Experimental investigation of the effects of friction stir processing and shot peening on mechanical properties of ductile iron

Abstract

Friction stir processing (FSP) and shot peening (SP) have been developed as surface hardening techniques and have been studied by several researchers to produce an upper surface modification of metallic materials for enhancing improved mechanical properties of different materials. In this study, the influences of these method son mechanical properties of ductile iron ASTM A536, grade (80-55-06) ferrite/pear lite have been investigated. The micro hardness, strength and fatigue life of the ductile iron have been analyzed. Microscopic investigations reveal graphite grain refinement and crashing of 100% of the original size with FSP and 50% with SP on the processed surfaces. The hardness increases by 200% and 100% compared to as cast for FSP and SP applications, respectively. The elongation, ultimate tensile strength and fatigue life have been increased by 28%, 22% and 233% using FSP respectively whereas, the increments are 18%, 8% and 66% using SP compared with the original ductile iron. The stated improvements have been related to surface modification, residual stresses and phase transformations through the employed processes in this study.