Ceramic Inserts

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.

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 SFM	150 - 400 mm/min 500 - 1300 SFM	100 - 400 mm/min 330 - 1300 SFN	N/A
Machining Aluminum	300 - 800 mm/min 1150 - 2600 SFM	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

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

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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