Just want to throw in one example showing that a piston can be very hard:

Take the OS .91 VR-DF engine. Well known for its exceptional performance. This ducted fan engine also comes with the [:'(] ABN liner.

Last year I had a FOD engine failure causing a lack of compression. What happened? Sand grains (yes 100% silicon) originated some deep scratches into the nickel plating. Surprisingly the piston skirt didn't show any grain wear pattern.

Pistons for high performance engines are made from high silicon aluminum with SI-contents of 20 to 30%. Obviously the OS nickel plating features less abrasivity resistance...