Study on High-Strength Corundum Ceramics Based on Dolomite Modification for Deep-Sea Oil Exploitation

The extreme environmental conditions with high temperature, high pressure, severe corrosion and severe wear in deep-sea oilfield exploitation impose stringent requirements for traditional oil/gas fracturing proppant ceramic materials. Due to performance limitations of the ceramic materials, failure problems from corrosion and breakage may frequently occur in the proppants which seriously affects the stability and efficiency of mining operations. In this study, high-strength corundum ceramics were prepared by solid phase sintering methods with secondary bauxite as matrix raw material, dolomite as core modifier, and pyrolusite as sintering aid. Effects of dolomite addition on the phase composition, microstructure, mechanical properties and corrosion resistance of the ceramic materials were systematically studied. The results showed that, when adding an appropriate amount of dolomite(the mass fraction is 5%), CaO generated by dolomite thermal decomposition might react with the matrix material to form anorthite liquid phase, thus promoting sintering densification and grain boundary strengthening. At the same time, the generated MgO could transform into a dispersed spinel phase in situ, which synergistically improved the mechanical properties and corrosion resistance of the ceramic materials. However, the excessive addition of dolomite(the mass fraction exceeds 5%) caused an excessive formation and agglomeration of spinel phase, thus destroying the matrix continuity and formed a continuous lamellar structure due to the excessive liquid phase of anorthite, thus increaseing the porosity ratio and structural deterioration, which ultimately leaded to a property deterioration of the ceramics. The ceramic material with an optimal comprehensive performance could be prepared with dolomite mass fraction of 5%, pyrolusite mass fraction of 6%, and being sintered at 1 400 ℃ for 2 h. The simultaneous improvement of densification and toughening through the synergistic effect of “anorthite liquid phase sintering-corundum grain refinement-spinel dispersion strengthening”, can provide technical solutions for upgrading the ceramic materials for deep-sea oil exploitation.