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A Comparative Research of Damaged Layers Formed in Surface Grinding and Wire-Electrodischarge Machining

Compared to surface grinding, wire-electrodischarge machining (WEDM) is competitive because WEDM allows the machining of any type of conductive material, regardless of its hardness. Nevertheless, WEDM is not preferred for final machining due to the existence of the process-induced damaged layers. In this study, the damaged layers formed in hardened AISI 52100 steel by surface grinding and WEDM are researched and compared. It is found that the damaged layers for both grinding and WEDM are composed of the white layer and dark layer, and the white layer possesses a highly refined grain structure compared to the bulk material. The retained austenite content of the ground white layer is lower than that of the unmachined material, while WEDM white layer has much high retained austenite volume fraction. The microhardness of the ground white layer is higher than that of the WEDM one. High residual tensile stresses are observed in the ground surface, and slight compressive stresses are observed just below the surface. WEDM generates residual tensile stresses in the surface. It is also found that mechanical deformation plays an important role in ground damaged layers compared to WEDM ones, where thermal effects are more dominant.