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Levine, S. R.

Publications and source records attributed to Levine, S. R..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Challenges and Opportunities in Design, Fabrication, and Testing of High Temperature Joints in Ceramics and Ceramic Composites

Ceramic joining has been recognized as an enabling technology for successful utilization of advanced ceramics and composite materials. A number of joint design and testing issues have been discussed for ceramic joints in silicon carbide-based ceramics and fiber-reinforced composites. These joints have been fabricated using an affordable, robust ceramic joining technology (ARCJoinT). The microstructure and good high temperature mechanical capability (compressive and flexural strengths) of ceramic joints in silicon carbide-based ceramics and composite materials are reported.

Singh, M.↗
NASA NTRS1998

Key Issues for Aerospace Applications of Ceramic Matrix Composites

Ceramic matrix composites (CMC) offer significant advantages for future aerospace applications including turbine engine and liquid rocket engine components, thermal protection systems, and "hot structures". Key characteristics which establish ceramic matrix composites as attractive and often enabling choices are strength retention at high temperatures and reduced weight relative to currently used metallics. However, due to the immaturity of this class of materials which is further compounded by the lack of experience with CMC's in the aerospace industry, there are significant challenges involved in the development and implementation of ceramic matrix composites into aerospace systems. Some of the more critical challenges are attachment and load transfer methodologies; manufacturing techniques, particularly scale up to large and thick section components; operational environment resistance; damage tolerance; durability; repair techniques; reproducibility; database availability; and the lack of validated design and analysis tools. The presentation will examine the technical issues confronting the application of ceramic matrix composites to aerospace systems and identify the key material systems having potential for substantial payoff relative to the primary requirements of light weight and reduced cost for future systems. Current programs and future research opportunities will be described in the presentation which will focus on materials and processes issues.

Clinton, R. G., Jr.↗
NASA NTRS1995

Low Cost Fabrication of Silicon Carbide Based Ceramics and Fiber Reinforced Composites

A low cost processing technique called reaction forming for the fabrication of near-net and complex shaped components of silicon carbide based ceramics and composites is presented. This process consists of the production of a microporous carbon preform and subsequent infiltration with liquid silicon or silicon-refractory metal alloys. The microporous preforms are made by the pyrolysis of a polymerized resin mixture with very good control of pore volume and pore size thereby yielding materials with tailorable microstructure and composition. Mechanical properties (elastic modulus, flexural strength, and fracture toughness) of reaction-formed silicon carbide ceramics are presented. This processing approach is suitable for various kinds of reinforcements such as whiskers, particulates, fibers (tows, weaves, and filaments), and 3-D architectures. This approach has also been used to fabricate continuous silicon carbide fiber reinforced ceramic composites (CFCC's) with silicon carbide based matrices. Strong and tough composites with tailorable matrix microstructure and composition have been obtained. Microstructure and thermomechanical properties of a silicon carbide (SCS-6) fiber reinforced reaction-formed silicon carbide matrix composites are discussed.

Singh, M.↗
NASA NTRS1992

Ceramic composites: Enabling aerospace materials

Ceramics and ceramic matrix composites (CMC) have the potential for significant impact on the performance of aerospace propulsion and power systems. In this paper, the potential benefits are discussed in broad qualitative terms and are illustrated by some specific application case studies. The key issues in need of resolution for the potential of ceramics to be realized are discussed.

Levine, S. R.↗
NASA NTRS1984

Surface protection

The surface protection subproject consists of three major thrusts: airfoil deposition model; metallic coating life prediction; and thermal barrier coating (TBC) life prediction. The time frame for each of these thrusts and the expected outputs are presented. Further details are given for each thrust such as specific element schedules and the status of performance; in-house, via grant, or via contract.

