Enhancing Chemical Mechanical Polishing Efficiency of Steel with Sulfate

Abstract

Excellent surface quality helps improve the tribological performance of gears. This study utilized chemical mechanical polishing (CMP) to process 18CrNiMo7–6 steel, a widely-used gear material. The results reveal that under the cooperative effect of oxidation and complexation, the material removal rate (MRR) can be significantly enhanced after adding K2SO4, while the surface roughness S a nearly remains unaltered. In particular, with 1 wt% H2O2 and citrate, the MRR increases by 251% after adding 100 mM K2SO4, while the S a slightly varies to 0.42 nm. No distinct surface defects are generated. For the mechanism, adding SO4 2− can promote iron corrosion and increase the amount of α-FeOOH. Citric acid can chelate α-FeOOH, forming complex compounds. The complex compounds and oxides form a relatively dense surface film, and thus the surface quality remains unchanged. In addition, the complex compounds may weaken the surface, and thereby the MRR increases. This study provides a simple approach for achieving high-efficiency CMP of steels.