<p>Nickel-based superalloy Inconel 718 has been widely used in critical fields such as aerospace and aviation. However, its high hardness and tendency to work harden make machining Inconel 718 particularly challenging. Chemical mechanical polishing (CMP) has been recognized as an effective method for achieving high-quality surface finishes. This study investigates the effects of pH, oxidizing agent (H₂O₂), and corrosion inhibitor (C₃H₃NS) on the polishing performance of Inconel 718 during CMP. The results show that variations in pH, oxidizing agent concentration, and corrosion inhibitor concentration significantly affect the polishing performance. The best results achieved at 0.5 wt% H₂O₂, 2 wt% C₃H₃NS, and pH 4. X-ray photoelectron spectroscopy (XPS) analysis of the oxide layer on Inconel 718, combined with electrochemical measurements, elucidated the removal mechanism. The introduction of 0.5 wt% H₂O₂ induces intense surface oxidation, forming a dense oxide layer that facilitates stable removal and significantly reduces the post-polishing <i>S</i>_a (arithmetic mean height, a parameter representing surface roughness by averaging the absolute height deviations over a given area). However, a dense oxide layer lead to a decrease in material removal rate. The addition of C₃H₃NS further reducing <i>S</i>_a, a small amount of C₃H₃NS can moderate the excessive oxidation rate, thereby enhancing material removal rate. The research findings provide a feasible CMP process for high-temperature nickel alloys, aiming to achieve satisfactory service performance.</p> Graphical Abstract <p></p>