Machinable Ceramics

COMBAT® Boron Nitride Machinable Ceramics are made by hot pressing boron nitride powders at high temperature and pressure. These ceramics can easily be machined into rods, bars, plates and even intricate custom shapes.

The unique combination of 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. 

  • Excellent thermal shock resistance
  • High electrical resistivity
  • High thermal conductivity
  • Good chemical inertness
  • High temperature material
  • Excellent lubricating properties -- low coefficient of friction
  • Non-wetting (without oxidation)
  • High dielectric breakdown strength
  • Excellent machinability
COMBAT Machinable Ceramics Grades

Learn more about our binder-bonded grades A and HP, with over 90% BN, our highest purity (>99.7% BN) grade AX05, and our composite grades M, M26 and ZSBN.


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 has been specified in many applications for over 50 years. 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 grade HP uses a calcium borate binder system. It is particularly useful for applications where low thermal expansion, high thermal shock resistance, and increased spallation resistance is required. With improved moisture resistance compared to grade A, grade HP is Saint-Gobain’s workhorse hBN grade sold in applications worldwide. HP is well known in the aerospace community as a mission-proven component in Hall Effect Thrusters for satellite propulsion.

Like all other hBN grades offered by Saint-Gobain, both HP and HPL are easily machinable to intricate shapes with precise tolerances.


The best in its class, COMBAT® Machinable Ceramics grade AX05 is the highest purity hBN available at 99.7%+. 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 particularly suitable for applications where other hBN ceramics fail, such as crucibles for high-purity molten metals, nozzles for specialty alloys and insulators for high temperature processes.

M & M26

COMBAT® Machinable Ceramics grades M & M26 are unique ceramic composites of hBN in a silica matrix, offered only by Saint-Gobain. The silica (SiO2) binder system contributes to its excellent moisture and 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. M Grade has an edge in applications where better mechanical strength is required. M26 has an advantage in applications where higher thermal conductivity and moisture resistance is required. M26 has been tested by NASA and is now a popular grade, in addition to HP, for hall effect thrusters. 

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.


COMBAT® Machinable Ceramics grade ZSBN combines the best properties of hot-pressed boron nitride with the non-reactivity and strength of zirconia and silicon carbide. Most commonly used as break rings for horizontal continuous casters, its unique thermal, chemical, electrical, wear and machinability properties permit a wide variety of molten metal contact applications. 

ZSBN, which is made up of hard ZrO2 particles evenly dispersed with soft BN platelets in a borosilicate glass matrix, offers outstanding wear resistance, non-wetting properties, high thermal conductivity and superior high temperature strength. ZSBN is ideal for molten metal applications such as continuous casting break rings, metal atomizing nozzles, and side dams for thin strip casting. Other potential areas for ZSBN include wear components, such as guides and rollers in diverse glass and light-metal baths. 

Related Documents

Data Sheets
COMBAT Machinable Ceramics (Datasheet)

Technical Datasheet for COMBAT Boron Nitride Solids. Revision March 2022.

PDF | 313.92 KB
COMBAT Machinable Ceramics (Datasheet)
Data Sheets
COMBAT Machinable Ceramics, Machining (Technical Bulletin)

Best practices for machining COMBAT BN Solids & Composites. Revision 2017.

PDF | 620.28 KB
COMBAT Machinable Ceramics, Machining (Technical Bulletin)
Data Sheets
COMBAT Machinable Ceramics, Grade ZSBN (Technical Bulletin)

Technical overview of grade ZSBN for Specialty Powder Metal Atomization. Revision 2017.

PDF | 201.35 KB
COMBAT Machinable Ceramics, Grade ZSBN (Technical Bulletin)


What is the difference between the various grades?

Our Combat® boron nitride grades are differentiated based on their composition, and therefore the specific properties they offer.

  • AX05 is the industry leading high purity grade, ideal for the highest temperature applications.
  • Grade HP and A are our standard purity grades that offer improved strength due to the binder phase.
  • M and M26 are composites of BN and silica, commonly used in low-loss, high frequency shielding applications.
  • ZSBN is a composite of BN, silica and zirconia, giving it high wear & corrosion resistance well suited for metal forming applications.

Please contact us for help with grade selection for your application. 

Are boron nitride machinable ceramics anisotropic?

The pressing process to create a solid BN block induces some alignment of BN platelets in the process.  This creates properties of the material that can vary based on the orientation of that part relative to the pressing direction.  The difference in values of several properties in parallel and perpendicular to the pressing direction can be noted in the technical data sheet on the product page.

Learn more on directionality of boron nitride machinable ceramics.

How can I ensure that my parts will be machined in the desired direction given that BN is an anisotropic material?

It is important to know the properties critical to your application, so parts are machined in appropriate direction. We encourage you clearly mark the desired directionality in your part drawing as well as PO. Without such specification, we cannot guarantee a particular directionality in your parts.

What are the maximum size parts you can make?

