Unlubricated tribological performance of advanced ceramics and composites at fretting contacts with alumina
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Jozef Vleugels and Omer Van Der Biest Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001, Belgium (Received 15 September 2002; accepted 12 February 2003)
Engineering ceramics and cermets are widely used for demanding tribological applications. In this perspective, the objective of this paper was to understand the friction and wear behavior of some of the potential tribomaterials, e.g., ZrO2–30 vol% TiB2 composite, sialon–40 vol% TiB2 composite, TiB2-based cermet with 16 vol% Ni3(Al,Ti) binder, and monolithic TiB2 in fretting contacts. Wear tests on the TiB2-containing materials under dry unlubricated conditions (23–25 °C, 50–55% relative humidity) were performed against corundum on a ball-on-flat tribometer. The obtained friction and wear data were critically analyzed to investigate how the binder phase in TiB2 matrix influences the tribological performance. Furthermore, morphological investigations of the transfer layers on the worn surfaces were performed and the wear mechanisms discussed. X-ray photoelectron spectroscopy analysis of the worn surfaces in the monolithic TiB2/alumina revealed the pronounced transfer of mixed oxides containing TiO2 and B2O3 to the alumina counterbody and also indicated the transfer of alumina to TiB2 flat. Tribochemical reactions and abrasion along with the material transfer between the counterbodies were observed to play a major role in the wear of the fretting couples.
I. INTRODUCTION
Advanced ceramics and cermets, due to their excellent mechanical properties (elastic modulus, hardness), are increasingly appreciated in tribological applications.1,2 High elastic modulus is beneficial in reducing the Hertzian contact damage, while high hardness imparts the ceramics high abrasive wear resistance. Because of its high modulus (around 500 GPa) and superior hardness (around 20–25 GPa at room temperature), TiB2 is considered to be a promising candidate material for tribological applications.3 In this study, the dry unlubricated fretting wear of a number of TiB2-based materials against alumina is investigated. The range of materials include a monolithic TiB2, sialon-based 40 vol% TiB2 material, ZrO2-based 30 vol% TiB2 composite, and a TiB2-based cermet with 16 vol% Ni3(Al,Ti) binder. Several researchers have studied the friction and wear behavior of structural ceramics and composites.4 Campbell et al. investigated the fretting wear behavior of a)
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J. Mater. Res., Vol. 18, No. 6, Jun 2003
several structural ceramics (Al2O3–TiC, Al2O3–ZrO2, and monolithic sialon) and cermets [Ti(C,N) and WC–Co] against steel and corundum counterbodies under ambient conditions of humidity and temperature.5 The wear against steel is reported to be higher than that against alumina. Sialon and Ti(C,N) materials showed much pronounced fretting wear against alumina than Al2O3–TiC, Al2O3–ZrO2, and WC–Co. The enhanced tribochemical interactions and the ability of the steel
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