Papers by Author: Anne Neville

Abstract: In oil drilling the failures of PDC drill bits are exhibited as erosive wear, dropping and breaking of cutters, so the erosion and corrosion resistance of the matrix is one of the key factors affecting the quality of PDC bits. In order to understand the degradation mechanism of matrix materials for drill bits, a kind of loop recirculation rig is adopted to measure total mass loss TML, mass loss E by pure mechanical erosion, and then through calculation the mass loss C+S by corrosion and synergy is obtained. The tested and calculated results show that TML of matrix materials is not only caused by pure mechanical erosion, but also by corrosion and their synergy of mechanical erosion and corrosion. In the discussed scope of this paper the volume loss produced by corrosion and synergy is 24.16% of the total volume loss (TVL) at most, which tells us that the corrosion resistance of matrix materials should be considered carefully besides their erosive resistance in the design and selection of PDC drill bits used in the corrosive drilling muds.

Abstract: Porous Al2O3 ceramics were produced by a dry pressing technique and their characteristics were assessed. In terms of their microstructure the results showed that the open porosity varies with the type of pore-making agents. The open porosity is increased but fracture strength is decreased with an increase in the amount of pore-making agent. The fracture strength of Al2O3 ceramic matrix is increased by adding 5-15wt% ZrO2 particles (ZTA). In terms of their wet erosive wear characteristics the results from liquid-solid impinging jet tests can be used to determine the weak aspects of their microstructure. From examination of worn surfaces it is apparent that grain pull-out is the dominant mechanism of erosive wear. For the porous ceramics, wet erosive wear rate depends on strength, porosity and pore size. For porous Al2O3 ceramics having the same level of porosity, the larger the biggest pore size the higher the erosive wear rate. ZTA composite ceramic has a higher erosive wear resistance than that of Al2O3 ceramic with an equivalent level of porosity primarily due to its higher strength.