OBTAINING CORUNDUM CERAMICS BASED ON ELECTROCORUNDUM MICROPOWDERS

The processes of sintering of micropowders of electrocorundum of different brands were studied, and it was found that the greatest activity has electrocorundum F1500, produced in Russia on an industrial scale. The phase composition of electrocorundum F1500 is α-Al2O3 with small admixtures of β-Al2O3, consists of particles of micron and submicron sizes and does not require any preliminary preparation before use. The effectiveness of a sintering additive consisting of a mixture of aluminum-magnesium spinel and mullite in a mass ratio of 1:4 for producing structural corundum ceramics based on it has been shown. This combination promotes the formation of a fine-crystalline structure of the material with high mechanical properties and creates the prerequisites for the development of resource-saving technology in which the synthesis of a sintering additive is combined with the firing process. The dependences of the properties of the resulting ceramics on the dispersion of the starting materials, the mutual ratio of the components, molding parameters and sintering temperature conditions were studied. High values of density 3.81-3.83 g/cm3, bending strength 370±30 MPa and microhardness 13.8-15.5 GPa of ceramics are ensured by introducing a sintering additive into electrocorundum in an amount of 4.0-10.0% wt., relatively low pressing pressure ~50 MPa and moderate firing temperature of 1600 °C. The achieved properties determine the possibility of using this material in products operating under conditions of increased shock, abrasion, static and dynamic loads.