Pistons are made from aluminium with high silicon content, resulting in a very abrasive material. 

High-silicon aluminum alloy has higher hardness and wear resistance than other aluminum alloys. When cutting, the cutting tool alternately cuts soft aluminum-based and hard silicon particles, the carbide insert are easy to wear and also easily produce BUE, which will affect the roughness and processing accuracy. 

In order to avoid the BUE and work hardening, the cutting edge must be sharp and the cutting edge must be smooth. PCD tool just meets all these requirements.Machining such material requires high wear resistant tooling, such as cutters and inserts made of PCD.