COMPOSITES SCIENCE AND TECHNOLOGY ELSEVIER Composites Science and Technology 59(1999)861-872 The application of ceramic-matrix composites to the automotive ceramic gas turbine Hiroshi Kaya' Petroleum Energy Center, Technology Research and Development, 3.9 Toranom 4-Chome, Mintao-ku, Tokyo 105, Japan Received 7 August 1997: received in revised form 24 August 1998: accepted 8 January 1999 Abstract A Japanese 100 kW automotive ceramic gas turbine(CGT) project was started in 1990 and was concluded successfully in 1997. This project was supported by the Ministry of International Trade and Industry and was conducted by the Petroleum Energy Center to achieve the targets of this project such as higher thermal efficiency over 40% at a turbine inlet temperature of 1350.C, lower exhaust emissions to meet Japanese regulations, and multi-fuel capabilities. Ceramic-matrix composites(CMCs)are expected to become one of the most reliable materials for high-temperature use to make up for the deficient properties of monolithic ceramics and heat-resistant alloys. Carbon fiber, silicon nitride fiber, silicon carbide fiber, silicon carbide whisker, in situ silicon nitride, TiB, milled carbon fiber were used as reinforcements for silicon carbide, Si-N-C, SiAION and silicon nitride matrix composites. Higher mechanical properties tested by the developed testing standards, and reliability against thermal shock, particle impact damage and creep resistance were con- firmed to apply these CMCs for engine components. Several screening test steps were performed before the engine tests and these con- firmed that CMC had strong potential for actual engine components. 1999 Elsevier Science Ltd. All rights reserved Keywords: A Ceramic-matrix composites(CMs): Ceramic gas turbine; Ceramic component; Long-fiber reinforced CMC; Short-fiber-reinforced CMC 1. Preface fields such as gas turbines operating under severe condi tions where CMC is considered to work effectively A Japanese 100 kW automotive ceramic gas turbine CMCs were also developed in the seven-year project (CGT)project was started in 1990 and was concluded and the applications of CMC for various components uccessfully in 1997. This project was supported by the have progressed positively in consideration of the lim Ministry of International Trade and Industry and was itations of the monolithic. This report deals with the conducted by the Petroleum Energy Center to achieve technologies for manufacturing components from a heat the targets such as higher thermal efficiency of 40%, resistant composite material for CGt taking into con sideration that the turbine inlet temperature (TIT)is 1350C, and deals with the superiority of the heat-resis- nese regulations, and multi-fuel capabilities [1, 2]. tant co mposite material for CGT, studied in the latte Finally, an output power of 92.3 kw, a thermal effi- stage of the project ciency of 35.6% were achieved [3-5I Ceramic-matrix composites(CMCs)produced by sev- eral kinds of reinforcements such as in fibers, particles and 2. Objectives whiskers with ceramics are known mainly in aerospace industries in Europe and the USA as high fracture resis- The thermal stress to be generated and life prediction tant materials capable of overcoming a fatal defect, speci- were estimated for every component whereby the target fically, brittleness of monolithic ceramic materials(here value for development of the mechanical characteristics after simply called"'monolithics'[6-11]. However, there is of a material, which were required for each CGT com- no precedent for the application of CMC in unknown ponent, was determined. With respect to, for example, a turbine rotor for which the highest strength at high tem- Tel:+8l-3-5402-8506;fax:+8l 8513: e-mail: shingen@ peratures is required, the target value for the monolithic was determined so that the failure probability after 10 0266-3538/99/.see front matter o 1999 Elsevier Science Ltd. All rights reserved. PlI:S0266-3538(99)00016
The application of ceramic-matrix composites to the automotive ceramic gas turbine Hiroshi Kaya1 Petroleum Energy Center, Technology Research and Development, 3-9 Toranom 4-Chome, Mintao-ku, Tokyo 105, Japan Received 7 August 1997; received in revised form 24 August 1998; accepted 8 January 1999 Abstract A Japanese 100 kW automotive ceramic gas turbine (CGT) project was started in 1990 and was concluded successfully in 1997. This project was supported by the Ministry of International Trade and Industry and was conducted by the Petroleum Energy Center to achieve the targets of this project such as higher thermal eciency over 40% at a turbine inlet temperature of 1350C, lower exhaust emissions to meet Japanese regulations, and multi-fuel capabilities. Ceramic-matrix composites (CMCs) are expected to become one of the most reliable materials for high-temperature use to make up for the de®cient properties of monolithic ceramics and heat-resistant alloys. Carbon ®ber, silicon nitride ®ber, silicon carbide ®ber, silicon carbide whisker, in situ silicon nitride, TiB2/milled carbon ®ber were used as reinforcements for silicon carbide, SiÿNÿC, SiAlON and silicon nitride matrix composites. Higher mechanical properties tested by the developed testing standards, and reliability against thermal shock, particle impact damage and creep resistance were con- ®rmed to apply these CMCs for engine components. Several screening test steps were performed before the engine tests and these con- ®rmed that CMC had strong potential for actual engine components. # 1999 Elsevier Science Ltd. All rights reserved. Keywords: A. Ceramic-matrix composites (CMCs); Ceramic gas turbine; Ceramic component; Long-®ber reinforced CMC; Short-®ber-reinforced CMC 1. Preface A Japanese 100 kW automotive ceramic gas turbine (CGT) project was started in 1990 and was concluded successfully in 1997. This project was supported by the Ministry of International Trade and Industry and was conducted by the Petroleum Energy Center to achieve the targets such as higher thermal eciency of 40%, output power of 100 kW at a turbine inlet temperature of 1350C and lower exhaust emissions to meet Japanese regulations, and multi-fuel capabilities [1,2]. Finally, an output power of 92.3 kW, a thermal e- ciency of 35.6% were achieved [3±5]. Ceramic-matrix composites (CMCs) produced by several kinds of reinforcements such as in ®bers, particles and whiskers with ceramics are known mainly in aerospace industries in Europe and the USA as high fracture resistant materials capable of overcoming a fatal defect, speci- ®cally, `brittleness' of monolithic ceramic materials (here after simply called `monolithics' [6±11]. However, there is no precedent for the application of CMC in unknown ®elds such as gas turbines operating under severe conditions where CMC is considered to work eectively. CMCs were also developed in the seven-year project and the applications of CMC for various components have progressed positively in consideration of the limitations of the monolithic. This report deals with the technologies for manufacturing components from a heatresistant composite material for CGT taking into consideration that the turbine inlet temperature (TIT) is 1350C, and deals with the superiority of the heat-resistant composite material for CGT, studied in the latter stage of the project. 2. Objectives The thermal stress to be generated and life prediction were estimated for every component whereby the target value for development of the mechanical characteristics of a material, which were required for each CGT component, was determined. With respect to, for example, a turbine rotor for which the highest strength at high temperatures is required, the target value for the monolithic was determined so that the failure probability after 10 Composites Science and Technology 59 (1999) 861±872 0266-3538/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S0266-3538(99)00016-0 1 Tel: +81-3-5402-8506; fax: +81-3-5402-8513; e-mail: shinnen@ plaza.pecj.or.jp
H. Kaya/Composites Science and Technology 59(1999)861-872 years of operation over 100,000 km, including 10,000 The number of the developing CMC components was starts and stops, specifically, and the failure probability finally limited to five, including a turbine rotor as a after a continuous running test for 300 h under the rated rotational component of high-strength material, a back conditions of 1350 C and 110, 000 rpm(design rotation plate as a stationary component of high-strength mate as reduced to 100,000 rpm afterwards) was 1x10-5 or rial, an orifice liner and an extension liner as stationary less. The target values for CMCs were then determined combustor components of high-temperature and oxida- according to the above designed target values for the tion- resistant material, and an inner scroll support as a monolithic. In addition to such mechanical character- stationary component of high-toughness material. The istic tests, various evaluation tests were performed, since major components(models) which have been developed CMC was expected to exhibit superiority against the at the present time are shown in Fig. 1. The approx thermal shock and particle impact dar mages ex pected imate sizes of the components are shown in Fig. 2. The under actual engine conditions characteristics of a material to be developed must first Extension Liner (Chopped Sic Fiber Reinforced SiNC) Out Inner Scroll Combustion Liner i In-Situ Si3N4 Reinforced Si3N4) (Carbon Fiber Reinforced Sic) Orifice Lin (Milled Carbon Fiber and TiB2 Powder Reinforced Sic) Turbine Rotor (SiC Whisker Reinforced SIAION) (SIC Fiber Reinforced SiNC)(n-Situ SiaNa Reinforced Si3N4) Inner Scroll Support (Carbon Fiber Reinforced Sic) SiN Fiber Reinforced SiNC) Turbine Rotor (Carbon Fiber Reinforced SiC) Back Plate Inner Shroud (SiC Whisker Reinforced SiAJON) Carbon Fiber Reinforced Sic) (In-Situ SiaNa Reinforced Si3N4) Fig 1. Major CMC components(models) for CGT. Orifice Liner Extension Liner Back Plate 21 中177 Turbine Rotor nner Scroll Support ts for cgt
