Cutting Performance Appraisement And Experiment Study Of Coating Tools

Coating technology has been used widely in cutting tools, coatings with excellent properties could significantly improve the surface properties of tools, like the high temperature hardness, heat insulation property, thermal stability, impact toughness and so on, thus the cutting speed and tool life could been improved obviously. Because of more and more novel coatings and new structures were used in cutting tools, the cutting performance appraisement of these new tools was necessary. Determination of the applicability and recommended cutting parameters of new tools would shorten development period, cut cost of research, and increase technical value of products.Cutting process was complicated for its characters of high temperature, large strain, high strain rate, high frequency vibration, high-speed friction and materials failure. A lot of factors influenced the cutting process, like the kinetic feature of machine tools, machining methods, work material, tool material, cutting tool geometry and so on. In this thesis, a series of cutting experiments had been completed, concerned of two kinds of typical coating process—PVD and CVD coating, three kinds of machining method—milling, drilling and turning, and two kinds of difficult-to-cut material—wheel steel and hardened die steel. Through these experiments, cutting force, cutting temperature, cutting vibration, machined surface quality and chip formation were researched. Based on the analysis of experimental data, the thesis had obtained these conclusions:1. The PVD coating AlTiN had good performance in dry milling hardened die steel. Among three AlTiN coatings with different composition and structures, nano-composited phase coating AlTiN was the best one. End mills with this coating were suitable for finish machining of die steel.2. The PVD self-lubricating coating AlTiN + WC/C had perfect performance in drilling hardened die steel, drills with this composited coating had lower cutting force and mild wear. AlTiN aluminum-rich coating was also suitable for drilling die steel, because of the oxidation and diffusion occurred in high temperature atmosphere, a stable and dense Al2O3 film formed, and would prevent the oxidation action going further, this film improved high temperature hardness, heat insulation property and thermal stability of coating.3. Chisel edge of drills influenced chip formation and chip removal significantly, optimization design of drills could improve chip removal in drilling.4. Round edge CVD composited coating insert was suitable for heavy duty rough turning, and led to higher material removal rate and better chip breaking; linear edge insert was suitable for finish turning, and led to better surface quality but tough chips.5. Cutting speed influenced chip deformation significantly, lower speed led to steady state chips, and higher speed led to saw-tooth chips.