The properties of synthetic diamond particles include particle size and size distribution, crystal morphology, impurity and inclusion content, mechanical strength (compressive strength and impact strength), and thermal stability. These properties are interconnected and together dictate the cutting/grinding efficiency, mechanical wear resistance, and ultimate service life of diamond tools.
The specific mechanisms by which each grain property determines tool performance are as follows:
1. Particle Size and Size Distribution
Cutting Force and Tool Life: In grinding processes, smaller particle sizes result in lower average cutting forces on individual grains, which helps reduce particle breakage rates and extends tool service life.
Cutting Rate and Usage Efficiency: Smaller abrasive particles reduce particle protrusion height (protrusion height determines cutting efficiency), leading to slower cutting rates and increased power consumption. Therefore, tool manufacturing must select the optimal particle size based on actual operating conditions to strike a balance between cutting rate and grain strength.
Uniformity of Size Distribution: Even for the same grade, abrasives with a more uniform particle size distribution exhibit superior overall mechanical performance and load-bearing stability, providing more consistent machining performance.
2. Crystal Morphology (Geometric Regularity and Surface Quality)
Meaning of Morphology Parameters: Parameters such as elongation, roughness, ellipticity, crystallinity, and roundness reflect the geometric features of the grains. The closer a parameter is to 1, the closer the grain shape is to a sphere or regular cube, with more complete crystal faces and smoother surfaces.
Direct Contribution to Strength: Regular crystal morphology and smooth surfaces significantly enhance a grain's resistance to fracture under external forces. For instance, abrasives with smooth surfaces show a 43% higher compressive strength than rough ones, and spherical abrasives are 20% stronger than needle-like ones. Grains with superior morphology are less prone to premature shattering during cutting or grinding, providing durable and stable mechanical support for the tool.
3. Impurities and Metallic Inclusions (Magnetic Content)
Detriment to Mechanical Strength: Metallic inclusions and other impurities entrapped during synthetic diamond synthesis (characterized by magnetic content) serve as internal structural defect sites. Lower magnetic content corresponds to higher compressive strength, impact strength, and thermal shock resistance in diamonds.
Impact on Thermal Stability and Tool Durability: During tool sintering or high-speed machining where high temperatures are generated, mismatched thermal expansion between metallic inclusions and diamond induces internal stress concentration or cleaving fractures. Abrasives with low impurity levels possess better resistance to thermal damage.
4. Mechanical Strength (Compressive Strength and Impact Strength)
Resistance to Shattering Under Static and Dynamic Loads: Compressive strength (static strength) represents the maximum static load a single diamond grain can sustain before crushing, while impact strength reflects the grain's ability to resist fragmentation under dynamic impact loading. High-strength grains can withstand heavy cutting, grinding, and polishing conditions, preventing premature crushing and directly guaranteeing tool wear resistance.
5. Thermal Stability (Thermal Toughness Index - TTI)
Performance Retention Under High Temperatures: Diamond tools undergo high-temperature environments during manufacturing sintering and friction during cutting (e.g., heating at 1100°C for 15 minutes reduces abrasive impact strength by 25%–35%).
Core Longevity Indicator: Thermal stability (impact strength after high-temperature treatment, or TTI) determines the diamond's capability to maintain high strength under harsh machining conditions and is a critical metric governing the actual working performance and service life of diamond tools.