Enhancing Chemical Mechanical Polishing Efficiency of Steel with Sulfate

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 K 2 SO 4 , while the surface roughness S a nearly remains unaltered. In particular, with 1 wt% H 2 O 2 and citrate, the MRR increases by 251% after adding 100 mM K 2 SO 4 , while the S a slightly varies to 0.42 nm. No distinct surface defects are generated. For the mechanism, adding SO 4 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.