years of operation over 100,000 km, including 10,000 starts and stops, speci®cally, and the failure probability after a continuous running test for 300 h under the rated conditions of 1350C and 110,000 rpm (design rotation was reduced to 100,000 rpm afterwards) was 110ÿ5 or less. The target values for CMCs were then determined according to the above designed target values for the monolithic. In addition to such mechanical characteristic tests, various evaluation tests were performed, since CMC was expected to exhibit superiority against the thermal shock and particle impact damages expected under actual engine conditions. The number of the developing CMC components was ®nally limited to ®ve, including a turbine rotor as a rotational component of high-strength material, a back plate as a stationary component of high-strength material, an ori®ce liner and an extension liner as stationary combustor components of high-temperature and oxidation-resistant material, and an inner scroll support as a stationary component of high-toughness material. The major components (models) which have been developed at the present time are shown in Fig. 1. The approximate sizes of the components are shown in Fig. 2. The characteristics of a material to be developed must ®rst Fig. 1. Major CMC components (models) for CGT. Fig. 2. Brief shapes of the developed main CMC components for CGT. 862 H. Kaya / Composites Science and Technology 59 (1999) 861±872
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Table 1 Evaluation methods of CMCs developed for CGT Classi®cation Developed components Material systems (reinforcement/matrix/CVD) Evaluation items Components Specimens Rotational component High strength material Turbine rotor LRC: C(f)/SiC SRC: SiC(w)/Si-Al-O-N : Si N3 4(is)/Si N3 4 Cold spin test : disk (LRC, SRC) : hub model (LRC)b Hot spin test : rotor (SRC)a Mechanical properties : ¯exural stength (1200C) : fracture toughness : oxidation resistance (1200C200 h) Superiorities Stationary component Back plate SRC: SiC(w)/Si-Al-O-N : Si N3 4(is)/Si N3 4 High temperature stationary component assembly test : 1350C (TIT), 5atmabs : FOD test, : TSFTd *: Only components were evaluated for LRC High temperature oxidation resistant material Ori®ce liner Extension liner SRC: TiB2(p).C(f)/SiC/SiC LRC: Si-C(f)/Si-C/SiC LRC: Si-C(f)/Si-N-C/SiC : screening test for CGT engine Engine combustion enviroment test : 1350C (TIT), 4atmabs : screening test for high temperature stationary component assembly test Mechanical properties : ¯exural strength (1450C) : fracture toughness (SRC) : fracture energy (LRC) : oxidation resistance (1450C200 h) Superiorities : FOD test, : TSFT : engine combustion environment test (1350C) High toughness material Inner scroll support LRC: Si-N(f), Si-C(f)/Si-N-C /SiC : C(f)/Si-C/SiC Hydrostatic pressure loading test : 120% of the expected thermal stress : screening test for high temperature stationary component assembly test Mechanical properties : ¯exural strength (1250C) : fracture energy : oxidation resistance (1250C200 h) Superiorities : FOD test, : TSFT a SRC: short ®ber reinforced CMC. b LRC: long ®ber reinforced CMC. c f: ®ber, w: whisker, p: powder, is: in situ, -: nonstoichometric. d TSFT: thermal shock fracture test. H. Kaya / Composites Science and Technology 59 (1999) 861±872 863
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Table 2 Development results of CMCs for CGT Developed components Material systems (reinforcement/matrix/CVD)h Developmental results : components Developmental targets and results : specimens (mechanical properties) Flexural strength (MPa) Fracture toughness (MPa-m1/2) Fracture energy (kj/m2 ) Oxidation resistance (MPa) High strength material (targets) Cold spin test (rpm) Hot spin test 750 (1200C) 8 (SEPB or SEVNB) ± 750 (1200C200h) Turbine rotor LRCb: C(f)/SiC 93700 (Disk: Max) 98600 (Hub: Max) Only components were evaluated SRCa: SiC(w)/Si-Al-O-N Weibull modulus m=23 (Disk) 910 8 (SEVNB)g ± 1000 SRC: Si N3 4(is)/Si N3 4 80100 (Disk: Av) Rotor: 1200C, 70000 rpm 960 7 (SEVNB) ± 890 High strength material (targets) HSATc (1350C, 5atmabs) 750 (1200C) 8 (SEPB or SEVNB) ± 750 (1200C200h) Back plate SRC: SiC(w)/Si-Al-O-N Achieved: 26 h 8 (SEVNB) ± 1000 SRC: Si N3 4(is)/Si N3 4 Achieved: 31 h 7 (SEVNB) ± 890 High temperature oxidation resistant material (targets) HSAT (1350C, 5atmabs) ECETd (1350C, 4atmabs) 400 (1450C) 7(SEPB or SEVNB) 4 400 (1450C200h) Ori®ce liner SRC: TiB2(p)/(f)/SiC/SiC Durable up to 1600C 540 7 (SEPB)f ± 420 LRC: Si-C(f)/Si-C/SiC ± Achieved: 31 h 230 ± 19 170 Extension liner LRC: Si-C(f)/Si-N-C/SiC ± Achieved: 31 h 420 ± 8 360 High toughness material (targets) HPLTe [120% of the expected thermal stress (ETS)] 500 (1250C) ± 10 500 (1250C200h) Inner scroll support LRC: Si-N(f), Si-C(f)/Si-N-C/SiC High oxidation resistant type Achieved: 156%(180 MPa) of the ETS 520 410 ± ± 19 6 310 460 SRC: C(f)/SiC/SiC Achieved: 2000% (20 MPa) of the ETS 390 ± 8 100 a SRC: short ®ber reinforced CMC. b LRC: long ®ber reinforced CMC. c HSAT: high temperature stationary component assembly test. d ECET: engine combustion environment test. e HPLT: hydrostatic pressure loading test. f SEPB: single edge precracked beam. g SEVNB: single edge V-notched beam. h f: ®ber, w: whisker, p: powder, is: in-situ, -: nonstoichiometric. 864 H. Kaya / Composites Science and Technology 59 (1999) 861±872
