Which tool to choose for machining superalloy?

30 November 2022
Challenge: What if carbide tools do not work with HRSA superalloys?
Solution: Correct application of ceramic insert grades can be a powerful alternative.
Sialon and whisker-reinforced ceramics are viable alternatives for both turning and milling of high-temperature alloys (HRSA).
An important part is Inconel alloys, commonly used in high-temperature applications in aircraft engines and energy production.
Another increasingly common application is welding hard materials in the oil and gas industry. 
ceramic inserts
Ceramics are hot-hardened and have low reactivity to the workpiece material, but they have the disadvantage of lower strength and toughness compared to cemented carbide.
This requires a highly rigid machining process that minimizes vibration. Tool overhangs should be short, entry and exit should be smooth and full slotting should be avoided during milling operations.
Ceramic turning and milling operations present some key differences.
In turning operations, cutting speeds are up to about 300 m/min; milling tools can be up to 1000 m/min. Ceramic turning requires uninterrupted, high-flow coolant; milling operations require no coolant at all to avoid thermal stress.
Round inserts are the best choice for turning or milling. A lower depth of cut is recommended to achieve a small entering angle to avoid groove wear.
ceramic inserts
The main guideline for ceramic milling is to use relatively low (compared to carbide) feed rates (0.05–0.08 mm/tooth) to achieve very high cutting speeds.
The resulting high temperature around the cutting area enhances the cutting action and promotes the efficient removal of hot, small chips. Face milling is superior to edge milling and waterline milling.
Climb milling is recommended for positive inserts. Up-cut milling is recommended for negative rake geometries, resulting in thick chips at the exit.
ceramic inserts
Through an optimized approach, the ultimate speed capability of ceramic tools dramatically increases metal removal rates for demanding HRSA superalloy applications.

Customer case

Workpiece: Inconel Parts


Fast feed tool



Carbide inserts

Ceramic insert RNGN 12 07 00-E

Cutting speed

Vc (m/min)



Feed per tooth

fz (mm)



Table feed

Vf (mm/min)



Depth of cut

ap (mm)



Cutting width

ae (mm)



Metal removal rate

Q (cm3/min)




This saves a total of 42 hours of cutting time per year and increases productivity by 469%.


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