Showing papers on "Thermal barrier coating published in 1982"

Quench-cracked ceramic thermal barrier coatings

Abstract: Plasma flame sprayed ceramic thermal barrier coatings on metal substrates are treated to make the coatings resistant to damage from thermal cycling The coating and substrate are heated to a temperature in the range of 820°-1150° C then are quenched in a medium capable of producing a surface heat flux of at least 13×10 5 watts/m 2 This causes creation of a fine network of cracks extending from the surface of the coating to the surface of the substrate whereby during thermal cycling, buildup of damaging stresses at the coating-substrate interface is avoided

Ceramic Thermal Barrier Coatings for Turbine Engine Components

Abstract: The durability of plasma sprayed ceramic thermal barrier coatings subjected to cyclic thermal environments has been improved substantially by improving the strain tolerance of the ceramic structure and also by controlling the substrate temperature during the application of the coating. Improved strain tolerance was achieved by using ceramic structures with increased porosity, microcracking or segmentation. Plasma spraying on a controlled-temperature substrate also has been shown to improve durability by reducing harmful residual stresses. The most promising of the strain tolerant ceramic coatings have survived up to 6000 cycles of engine endurance testing with no coating or vane platform damage. In side-by-side engine tests, thermal barrier coatings have shown that they greatly reduce platform distress compared to conventionally coated vanes in addition to permitting reductions in cooling air and attendant increases in engine efficiency.© 1982 ASME

Recent Approaches to the Development of Corrosion Resistant Coatings

Abstract: Two types of protective coatings are applied on the Ni or Co-base superalloys used in the high temperature - parts of aircraft or industrial turbines.

Physical Vapor Deposition of Ceramic Coatings for Gas Turbine Engine Components

Abstract: The use of ceramic coatings on gas turbine engine hot section airfoils has the potential for major improvements in engine performance, durability, and fuel economy, for both industrial/utility and flight engine applications. Major improvements in the durability of ceramic thermal barrier coatings for turbine engine application have been made in both hot corrosion resistance and ceramic thermal cycle fatigue. This paper describes the early history, as well as, recent success in the development of mechanically segmented or “microcolumnar” structured coatings that are produced by electro-beam, physical vapor deposition (P. V.D.) of ceramic materials on metallic turbine airfoil components. Due to their columnar structure, these coatings accommodate the thermal cycle stresses that develop between the ceramic coating and the metal substrate due to their very different coefficients of thermal expansion. The hot corrosion, erosion, and thermal fatigue protection properties are also discussed.Copyright © 1982 by ASME

Composite window section assembly device - locks together aluminium section and thermal barrier section using travelling bevelled rollers

Abstract: The composite window section (1) consists of frame parts (2,3) fitted at a distance from each other. The two frame parts are made of aluminium and are kept apart by the plastics heat barrier (7). The two parts are placed next to each other on a supporting surface (11) and the box-shaped heat barrier section (7) is slid-in so that the raised edges (13) engage with the grooves formed by the protrusions (6) of the sections (4,5). The parts are clamped together by jaws (12) and in this condition a pair of bevel rollers (14), rotatingly seated on a ram (15) and vertically loaded by a pressure element (17), are made to travel along the protrusions (6) on the top part of the aluminium sections. The rollers (14) deform the protrusions (6) downwards producing a complete locking fit between the raised edges (13) and the protrusions (6).

Evaluation of present thermal barrier coatings for potential service in electric utility gas turbines

Abstract: The resistance of present-day thermal barrier coatings to combustion gases found in electric utility turbines was assessed. The plasma sprayed coatings, both duplex and graded types, were primarily zirconia-based, although a calcium silicate was also evaluated. Both atmospheric burner rig tests and high pressure tests (135 psig) showed that several present-day thermal barrier coatings have a high potential for service in gas turbines burning the relatively clean GT No. 2 fuel. However, coating improvements are needed for use in turbines burning lower grade fuel such as residual oil. The duplex ZrO2.8Y2O3/NiCrA1Y coating was ranked highest and selected for near-term field testing, with Ca2SiO4/NiCrA1Y ranked second. Graded coatings show potential for corrosive turbine operating conditions and warrant further development. The coating degradation mechanisms for each coating system subjected to the various environmental conditions are also described.

Strain tolerant thermal barrier coatings

Abstract: Methods are described for producing metallic substrates having strain tolerant ceramic coatings thereon. The metallic substrate is provided with an adherent dense ceramic coating. The ceramic coating is then partially melted and allowed to solidify. Cracks develop upon solidification which improve the strain tolerance of the ceramic, and render it resistant to spallation during thermal cycling.

