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What is a Ceramic Insert?

Ceramic Inserts are indexable inserts made from Aluminium Oxide Al2O3 or Silicon Nitride Si3N4. They have a hardness of 2,100-2,500 HV (About 40% above carbide), which enables them to machine Hard Steel up to 55 HRC. It can also machine cast iron and nickel-based alloys six times faster compared to coated carbide inserts.

Ceramic Insert

What are Ceramic inserts used for?

  • Machine Steel heat treated up to 55 HRC. (Coated carbide inserts cannot machine materials above 45 HRC).
  • Machine Cast Iron 6 times faster compared with coated carbide inserts.  (~ 2,000 mm/min, 6,50 SFM)
  • Machine Nickel-based superalloys seven times faster compared with coated carbide (400 mm/min, 1,300 SFM)

CERAMIC inserts working materials and cutting speeds

PROPERTY CARBIDE CERAMIC CBN PCD
Hardness [HV] 1,300-1,800 2,100-2,400 4,500-5,000 5,000-6,000
Price per Cutting Edge [USD] 4$ 10$ 40$ 160$
Machining Hard Steel
  • 10 - 45 HRC
  • 50 - 100 mm/min
  • 160 - 320 SFM
  • 40 - 60 HRC
  • 100 - 300 mm/min
  • 330 - 660 SFM
  • 50 - 70 HRC
  • 150 - 350 mm/min
  • 500 - 1150 SFM
N/A
Machining Cast Iron
  • 200 - 300 mm/min
  • 650 - 1000 SFM
  • 400 - 800 mm/min
  • 1300 - 2600 SFM
  • 500 - 2000 mm/min
  • 1500 - 6500 SFM
N/A
Machining Super Alloys
  • 20 - 60 mm/min
  • 65 - 200 SFN
  • 150 - 400 mm/min
  • 500 - 1300 SFM
  • 100 - 400 mm/min
  • 330 - 1300 SFN
N/A
Machining Aluminum
  • 300 - 800 mm/min
  • 1150 - 2600 SFN
N/A N/A
  • 600 - 2500 mm/min
  • 2000 - 8000 SFM

Main Types of Ceramic Inserts

NAME COLOR COMPOSITION APPLICATIONS
Silicon Nitride Grey Silicon Nitride (Si3N4) Used for roughing and finishing applications in grey cast iron.
White Ceramics White Aluminium Oxide (Al2O3) Used for roughing and finishing applications in alloyed cast iron.
Black Ceramics / Mixed Ceramics / Composite Ceramics Black Aluminium Oxide (Al2O3) with Titanium Finishing applications on Hard Steel and Cast Iron
Sialon Grey α and β SiAlON Used for turning Nickel-Based alloys at very high cutting Speeds. Provide slightly lower performance when compared to Whiskers but at a much lower price
Whiskers Green silicon carbide whiskers (SiCw) Exterme toghness. Used for turning Nickel-Based alloys at very high cutting Speeds

Machining Nickel-based superalloys with Ceramic Inserts

Super Alloys ISO S

Machining Nickel-Based Superalloys is the most popular application for Ceramic inserts because it enables machining these difficult-to-cut materials 5-7 times faster than with the best suitable carbide grades. For example, Inconel 718 is cut at 40 mm/min (130 SFM) with suitable carbide grades. Can be machine at 400 mm/min (1,300 SFM) with Ceramic inserts. Manu typical parts from this material are vast in size, and it can take many hours to machine a single part. In such cases, the higher price of the inserts is negligible compared to the money saved on machining time.

Best machined with Sialon Grades.

Advantages:

  • Lower price when compared with CBN.
  • High hardness level.
  • High wear resistance.
  • Low thermal conductivity
  • Very good stability in high temperatures
  • Very high cutting speeds

Disadvantages:

  • Higher price compared with carbide.
  • Low toughness.
  • Problematic for interrupted cuts.

Machining Cast Iron with Ceramic inserts

Cast Iron ISO K

Ceramic inserts can machine Cast Iron at phenomenal speeds up to 800 (2600 SFM). The higher price of the inserts is negligible compared to the money saved the increased productivity.

Best machined with White and Silicon Nitrite Grades.

Machining Hard Steel with Ceramic Inserts

The more common and also technically superior solution to machine hard steel is with CBN inserts. They can work on harder materials at higher cutting speeds and produce a superior surface finish. The major drawback is their very high price. Ceramic inserts fall in the middle between coated carbide and CBN in both price and performance and are the preferred option to machine hard steel in the range of 45-55 HRC.

Best machined with Black (composite) Grades.

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