Structure and Properties of a Tool Material Prepared by Hot Pressing from the Exothermic Mixture of Cr2O3–AlN Micropowders

Abstract—The results of studying the structure of materials with maximum hardness and fracture toughness values, which are obtained by hot pressing of mixtures of commercial Cr2O3 micro powders with 15, 25, and 35 wt % AlN, are reported. It is shown that these materials have the dispersed heterophase structure regardless of the composition of the initial mixture. It includes new phases, namely, a matrix of solid solutions of variable compositions of the (Cr1 – x–Alx)2O3 (0 < x < 0.9) type and dispersed inclusions based on Cr2N. The content and size of the latters increase with an increase in the content of aluminum nitride in the starting mixture. The ratio of Al and Cr in the solid solution depends on the composition of the starting mixture. The content of aluminum present in dispersed inclusions based on Cr2N increases from 1.8 to 4 wt % with an increase the amount of aluminum nitride in the original mixture from 15 to 35 wt %. The hardness and fracture toughness of the materials are reduced by 2.4 GPa and 1.1 MPa m1/2, respectively. It is shown that the cutting blades obtained from the Cr2O3–15AlN mixture are competitive, under conditions of fine grinding of carbon steel ShKh15 (HRC 62), to the blades of traditional CC650 ceramics most widespread today when scored by the price–quality criterion.