Yttrium. alpha. -sialon ceramics by hot isostatic pressing and post-hot isostatic pressing

Journal Article · Sat Feb 01 00:00:00 EST 1992 · Journal of the American Ceramic Society; (United States)

DOI:https://doi.org/10.1111/j.1151-2916.1992.tb08198.x· OSTI ID:5332540

Bartek, A; Johansson, T ^[1]; Ekstrom, T ^[2]; Herbertsson, H ^[3]

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1. Dept. of Engineering Materials, Lulea Univ. of Technology, S-951 Lulea (SE)
2. AB Sandvik Hard Materials, S-126 80 Stockholm (SE)
3. School of Materials Science and Engineering, University of New South Wales, Kensington, NSW 2033 (AU)

This paper reports on dense {alpha}-sialon materials that were produced by hot isostatic pressing (HIP) and post-hot isostatic pressing (post-HIP) using composition with the formula Y{sub x}(Si{sub 12{minus}4.5x}), Al{sub 4.5x}-O{sub 1.5x},N{sub 16{minus}1.5x} with 0.1 {le} x {le} 0.9 and with the same compositions with extra additions of yttria and aluminum nitride. X-ray diffraction analyses show how the phase content changes from large amounts of {beta}-sialon (x = 0.1) to large amounts of {alpha}-sialon (x = 0.4) and increasing amounts of mellilite and sialon polytypoids (x = 0.8). Samples HIPed at 1600{degrees}C for 2 h contained unreacted {alpha}-silicon nitride, while those HIPed at 1750{degrees}C for 1 h did not. This could be due to the fact that the time is too short to achieve equilibrium or that the high pressure (200 MPa) prohibits {alpha}-sialon formation. Sintering at atmospheric pressure leads to open porosity for all compositions except those with excess yttria. Therefore, only samples with excess yttria were post-HIPed. Microstructural analyses showed that the post-HIPed samples had the highest {alpha}-sialon content.

• OSTI ID: 5332540
• Journal Information: Journal of the American Ceramic Society; (United States), Vol. 75:2; ISSN 0002-7820
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CERAMICS
CHEMICAL COMPOSITION
PHASE TRANSFORMATIONS
YTTRIUM COMPOUNDS
HARDNESS
HOT PRESSING
X-RAY DIFFRACTION
ADDITIVES
ALUMINIUM NITRIDES
EQUILIBRIUM
HIGH PRESSURE
MICROSTRUCTURE
SINTERING
ALUMINIUM COMPOUNDS
COHERENT SCATTERING
CRYSTAL STRUCTURE
DIFFRACTION
FABRICATION
MATERIALS WORKING
MECHANICAL PROPERTIES
NITRIDES
NITROGEN COMPOUNDS
PNICTIDES
PRESSING
SCATTERING
TRANSITION ELEMENT COMPOUNDS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies
360203 - Ceramics
Cermets
& Refractories- Mechanical Properties
360201 - Ceramics
Cermets
& Refractories- Preparation & Fabrication