How to use ceramic insert for hardened steel
The primary use case for ceramic inserts is machining hardened metal, including Hard Steel heat treated up to 55 HRC (coated carbide inserts cannot machine materials above 45 HRC). These indexable cutting tools also work very well on cast iron and nickel-based alloys six times faster than coated carbide.
A big disadvantage of using ceramics is the extreme brittleness that comes with their high hardness. To address this problem, we introduced whisker-reinforced ceramic inserts that have small crystals of silicon carbide in them. These small crystals act as a reinforcing material, similar to glass threads in fiberglass.
Getting started with ceramics
To reduce the brittleness of a ceramic cutter, it's important to properly edge prep the part before milling or turning. This is especially true for parts that have a lot of scale or roughness on the outside diameter (OD).
Preventing brittleness in the first place
The main reason for breakage in ceramic cutters is entering the cut on a sharp corner, to prevent this, a chamfer should be created on the end of the part before milling or turning and then the cut should be entered with the ceramic insert.
Another thing to consider is running coolant in the cut. This is not a good idea because it dissipates the insert's heat, which can lead to thermal cracking and chipping. The best way to avoid these problems is to program the tool correctly and not run coolant when you're milling or turning.