Boron Nitride machinable ceramic is made by hot pressing Boron Nitride powders at high temperature and pressure. Combat Boron Nitride can easily be machined into rods, bars, plates and even intricate custom shapes.
The unique combination of highly exceptional thermal, physical and chemical characteristics of Combat Boron Nitride ceramic makes it ideal for solving tough challenges in a wide range of industrial applications.
Hot pressed boron nitride, sometimes referred to as "white graphite" has a platey, hexagonal structure. Atoms in the basal or platelet plane are held together by strongly directed covalent bonds in a hexagonal array. This type of bond, similar to that found in diamonds, yields excellent physical, thermal and electrical performance under a wide range of uses.
In contrast, the bonds between platelet layers are weak Van der Waals forces, resulting in highly directional or anisotrophic properties. Although these weak bonds can reduce the physical strength of the overall material, they impart many unique electrical and mechanical properties, most notably, its lubricious nature. Hexagonal Boron Nitride can be easily machined into complex shapes using conventional high speed cutting tools.
During the formation of Combat Boron Nitride Ceramic, this undirectional hot pressing results in the orderly arrangement of the boron nitride platelets (see illustration).
When ordering Combat® Boron Nitride Solids, standard shapes are generally fabricated as shown in the illustration unless specific orientation is requested.
The best in its class, Combat® Machinable Ceramics Grade AX05 is the highest purity hBN available at 99.7%+. With its high purity, it offers the highest temperature resistance in excess of 2000ºC in inert or vacuum environments, while maintaining its outstanding electrical insulator properties at a dielectric strength of >40kV/mm. This makes it an excellent choice for applications where high temperature capabilities and corrosion resistance are important.
AX05 is a unique, binder-less ceramic with exceptional thermal conductivity and thermal shock resistance. Its high purity makes it exceptionally suitable for applications where other hBN ceramics fail - crucibles for high-purity molten metals, nozzles for specialty alloys, insulators for high temperature etc.
Combat® Machinable Ceramics Grade A uses B2O3 binder system to add mechanical strength to hot pressed hBN. One of the legacy products since the scientific community discovered the benefits of hot pressed hBN, Grade A is specified into applications from a long time ago. Grade A offers a practical choice for high temperature insulators, kiln furniture, and general purpose applications, and continues to finds new applications.
Due to the hygroscopic binder system, care must be taken during storage and use to avoid exposure to moisture.
Combat® Machinable Ceramics HP Grade uses calcium borate binder system. It is particularly useful for applications where low thermal expansion, high thermal shock resistance, and increased spall resistance is required. A great alternative for minimal moisture exposure due to its binder system, Grade HP is Saint-Gobain’s workhorse hBN grade sold in applications worldwide.
Like all other hBN grades offered by Saint-Gobain, both HP and HPL are easily machinable to intricate shapes with precise tolerances.
Combat® Machinable Ceramics Grade M and M26 are unique ceramic composites of hBN in a silica matrix, offered only by Saint-Gobain. Silica (SiO2) binder system contributes to its excellent moisture/thermal shock resistance. These grades can operate up to 1400°C,
M26 Grade has 60% hBN and 40% semiconductor grade SiO2, whereas M has 40%hBN and 60% semiconductor grade SiO2. M26 Grade has an edge in applications where better mechanical strength is required. M has an advantage in applications where higher thermal conductivity and moisture resistance is required.
While both Grades M and M26 are both thermally excellent materials, the most important features these grades offer is the electrical properties - high dielectric strength (>40KV/mm) along with a low dielectric constant k (<4), making them exceptionally useful in microwave environments in the GHz ranges. These grades have successfully passed MIL-I-10A grade of L542 test, a procedure requiring immersion in water for 48 hours prior to testing at elevated frequencies.