M.B. Ruggles-Wrenn et al Composites: Part A 37(2006)2029-2040 1200C). The material retains M90% of its tensile 6 More KL, Tortorelli PF, Ferber MK, Walker LR, Keiser JR, strength. Stiffness loss is limited to 37% Brentnall WD, et al. Exposure of ceramic and cerami (3)Fatigue resistance at 1330C is poor, run-out was not composites in simulated and actual combustor environmen achieved Proceedings of international gas turbine and aerospace co 1999. Paper No. 99-GT-292 (4)Ratcheting is observed in all fatigue tests. Presence of [7] Ferber MK, Lin HT, Keiser JR. Oxidation behavior of non-oxide steam accelerates ratcheting at 1200 and 1330C ceramics in a high-pressure, high-temperature steam environment. In: Jenkins MG, Lara-Curzio E, Gonczy ST. editors. Mechanica thermal, and environmental testing and performance of ceramic 4.2. Creep-rupture behavior Testing and Materials: 2000.. 210-515392 American Society for [8] Haynes JA, Lance MJ, Cooley KM, Ferber MK, Lowden RA. Tensile creep behavior of the N720/A CMC was studied Stinton DP CVD mullite coatings in high-temperature, high-pressure for creep stresses ranging from 80 to 154 MPa at 1200C, -HO. J Am Ceram Soc 2000: 83(3): 657-9 and for creep stresses and100 MPa at1330°C. [9] Opila EJ. Hann Jr RE. Paralinear oxidation of Sic in water vapor. J Results suggest the following conclusions Am Ceram Soc1997;801):197-205 [10] Opila EJ. Oxidation kinetics of chemically vapor deposited silicon carbide in wet oxygen. J Am Ceram Soc 1994: 77(3): 730-6 (1) The creep curves produced at 1200 and 1330C in [] Opila eJ Variation of the oxidation rate of silicon carbide with water laboratory air and in steam environment exhibit very [12] Jacobson NS. Corrosion of silicon-based ceramics in combustion apor pressure. J Am Ceram Soc 1999: 82(3): 625-36 secondary creep. Secondary creep remains nearly lin- (13)Thomas-Ogbuji L. A pervasive model of oxidation degradation in a ear to failure. In all creep tests, the accumulated creep SiC-SiC composite. J Am Ceram Soc 1998: 81(11): 2777-84 strain significantly exceeds failure strain obtained in [14] More KL, Tortorelli PF, Lin HT, Lara-Curzio E, Lowden RA tension test Degradation mechanisms of BN interfaces in SiC/SiC composites in (2)Minimum creep rate was reached in all tests and water-contain rates ranged from 10 to 10s at 1200C cand 1998;98-99:382-95 from10-7to10-5s-at1330°C.At1200°C [15] Cofer CG, Economy J Oxidative and hydrolytic stability of boron nitride-a new approach to improving the oxidation resistance of environment, creep rates of the composite are close carbonaceous structures. Carbon 1989: 33(4): 389-95. to what may be expected from Nextel 720 fibers (6 Matsuda T. Stability to moisture for chemically vapor deposited and applied stress can be represented by a power law. [17] Morsch itride. J Mater Sci 1989 24: 2353-7 alone. The relationship between minimum creep rate GN, Bryant D, Tressler RE. Environmental durability of different BN interphases (for SiC/SiC) in H,O-containing atmo- Due to the contribution from the matrix. the stress spheres at intermediate tem exponent of the composite is higher than that 1997; 18(3):525-33 reported for the fibers alone. Presence of steam signif- [18] Thomas-Ogbuji L. Degradation SiC/BN/SiC composite in the burner icantly accelerates creep rates at both temperatures rig. Ceram Eng Sci Proc 1998: 19(4): 257-6 (3)Creep-rupture lives ranged from 0.3 h(154 MPa [19] Jacobson N, Farmer S, Moore A, Sayir H. High-temperature oxidation of boron nitride: I: ithic boron nitride. J Am Ceram test)to 255 h(80 MPa test) at 1200C, and from Socl99982(2):939-98 1.2 h(100 MPa test) to 87h (50 MPa test) at [20] Jacobson NS, Morscher GN, Bryant DR, Tressler RE. High- 1330C. Presence of steam dramatically reduces temperature oxidation of boron nitride: II. boron nitride layers in mposites. J