Study on grain removal characteristics and influencing factors of polycrystalline tungsten during polishing process

In this paper, the polishing mechanism of polycrystalline tungsten has been studied, focusing on the reasons for the appearance of grain steps and the effects of different polishing factors on the polishing effect. The surface morphology and mechanical properties after polishing were analyzed by electron backscatter diffraction, scanning electron microscope, nanoindentation and other characterization tools. Effects of different polishing factors on the polishing effect were also analyzed by orthogonal and single factor experiments. Results show that the effects of abrasive size, polishing pressure, polishing speed, and abrasive concentration on the polishing effectiveness decrease in turn. The optimal polishing parameters obtained by orthogonal experiments are 60 rpm polishing speed, 5.0 μm abrasive size, 5 wt% abrasive concentration, and 30 kPa polishing pressure. In the single factor experiment, with the increase of abrasive size, the height of grain step decreased from 0.5 μm to 0.11 μm, and the surface roughness (Ra) decreases from 11.3 nm to 5.2 nm. Grain anisotropy is the main reason for the appearance of grain steps on the surface after polishing. Different grain orientations lead to different surface mechanical properties. The hardness of high grain step is higher than that of low grain step. In addition, the increase of abrasive size can effectively suppress the grain step phenomenon, thereby improving the surface polishing effect.