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Free Sintering vs. Hot Pressing Sintering in Diamond Tool Manufacturing
2026-02-25
Sintering, the core process in diamond tool production, features two distinct technical routes: free sintering and hot pressing sintering. These two methods directly determine the final performance and cost structure of the tools. Understanding their differences is analogous to distinguishing between baking and forging—it serves as the foundation for rational material selection and process design.
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The fundamental difference between these two processes lies in whether external uniaxial mechanical pressure is applied during sintering.
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1. Hot Pressing Sintering: Active "Forging"
Core Principle: High pressure (dozens of megapascals) is applied simultaneously with high temperature. This is equivalent to using a “forging hammer” to compact the powder while it softens, forcing plastic deformation, flow, and tight rearrangement of powder particles.
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Results: Virtually all porosity is eliminated, producing a matrix with extremely high density (over 98% of theoretical density). The matrix exhibits high strength and hardness, providing exceptional mechanical retention for diamond particles.
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Drawback: High pressure may cause micro-damage to diamonds, especially brittle diamond grades.
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2. Free Sintering: Passive "Baking"
Core Principle: Densification occurs solely under high temperature and protective atmosphere, driven by surface diffusion, mass transport, and alloying reactions among powder particles—without external pressure.
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Results: A certain level of residual porosity remains (typical density ranges from 85% to 95%). The matrix offers relatively good toughness, preserves diamond integrity extremely well, and delivers excellent initial sharpness.
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Drawback: The absolute strength and wear resistance of the matrix “skeleton” are generally lower than those of hot-pressed products, which is the main reason why tool life is often a limiting factor.
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