*Article* **Effects of pH Values and H2O<sup>2</sup> Concentrations on the Chemical Enhanced Shear Dilatancy Polishing of Tungsten**

**Liang Xu <sup>1</sup> , Lin Wang <sup>1</sup> , Hongyu Chen 1,2,\* , Xu Wang 1,2 , Fangyuan Chen <sup>1</sup> , Binghai Lyu 1,2, Wei Hang 1,2 , Wenhong Zhao 1,2 and Julong Yuan 1,2**


**Abstract:** In order to obtain tungsten with great surface qualities and high polishing efficiency, a novel method of chemical enhanced shear dilatancy polishing (C-SDP) was proposed. The effects of pH values and H2O<sup>2</sup> concentrations on the polishing performance of tungsten C-SDP were studied. In addition, the corrosion behaviors of tungsten in solutions with different pH values and H2O<sup>2</sup> concentrations were analyzed by electrochemical experiments, and the valence states of elements on the tungsten surface were analyzed by XPS. The results showed that both pH values and H2O<sup>2</sup> concentrations had significant effects on tungsten C-SDP. With the pH values increasing from 7 to 12, the *MRR* increased from 6.69 µm/h to 13.67 µm/h. The optimal surface quality was obtained at pH = 9, the surface roughness (*R*a) reached 2.35 nm, and the corresponding *MRR* was 9.71 µm/h. The *MRR* increased from 9.71 µm/h to 34.95 µm/h with the H2O<sup>2</sup> concentrations increasing from 0 to 2 vol.%. When the concentration of H2O<sup>2</sup> was 1 vol.%, the *R*<sup>a</sup> of tungsten reached the lowest value, which was 1.87 nm, and the *MRR* was 26.46 µm/h. This reveals that C-SDP technology is a novel ultra-precision machining method that can achieve great surface qualities and polishing efficiency of tungsten.

**Keywords:** chemical enhanced shear dilatancy; tungsten; polishing; surface quality
