Enhancement of bronze alloy surface properties by FSP second-phase particle incorporation

Abstract

This paper presents results of an experimental study to evaluate friction stir processing (FSP) with and without hard second-phase particle incorporation as a means to enhance surface properties and wear performance of C86300 manganese bronze alloy. FSP of flat bronze alloy specimens was conducted with hardened H-13 tool steel to create a 3-mm-thick processed surface layer. The process was also used to incorporate B4C particles, thereby creating a metal-matrix composite layer on the alloy surface. FSP alone was observed to produce substantial reduction in grain size (from an initial value of 350μm to 1–5μm). FSP without particle incorporation resulted in modest surface hardening due to grain refinement and dispersion hardening. Under lubricated contact in block-on-ring testing with a hardened steel counterface, FSP produced substantial reduction (about 3X) in bronze wear after polishing of processing surface roughening. FSP with hard B4C second-phase particle incorporation further reduced wear by up to 20X. The improvement in wear behavior is attributed to grain refinement and load shielding by second-phase particles, as determined by wear mechanism analysis.