In order to solve the trade-off between thermal stability and impact toughness, PDC tool technology mainly includes the deep leaching technology of the tool, the interface design, and the diamond distribution. In the manufacturing process, the deep leaching technology is used to remove the cobalt catalyst (to prevent thermal degradation), the non-planar interface design is used to optimize the residual stress distribution (to prevent delamination), and the multi-mode diamond distribution is used to improve the bulk density.

Choosing the right PDC technology is not about finding the hardest material, but rather about choosing a specific tool grade based on the specific lithology, determined by the chamfer geometry and leaching depth, thereby reducing the number of starts and significantly reducing the cost per foot.

Thermal Stability vs. Impact Toughness

If you want to understand the current PDC cutting technology, you have to start with a problem that comes out of its mother’s womb: polycrystalline diamond compact (PDC) has an inherent conflict in its manufacturing. For a long time in the past, if you want to improve the wear resistance (that is, hardness) of cutting teeth, you often have to sacrifice its impact toughness (that is, the ability to resist impact).

The “culprit” behind this is actually the cobalt (Cobalt) binder used in the high temperature and high pressure (HPHT) sintering process. Cobalt is essential for bonding diamond crystals together, but down the well, it becomes a problem. When the temperature is increased, the thermal expansion rate of cobalt is much higher than that of diamond. In the high-temperature drilling environment, this uneven thermal expansion will generate huge stress in the diamond layer, and compete with itself, which will eventually lead to cracking or performance degradation of the diamond layer-we call this “thermal damage” in the jargon “.

Deep Leaching Technology Enhancing Thermal Stability

So how to solve this problem of thermal damage? At present, the most effective progress in PDC cutting technology is deep leaching (Deep Leaching). The previous standard practice was to wash the cobalt catalyst on the most surface of the diamond layer. However, the current deep leaching technology is more thorough, it can remove the metal binder in a range quite deep below the working surface. The benefits are immediate:

• Eliminate internal stress: remove the cobalt, in the key cutting area, the binder and the diamond lattice because of the different expansion rate and “fight” with each other.
• To prevent graphitization: cobalt at high temperature will also catalyze the reversal of diamond into graphite, equivalent to the good diamond to waste. Deep leaching removes this catalyst, and the diamond structure remains stable even when drilling hard, abrasive formations to produce extreme high temperatures.

This process can ensure that the cutting edge of the cutting tooth is more durable, especially in geothermal or deep well operations, which can effectively maintain the rate of penetration (ROP).

Non-Planar Interface Designs Optimize Impact Toughness

Well, leaching technology solves the problem of thermal stability. Let’s look at mechanical bonding again. Light wear resistance is not resistant to building, is also useless. The diamond layer and the tungsten carbide substrate below are not firmly combined, which directly determines the impact toughness of the cutting teeth. In this area, the emergence of non-planar interface design (Non-Planar Interface) can be said to be a revolutionary progress. Instead of the flat contact surface of the past, the current technology has come up with a variety of complex, non-planar geometric shapes:

• Stress management: Well-designed ridged, wavy or concentric ring interfaces can effectively redistribute the residual stress generated during the sintering process.
• Stop crack propagation: A non-planar interface is itself a physical barrier. In the event of a crack in the diamond layer, this complex geometry can seize it and prevent it from spreading catastrophically over the entire cutting tooth surface.
• Preventing flake-off: By increasing the combined surface area, these designs “lock” the diamond layer more firmly to the substrate, allowing the cutting teeth to withstand the severe impact encountered in hard and soft staggered formations.

Multi-Modal Diamond Distributions Increasing Packing Density

Having said the interface, let’s talk about the diamond layer itself. Its durability depends essentially on the degree of tightness between the diamond and the diamond. Standard PDC cutters typically rely on uniformly sized diamond particles, which leave voids between the particles, filled with binder material. Current PDC cutter technology uses a multi-modal diamond distribution (Multi-Modal Diamond Distributions). This technique is to mix diamond particles of various sizes, such as coarse, medium and fine, together before sintering.

• Maximize density: This principle is actually very simple, just like you put something in a jar, first enlarge the stone, then put the pebbles, and finally fill in the sand. Multimodal distribution is the use of small particles of diamond to fill the gaps between large particles of diamond.
• Reduced binder content: By maximizing the volume of diamond material while minimizing the volume of cobalt binder, the overall hardness and wear resistance of the cutting teeth are significantly improved without sacrificing structural integrity.

PDC CUTTERS

Meet the Demands of High lmpact, High-Wear Oil-Drilling Operations. Delivering Longer Lifespan and Less Downtime De signed for. Efficient and Durable Oil Drilling Applications with PDC Cutters.

Learn More

Learn More

Learn More

Learn More

Matching Grades to Lithology for Lower CPF

Success depends entirely on the engineering application-specifically, the precise matching of the cutting tooth grade to the formation lithology.

Chamfer Geometry

The geometry of the cutting edge, especially the chamfer, plays a decisive role in the performance:

• Large chamfer/double chamfer: It can disperse the impact force to a wider area, and can effectively protect the diamond layer in the soft and hard staggered formation with strong impact.
• Small chamfer/standard chamfer: The cutting structure is sharper, which is very suitable for maximizing the drilling rate in homogeneous, non-abrasive mudstone.

Leaching Depth and Formation Type

• Deep leaching cutters: It is essential for highly abrasive sandstone and hard rock. In these formations, heat is the main failure mode.
• Standard leaching cutters: may be sufficient for softer formations, where impact is the main problem, but thermal wear is relatively small.

Author: Frank

“With over a decade of experience in downhole tool engineering, I specialize in drill bit optimization and PDC material science. My focus is on helping operators reduce Cost Per Foot (CPF) by matching advanced cutter technologies—specifically deep leaching processes and multi-modal designs—to complex lithologies for superior drilling performance.”