Analysis of Core Performance Parameters for Cemented Carbide Chisels

The cemented carbide chisel is the heart of modern rock drilling tools, and its performance directly determines drilling efficiency and tool life. To scientifically select and use these chisels, it is essential to deeply understand the following core performance parameters.

1. Hardness: The Primary Indicator of Resistance to Penetration and Wear

Hardness is a parameter that measures the ability of a cemented carbide chisel's surface to resist penetration or scratching by foreign objects, typically expressed in Rockwell Hardness (HRA). It is primarily determined by the hardness, grain size, and distribution of the tungsten carbide (WC) within the material. High hardness means the chisel can more effectively bite into hard rock and resist abrasive wear from rock cuttings, thereby maintaining a sharp edge and extending service life. In highly abrasive rock formations, hardness is the primary selection criterion.

2. Toughness: The Key Guarantee Against Impact and Fracture

Toughness represents the material's ability to absorb energy without fracturing. Drilling is a high-frequency, high-stress impact process. If the chisel lacks sufficient toughness, it is highly prone to chipping, cracking, or even complete failure. Toughness primarily depends on the content and distribution of the cobalt (Co) binder phase. Generally, a higher cobalt content results in better toughness. In fractured and heterogeneous rock formations, high toughness is the lifeline preventing premature chisel failure.

3. Flexural Strength: The Measure of Load-Bearing Capacity

Flexural strength is the maximum stress a material can withstand before fracturing under a bending load. It comprehensively reflects the "strength" and "toughness" of the cemented carbide and is directly related to the chisel's ability to resist fracture under immense impact forces and complex bending moments. A chisel with high flexural strength is like having a robust "backbone," enabling it to stably endure the various stresses encountered in harsh working conditions and ensuring operational safety and reliability.

4. Fracture Toughness: The Resistance to Crack Propagation

Fracture toughness is a more advanced indicator of toughness, specifically referring to the ability of a material containing micro-cracks to resist unstable crack propagation. In practical production, microscopic defects within the material are inevitable. High fracture toughness means that even if micro-cracks develop, they are unlikely to rapidly propagate and cause complete failure. This parameter is crucial for ensuring tool safety under extreme conditions involving eccentric loads (e.g., bit slippage).

Conclusion: The Balance and Synergy of Properties

It is important to emphasize that these core parameters do not exist in isolation but are interdependent and often involve trade-offs. The pursuit of extremely high hardness often comes at the cost of reduced toughness and strength, and vice versa. For instance, chisels with fine grains and low cobalt content exhibit high hardness and wear resistance but relatively lower toughness. Conversely, chisels with coarse grains and high cobalt content offer better toughness and strength but somewhat lower hardness.

Therefore, selecting a cemented carbide chisel is not about pursuing the ultimate in a single parameter. Instead, it is about finding the optimal balance point between hardness, toughness, and strength based on the specific rock formation conditions (e.g., whether they are hard and intact or fractured and complex). This approach achieves the longest service life and highest efficiency.