The effects of cutting parameters and tool wear on the surface damage generated in hole making of cast GH625 nickel-based alloy were investigated. The machined surfaces were examined by employing a scanning electron microscopy (SEM). The SEM micrographs of the machined surfaces showed that surface damages induced by boring operation comprised surface cavities, smeared material and ridges parallel to feed marks. Surface cavities were associated with the carbide particles contained in workpiece material and the intrinsic defect of cast GH625 alloy. The cutting conditions had little impact on the extent of surface cavities, but they significantly affected the extent of smearing. Severe smearing of workpiece material could occur at higher cutting speed due to the relatively high cutting temperature generated and the relatively rapid tool wear.