What Conditions Must Be Met for Pressureless Sintering to Achieve Density Comparable to Hot Pressing?

2025-12-23

It is widely recognized in the industry that tools produced via pressureless sintering are primarily limited by insufficient service life—reaching 90% of the lifespan of hot-pressed sintered tools is already considered excellent. Achieving hot-pressed sintering performance with pressureless sintered tools is by no means a default outcome; instead, it strictly depends on the simultaneous fulfillment of the following conditions:

Superior Powder Characteristics:

Using Pre-Alloyed Powders with fine particle size and low oxygen content reduces the bridging effect, enhancing sintering activity and liquid phase uniformity.

Scientific Formulation Design:

The binder must generate an optimal liquid phase within a precise sintering window and exhibit good interfacial compatibility with diamond (this can be improved by adding active elements such as Cr or Ti).

Precise Process Control:

Sintering temperature, heating rate, holding time, and protective atmosphere (e.g., vacuum or reducing atmosphere) must be precisely matched to the material system to provide optimal kinetic conditions for liquid phase formation, mass transfer, and pore elimination.

When the above conditions are satisfied, pressureless sintering not only achieves bulk density equivalent to hot pressing but also yields a homogeneous structure with isotropy and no density gradient—this is the fundamental reason it is regarded as a high-performance manufacturing route.

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