Fabrication And Cutting Performance Of Soft Coated Micro-nano Textured Self-lubricating Tools

The concept and design ideas of soft coated micro-nano textured self-lubricating tools which combine effect of soft coatings and micro-nano textures are proposed in this paper. The key preparation technologies and processes of fabricating micro-nano textures on the surface of cutting tools and depositing soft coatings on the surface of micro-nano textured tools are studied. The soft coated micro-nano textured self-lubricating tool which combines dual function of soft coated self-lubricating and micro-nano textured self-lubricating has been developed successfully, as well as its cutting performance, effect of micro-nano textures and soft coatings on cutting forces and cutting temperature, more over, the lubricating mechanisms are analyzed in detail.Based on the analysis of the theories of cutting forces and cutting temperature during the traditional cutting process, the effect of micro-nano textures and soft coatings on cutting forces and cutting temperature are studied. Optimize the most suitable soft coating WS2through the analysis of performance characteristics of different soft coatings. The Gibbs free energy function method is used to analyze the chemical compatibility of the soft coating material and the substrate material. It is found that’the resultant of reaction ZrC, ZrS2and TiS2will not weaken the good lubricity of WS2coating, but will increase the coating/substrate critical load and enhance the strength and pressure resistance of the soft coated tool. The finite element method (FEM) modeling for thermal residual stress analysis of the coatings was established and used to analyze physical compatibility of coating and substrate. The optimum substrate and interlayer materials matched with WS2coating were YS8cemented carbide and Zr, respectively. And found that Zr as interlayer material will improve the stress status of junction interface of WS2soft coated tool.Femtosecond laser micromachining technology is proposed in the preparation of micro-nano textured tool. It is thought that the interference model of the surface plasma wave and the incident light wave can be used to explain the principle of femtosecond laser machining micro-nano periodic stripes on YS8cemented carbide tools. The effect of various processing parameters on surface micro-nano textures is studied. The optimum parameters are obtained:tool material is YS8cemented carbide, pretreatment process is polishing, femtosecond laser single pulse energy is2μJ, scanning speed is1000μm/s, scanning spacing is5μm and number of scans is1. The micro-nano textured tool has been fabricated successfully with micro-nano textures on the rake face and the flank face of cutting tool.WS2soft coating is successfully developed by medium-frequency magnetron sputtering, multi-arc ion plating coupled with ion-beam-assisted deposition technique on the surface of micro-nano textured tool. The effect of various preparation process parameters on the performance of WS2soft coating is studied. The optimum parameters are obtained:WS2target current is1A, deposition temperature is200℃, substrate bias voltage is-100V and deposition time is180min. The optimum performance parameters of WS2soft coating on the surface of micro-nano textured tool are obtained:surface morphology of soft coated micro-nano textures is uniform and regular, crystal linity of II type crystal structure of WS2is good, coating/substrate critical load is58.47N, coating thickness is0.48μm and coating microhardness is388.85Hv. The soft coated micro-nano textured self-lubricating tool has been developed successfully afterwards.Cutting tests on45#quenched and tempered steel are carried out with soft coated micro-nano textured self-lubricating tool (WTT), micro-nano textured tool (TT), soft coated tool (WCT) and conventional cutting tool (CT). The results show:compared with CT tool, WCT, TT and WTT tools can reduce three direction cutting forces, cutting temperature and average friction coefficient at the tool-chip interface, and increase shear angle. WTT tool shows the most significant effects among them. The WCT, TT and WTT tools can reduce tool wear, workpiece material adhesion and workpiece material surface roughness compared with the CT tool, operation with the WTT tool could obtain the least tool wear and workpiece material adhesion.The effect of micro-nano textures and soft coatings on cutting forces and cutting temperature are illuminated. The micro-nano texture can reduce tool-chip contact length and the soft coating can decrease the average shear strength at the tool-chip interface. Both micro-nano textures and soft coatings can significantly reduce cutting forces and cutting temperature. In addition, the lubricating mechanisms of soft coated micro-nano textured self-lubricating tools are revealed. The micro-nano texture of WTT tool can play a role of reserving WS2soft coating. During cutting process, WS2soft coating on the surface of micro-nano textures is smeared on the tool-chip interface and form a thin lubricating film. The soft coating in the grooves could be released and smeared on the tool-chip interface and re-form the lubricating film when the original lubricating film is wear out and broken. As a result, the adhesion resistance and the abrasion resistance of WTT tool are significantly improved and the tool life is increased.