Creep behavior of NextelTM610/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°/90°/0°/90°)S orientation. The tensile stress–strain behavior was investigated and the tensile properties measured at room temperature and in the 900–1200°C range. The addition of monazite coating resulted in ∼50% improvement in ultimate tensile strength (UTS) at temperatures ⩽1100 °C, and in 37% improvement in UTS at 1200 °C. Tensile creep behavior was examined at temperatures in the 900–1100 °C range for creep stresses ranging from 40 to 150 MPa. Primary and secondary creep regimes were observed in creep tests at 900 °C. At temperatures above 900 °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 °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 °C. Creep performance deteriorated rapidly as temperatures increased above 900 °C. Composite microstructure, as well as damage and failure mechanisms were investigated.