MATERIALS HIENGE& ENGIEERING ELSEVIER Materials Science and Engineering A 454-455(2007)590-601 www.elsevier.com/locate/msea Compressive creep behavior of an oxide-oxide ceramic composite with monazite fiber coating at elevated temperatures P.R Jackson a M.B. Ruggles-Wrenn a, *. S.S. Baek D K.A. Keller C, Department of Aeronautics and Astronautics, Air Force Institute of Technology, Wright-Patterson Air Force Base, OH 45433-7765 USA UES, Inc, 4401 Dayton Xenia Road, Dayton, Oh, oath Korea Received 26 June 2006: received in revised form 13 November 2006: accepted 23 November 2006 The compressive creep behavior of a N610/LaPO/Al2O3 composite was investigated at 900 and 1100C. The composite consists of a poro alumina matrix reinforced with Nextel M610 fibers coated with monazite in a symmetric cross-ply (0/90 /0/90% ),orientation. The compressive tress-strain behavior was investigated and the compressive properties were measured. Compressive creep behavior was examined for creep stresses in the -50to-95 MParange. Minimum creep rate was reached in all tests At 900C, both monazite-containing and control(N61O/Al2O3)specimens produced creep strains<-0.05%. At 1100C, compressive creep strains approached-9%, and compressive creep strain rates, -10-7s-I Creep run-out defined as 100 h at creep stress, was achieved in all tests. Composite microstructure, damage and failure mechanisms, as well as effects of variation in microstructure on mechanical response were examined. Differences in processing and consequently in the composite microstructure had a significant effect on compressive response of the ceramic-matrix composite(CMC) o 2006 Elsevier B. v. All rights reserved Keywords: Ceramic-matrix composites( CMCs): Oxides; Fibres; Coatings; Creep: High-temperature properties; Mechanical properties; Fractography 1. Introduction the CMCs into aerospace turbine engine applications, such as ombustor walls [3-5]. Because these applications require expo- Advances in aerospace propulsion technologies have raised sure to oxidizing environments, the thermodynamic stability and the demand for structural materials that have superior long-term oxidation resistance of CMCs are vital issues. mechanical properties and retained properties under high tem- The main advantage of CMCs over monolithic ceramics perature, high pressure and varying environmental factors, such their superior toughness, tolerance to the presence of cracks as moisture [1]. Ceramic-matrix composites(CMCs), capable and defects, and non-catastrophic mode of failure. It is widely of maintaining excellent strength and fracture toughness at high accepted that in order to avoid brittle fracture behavior in CMCs temperatures are prime candidate materials for such aerospace and improve the damage tolerance, a weak fiber/matrix inter- applications. Additionally, the lower densities of CMCs and their face is needed, which serves to deflect matrix cracks and to higher use temperatures, together with a reduced need for cool- allow subsequent fiber pullout [6-9. Historically, following ing air, allow for improved high-temperature performance when the development of SiC fibers, fiber coatings such as C or BN compared to conventional nickel-based superalloys[2]. Con- have been employed to promote the desired composite behav current efforts in optimization of the CMCs and in design of the ior. However, the non-oxide fiber/non-oxide matrix composites combustion chamber are expected to accelerate the insertion of generally show poor oxidation resistance [10, 11], particularly at intermediate temperatures(800C). These systems are sus- ceptible to embrittlement due to oxygen entering through the The views expressed are those of the authors and do not reflect the official matrix cracks and then reacting with the interphase and the policy or position of the United States Air Force, Department of Defense or the U.S. Government fibers [12-15]. The degradation, which involves oxidation of Corresponding author. Tel: +1937 255 3636x4641: fax: +1 9376567621. fibers and fiber coatings, is typically accelerated by the pres- E-mail address: marina. ruggles-wrenn@ afit. edu(M B. Ruggles-w ence of moisture [16-22]. Using oxide fiber/non-oxide matrix I Under USAF Contract # F33615-01-C-5214 or non-oxide fiber/oxide matrix composites generally does not 0921-5093/S-see front matter 2006 Elsevier B v. All rights reserved doi:10.1016/1msea.2006.11.131Materials