Performance of Carboxyl Groups in Chemical Mechanical Polishing of GCr15 Bearing Steel: Effects of Carbon Chain Length and pH

Bearing steels have been used in mechanical components, and an ultra-smooth surface is required in high-precision occasions. In this study, chemical mechanical polishing (CMP) was used to process GCr15 bearing steel. Dicarboxylic acids were used as complexing agents to enhance the CMP efficiency. In synergy with H2O2, carboxyl groups of the dicarboxylic acids react with iron ions to form complex compounds, promoting the corrosion and the resultant material removal rate (MRR) of GCr15 steel. The carbon chain length and pH are the two critical factors to influence the performance of carboxyl groups in the GCr15 steel CMP, which is realized by changing the corrosion and corrosive wear. With the increased carbon chain length, the MRR of GCr15 steel decreases, which may be attributed to the decrease in the proportion of the monohydrogen anion and the dissolution of the complex compounds. As pH increases from 4.0 to 10.0, the MRR and the surface roughness R-a of GCr15 steel decrease, which may be due to the transformation from soluble Fe2+ complex compounds to insoluble Fe3+ oxides. This study provides a feasible way to tune the CMP performance of steels by carefully selecting the carbon chain length and pH for carboxylic acids.