Scuffing Resistance of Selected Materials as Protection for Bores in Aluminum Engine Blocks

This paper describes alternatives for cylinder bore protection based on liners fabricated from hypereutectic A1-Si alloys, A1 based metal matrix composites, and hard oxide, plasma sprayed synthetic iron and electrodeposited Ni-SiC coatings.

An effective and economical bench test was developed which simulated the interactions of piston rings and cylinder bore surfaces to rank the different alternative materials. Scuffing was characterized microscopically by material transfer between the ring and the cylinder bore surface.

The scuffing resistance was rated by the scuffing-start time under different pressures exerted by the ring against the liner. The experimental results showed that among all alternative materials, hard oxide and electrodeposited Ni-SiC coatings had the best scuffing resistance; however, damage to the piston rings was observed. Hypereutectic A1-Si alloys and A1 based composites also are acceptable, but less abrasive to the ring.