Surface Modification and Nanocomposite Layering of Fastener-Hole through Friction-Stir Processing

Abstract

This investigation studied the surface modification and nanocomposite layering of the cylindrical surface of a fastener-hole using friction-stir processing. A tapered tool rotates and transverses a predrilled hole that gradually expands and simultaneously stirs the surface. The stirring modifies the hole's cylindrical surface to help improve the hardness and resist against fatigue loading. Introduction of nanoparticles between the tool and the hole during the friction stirring results in formation of a nanocomposite layer that further improves the fatigue performance. The process development and resulting changes in surface finish, hardness, compressive residual stress near the hole, and fatigue life are presented; the strengthening mechanisms and their relationship with the process parameters are discussed.