Levine, S. R.↗
NASA NTRS1984

Coating with overlay metallic-cermet alloy systems

A base layer of an oxide dispersed, metallic alloy (cermet) is arc plasma sprayed onto a substrate, such as a turbine blade, vane, or the like, which is subjected to high temperature use. A top layer of an oxidation, hot corrosion, erosion resistant alloy of nickel, cobalt, or iron is then arc plasma sprayed onto the base layer. A heat treatment is used to improve the bonding. The base layer serves as an inhibitor to interdiffusion between the protective top layer and the substrate. Otherwise, the 10 protective top layer would rapidly interact detrimentally with the substrate and degrade by spalling of the protective oxides formed on the outer surface at elevated temperatures.

Gedwill, M. A.↗
NASA NTRS1984

Overlay metallic-cermet alloy coating systems

A substrate, such as a turbine blade, vane, or the like, which is subjected to high temperature use is coated with a base coating of an oxide dispersed, metallic alloy (cermet). A top coating of an oxidation, hot corrosion, erosion resistant alloy of nickel, cobalt, or iron is then deposited on the base coating. A heat treatment is used to improve the bonding. The base coating serves as an inhibitor to interdiffusion between the protective top coating and the substrate. Otherwise, the protective top coating would rapidly interact detrimentally with the substrate and degrade by spalling of the protective oxides formed on the outer surface at elevated temperatures.

Gedwill, M. A.↗
NASA NTRS1984

Ceramic-coated metals can survive contact with hot working fluid

Thermal barrier coatings (TBCs) have been developed as a means of protecting turbine blades and other engine hot section components whose surfaces are exposed to the most extreme operating conditions. By adding a thin, insulating ceramic oxide layer to an air-cooled turbine blade, the difference between the gas temperature and the metal temperature is further increased as a function of ceramic coating thickness, heat flux, and oxide thermal conductivity. An 0.04-cm thick ceramic layer can typically yield a 100-300 C temperature drop. Of the various techniques available for the deposition of thermal barrier coatings, the most common is that of plasma spraying. Significant improvements have been made in TBC durability through the use of bond coat compositions with increased oxidation resistance.

Levine, S. R.↗
NASA NTRS1984

Deposition stress effects on thermal barrier coating burner rig life

A study of the effect of plasma spray processing parameters on the life of a two layer thermal barrier coating was conducted. The ceramic layer was plasma sprayed at plasma arc currents of 900 and 600 amps onto uncooled tubes, cooled tubes, and solid bars of Waspalloy in a lathe with 1 or 8 passes of the plasma gun. These processing changes affected the residual stress state of the coating. When the specimens were tested in a Mach 0.3 cyclic burner rig at 1130 deg C, a wide range of coating lives resulted. Processing factors which reduced the residual stress state in the coating, such as reduced plasma temperature and increased heat dissipation, significantly increased coating life.

Watson, J. W.↗
NASA NTRS1984

Deposition stress effects on the life of thermal barrier coatings on burner rigs

A study of the effect of plasma spray processing parameters on the life of a two layer thermal barrier coating was conducted. The ceramic layer was plasma sprayed at plasma arc currents of 900 and 600 amps onto uncooled tubes, cooled tubes, and solid bars of Waspalloy in a lathe with 1 or 8 passes of the plasma gun. These processing changes affected the residual stress state of the coating. When the specimens were tested in a Mach 0.3 cyclic burner rig at 1130 deg C, a wide range of coating lives resulted. Processing factors which reduced the residual stress state in the coating, such as reduced plasma temperature and increased heat dissipation, significantly increased coating life.

Watson, J. W.↗
NASA NTRS1984

Deposition stress effects on the life of thermal barrier coatings on burner rigs

A study of the effect of plasma spray processing parameters on the life of a two layer thermal barrier coating was conducted. The ceramic layer was plasma sprayed at plasma arc currents of 900 and 600 amps onto uncooled tubes, cooled tubes, and solid bars of Waspalloy in a lathe with 1 or 8 passes of the plasma gun. These processing changes affected the residual stress state of the coating. When the specimens were tested in a Mach 0.3 cyclic burner rig at 1130 deg C, a wide range of coating lives resulted. Processing factors which reduced the residual stress state in the coating, such as reduced plasma temperature and increased heat dissipation, significantly increased coating life.

