Surface Structure Differences: The surface of ordinary diamond crystals has dangling bonds (extra valence electrons), making it prone to oxidation or bonding with external electron-deficient atoms. In contrast, the boron atoms on the surface of boron-doped diamonds form stable covalent bonds with the inner carbon atoms, resulting in a stable state with no dangling bonds on the crystal surface. This leads to a fundamental difference in their physical and chemical properties.

Heat Resistance and Oxidation Resistance: The heat and oxidation resistance of boron-doped diamond is significantly superior to that of ordinary diamond. Its initial surface oxidation temperature is about 200°C higher than that of undoped diamond. In high-temperature environments (e.g., 800°C to 1000°C), the wear ratio of boron-doped polycrystalline diamond decreases very little, and the weight loss is minimal, whereas the wear ratio of ordinary polycrystalline diamond drops significantly.

Electrical Properties: Ordinary diamond has extremely low electrical conductivity (about 10?¹? to 10?¹³ Ω?¹·cm?¹), while boron-doped diamond has good electrical conductivity (up to 10?? to 10?¹ Ω?¹·cm?¹) as a hole-conducting type conductor, and its conductivity exhibits anisotropy on different crystal faces.

Chemical Inertness: When machining iron-group metals (such as quenched steel, high-speed steel, etc.), the extra valence electrons on the surface of ordinary diamond easily bond with the iron atoms on the metal surface, causing a "sticking" phenomenon and forming a built-up edge. On the contrary, boron-doped diamond exhibits strong chemical inertness because it has no extra valence electrons on its surface. It neither bonds with oxygen atoms nor sticks to iron-group metals, and no built-up edge is formed, which significantly improves the quality of the machined parts.

Mechanical Properties (Wear Resistance, Compressive Strength, and Impact Toughness):
Wear Resistance and Grinding Ability: Boron-doped diamond is highly efficient in grinding operations. For example, when grinding optical glass or hard and tough materials, its wear resistance and processing efficiency are usually several times higher than those of ordinary diamond.
Compressive Strength: The compressive strength of boron-doped diamond crystals is higher than that of ordinary diamond crystals.

Impact Toughness: When drilling into hard rock formations, boron-doped polycrystalline diamond rarely fractures, showing significantly better impact toughness compared to ordinary polycrystalline diamond drill bits and natural single-crystal diamond drill bits.

Color Differences: Pure ordinary diamond is usually colorless, and impurities entering the crystal lattice cause coloration. Due to the incorporation of boron atoms, boron-doped diamonds can appear black, blue, gray, dark green, brownish-red, or transparent yellow, depending on the boron content and distribution. When the boron content is high enough, the crystal appears black.

Thermal Conductivity: Boron-doped diamond and its polycrystals possess good thermal conductivity, which helps lower the temperature during tool usage, reducing plastic deformation and wear.