Drilling Tip Hardness and Fracture Resistance via cBN Ceramic Binder
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Solution Overview
Problem
Existing drilling tips made of polycrystalline diamond sintered materials have low toughness, leading to poor fracture resistance and wear resistance issues, especially in high-temperature drilling conditions and Fe or Ni mines. Additionally, cubic boron nitride sintered materials suffer from low hardness and thermal expansion differences with metal binders, causing cracks under high-temperature drilling.
Innovation Solution
A drilling tip with an outermost layer having a Vickers hardness of 3,700 to 4,250, featuring cubic boron nitride grains with an average grain size of 0.5 to 8.0 µm, and an intermediate layer containing 30 to 70 vol% of cubic boron nitride or diamond grains. The method involves pretreating the cubic boron nitride grains with an AlN film, mixing with a binder phase powder, and sintering at high pressure and temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a polycrystalline diamond sintered material is used for the hard layer, then wear resistance is improved, but fracture resistance deteriorates due to low toughness
Solution Approach 1:
The patent uses a composite material consisting of cubic boron nitride grains (providing hardness and wear resistance) and a ceramic binder phase (providing toughness and fracture resistance). This composite structure allows the hard layer to simultaneously achieve high wear resistance and improved fracture resistance compared to pure polycrystalline diamond.
2Reliability
If a cubic boron nitride sintered material with metallic catalyst is used, then fracture resistance is improved, but hardness decreases under high-temperature drilling conditions
Solution Approach 1:
The patent changes the binder phase from metallic to ceramic material, which fundamentally alters the thermal stability parameters. The ceramic binder phase maintains its structural integrity at high temperatures (above 700°C), preventing the graphitization of diamond and maintaining the hardness of the cubic boron nitride grains under high-temperature drilling conditions.
Solution Approach 2:
The patent addresses thermal expansion issues by using a ceramic binder phase that has better thermal expansion compatibility with cubic boron nitride grains compared to metallic catalysts. This reduces thermal stress and prevents crack formation under high-temperature drilling conditions, thereby maintaining both fracture resistance and hardness.
3Strength
If the content of cubic boron nitride grains is increased to improve hardness, then wear resistance is improved, but sintering difficulty increases due to unsintered portions
Solution Approach 1:
The patent optimizes the particle size parameters of cubic boron nitride grains to a specific range (0.5 to 8.0 µm) that facilitates complete sintering. This parameter optimization ensures that even with high cubic boron nitride content (70-95 vol%), the grains can be fully densified during sintering without leaving unsintered portions, thereby achieving both high hardness and ease of manufacture.
4Strength
If diamond sintered material is used in Fe or Ni mines, then wear resistance is improved, but chemical stability deteriorates due to high affinity with Fe and Ni
Solution Approach 1:
The patent changes the chemical composition parameters by replacing diamond with cubic boron nitride, which has fundamentally different chemical properties. Cubic boron nitride exhibits low chemical affinity with Fe and Ni, providing excellent chemical stability in these mining environments while maintaining the required wear resistance through its high hardness.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting drilling tip achieves a hardness comparable to polycrystalline diamond sintered materials, providing enhanced wear resistance and fracture resistance, suitable for use in Fe or Ni mines and high-temperature drilling conditions.
Implementation Method 1
The method involves pretreating the cubic boron nitride grains with an AlN film, mixing with a binder phase powder, and sintering at high pressure and temperature
Implementation Method 2
The method involves pretreating the cubic boron nitride grains with an AlN film
Data Source
Figure 1
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AI summary
A drilling tip according to the disclosure has a tip body which is provided with a tip portion tapered toward a tip side of the tip body; and a hard layer which is formed on a surface of the tip portion of the tip body, an outermost layer of the hard layer is a cBN sintered material having 70 to 95 vol% of cBN grains, and when a cross-sectional structure of the outermost layer is observed, a binder phase having a width of 1nm or greater and 30nm or less and containing Al, B, and N, and in which a ratio of an O content to an Al content is 0.1 or less exists between neighboring cBN grains.