Watson, J. W.↗
NASA NTRS1983

Improved performance thermal barrier coatings

Thermal barrier coatings offer an attractive approach to improving the durability and efficiency of the hot section of heat engines. The coatings typically consist of an inner alloy bond coating about 0.01 cm thick resistant to oxidation and hot corrosion and an outer ceramic layer, usually a stabilized zirconia, 0.01-0.05 cm thick. Here, the materials, thermomechanical stress, and hot corrosion problems associated with thermal barrier coatings are reviewed along with the capabilities and limitations of current technology. The coatings discussed include ZrO2-Y2O3/NiCrAlY, ZrO2-Y2O3/NiCoCrAlY, ZrO2-MgO/NiCoCrAlY, CaO-SiO2/Co-Cr-Al-Y, and CaO-SiO2/NiCrAlY systems. It is emphasized that the performance of thermal barrier coatings is governed by many complex and interrelated factors, so that optimization of these coatings always involves certain tradeoffs.

Levine, S. R.↗
NASA NTRS1982

Surface protection overview

A first-cut integrated environmental attack life prediction methodology for hot section components is addressed. The HOST program is concerned with oxidation and hot corrosion attack of metallic coatings as well as their degradation by interdiffusion with the substrate. The effects of the environment and coatings on creep/fatigue behavior are being addressed through a joint effort with the Fatigue sub-project. An initial effort will attempt to scope the problem of thermal barrier coating life prediction. Verification of models will be carried out through benchmark rig tests including a 4 atm. replaceable blade turbine and a 50 atm. pressurized burner rig.

Levine, S. R.↗
NASA NTRS1982

Further industrial tests of ceramic thermal barrier coatings

The NASA Lewis Research Center made technical assistance arrangements (contracts) with several commercial organizations under which Lewis designed plasma-sprayed thermal-barrier coatings (TBC) for their products. Lewis was then furnished with the test conditions and evaluations of coating usefulness. The coating systems were developed and sprayed at Lewis. All of the systems incorporated a two-layer, ceramic-bond coating concept. Coating thickness and chemical composition were varied to fit three applications: the leading edges of first-stage turbine vanes for an advanced gas turbine engine; the flame impingement surfaces of a combustor transition section; and diesel engine valves and head surfaces. The TBC incorporated yytria-stabilized zirconia, which lowered metal temperatures, protected metal parts, and increased metal part life. In some cases metal burning, melting, and warping were eliminated. Additional benefits were realized from these endeavors: hands-on experience with thermal-barrier coatings was provided to industry; the success of these endeavors encourages these and other organizations to accelerate the implementation of TBC technology.

Liebert, C. H.↗
NASA NTRS1982

Thermal-barrier coatings for utility gas turbines

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.

Levine, S. R.↗
NASA NTRS1981

A new diffusion-inhibited oxidation-resistant coating for superalloys

A concept for enhanced protection of superalloys consists of adding an oxidation- and diffusion-resistant cermet layer between the superalloy and the outer oxidation-resistant metallic alloy coating. Such a duplex coating was compared with a physical-vapor-deposited (PVD) NiCrAlY coating in cyclic oxidation at 1150 C. The substrate alloy was MA 754 - an oxide-dispersion-strengthened superalloy that is difficult to coat. The duplex coating, applied by plasma spraying, outperformed the PVD coating on the basis of weight change and both macroscopic and metallographic observations.

Gedwill, M. A.↗
NASA NTRS1981

Corrosion resistant thermal barrier coating

A thermal barrier coating system for protecting metal surfaces at high temperature in normally corrosive environments is described. The thermal barrier coating system includes a metal alloy bond coating, the alloy containing nickel, cobalt, iron, or a combination of these metals. The system further includes a corrosion resistant thermal barrier oxide coating containing at least one alkaline earth silicate. The preferred oxides are calcium silicate, barium silicate, magnesium silicate, or combinations of these silicates.

Levine, S. R.↗