Improvement of friction characteristics of cast aluminum-silicon alloy by laser shock peening

Abstract

Piston friction is the primary cause of power loss in automotive engines and thus reducing the friction on piston surface is crucial for the improvement of engine performance. In this work, the effects of laser shock peening on friction characteristics of JIS-AC8A aluminum-silicon alloy, a piston material for automotive engines, were investigated experimentally. Laser shock peening was carried out using a Nd:YAG laser (wavelength = 532 nm, pulse width = 8 ns) at the conditions of laser intensity 4 GW/cm2, overlapping ratio 50% and spot diameter 2.06 mm with no protective coating. When laser shock peening was applied, surface hardness increased by 22% and significant enhancement of compressive residual stress was achieved. Friction coefficients of the laser peened surface decreased by 19%, 41% and 45% from those of unpeened surface at the 50, 100 and 150 N normal load conditions, respectively, demonstrating the effectiveness of laser shock peening in reducing surface friction. Also, the mass loss by wear decreased by 94%. ? 2018 Elsevier B.V.