Science and Engineering A 454–455 (2007) 590–601 Compressive creep behavior of an oxide–oxide ceramic composite with monazite fiber coating at elevated temperatures P.R. Jackson a, M.B. Ruggles-Wrenn a,∗, S.S. Baek b, K.A. Keller c,1 a Department of Aeronautics and Astronautics, Air Force Institute of Technology, Wright-Patterson Air Force Base, OH 45433-7765, USA b Agency for Defense Development, Daejeon, South Korea c UES, Inc., 4401 Dayton Xenia Road, Dayton, OH 45433-7817, USA Received 26 June 2006; received in revised form 13 November 2006; accepted 23 November 2006 Abstract The compressive creep behavior of a N610/LaPO4/Al2O3 composite was investigated at 900 and 1100 ◦C. The composite consists of a porous alumina matrix reinforced with NextelTM610 fibers coated with monazite in a symmetric cross-ply (0◦/90◦/0◦/90◦)s orientation. The compressive stress–strain behavior was investigated and the compressive properties were measured. Compressive creep behavior was examined for creep stresses in the−50 to−95 MPa range. Minimum creep rate was reached in all tests. At 900 ◦C, both monazite-containing and control (N610/Al2O3) specimens produced creep strains ≤ −0.05%. At 1100 ◦C, compressive creep strains approached −9%, and compressive creep strain rates, −10−7 s−1. Creep run-out defined as 100 h at creep stress, was achieved in all tests. Composite microstructure, damage and failure mechanisms, as well as effects of variation in microstructure on mechanical response were examined. Differences in processing and consequently in the composite microstructure had a significant effect on compressive response of the ceramic–matrix composite (CMC). © 2006 Elsevier B.V. All rights reserved. Keywords: Ceramic–matrix composites (CMCs); Oxides; Fibres; Coatings; Creep; High-temperature properties; Mechanical properties; Fractography 1. Introduction Advances in aerospace propulsion technologies have raised the demand for structural materials that have superior long-term mechanical properties and retained properties under high tem￾perature, high pressure and varying environmental factors, such as moisture [1]. Ceramic–matrix composites (CMCs), capable of maintaining excellent strength and fracture toughness at high temperatures are prime candidate materials for such aerospace applications. Additionally, the lower densities of CMCs and their higher use temperatures, together with a reduced need for cool￾ing air, allow for improved high-temperature performance when compared to conventional nickel-based superalloys [2]. Con￾current efforts in optimization of the CMCs and in design of the combustion chamber are expected to accelerate the insertion of The views expressed are those of the authors and do not reflect the official policy or position of the United States Air Force, Department of Defense or the U.S. Government. ∗ Corresponding author. Tel.: +1 937 255 3636x4641; fax: +1 937 656 7621. E-mail address: marina.ruggles-wrenn@afit.edu (M.B. Ruggles-Wrenn). 1 Under USAF Contract # F33615-01-C-5214. the CMCs into aerospace turbine engine applications, such as combustor walls[3–5]. Because these applications require expo￾sure to oxidizing environments, the thermodynamic stability and oxidation resistance of CMCs are vital issues. The main advantage of CMCs over monolithic ceramics is their superior toughness, tolerance to the presence of cracks and defects, and non-catastrophic mode of failure. It is widely accepted that in order to avoid brittle fracture behavior in CMCs and improve the damage tolerance, a weak fiber/matrix inter￾face is needed, which serves to deflect matrix cracks and to allow subsequent fiber pullout [6–9]. Historically, following the development of SiC fibers, fiber coatings such as C or BN have been employed to promote the desired composite behav￾ior. However, the non-oxide fiber/non-oxide matrix composites generally show poor oxidation resistance [10,11], particularly at intermediate temperatures (∼800 ◦C). These systems are sus￾ceptible to embrittlement due to oxygen entering through the matrix cracks and then reacting with the interphase and the fibers [12–15]. The degradation, which involves oxidation of fibers and fiber coatings, is typically accelerated by the pres￾ence of moisture [16–22]. Using oxide fiber/non-oxide matrix or non-oxide fiber/oxide matrix composites generally does not 0921-5093/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2006.11.131