Shot Peening Materials Science

Author:  Dr. David Kirk | Coventry University
Source:  The Shot Peener magazine, Vol 37, Issue 2, Spring 2023
Doc ID:  2023018
Year of Publication:  2023
Abstract:  
INTRODUCTION The most important question in the Universe is probably “Why?” For shot peening it applies to the several materials that are at the heart of the process. For example, “Why is steel shot so commonly used?”. Materials science covers all of the materials used in shot peening—metals, ceramics and polymers. This article attempts to provide answers to why particular materials are selected for shot peening applications. SHOT PARTICLES The ideal shape for a shot particle is a sphere, but real shot particles are not perfect spheres. The most commonly employed media are cast steel and iron shot, cut steel wire shot, glass beads and ceramic beads. These media are manufactured either by spheroidizing solid particles (cut steel wire and some glass beads) or by direct production of near-spherical shapes. Because of the method of manufacture, variations from sphericity are inevitable. Cast Shot Steel, cast iron and glass shot particles are produced by liquefying the material and then dispersing it as fine particles that solidify as they cool. The controlling factor affecting shape in these particles is surface tension. Surface tension is present in both liquid and solid particles, but reveals itself more dramatically for the liquid state.