Development of oxide-free oxide materials under conditions of plasma-spark sintering of a mixture of oxide-free components and the addition of various metal powders

Abstract

Effect of powder additives of W and Mo during spark plasma sintering of com-positions at pressing loading of 60 MPa in the range 1200‒1600 °С on the phase composition, microstructure, grain sizes of crystalline phases, relative density, linear shrinkage, physical-mechanical properties and linear correlation of modulus of Elasticity and fracture toughness of mullite‒ZrB₂‒β-SiC‒TaC samples was shown. Synthesised powders of ZrB₂, β-SiC and TaC are characterisized by intensive crystal-lization of ZrB₂, β-SiC and TaC_cub, respectively. Sintered samples with additives of W and Mo powders show intensive mullitization, active crystallization of β-SiC, (Zr, Ta)B, C, β-WC and β-WB in comparison with lower crystallization of (Ta, Zr)C, B, β-MoC, β-MoB and MoB₂ in the range 1200‒1600 °С. Microstructure of sample with molybdenum additive at 1500 °С more uni-formly and densely sintered, crystalline, containing less quantity of pores and weakly sintered areas, more reinforced at the boundaries areas of oxide-nonoxide and nonoxide crystalline phases. Such sample is characterisized by smaller grains sizes of crystalline phases in the range 1400‒1600 °С and show uniform growing of relative density and linear shrinkage, physical-mechanical properties with larger their values, higher resistance to the cracking with propagation of micro-cracks by meandering path as well as larger linear correlation of modulus of Elasticity and fracture toughness in the range 1200‒1600 °С.