasuhiro YAMAZAKI ◽  
Taisuke ENDO ◽  
Hirotaka FUKANUMA ◽  
Naoyuki OHNO
Keyword(s):  
Thermal Barrier Coatings ◽  
Thermal Cycle ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Damage Behavior ◽  
Plasma Sprayed

MICROSTRUCTURAL EVOLUTION AND RESIDUAL STRESSES OF AIR-PLASMA SPRAYED THERMAL BARRIER COATINGS UNDER THERMAL EXPOSURE

2010 ◽  
Vol 17 (03) ◽  
pp. 337-343 ◽  
Author(s):  
JAE-YOUNG KWON ◽  
JAE-HYOUN KIM ◽  
SANG-YEOP LEE ◽  
YEON-GIL JUNG ◽  
HYUN CHO ◽  
...  
Keyword(s):  
Thermal Barrier Coatings ◽  
Microstructural Evolution ◽  
Thermal Exposure ◽  
Thermally Grown Oxide ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Before And After ◽  
Peak Areas ◽  
Plasma Sprayed

Microstructural evolution and fracture behavior of zirconia ( ZrO2 )-based thermal barrier coatings (TBCs) were investigated under thermal exposure. New ZrO 2 granule with 8 wt.% yttria ( Y2O3 ) with a deformed hollow morphology was developed through a spray drying process and employed to prepare TBCs. The thermal exposure tests were conducted at 1210°C with a dwell time of 100 h till 800 h. The residual stress at the interface between top coat and thermally grown oxide (TGO) layer was measured using a nanoindentation technique before and after thermal exposure. Vertical cracks on the top coat were newly formed and interlamellar cracks at the interface were enhanced after the thermal exposure of 800 h. Especially, partial delamination was observed at the interface after the thermal exposure of 800 h in TBC samples tested. The microstructural evolution in the top coat could be defined through load–displacement curves, showing a higher load or a less displacement after the thermal exposure of 800 h. The stress state was strongly dependent on the TGO geometry, resulting in the compressive stresses at the "valleys" or the "troughs," and the tensile stresses at the "crests" or peak areas, in the ranges of -500 to -75 MPa and of +168 to + 24 MPa, respectively. These stress terms incorporated with resintering during thermal exposure affected the mechanical properties such as hardness and elastic modulus of the top coat.

Comparative Study on Nano-Structural and Traditional Al2O3-13TiO2 Air Plasma Sprayed Coatings and their Thermal Shock Performance

2017 ◽  
Vol 739 ◽  
pp. 103-107 ◽  
Author(s):  
Sun Hui Yao ◽  
Yan Liang Su ◽  
Hung Yu Shu ◽  
Chia I Lee ◽  
Zong Ling You
Keyword(s):  
Comparative Study ◽  
Thermal Shock ◽  
Raw Materials ◽  
Thermal Shock Test ◽  
Air Plasma ◽  
Cyclic Heat Treatment ◽  
Shock Test ◽  
Before And After ◽  
Nanostructural Coating ◽  
Plasma Sprayed

This paper reports a comparative study on characterization and thermal shock behavior of air plasma sprayed Al2O3-13wt.%TiO2 coatings using two kinds of raw materials, i.e. nanostructural and micro-structural (traditional) feedstock powders. The characterization, before and after thermal shock test, was carried out using micro-Vickers hardness tester, XRD and SEM. The thermal shock test was carried out using a water quenching method by employing cyclic heat treatment between ambient temperature and 650°C in air. The results showed that in spite of having denser structure, the nanostructural coating showed hardness a little lower than the traditional one at both conditions of before and after thermal shock tests. However, the nanostructural coating showed very good thermal shock behaviour.

