Improvements on the thermal shock behaviour of MgO–spinel composite refractories by incorporation of zircon–3 mol% Y2O3

Abstract

The effects of incorporations of zircon–3mol% Y2O3 (Y) into MgO–spinel (M–S) compositions to improve mechanical properties and thermal shock behaviour were investigated. Mechanical properties were measured, R−Rst parameters were calculated, and thermal shock tests were performed. Microstructural features were examined using SEM and XRD. By adding zircon+Y to M–S: (i) up to ∼2 and ∼3-fold improvements were achieved in mechanical properties and R−Rst parameters, (ii) there were improvements up to ∼2-fold in strength data measured after performing thermal shock tests at 1000°C. Parameters improving mechanical properties and thermal shock behaviour of M–S–(zircon+Y) materials are given as follows: (i) interlinking and arresting or deviation of microcracks when reaching the ZrO2–Y2O3 grains or pores, increases in (ii) KIc, (iii) critical defect size and (iv) bulk density, (v) formation of forsterite phase, (vi) coexistence of intergranular and transgranular fractures, and (vii) reduction in MgO grain size, leading to longer service life.