Rare Earth Containing SiAlONS: Microstructure, Mechanical and Tribological Properties

Stefan Holzer; Jan Patrick Häntsche; Ulrich Spicher; Bernd Huchler; Alwin Nagel; Rainer Oberacker; Dirk Badenheim; Michael J. Hoffmann

doi:10.4028/www.scientific.net/KEM.287.282

Paper Titles

Viscosities of Oxynitride Glass and the Effects on High Temperature Behaviour of Silicon Nitride-Based Ceramics
p.259

Grain Growth of β-Silicon Nitride in RE-Mg-Si-O-N Liquid
p.265

Microstructure and Properties of Sintered Reaction Bonded Silicon Nitride with Aligned Whisker Seeds
p.271

Fabrication and Properties of Porous RBSN
p.277

Rare Earth Containing SiAlONS: Microstructure, Mechanical and Tribological Properties
p.282

Influence of Amount of Nitrogen on Crystallisation of Y-SiAlON Glasses: In Situ XRD Analysis
p.293

Fabrication of Heat-Resistant Silicon Carbide Ceramics by Controlling Intergranular Phase
p.299

Hardness Limits of SiC and Si₃N₄ Ceramic Materials
p.311

Nano Stress Measurement and Microstructural Characterization of Silicon-Based Optical Devices Using Their Native Luminescence
p.317

HomeKey Engineering MaterialsKey Engineering Materials Vol. 287Rare Earth Containing SiAlONS: Microstructure,...

Rare Earth Containing SiAlONS: Microstructure, Mechanical and Tribological Properties

Abstract:

Silicon nitride based ceramics have been investigated since more than forty years. Nevertheless, a good understanding of the microstructure-properties relationships on the level of small samples is not enough to bring ceramic parts into the industrial market. More convincing is a demonstration of the excellent potential in specific applications where the requirements of a more complex system are considered. In this work, sialons are investigated for a use in lubricated wear applications. The target system is a fuel injection pump for pressures up to 30 MPa. It requires very small friction coefficients and wear rates. Isooctane was used as lubricating liquid. A friction coefficient of 0.3 has been achieved with a piston-on-plate configuration for two sialon ceramics with different a/b-ratios. The sample surfaces were in a ground condition. For comparison, tribological testing was also performed with commercial alumina and silicon nitride materials which exhibited higher friction coefficients. In order to be closer to the real conditions a test rig has been designed and constructed with a piston running in a cylinder that actually pumps isooctane at the desired pressures of up to 30 MPa. With it, the high potential of sialon ceramics for lubricated sliding applications was proven. In the fields of microstructural design neodymia and ytterbia containing sialons with varying a/b-sialon ratios and different amounts of additives have been investigated. These parameters have a strong effect on the achieved aspect ratios of the sialon grains which can be correlated to the amount of liquid phase during sintering, kinetic considerations and the additives' cationic radii. Finally, the effect of these varying grain shapes on the mechanical properties hardness and fracture toughness has been determined.