Effect of Polishing Nozzle Wear Evolution on BK7 Topography.

In ultra-precision polishing tests, due to the corrosive and adhesive properties of the polishing abrasive, the spray system faces wear, blockage and oxidation problems. To solve these problems, this paper studied nozzles and verified the wear mechanism of the coated and uncoated nozzles by simulating the operating conditions after assembling the spray system. In the early stages of the experiment, the polishing speed of the spray system ( = 10 L/min), the feed rate ( = 7.8 mm/min) and the polishing pressure (2~3.5 MPa) were maintained. The wear mechanism and surface morphology features of the nozzles in each case were analyzed by Hitachi S-3400N electron microscopy. When comparing the surface morphology of the nozzle coated with titanium alloy and the uncoated one, the results show that there is a significant difference in the corrosion resistance of the coatings to the abrasive particles. A significant effect was seen on the wear morphology, proving that the nozzle wear mechanism includes wear, adhesion and diffusion. Under the experimental conditions of a lateral velocity of 7.8 mm/min and a polishing force of 2 MPa, BK7 was polished using nozzles 1 and 2, resulting in a surface roughness of 75 nm and 35 nm while PV values were 125 nm and 67 nm, respectively. The excellent quality of nozzle 2 (coating nozzle) was proven, further demonstrating the superiority of the coating nozzle. Finally, the lifespan of the nozzle was extended and the surface accuracy of BK7 was improved by coating titanium alloy composite material on the 304 stainless steel nozzle.