Effects of Shot Peening on Mechanical Properties and Microstructural Evolution of AMS 6265 Steel Surface Treated for Critical Aircraft Components

Abstract

Considering its very good mechanical properties, especially the high strength and toughness, and also its well-known case-hardening ability, the AMS 6265 (9310 VAR) low alloy steel is widely used in the aeronautical industry for manufacturing heavy-duty products and parts, like pinions, shafts, gears, piston pins, and other critical aircraft components. In this study, a surface modification treatment via shot peening method was applied to an initially case-hardened (quenched and carburized) AMS 6265 aircraft steel. In shot peening, the mechanical properties of the surface layer are improved, by generating plastically deformed micro-areas when exposing the metal surface to a stream of steel, glass, or ceramic shots. The initial case-hardened AMS 6265 alloy steel and all surface treated samples were structurally investigated by means of OM (optical microscopy), SEM-BSE (scanning electron microscopy – backscattered electrons imaging), and XRD (X-Ray diffraction) analysis, being also mechanically tested in tensile and microhardness tests. The influence of different shot peening parameters (shot size, peening pressure, and exposure time) on mechanical properties evolution and microstructural features, for the analyzed AMS 6265 alloy steel, was established in this present research.