Two-layer thermal-barrier systems for Ni-Al-Mo alloy and effects of alloy thermal expansion on system life

Abstract: Cyclic furnace and cyclic natural gas-oxygen torch rig tests were conducted to (1) identify a thermal-barrier system for a nickel-aluminum-molybdenum alloy, (2) study the oxidation of the bond coating, and (3) study the effect of the substrate coefficient of thermal expansion on thermal barrier system life. It is found that the latter is affected by the composition of the bond coating, yttria concentration in zirconia, and the coefficient of thermal expansion of the substrate material. In addition, small compositional changes in the bond and thermal barrier coatings have greater effect on thermal barrier system life than the 40% increase in the coefficient of thermal expansion of the substrate material. No simple relation exists between the weight gain caused by bond-coating oxidation with increasing yttria concentration in zirconia and increasing bond coating thickness on the one hand, and thermal barrier system life on the other.

Advanced ceramic coating development for industrial/utility gas turbines

Abstract: A program was conducted with the objective of developing advanced thermal barrier coating (TBC) systems. Coating application was by plasma spray. Duplex, triplex and graded coatings were tested. Coating systems incorporated both NiCrAly and CoCrAly bond coats. Four ceramic overlays were tested: ZrO2.82O3; CaO.TiO2; 2CaO.SiO2; and MgO.Al2O3. The best overall results were obtained with a CaO.TiO2 coating applied to a NiCrAly bond coat. This coating was less sensitive than the ZrO2.8Y2O3 coating to process variables and part geometry. Testing with fuels contaminated with compounds containing sulfur, phosphorus and alkali metals showed the zirconia coatings were destabilized. The calcium titanate coatings were not affected by these contaminants. However, when fuels were used containing 50 ppm of vanadium and 150 ppm of magnesium, heavy deposits were formed on the test specimens and combustor components that required frequent cleaning of the test rig. During the program Mars engine first-stage turbine blades were coated and installed for an engine cyclic endurance run with the zirconia, calcium titanate, and calcium silicate coatings. Heavy spalling developed with the calcium silicate system. The zirconia and calcium titanate systems survived the full test duration. It was concluded that these two TBC's showed potential for application in gas turbines.

Thermal barrier for thermally addressed liquid crystal devices

Abstract: A thermally addressed liquid crystal display device (10) is disclosed, (see Figure 1) which includes a liquid crystal medium (11) on a substrate (13) and at least one electrode (8 1 , 8 2 , 8 3 ) in thermal contact with the liquid crystal medium for thermally addressing the medium, and in which a thermal insulative barrier is provided between the electrode and substrate to reduce heat flow from the electrode to the substrate.

Creep of plasma sprayed zirconia

Abstract: Specimens of plasma-sprayed zirconia thermal barrier coatings with three different porosities and different initial particle sizes were deformed in compression at initial loads of 1000, 2000, and 3500 psi and temperatures of 1100 C, 1250 C, and 1400 C. The coatings were stabilized with lime, magnesia, and two different concentrations of yttria. Creep began as soon as the load was applied and continued at a constantly decreasing rate until the load was removed. Temperature and stabilization had a pronounced effect on creep rate. The creep rate for 20% Y2O3-80% ZrO2 was 1/3 to 1/2 that of 8% Y2O3-92% ZrO2. Both magnesia and calcia stabilized ZrO2 crept at a rate 5 to 10 times that of the 20% Y2O3 material. A near proportionality between creep rate and applied stress was observed. The rate controlling process appeared to be thermally activated, with an activation energy of approximately 100 cal/gm mole K. Creep deformation was due to cracking and particle sliding.

Thermal-barrier coatings for utility gas turbines

Abstract: The potential of thermal barrier coatings for use in utility gas turbines was assessed. Pressurized passage and ambient pressure doped fuel burner rig tests revealed that thermal barrier coatings are not resistant to dirty combustion environments. However, present thermal barrier coatings, such as duplex partially stabilized zirconia and duplex Ca2SiO4 have ample resistance to the thermo-mechanical stress and temperature levels anticipated for heavy duty gas turbines firing clean fuel as revealed by clean fuel pressurized passage and ambient pressure burner rig tests. Thus, it is appropriate to evaluate such coatings on blades, vanes and combustors in the field. However, such field tests should be backed up with adequate effort in the areas of coating application technology and design analysis so that the field tests yield unequivocal results.

