Processing, microstructure, and wear behavior of silicon nitride hot-pressed with alumina and yttria
- Rutgers Univ., Piscataway, NJ (United States). Center for Ceramic Research
- Oak Ridge National Lab., TN (United States)
- National Inst. of Standards and Technology, Gaithersburg, MD (United States)
Commercial silicon nitride powder with Al[sub 2]O[sub 3] and Y[sub 2]O[sub 3] additives was hot-pressed to complete density. The resulting microstructure contained elongated grains with no trace of remaining [alpha]-Si[sub 3]N[sub 4]. The aspect ratio of the elongate grains increased with increasing soak time at a fixed hot-pressing temperature. X-ray diffraction analysis showed that the crystalline phase in the hot-pressed samples was [beta]-sialon (Si[sub 6[minus]z]Al[sub z]O[sub z]N[sub 8[minus]z]) with z values that increased with soak time. The fracture strength and fracture toughness of the samples increased as the aspect ratio of the grains increased. The Vickers hardness decreased slightly as the soak time was increased, which was attributed to a grain size effect. Wear tests of silicon nitride against silicon nitride were conducted on a reciprocating pin-on-disk apparatus with paraffin oil as a lubricant. Correlation studies of wear with microstructure and mechanical properties were performed. The wear rate increased rapidly with increasing soak time in spite of the increased strength and toughness. this was attributed to increased third-body wear cause by pullout of pieces from the wear surface. The pullout mechanism was not conclusively identified. However, TEM examination showed clear evidence of dislocation motion under the wear scar. Grain boundary microstresses caused by the anisotropic thermal expansion and elastic properties of the elongated grains may have contributed to the observed pullout.
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 7045390
- Journal Information:
- Journal of the American Ceramic Society; (United States), Journal Name: Journal of the American Ceramic Society; (United States) Vol. 77:4; ISSN 0002-7820; ISSN JACTAW
- Country of Publication:
- United States
- Language:
- English
Similar Records
Effect of microstructure on mechanical properties of silicon nitride ceramics. Progress report, April 1, 1984-March 31, 1985. [Sialon-Y/sub 3/Al/sub 5/O/sub 12/]
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Related Subjects
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360203 -- Ceramics
Cermets
& Refractories-- Mechanical Properties
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CHALCOGENIDES
DATA
ELECTRON MICROSCOPY
EXPERIMENTAL DATA
FABRICATION
FRACTURE PROPERTIES
HOT PRESSING
INFORMATION
MATERIALS WORKING
MECHANICAL PROPERTIES
MICROSCOPY
MICROSTRUCTURE
NITRIDES
NITROGEN COMPOUNDS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PNICTIDES
PRESSING
SILICON COMPOUNDS
SILICON NITRIDES
TRANSITION ELEMENT COMPOUNDS
TRANSMISSION ELECTRON MICROSCOPY
WEAR
YTTRIUM COMPOUNDS
YTTRIUM OXIDES