Journal of the European Ceramic Society 27 (2007) 3351–3357 Microstructural design of sliding-wear-resistant liquid-phase-sintered SiC: An overview Oscar Borrero-L´ opez a , Angel L. Ortiz a , Fernando Guiberteau a,∗ , Nitin P. Padture b a Departamento de Electr ´ onica e Ingenier´ıa Electromec´ anica, Escuela de Ingenier´ıas Industriales, Universidad de Extremadura, 06071 Badajoz, Spain b Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210, USA Available online 3 April 2007 Abstract We have reviewed the effect of microstructure – content of intergranular phase, grain size, and grain shape – on the lubricated, sliding-wear of pressureless liquid-phase-sintered (LPS) SiC ceramics. The sliding-wear resistance in LPS SiC decreases with an increase in the content of the intergranular phase or an increase in the equiaxed-grain coarsening. However, the sliding-wear resistance is dramatically improved with anisotropic- grain coarsening. Based on these results we suggest two strategies for the microstructural design of low-cost, sliding-wear resistant SiC-based ceramics: (1) grain refinement, and (2) grain elongation. The latter strategy allows the materials to be simultaneously in situ toughened, and we describe its optimization by judicious selection of the SiC starting powder. © 2007 Elsevier Ltd. All rights reserved. Keywords: Wear resistance; SiC; Sintering; Liquid-phase sintering; Microstructure 1. Introduction Ceramics are innately hard and stiff, which makes them very attractive materials for use in contact-mechanical and tribo- logical applications. In addition, due to their high-temperature tolerance and chemical inertness, many ceramics are appropri- ate for applications where lightness and/or resistance to hostile environments are required. It is not surprising then that many tribocomponents – such as bearings, wear-parts, valves, seals, rollers, cutting tools, nozzles, dies, gears, tappets, etc. – are increasingly being made of ceramics. In this context, silicon carbide (SiC), which has one of the highest hardnesses of all single-phase ceramics, has been identified as a promising candidate for its use in the above applications. 1–8 What distinguishes SiC from the majority of the ultra-hard ceramics is its high thermal conductivity 9 and high melting point, 10 which help to relieve and resist the frictional heating in sliding contacts. However, conventional solid-state sintering of SiC bulk ceramics involves the use of extremely high temperatures and pressures, which makes SiC tribocompo- nents expensive, at the same time as imposing severe restrictions ∗ Corresponding author. Tel.: +34 924 28 9530; fax: +34 924 289601. E-mail address: guiberto@unex.es (F. Guiberteau). on their shapes and sizes. Fortunately, pressureless liquid-phase sintering enables the limitations of solid-state sintering to be overcome, paving the way towards low-cost processing of SiC ceramics. Hence, it is not surprising that liquid-phase-sintered (LPS) SiC has recently been investigated (although as yet not extensively) for its potential as a low-cost, highly sliding-wear resistant, ceramic. 7,8,11–14 The design of SiC-based tribocomponents with improved performance requires their microstructure–properties relation- ship to be established. In this paper we review the effect of the microstructure on the lubricated sliding-wear of LPS SiC ceramics under initial elastic contact, in an effort to provide guidelines for the processing of low-cost SiC ceramics with tailored contact-mechanical and tribological properties. 2. Experimental procedure 2.1. Processing Four powder batches were individually prepared, each con- taining -SiC (UF-15, H.C. Stark, Germany) or -SiC (Ultrafine SiC, Ibiden Corp., Ogaki, Japan) powder, plus a combination of Al 2 O 3 (AKP-30, Sumitomo Chemical Company, New York, NY) and Y 2 O 3 (Fine Grade, H.C. Starck Inc., Newton, MA) powders in the molar ratio Y 2 O 3 :Al 2 O 3 ::3:5 to result in YAG 0955-2219/$ – see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jeurceramsoc.2007.02.190