A surface modification method has been developed that uses shot peening to reduce the rubbing resistance on piston wear surfaces. This technique shoots roughly spherical ceramic bead having a central particle diameter of 40 μm with compressed air at a speed of 100 m/sec or more against the surface of the object to be processed. This peening treatment produces countless microscopic dimples that improve the oil retention capability of the treated surface and results in a 2–2.6% reduction of the lost output from an engine unit due to friction. Engine units with this treatment were subjected to an extended operation test to verify the sustainability of the effects from this treatment. The results showed that dimples remained on the parts even after an extended period of operation. The treatment was also proven to be effective in increasing the anti-seizure characteristics of the pistons.
Article of Honda R&D Technical Review Vol.12 No.2 (93 - 98)