Development of dense materials by plasmaspark sintering of oxide‒oxide-free components with different mixtures of metal powders

Abstract

The effect of powders mixtures of Zr and Mo, Zr and Ta during spark plasma sintering of compositions at pressing loading of 60 MPa in the range 1200‒1600 °С on the phase composi-tion, microstructure, grain sizes of crystalline phases, relative density, linear shrinkage, physicalmechanical properties and linear correlation of modulus of elasticity and fracture toughness of mullite‒β-SiAlON‒cBN samples were shown in this work. Synthesised powders of β-SiAlON and c-BN are characterisized by intensive crystalliza-tion of β-SiAlON and c-BN, respectively. Sintered samples with mixtures of Zr and Mo, Zr and Ta show intensive mullitization, active growing of β-SiAlON and less intensive growing of c-BN in the range 1200‒1600 °C. Active growing of crystalline β-Mo,Zr, Mo and Mo2Zr phases are noticeable in the sample with mixtures of Zr and Mo, but intensive growing of crystalline β-Ta,Zr, α-Zr,Ta, α-Ta, Ta₃Zr and Ta₃Zr₂ phases are observed in the sample with mixtures of Zr and Ta with increase of temperature. Mixture of Zr and Mo favour the formation of more uniformly and densely sintered microstructure of ceramic phase, round shape of metallic Mo, β-Mo,Zr particles, more reinforced boundaries areas of ceramic‒metallic, metallic phases and facilitate the reduction grains sizes of crystalline phases in the range 1400‒1600 °С. As a result, composition with mixture of Zr and Mo sinters more uniformly and gradually, corresponding sample shows larger values of physicalmechanical properties, higher resistance to the cracking with insignificant quantity of microcracks as well as larger linear correlation of modulus of elasticity and fracture toughness in the range 1200‒1600 °С.