Study on the Fabrication and Grinding Performance of the Self-sharpening Cr₂O₃ Gel Abrasive Tool

This paper proposes a chromium oxide (Cr₂O₃) gel abrasive tool with the coated aluminum nitride (AlN) powder to give the tool with self-sharpening ability. The SiO₂/AlN powder (S/A powder) is prepared through the sol–gel method. Effect of acetic acid solution content on the Tetraethyl orthosilicate (TEOS) hydrolysis reaction is explored. Effect of sintering temperature on the moisture resistance of the S/A powder are studied. The viscosity experiments, porosity tests, pre-grinding experiments and hardness tests are conducted to test the properties of the abrasive tool. The force–displacement curves are tested to evaluate the uniformity of the tool. The grinding effect on the sapphire substrate of tool with S/A powder, normal abrasive tool and tool with pore forming agent are compared. Results show that the SiO₂ gel has great stability when the acetic acid solution content reached 0.6 g, and the gel does not crack after a week’s rest, which is suitable for the coating of the AlN powder. In the powder sintering experiment, 700 °C is found to be the optimal sintering temperature for the S/A powder preparation. The viscosity experiments show that the viscosity of the slurry will surge when the content of S/A powder reached 12 wt%, which impairs the uniformity of the gel abrasive tool. In the pre-grinding test, the abrasive tool with the S/A powder of 9 wt% shows great grinding stability, material removal rate (MRR) and wear resistance. The grinding experiments show that tool with S/A powder can achieve better surface quality and have a stable grinding process, and the glazing phenomena is ameliorated. After grinding, the average roughness R_a of the sapphire substrate reaches 1.57 nm and its flatness reached 0.725 μm. After chemical mechanical polishing (CMP), the average R_a of sapphire substrate reaches 0.64 nm and the scratch-free surface can be obtained.