Role of fabrication route and sintering on wear and mechanical properties of liquid-phase-sintered alumina

Liquid-phase-sintered Al2O3 (LPS) fabricated by slip casting, tape casting, isopressing, uniaxial pressing, piston and auger extrusion showed substant ial differences in wear due to differences in morphology as observed in ima ge analyses of SEM micrographs. The abrasive wear was low in the case of un iaxial pressing and high in the case of tape casting in the 'dry sand and r ubber wheel' test. The wear surface of the tape cast specimen exhibited ext ensive microcracking possibly due to orientation of Al2O3 platelet (major f ace) parallel to the abraded surface whereas some degree of perpendicular o rientation in extruded surface resulted in lower wear loss. In wet-milling wear test, the isopressed balls of a 95-97 wt% LPS derived from reactive po wder (< 1 <mu>m) showed 25% lower wear loss than that of the extruded balls of a 91-94 wt% LPS derived from coarse powder (70-100 mum). Sintering at a lower temperature with longer duration and batch milling of the compositio n in between 12 and 16 h resulted in low wear loss. Flexural strength also improved by longer sintering time but did not show any improvement by incre asing milling time. However, the variation in flexural strength was minimiz ed by isopressing the extruded specimen. A high indentation fracture toughn ess at 49.03 N test load was associated with (1) large elongated reinforcem ent grains in a fine-grained microstructure with overall elongated morpholo gy and (ii) with an intergranular fracture. (C) 2000 Elsevier Science Ltd a nd Techna S.r.l. All rights reserved.