Advanced ceramic-coating development for industrial/utility gas turbines. Final report

Abstract: A program was conducted with the objective of developing advanced thermal barrier coating (TBC) systems. Coating application was by plasma spray. Duplex, triplex and graded coatings were tested. Coating systems incorporated both NiCrAlY and CoCrAlY bond coats. Four ceramic overlays were tested: ZrO/sub 2/.8Y/sub 2/O/sub 3/; CaO.TiO/sub 2/; 2CaO.SiO/sub 2/; and MgO.Al/sub 2/O/sub 3/. The best overall results were obtained with a CaO.TiO/sub 2/ coating applied to a NiCrAlY bond coat. This coating was less sensitive than the ZrO/sub 2/.8Y/sub 2/O/sub 3/ coating to process variables and part geometry. Testing with fuels contaminated with compounds containing sulfur, phosphorus and alkali metals showed the zirconia coatings were destabilized. The calcium titanate coatings were not affected by these contaminants. However, when fuels were used containing 50 ppM of vanadium and 150 ppM of magnesium, heavy deposits were formed on the test specimens and combustor components that required frequent cleaning of the test rig. During the program Mars engine first-stage turbine blades were coated and installed for an engine cyclic endurance run with the zirconia, calcium titanate, and calcium silicate coatings. Heavy spalling developed with the calcium silicate system. The zirconia and calcium titantate systems survived the full test duration. It was concludedmore » that these two TBC's showed potential for application in gas turbines. Process variables and substrate composition were found to be critical and further work is required to relate them to coating performance.« less

Use of ICRH for startup and initial heating of the TMX-U central cell

Abstract: Ion cyclotron resonance heating (ICRH) was evaluated and it was found to be satisfactory for use in establishing the conditions necessary to form a thermal barrier in TMX-upgrade (TMX-U). We discuss the constraints that must be satisfied in order to maintain a plasma, and outline a complete startup scenario that ends with the plasma at design parameters. The detailed discussions in this report concentrate on those parts of startup where ICRH is necessary. The ability of ICRH to couple power into a plasma at the fundamental ion cyclotron resonance, w/sub ci/, is determined from experiments with a half-turn loop antenna in the Phaedrus tandem mirror central cell. From these experiments, we get the empirical scaling that shows power deposited in the plasma is proportional to the plasma density.

Heat-isolating coating composition

Abstract: A thermal barrier coating adapted to provide a thermally insulating protective barrier on a component, the coating being capable of being applied to the components by spraying methods and being ductile when exposed to high temperatures. The coating comprises a mixture containing constituents of finely divided hollow glass microspheres; a ceramic frit of finely divided particles of alkali silicate titanate glass; and a refractory filler material of finely divided partiles such as micronized mica; aluminum oxide of mullite. All of the constituents of the mixture are suspended in a high temperature resistant binder material such as potassium silicate, sodium silicate or aluminum orthophosphate.

Ceramic thermal-barrier coating by electron-beam physical vapor deposition: microstructural dependence on the temperature of formation. Final report, June 1-August 31, 1981

Abstract: It is shown that the temperature of formation of a ceramic thermal barrier coating (TBC) can be controlled in vacuo by internal substrate impingement cooling using both compressed air and water. It is further demonstrated that major changes in TBC columnar morphology can be achieved and controlled in this fashion. Implications for potential thermal cycle durability are discussed.

Improvements in or relating to thermally protected alloys

Abstract: Protective coatings for nickel- and cobalt-base superalloys are obtained by applying to the base metal a bond coating of an alloy of chromium, aluminum, yttrium and nickel or cobalt and applying thereover a thermal barrier coating based on ternary silicate compounds such as CaO &cirf& MgO &cirf& SiO2 and 3CaO &cirf& MgO &cirf& 2SiO2.

The Contribution of Thermal Barrier Coatings to Improvements in the Life and Performance of Gas Turbine Components

Abstract: Ceramic coatings have significantly increased the lives of components in high temperature environments by insulating metal substrates from a hot gas stream. Service applications are on combustors; ...

