Brief introduction of PDC cutters

 

Today’s PDC drill Bits Design as a matrix has little resemblance to that of even a few years ago. Tensile strengths and impact resistance have increased by at least 33%, and cutter brazes strength has increased by ≈80%. At the same time, geometries and the technology of supporting structures have improved, resulting in robust and productive matrix products.
Cutters Material
PDC Cutters are made from carbide substrate and diamond grit. The high heat of around 2800 degrees and high pressure of approximately 1,000,000 psi forms the compact. A cobalt alloy also acts as a catalyst for the sintering process. The cobalt helps bond the carbide and diamond.
Number of Cutters
We usually use fewer cutters on soft PDC bits as each cutter removes a greater depth of cut. For harder formations, it is essential to use more cutters to compensate for the smaller depth of cut.

 

PDC Drill Bits – Cutters Size
For softer formations, we typically choose larger cutters than in harder formations. Usually, the standard range of sizes is from 8 mm to 19 mm on anyone bit.

 

 

We generally describe the cutter rack design orientation by back rake and side rake angles.
●The cutter back rake is the angle presented by the face of the cutter to the formation and is measured from the vertical. Back rake angles vary between, typically, 15° to 45°. They are not constant across the bit, nor from bit to bit. The magnitude of the cutter rake angle for PDC drill bits affects Penetration Rate (ROP) and cutter resistance to wear. As the rake angle increase, ROP decreases, but the resistance to wear increases as the applied load is now spread over a much larger area. PDC cutters with small back rakes take large depths of cut and are therefore more aggressive, generate high Torque, and are subject to accelerated wear and greater risk of impact damage.

 

 

●The cutter side rake is an equivalent measure of the orientation of the cutter from left to right. Side rake angles are usually small. The side rake angle assists hole cleaning by mechanically directing cuttings toward the annulus.