Bibliographic Information

"Mechanical Properties Characterization of One SiC and Two Si₃N₄ Commercially Available Ceramics," N.L. Hecht, S.M. Goodrich, L. Chuck, D.E. McCullum, and V.J. Tennery, American Ceramic Society Bulletin, Vol. 71 [4], pp. 653-659 (1992), published by American Ceramic Society.

General Materials Processing Notes

"Test-ready flexural bars and cylindrical buttonhead tensile specimens of two Si₃N₄ and one SiC materials used in this study were prepared from three different manufacturers (GTE Labs, Inc., Waltham, MA; Norton/TRW, Waltham, MA; and Carborundum Company, Niagara Falls, NY). ...

Carborundum Hexoloy SA

Cold-formed (injection molded or isostatic pressed) and pressureless sintered α-SiC with additions of B and C.

GTE PY6

Injection molded and HIPed β-Si₃N₄ with additions of 6% Y₂O₃.

Norton/TRW NT-154

Sintered and HIPed β-Si₃N₄ with additions of 4 wt.% Y₂O₃; the tensile specimens were aged at 1400 °C for 5 h after machining prior to shipping."

Measurement Methods

"Flexural strength was measured using four-point bend fixtures in universal testing machines (Instron Model 1123, Instron Corp., Canton, MA) following MIL-STD-1942 (MR). Measurements from 1000 °C to 1400 °C were conducted in high-temperature furnaces (ATS Model 3320, ATS Applied Test Systems, Inc., Butler, PA) adapted for use in the testing machines. Test spcimens were 3 mm x 4 mm x 50 mm with the tensile surfaces were beveled to minimize failures initiated by edge chips. Specimens were loaded at machine crosshead rates of 4x10^-2 mm/s and 4x10^-4 mm/s."

"Tensile strengths were measured using cylindrical buttonhead specimens configured for a special tensile test fixture (Instron Corp. design for Instron's "Super-Grip"). These specimens were tested in a universal testing machine with water-cooled specimen holders in a high-temperature furnace (Instron Model 1361 Electro-Mechanical Test system equipped with the Instron "Super-Grip" universal coupling and water-cooled specimen holders and Instron short furnaces). Specimens were tested at 20 °C, 1000 °C, 1200 °C, and 1400 °C using crosshead rates of 4x10^-2 mm/s and 4x10^-4 mm/s."

"Young's modulus of all three materials was measured at room temperature using the impulse excitation technique. This technique utilizes a sensitive microphone and associated electronics to analyze the flexural vibratory movement of a specimen after a light mechanical impulse to determine the fundamental resonant frequency. The impulse excitation apparatus (Grindo-Sonic Model MR35T Transient Impulse Response Elastic Modulus Apparatus, J.W. Lemmens, Inc., St. Louis, MO) was modified... Room temperature values of Poisson's ratio were used to calculate all Young's modulus values: 0.14 for Hexoloy SA SiC, 0.24 for NT-154 Si₃N₄, and 0.21 for PY6 Si₃N₄."

"The hardness of each material was measured with a Vickers micorindent hardness tester. A 500 g load was used to obtain hardness values for Hexoloy SA SiC and NT-154 Si₃N₄. A 300 g load was used to obtain hardness values for PY6 Si₃N₄."

"Bulk density of each candidate ceramic was meaured by the immersion method."

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