JT90 thermal barrier coated vanes

Abstract: The technology of plasma sprayed thermal barrier coatings applied to turbine vane platforms in modern high temperature commercial engines was advanced to the point of demonstrated feasibility for application to commercial aircraft engines. The three thermal barrier coatings refined under this program are zirconia stabilized with twenty-one percent magnesia (21% MSZ), six percent yttria (6% YSZ), and twenty percent yttria (20% YSZ). Improvement in thermal cyclic endurance by a factor of 40 times was demonstrated in rig tests. A cooling system evolved during the program which featured air impingement cooling for the vane platforms rather than film cooling. The impingement cooling system, in combination with the thermal barrier coatings, reduced platform cooling air requirements by 44% relative to the current film cooling system. Improved durability and reduced cooling air requirements were demonstrated in rig and engine endurance tests. Two engine tests were conducted, one of 1000 cycles and the other of 1500 cycles. All three coatings applied to vanes fabricated with the final cooling system configuration completed the final 1500 cycle engine endurance test. Results of this test clearly demonstrated the durability of the 6% YSZ coating which was in very good condition after the test. The 21% MSZ and 20% YSZ coatings had numerous occurrences of significant spalling in the test.

Turbine engine materials durability research

Abstract: High temperature environmental attack of dollar intensive turbine components reduces turbine efficiency and can limit life. The mechanisms of alloy and coating attack and the effects of interaction with the environment on mechanical behavior. This base of understanding provides the foundation for developing life prediction methods and identifying strategies for controlling attack. Subjects discussed in detail include oxidation and new developments in thermal barrier coating research.

Effects of arc current on the life in burner rig thermal cycling of plasma sprayed ZrOsub2-Ysub2Osub3

Abstract: An analysis of thermal cycle life data for four sets of eight thermal barrier coated specimens representing arc currents (plasma gun power) of 525, 600, 800, or 950 amps is presented. The ZrO2-8Y2O3/NiCrAlY plasma spray coated Rene 41 rods were thermal cycled to 1040 C in a Mach 0.3-Jet A/air burner flame. The experimental results indicate the existance of a minimum or threshold power level which coating life expectancy is less than 500 cycles. Above the threshold power level, coating life expectancy more than doubles and increases with arc current.

Ceramic to Metal Attachment Using Low Modulus BRUNSBOND® Pad

Abstract: BRUNSBOND® Pad is a low modulus sintered fiber metal material developed for attaching high temperature ceramic coatings to metal substrates. The fiber metal pad acts as a compliant strain absorbing interlayer to accomodate the differences in thermal expansivity and operating temperature between the ceramic and metal substrate. Ceramic coatings, 0.060 – 0.125 in. thick, remain intact on metal substrates through severe multiple cycle thermal excursions. The fiber metal pad is comparable in insulating value to the ceramic coating. Applications include ceramic thermal barrier coatings for high temperature gas turbine engine seals and combustors, MHD electrodes, and internal combustion engine insulators.

Blade Repair and Recovery

Abstract: The repair and recovery of both the stationary and the rotating parts of the hot section of a gas turbine are becoming more and more generally accepted practice.

Ceramic Thermal Barrier Coatings for Gas Turbine Engines

Abstract: The results of studies concerning the high temperature corrosion resistance of ZrO2-Y2O3, ZrO2-MgO, and Ca2SiO4 plasma-sprayed coatings, which may be used as gas turbine engine thermal barriers, are reported. The coatings were evaluated in atmospheric burner rig and pressurized passage tests, using GT No. 2 fuel in pure form and with sodium, sulfur and vanadium corrosive impurities doping. It is found that, while the coatings performed well in both pressurized passage and burner rig tests with pure fuel chemical reactions between the ceramic coatings and combustion gases/condensates resulted in coating degradation with impure fuels. Chemical reactions between the ceramic coatings and vanadium compounds played a critical role in coating degradation.

Effect of fuel to air ratio on Mach 0.3 burner rig hot corrosion of ZrO2-Y2O3 thermal barrier coatings

Abstract: A Mach 0.3 burner rig test program was conducted to determine how the fuel to air mass ratio affects the durability of ZrO2-Y2O3/Ni-16Cr-6Al-0.31Y thermal barrier coating systems in combustion products containing 5 ppm Na and 2 ppm V. As the fuel to air mass ratio was increased from 0.039 to 0.049, the durability of ZrO2-6Y2O3, ZrO2-8Y2O3 and ZrO2-12Y2O3 coatings decreased. ZrO2-8Y2O3 coatings were approximately 2X and 1.3X more durable than ZrO2-12Y2O3 and ZrO2-6Y2O3 coatings respectively at the fuel to air mass ratio of 0.039. The number of one hour cycles endured by ZrO2-8Y2O3 coatings varied from averages of 53 to 200 for the fuel to air mass ratios of 0.049 and 0.039, respectively. At the fuel to air mass ratio of 0.049, all ZrO2-Y2O3 coated specimens failed in 40 to 60 one hour cycles