H. Kaya/Composites Science and Technology 59(1999)861-872 be evaluated at a test piece size. Next, the developed Long fiber reinforced CMCs such as silicon-carbide- component is evaluated prior to the actual engine test fiber-reinforced Si-N-C composite for the extension by the tests equivalent to the engine test or a screening liner and silicon-nitride-fiber-reinforced Si-N-Ccom test [12]. Five engine components manufactured, using8 posite for the inner scroll support attained the target kinds of CMCs shown in Table 1, were evaluated values for the flexural strength at high temperatures according to each development situation. and fracture energy, but their oxidation resistances were lower than the target value. It is important that the properties of reinforcements reflect the properties 3. Results of long-fiber-reinforced CMC. The control of the shear strength at the interface between the fiber and 3. 1. Characteristics of CMC a matrix, specifically, how to pull out the reinforcing fiber from the matrix under load is a key point [13] Table 2 shows the target values of the CMCs under Also, it is important to pull out the fiber without elopment and he resulting mechanical properties damage to the interface in a high temperature and Short-fiber-reinforced and /or powder-reinforced CMCs oxidation environment, for improving the oxidation uch as silicon-carbide-whisker reinforced silicon-carbide resistance. A continuous Si-B-c type self-healing composite for the turbine rotor and the back plate and CVD coating technology as shown in Fig 3 has been TiB,/milled-carbon-fiber-reinforced silicon-carbide cor developed for silicon-nitride- fiber-reinforced Si-N-C posite for the orifice finer satisfied all target values. These type CMC and has attracted attention as a technol- CMCs attracted considerable attention as a material in ogy for improving the oxidation resistance at high which toughness and strength are compatible temperatures [14] Reactants Fiber Cleaning Furnace CVD Furnace Coated Fiber Fig 3. Continuous CVD coating method on ceramic fiber(Reactants SiCl4 BCl3. CH4. NH, N2 H2, Reaction conditions temp. <1500C, Press <I atm) c≈o 2。S Fig 4. Thermal shock fracture test result of CMCs
be evaluated at a test piece size. Next, the developed component is evaluated prior to the actual engine test by the tests equivalent to the engine test or a screening test [12]. Five engine components manufactured, using 8 kinds of CMCs shown in Table 1, were evaluated according to each development situation. 3. Results 3.1. Characteristics of CMC Table 2 shows the target values of the CMCs under development and the resulting mechanical properties. Short-®ber-reinforced and/or powder-reinforced CMCs such as silicon-carbide-whisker reinforced silicon-carbide composite for the turbine rotor and the back plate and TiB2/milled-carbon-®ber-reinforced silicon-carbide composite for the ori®ce ®ner satis®ed all target values. These CMCs attracted considerable attention as a material in which toughness and strength are compatible. Long ®ber reinforced CMCs such as silicon-carbide- ®ber-reinforced SiÿNÿC composite for the extension liner and silicon-nitride-®ber-reinforced SiÿNÿC composite for the inner scroll support attained the target values for the ¯exural strength at high temperatures and fracture energy, but their oxidation resistances were lower than the target value. It is important that the properties of reinforcements re¯ect the properties of long-®ber-reinforced CMC. The control of the shear strength at the, interface between the ®ber and a matrix, speci®cally, how to pull out the reinforcing ®ber from the matrix under load is a key point [13]. Also, it is important to pull out the ®ber without damage to the interface in a high temperature and oxidation environment, for improving the oxidation resistance. A continuous SiÿBÿC type self-healing CVD coating technology as shown in Fig. 3 has been developed for silicon-nitride-®ber-reinforced SiÿNÿC type CMC and has attracted attention as a technology for improving the oxidation resistance at high temperatures [14]. Fig. 4. Thermal shock fracture test result of CMCs. Fig. 3. Continuous CVD coating method on ceramic ®ber (Reactants:SiCl4,BCl3,CH4,NH3,N2,H2, Reaction conditions:temp.<1500C,Press.<1 atm). H. Kaya / Composites Science and Technology 59 (1999) 861±872 865