Simulated Land-Based Turbine Deposits Generated in an Accelerated Deposition Facility

2004 ◽  
Author(s):  
Jared W. Jensen ◽  
Sean W. Squire ◽  
Jeffrey P. Bons ◽  
Thomas H. Fletcher
Keyword(s):  
Mach Number ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Threshold Temperature ◽  
Chemical Compositions ◽  
Air Plasma ◽  
Impingement Angle ◽  
Concentration Test ◽  
Plasma Sprayed ◽  
Validation Tests

This report presents a validation of the design and operation of an accelerated testing facility for the study of foreign deposit layers typical to the operation of land-based gas turbines. This facility was designed to produce turbine deposits in a 4-hour test that would simulate 10,000 hours of turbine operation. This is accomplished by matching the net foreign particulate throughput of an actual gas turbine. Flow Mach number, temperature and particulate impingement angle are also matched. Validation tests were conducted to model the ingestion of foreign particulate typically found in the urban environment. The majority of this particulate is ceramic in nature and smaller than 10 microns in size, but varies up to 80 microns. Deposits were formed for flow Mach number and temperature of 0.4 and 1150degC respectively, using air plasma sprayed (APS) TBC material coupons donated from industry. Investigations over a range of impingement angles yielded samples with deposit thicknesses from 20 to 100 microns in 4-hour, accelerated-service simulations. Above a threshold temperature, deposit thickness was dependent on impingement angle and particle concentration. Test validation was achieved using direct comparison with deposits from service hardware. Deposit characteristics affecting blade heat transfer via convection and conduction were assessed. Surface topography analysis indicated that the surface structure of the generated deposits were similar to those found on actual turbine blades. Scanning electron microscope (SEM) and x-ray spectroscopy analyses indicated that the deposit microstructures and chemical compositions were comparable to turbine blade deposit samples obtained from industry.

scholarly journals The Effect of Coating Composition and Geometry on Thermal Barrier Coatings Lifetime

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Bruce A. Pint ◽  
Michael J. Lance ◽  
J. Allen Haynes
Keyword(s):  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Average Lifetime ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Bond Coatings ◽  
Bond Coating ◽  
Negative Effect ◽  
Plasma Sprayed

Several factors are being investigated that affect the performance of thermal barrier coatings (TBC) for use in land-based gas turbines where coatings are mainly thermally sprayed. This study examined high velocity oxygen fuel (HVOF), air plasma-sprayed (APS), and vacuum plasma-sprayed (VPS) MCrAlYHfSi bond coatings with APS YSZ top coatings at 900–1100 °C. For superalloy 247 substrates and VPS coatings tested in 1 h cycles at 1100 °C, removing 0.6 wt %Si had no effect on average lifetime in 1 h cycles at 1100 °C, but adding 0.3%Ti had a negative effect. Rod specimens were coated with APS, HVOF, and HVOF with an outer APS layer bond coating and tested in 100 h cycles in air + 10%H2O at 1100 °C. With an HVOF bond coating, initial results indicate that 12.5 mm diameter rod specimens have much shorter 100 h cycle lifetimes than disk specimens. Much longer lifetimes were obtained when the bond coating had an inner HVOF layer and outer APS layer.

Some Problems on Evaluating Elastic Modulus of APSed Ceramic Top Coat for TBCs by Indentation Method

2007 ◽  
Vol 353-358 ◽  
pp. 1802-1805
Author(s):  
Masakazu Okazaki ◽  
T. Ozaki
Keyword(s):  
Elastic Modulus ◽  
Size Effect ◽  
Gas Turbines ◽  
Air Plasma ◽  
Ceramic Powders ◽  
Barrier Coating ◽  
Pile Up ◽  
Indentation Methods ◽  
Plasma Sprayed ◽  
Significant Size

Elastic modulus of air plasma sprayed (APSed) YSZ (; ZrO2 stabilized by 8 wt. pct. Y2O3) top coat specimen, which is frequently used for thermal barrier coating (TBC) system for advanced gas turbines, was measured by employing the macro-, micro-, and nano-indentation methods. The elastic modulus was measured, following the Oliver-Pharr method. It was shown that the elastic modulus of the YSZ, as well as the microstructure, was significantly influenced by the spraying conditions employed. Especially the size of ceramic powders used was found to have the most pronounced effect. It was also shown that the elastic modulus revealed significant size effect: that is, there were significant differences in elastic modulus measured by the instruments on the macro-, micro-, and nano-levels. This size effect was discussed, correlating with some relating phenomena: crackings, sink-in, pile-up and spalling; as well as with the characteristic microstructures of the sprayed top coat.

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