Wet Erosive Wear of Alumina Densified with Magnesium Silicate Additions

Abstract

A study was made of the wet erosive wear of polycrystalline alumina of mean grain size >1 m, containing up to 10 wt% of magnesium silicate sintering aid. For pure polycrystalline alumina, the dominant wear mechanism was grain-boundary microfracture, leading to partial or complete grain removal. In the case of the liquid-phase-sintered materials, wear rates could be as low as 25% of those of pure alumina of the same mean grain size, and the main material removal mechanism was transgranular fracture combined with tribochemical wear. The use of Cr 3؉ photoluminescence line broadening showed much higher levels of local stress in the magnesium silicate-sintered materials (ϳ450 MPa) than in the purealumina materials (ϳ200 MPa). Grain-boundary compressive hoop stresses, caused by the thermal expansion mismatch between a continuous magnesium silicate film and the alumina grains, provided an explanation for the improved wear resistance of the alumina sintered with magnesium silicate.

A comparison of the microstructure and mechanical properties of two liquid phase sintered aluminas containing different molar ratios of calcia–silica sintering additives

“…Previous work 5,7,8 has shown that ceramic materials with smaller median grain size show lower wear rates. This is summarized in the graph shown in Fig.…”

“…A similar behaviour has been found in previous studies where chemical etching was employed. 5 It is possible that this behaviour can be linked to the chemistry of the intergranular and secondary crystalline phases and also to the thermal shock applied during etching on the heavily defective microstructure of the CSp specimen.…”

“…7 Different amounts of magnesia 5,6 and calcia 4,7 are also used to obtain intergranular silicate glasses with differing molar ratios of silica/magnesia or silica/calcia. A comparison of the properties of some of these materials is shown in Table 1 where the data has been extracted from a number of our previous studies.…”

Synthesis and two-step sintering behavior of sol–gel derived nanocrystalline corundum abrasives

“…Because they as the silicate had a marked grain-boundarystrengthening action and as grain-boundary phase could clearly suppressed grain-growth when the grain zone were completely covered by the continuous silicate phase, even at extremely low concentrations. 30 The calcium silicate-densified alumina examined earlier showed the amorphous silicate films at all the two-grain boundaries, of order of 2 nm thickness. 31 The SEM examinations ( Fig.…”

Role of carbon nanotube dispersion in fracture toughening of plasma sprayed aluminum oxide - carbon nanotube nanocomposite coating

“…Toughening of A1 2 0 3 is worked upon by using secondary phases as additives, consolidating nanocrystalline A1 2 0 3 powder particles via pressing and sintering, and reinforcing with particulates, fibers or whiskers [35,[121][122][123][124][125][126][127][128][129][130][131][132][133][134][135][136]. Following example elicit specific examples of toughened A1 2 0 3 ceramic.…”