Effect of LZSA glass-ceramic addition on the erosive wear of pressureless sintered alumina

Abstract

This study aims to evaluate the influence of the 11.6Li2O-16.8ZrO2-68.2SiO2-3.4Al2O3 (mol%) glass-ceramic addition (LZSA, 7 to 21 vol%) on the erosive wear of alumina in comparison to values of pure alumina obtained from the literature. Thus, composites were prepared from three commercial alumina of different initial particle sizes. Specimens were obtained by uniaxial pressing. Sintering temperatures and holding times were found to be different for each composite. The erosive wear test was carried out in an apparatus based on the standard ASTM G 76-4. The volumetric erosive wear (Tvol) was correlated to the initial mean particle size of alumina, LZSA glass-ceramic content, average grain size of sintered alu-mina (AGS), porosity (P), elastic modulus, fracture toughness, natural defect size, and fracture energy based on a correlation matrix of statistical analyses. The ex-perimental data of Tvol fit very well with P and AGS, individually, in a 3rd degree equation, except for composite AF21. Composite AF21, i.e. 21 vol% LZSA added to 0.5 µm mean particle size alumina (AF, fine alumina) and sintered at 1470oC for 3 h, showed interesting results of T (2.05 × 10-8 m3·kg-1) related to the other investigated compositions, which variedvolfrom 1.90–4.37 × 10-8 m3·kg-1, and those existing in literature (0.55 × 10-8 to 10.78 × 10-8 m³·kg-1), mostly when consider-ing the lower sintering temperature (1470 against 1600oC). Thus, although the AC7 composite had shown the lowest Tvol value (1.90 × 10-8 at 1600oC/7 h), the composite AF21 can be considered as the best result because of its lower sintering temperature and holding time (2.05 × 10-8 at 1470oC/4 h). The formation of a viscous liquid phase, which crystallizes during the controlled cooling in the mi-crostructure of the LZSA/alumina-based composites, improves the erosive wear of the alumina.