The parent billet for our grades HP, M and M26 are 19” x 19” x 16”. Parent billet size for ZSBN is 19” x 19” x 6”. We can make parts that fit the envelop of the parent billet. 
Due to the unique processing steps of our industry leading, high purity grade AX05, we can make parts that fit the parent billet envelop of 19” x 19” x 16”; however, the maximum wall thickness can not exceed 1.5”.  For example, we cannot supply a rod 12” dia x 12” long, but we can supply a tube 12” OD, 10.5” ID and 12” long.

Do you offer standard sizes of machinable ceramics?

Standard shapes are available for ALL GRADES. Dimensions below are shown in inches. Note that due to the parent billet size limitation, ZSBN square bars & rods are only available with 6" length.

Plates Square Bars Rods
Thickness Width Length Width x Height Length Diameter Length
0.25" 5" 6" 0.25" x 25" 8" or 16" 0.25" 8" or 16"
0.25" 5" 12" 0.38" x 0.38" 8" or 16" 0.38" 8" or 16"
0.25" 10" 12" 0.50" x 0.50" 8" or 16" 0.50" 8" or 16"
0.50" 5" 6" 0.63" x 0.63" 8" or 16" 0.63" 8" or 16"
0.50" 5" 12" 0.75" x 0.75" 8" or 16" 0.75" 8" or 16"
0.50" 10" 12" 1.00" x 1.00" 8" or 16" 1.00" 8" or 16"
0.75" 5" 6" 1.5" x 1.5" 8" or 16" 1.5" 8" or 16"
0.75" 5" 12" 2.00" x 2.00" 8" or 16" 2.00" 8" or 16"
0.75" 10" 12" *ZSBN only available  with 6" length

*ZSBN only available  with 6" length



1.00" 5" 6"
1.00" 5" 12" **Tolerance:

+0.200/-0.000" on diameter

+0.063/-0.00" on length

1.00" 10" 21"



Plates & bars available in saw cut or finished tolerances

Saw Cut Tolerance: +0.250"/-0.000" on ALL dimensions

Finished Tolerance: +/-0.010" on (wdth/thck) / +0.063"/-0.000" length

What are the standard tolerances you offer?

Our standard tolerance for saw cut parts are +0.250 (+6.35mm) / -0.000 (0.0mm). Below are our standard tolerance guideline for machined parts, unless specified otherwise by our customers. 

Standard Tolerances
Part Name Diameter Thickness Length O.D. I.D.
  inches mm inches mm inches mm inches mm inches mm

<0.250" thk w/max dia/width 6")

±0.015 ±0.4 +0.000
n/a n/a n/a
Rods +0.020
n/a +0.063


n/a n/a
(<1" thk)
±0.020 ±0.5 ±0.010 ±0.3 n/a n/a  n/a 
Washer / Ring
(disc w/I.D.; <1" thk)
n/a ±0.010 ±0.3 +0.063
±0.020 ±0.5 ±0.010 ±0.3
Tubes n/a n/a +0.063
±0.020 +0.5 ±0.010 ±0.3
Crucible n/a n/a +0.063
±0.020 +0.5 ±0.010 ±0.3
  Width Thickness Length  
  inches mm inches mm inches mm  
Bars ±0.010 ±0.3 ±0.010 ±0.3 +0.063
n/a n/a
Plates ±0.010 ±0.3 ±0.010 ±0.3 +0.063
n/a n/a




I would like to buy a machined part with intricate features. How do I go about that?

We have machining facilities inhouse that allow us to serve the customers that want machined components. We ask you send us your drawing or sketch with grade reference, directionality preference if any, and tolerance specifications. All Combat® BN grades are easily machined and detailed surfaces, pockets, channels, grooves, holes, threads, etc. can be designed into the finished part. 

I have a machine shop, but I have never machined boron nitride. What do I need to know about boron nitride machining?

The key feature to note is that boron nitride is machined dry - without coolants or lubricants. Most grades can be machined with standard carbide tip tooling. ZSBN requires diamond tipped tooling for efficient operation. 


What is the shelf life of BN machinable ceramics? What are the recommended storage guidelines?

The shelf life for solid BN grades is 3 years. Boron nitride should always be stored in a dry space, tightly sealed, in its original packaging if possible, to avoid exposure to moisture.

I purchased some boron nitride that is past its shelf life. Can I still use it?

Boron nitride ceramic that has been sitting past its shelf life or has not been stored according to the storage guidelines may have picked moisture and will not perform as intended. The best way to use such material is by baking it to ensure it is restored to its original condition. We recommended soaking for 6 hours or longer in Nitrogen at the rate of 10°C/min to 450°C, followed by cooling down at the same rate. If heated too quickly, spalling may take place. Other protecting atmosphere, such as Ar, can also be used. If the materials are in a protecting atmosphere, the soak temperature can be as high as 1200°C.

What makes boron nitride ceramic resistant to thermal shock?

The coefficient of thermal expansion for BN is so small that it is nearly zero, giving it dimensional stability across a wide range of temperatures. Coupled with its low thermal mass, due to instrinsically high thermal conductivity and low density (about 50% lower than alumina), BN is virtually unaffected by rapid increases and decreases in temperature.

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