PDC Drill Bits
PDC bits are designed and manufactured in two structurally dissimilar styles: Matrix-body bit and Steel-body bits. The two provide significantly different capabilities, because both types have certain advantages, a choice between them would be decided by the needs of the application.
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Polycrystalline diamond materials for use in polycrystalline diamond compact (PDC) bits, are one of the most important material advances for oil drilling tools in recent years. Fixed-head bits rotate as one piece and contain no separately moving parts. When fixed-head bits use PDC cutters, they are commonly called PDC bits. Since their first production in 1976, the popularity of bits using PDC cutters has grown steadily, and they are nearly as common as roller-cone bits in many drilling applications.
1 Matrix-body
“Matrix” is a very hard, rather brittle composite material comprising tungsten carbide grains metallurgical bonded with a softer, tougher, metallic binder. Matrix is desirable as a bit material, because its hardness is resistant to abrasion and erosion. It is capable of withstanding relatively high compressive loads, but, compared with steel, has low resistance to impact loading.Matrix is relatively heterogeneous, because it is a composite material. Because the size and placement of the particles of tungsten carbide it contains vary (by both design and circumstances), its physical properties are slightly less predictable than steel.Matrix body bits are manufactured by mold process. The tungsten carbide and binder materials are arranged into the mold. The mold get placed in to the furnace for certain period of the time and materials are cooked to certain temperature. The mold later cooled down and broken to remove the unfinished matrix bit.2 Steel-body
Steel is metallurgical opposite of matrix. It is capable of withstanding high impact loads, but is relatively soft and without protective features, would quickly fail by abrasion and erosion. Quality steels are essentially homogeneous with structural limits that rarely surprise their users. Steel body bits are manufactured by machining the steel bars per design.
3 Advantage of matrix-body PDC bits
Matrix-body PDC bits are commonly preferred over steel-body bits for environments in which body erosion is likely to cause a bit to fail. For diamond-impregnated bits, only matrix-body construction can be used.4 Advantage of steel-body PDC bits
The strength and ductility of steel give steel-bit bodies high resistance to impact loading. Steel bodies are considerably stronger than matrix bodies. Because of steel material capabilities, complex bit profiles and hydraulic designs are possible and relatively easy to construct on a multi-axis, computer-numerically-controlled milling machine. A beneficial feature of steel bits is that they can easily be rebuilt a number of times because worn or damaged cutters can be replaced rather easily. This is a particular advantage for operators in low-cost drilling environments.Important factors to consider before the use and design of PDC bits
- PDC bit design principles
- PDC bit profile
- PDC bit configurations
- Bit hydraulics
- Bit economics
- Bit classification
Understanding of operating practices and conditions the bit will be exposed to.
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