Fabrication And Cutting Performance Of Ceramic Tools With Multiscaled Surface Textures

The concept of the ceramic tools with multiscaled surface textures is proposed in this paper, and the ceramic tools with multiscaled surface textures are developed combined with the preparation process of mutilscaled surface textures and the solid lubricant technology. Meanwhile, the tribological behavior and the cutting performance of the developed tools are investigated. The effect mechanism of the ceramic tools with multiscaled surface textures is investigated.The formation mechanism of microtextures induced by nanosecond laser and nanotextures induced by femtosecond laser on ceramic tool materials is analysed. The static model of the textured surface contact with the smooth surface is founded, and the friction-reduction mechanism of the surface textures during the friction process is analysed theoretically. Meanwhile, the effect of the textured tools on cutting force and cutting temperature is analysed. Results show that the friction coefficient and friction temperature between the contact interfaces are reduced, which are due to the fact that the contact area is reduced by the surface textures. The cutting force and cutting temperature can be decreased during the cutting process.The concept of the preparation method of the ceramic tools with multiscaled surface textures is proposed. The effect of the laser process parameters on the evolution of the microtextures induced by nanosecond laser and nanotextures induced by femtosecond laser is investigated, and the optimum laser process parameters for the uniform microtextures and nanotextures are obtained. For optimum nanosecond laser process parameters:voltage is 19.5 V, scanning speed is 5 mm/s, frequency is 6000 Hz and the overscan is 1; according to the process parameters, the width of the microtextures is about 50 μm, and the depth is about 43 μm. For optimum femtosecond laser process parameters:pulse energy is 1.75 μJ, scanning speed is 500 μm/s and the overscan is 1; according to the process parameters, the period of the microtextures is about 750 nm, and the depth is about 150 nm. The ceramic tools with multiscaled surface textures are fabricated.The tribological properties of the microtextured ceramic tool materials are investigated by sliding friction and wear tests. Results show that, under dry friction condition, the microtextured surface (AT) increases the friction coefficient and friction temperature, while it reduces the abrasive wear and adhesions. A combination of microtextures and solid lubricants (AT-W) can effectively reduce the friction coefficient, friction temperature, abrasive wear and adhesions of the ceramic surface. Compared with the untextured sample (AS), the friction coefficient of the AT-W sample is reduced by 70-80% and the friction temperature is reduced by 40-50%. The effect mechanism of the AT-W sample is attributed to the lubricant film formed on the friction contact interfaces by the friction effect and then reduces the friction coefficient and friction temperature. Meanwhile, the grooves mainly serve for depositing wear debris, which reduces the abrasive wear and adhesions.The tribological properties of the nanotextured ceramic tool materials are investigated by friction and wear tests. Results show that the friction coefficient of the nanotextured sample (TS) is reduced by 6-13% compared with the untextured sample (SS). The sample combined with nanotextures and WS2/Zr coatings (TCS) shows the best efficiency; compared with the untextured surface deposited with WS2/Zr coatings (SCS) and the untextured sample (SS), the friction coefficient of the TCS sample is reduced by 16-38% and 85-93%, respectively. The effect mechanism of the TCS sample is attributed to the fact that nanotextures increase the adhesive strength between the coatings and substrate. On the other hand, the solid lubricants are squeezed and transferred to the untextured surface between the nanotextures to maintain the lubricant film when the initial lubricant film is run out, which increases the wear life of the initial lubricant coatings.Dry cutting tests are carried out on 45 hardened steel with untextured ceramic tool (AS), coated ceramic tool (AS-L), coated ceramic tool with nanotextures (AN-L) and coated ceramic tool with multiscaled surface textures (AT-L). Results show that the AT-L tool is the most effective in improving the cutting performance. Compared with the AS tool, three cutting forces of the AT-L tool are reduced by 25-40%, the cutting temperature is reduced by 10-20%; the average friction coefficient at the tool-chip interface is decreased by 17-22%, the tool-chip contact length is reduced by 8-17%; the average shear stress at the tool-chip interface is reduced by 11-13%, while, the normal stress at the tool tip and the average normal stress at the tool-chip interface are increased by 7-11%. The tool life of the AT-L tool is increased by 14.7% compared with the AS tool at the cutting speed of 200 m/min.The effect mechanism of the AT-L tool is illuminated. On one hand, during the cutting process, the prefabricated lubricants can be smeared on the tool-chip interface and form a lubricant film, which has a low shear strength and then reduces the friction at the tool-chip interface. On the other hand, the micro/nanotextures can effectively reduce the tool-chip contact length, and decrease the ratio of sticking contact length to the total tool-chip contact length. Meanwhile, the nanotexrtures increase the adhesive strength between the coatings and substrate, microtextures can capture the wear debris and the lubricants, and then reduce the abrasive wear of the rake face and provide the secondary lubrication. As a result, the effect mechanism of the AT-L tool for reducing friction and wear is attributed to the synergistic action of solid lubricants, microtextures and nanotextures.