Increased hardness and wear resistance of 1.1% C-13% Mn steel after shot peening

<jats:p>Introduction. Cast high-manganese steel exhibits excellent work hardening and high impact toughness, making it well suited for impact wear applications. Significant wear may occur in the early stages of steel service before sufficient work hardening develops near the surface. To mitigate this initial wear, this study investigates the microstructural characteristics of the hardened layer formed by shot peening and its effect on wear. The purpose of this work is to investigate the effect of pre-strain induced by shot peening on hardness and abrasive wear. Materials and methods. Specimens of 1.1% C-13% Mn steel were shot peened using a machine with a treatment area of 100% of the specimen surface. A cast steel ball with a nominal diameter of 2 mm was used, and the direction of impact on the specimen surface was set at 85°. The air pressure was 0.35–0.50 MPa, and the treatment duration was in the range of 5–120 min. Vickers microhardness was measured using a microhardness tester under an applied load of 0.49 N for 10 s. The morphology of the worn surface was examined using an optical microscope and a scanning electron microscope (SEM). The surface wear profile was measured with an optical profilometer. The surface structure of the specimens was examined by X-ray diffraction (XRD) with Cu Kα radiation using a Shimadzu XRD-7000 diffractometer. Results and discussion. Severe non-uniform plastic deformation was observed at a depth of approximately 60 μm from the surface. It was shown that the surface layers of the shot-peened samples consist of austenite, without any martensitic transformations. To confirm whether stress-induced austenite-to-martensite transformation occurs in the strain-induced twin layers formed by steel shot peening, the subsurface cross-sectional microstructure was analyzed using EBSD. The surface hardness of the original 1.1% C-13% Mn steel specimen increased by a factor of 1.2–2.5 after varying treatment times. An increase in abrasion resistance in wear tests was observed after shot peening. A cutting wear pattern was dominant for the original untreated specimen. However, for the shot-peened specimen, the cutting-mark morphology completely disappeared. Abrasion wear tests showed that higher maximum hardness in the hardened layer corresponds to lower wear loss. These results demonstrated that shot peening effectively improves the wear resistance of high-manganese cast steel by promoting the formation of a hardened surface layer.</jats:p>