Am Ceram Soc 1999 82(6): 1473-8 creep life. Reductions in creep life due to steam we /21] Hermes EE, Kerans RJ. Degradation of non-oxide rei 82-90%atl200°,and9698%at1330°C oxide matrix composites. Mater Res Soc, Symp P [22]Szweda A, Millard ML, Harrison MG. Fiber-reinforced cerar matrix composite member and method for making. US Pat. No 5 601 References [23] Sim SM, Kerans RJ Slurry infiltration and 3-D woven Ceram Eng Sci Proc 1992: 13(9-10): 632-41 [ Verrilli M, Opila EJ, Calomino A, Kiser JD. Efect of environment [24] Moore EH, Mah T, Keller KA. 3D composite fabricat Ition through on the stress-rupture behavior of a carbon-fiber-reinforced silico matrix slurry pressure infiltration. Ceram Eng Sci Proc arbide ceramic matrix composite. J Am Ceram Soc 2004 87(8) 1994:15(4):113-20 1536-42 [25] Lewis MH, Cain MG, Doleman P, Razzell AG, Gent J Development 22] Zawada LP, Staehler J, Steel S. Consequence of intermittent ex of interfaces in oxide and silicate matrix composites. In: Evans AG to moisture and salt fog on the high-temperature fatigue dura Naslain RG, editors. High-temperature ceramic-matrix composites several ceramic-matrix composites. J Am Ceram Soc 200 II: manufacturing and materials development. American Ceramic Society: 1995. p. 41-52. [3]Prewo KM, Batt JA. The oxidative stability of carbon fibre [26] Lange FF, Tu Wc, Evans AG. Processing of damage-tolerant, opposites. J Mater Sci 1988: 23: 523-7. oxidation-resistant ceramic matrix composites by a precursor 4 Mah T, Hecht NL. McCullum DE, Hoenigman JR, Kim HM, Katz infiltration and pyrolysis method. Mater Sci Eng A 1995: A195: AP, et al.. Thermal stability of Sic fibres (nicalon). J Mater Sci 98419:1191-201 [27]Underberg R, Eckerbom L. Design and processing of all-oxide More KL, Tortorelli PF, Ferber MK, Keiser JR. Observations of omposites. In: Evans AG, Naslain RG, editors. High-temperature accelerated silicon carbide recession by oxidation at high water-vapor ceramic-matrix composites Il: manufacturing and materials devel- pressures. J Am Ceram Soc 2000: 83(1): 211-3 opment. American Ceramic Society: 1995. p 95-1041200 C). The material retains 90% of its tensile strength. Stiffness loss is limited to 37%. (3) Fatigue resistance at 1330 C is poor, run-out was not achieved. (4) Ratcheting is observed in all fatigue tests. Presence of steam accelerates ratcheting at 1200 and 1330 C. 4.2. Creep-rupture behavior Tensile creep behavior of the N720/A CMC was studied for creep stresses ranging from 80 to 154 MPa at 1200 C, and for creep stresses of 50 and 100 MPa at 1330 C. Results suggest the following conclusions: (1) The creep curves produced at 1200 and 1330 C in laboratory air and in steam environment exhibit very short primary creep, which rapidly transitions into secondary creep. Secondary creep remains nearly lin￾ear to failure. In all creep tests, the accumulated creep strain significantly exceeds failure strain obtained in tension test. (2) Minimum creep rate was reached in all tests. Creep rates ranged from 108 to 105 s 1 at 1200 C, and from 107 to 105 s 1 at 1330 C. At 1200 C in air environment, creep rates of the composite are close to what may be expected from Nextel 720 fibers alone. The relationship between minimum creep rate and applied stress can be represented by a power law. Due to the contribution from the matrix, the stress exponent of the composite is higher than that reported for the fibers alone. Presence of steam signif￾icantly accelerates creep rates at both temperatures. (3) Creep-rupture lives ranged from 0.3 h (154 MPa test) to 255 h (80 MPa test) at 1200 C, and from 1.2 h (100 MPa test) to 87 h (50 MPa test) at 1330 C. Presence of steam dramatically reduces creep life. Reductions in creep life due to steam were 82–90% at 1200 C, and 96–98% at 1330 C. 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