WEAR RESISTANCE OF HARD MATERIALS IN DRILLING APPLICATIONS

The world-wide use of hard materials in the oilfield industry encounters the challenges with increasingly complex and costly drilling operation. Focus has been made into engineering ceramics and tungsten carbide cermet as drilling tool hardfacing materials, due to the continued advancement of drilling technology and high demand on wear resistance performances. The wear behaviors of seven types of hard materials have been systematically investigated at two different wear conditions, namely the wet sand/rubber wheel abrasive wear and the high speed particle/water jet erosive wear. Ranking of wear resistance among those hard materials is made for industrial specification and evaluation purpose. Results show that WC-3Co exhibits the highest wear resistance and Al(2)O(3) is of the lowest wear resistance among all of the materials evaluated. Abrasive wear testing results are in accordance with erosive wear testing results, regarding to the wear resistance ranking. Results showed that size ratio between hard materials grain size and erodent/abrasive particle size plays role in wear characteristics by affecting the wearing mechanisms. For the tungsten carbide cermet system, WC-Co, the influence of binder content on the hardness and wearing behaviors is discussed. Results show that the higher was the binder content, the lower were the hardness and wear resistance. The variance in wear resistance coincides with a change in the mechanism of materials removal. The present study indicates that the wearing mechanism is mainly plastic deformation, bulk gouging, cutting and removal. However, fragmentation and microchipping of material grains also occur with impact of erodent/abrasive particle size. The research achievements will allow one to establish the procedures for the evaluation and selection of hard materials in drilling applications and help to optimize the current development strategy of engineering ceramics and tungsten carbide cermet.