Creep behavior of Nextel™610/monazite/alumina composite at elevated temperatures

The creep behavior of a N610/LaPO4/Al2O3 Composite was evaluated in this work. The composite consists of a porous alumina matrix reinforced with Nextel 610 fibers coated with monazite in a symmetric cross-ply (0 degrees/90 degrees/0 degrees/90 degrees)s orientation. The tensile stress-strain behavior was investigated and the tensile properties measured at room temperature and in the 900-1200 degrees C range. The addition of monazite coating resulted in similar to 50% improvement in ultimate tensile strength (UTS) at temperatures <= 1100 degrees C, and in 37% improvement in UTS at 1200 degrees C. Tensile creep behavior was examined at temperatures in the 900-1100 degrees C range for creep stresses ranging from 40 to 150 MPa. Primary and secondary creep regimes were observed in creep tests at 900 degrees C. At temperatures above 900 degrees C, the composite exhibited primary, secondary and tertiary creep. Minimum creep rate was reached in all tests. Creep rates accelerated with increasing temperature and creep stress. At 900 degrees C creep run-out, defined as 100 h at creep stress, was achieved for stress levels <= 120 MPa. The residual strength and modulus of all specimens that achieved run-out were characterized. Comparison with results obtained for N610/Al2O3 (control) specimens revealed that the use of the monazite coating resulted in improved creep resistance at 900 degrees C. Creep performance deteriorated rapidly as temperatures increased above 900 degrees C. Composite microstructure, as well as damage and failure mechanisms were investigated. (c) 2006 Elsevier Ltd. All rights reserved.