Investigations On Friction And Wear Behavior Of High Speed Turning Nickel-based Alloy Inconel 718

Nickel-based superalloys play quite an important role in the field of high-temperature alloys. It is widely used in manufacturing of heat resistant components of jet aeroengine and kinds of industrial gas turbine. Inconel 718 is a kind of most widely used Nickel-based superalloys and also a kind of typical difficult-to-process material, therein causing the problems of high cutting force, high cutting temperature, high tendency of work-hardening and serious tool wear. With the popularization and application of high speed cutting technologies, high speed cutting of Nickel-based superalloys has become a hot research at home and abroad in recent years.Using Inconel 718 as experimental material, the cutting force, surface roughness, chip shape, tool life and wear mechanism are studied when high speed cutting nickel-based superalloys using PVD coated carbide tool. Additionally, the friction and wear performance of Inconel 718/ carbide tool are also researched. For further study on mechanism of high speed cutting Inconel 718, high speed cutting of Inconel 718 is simulated using finite element software DEF0RM-2D. The effects of cutting speed on cutting temperature, cutting force and shear angle as well as the stress distribution of tool and workpiece during cutting process are analyzed. Through the research of this thesis, optimum cutting parameters for high speed cutting Inconel 718 are determined and ideas of developing new tool materials to machine nickel-based alloys and increasing tool life are provided.The experiment of high speed cutting nickel-based superalloys using coated carbide tool shows that cutting force and surface roughness are similarly influenced by cutting parameters, feed rate the most, followed by depth of cut, cutting speed the minimum. So when finish turning Inconel 718 using coated carbide blades, small cutting force and surface roughness can be guaranteed by using low value of feed rate, depth of cut and high cutting speed. The microstructure of Inconel 718 chip is continuous under low cutting speed and serrated under high cutting speed because of adiabatic shearing.With the increase in cutting parameters, tool life is shortened. Under dry cutting state, tool life is affected mostly by cutting depth. When cooling by emulsion, tool life is greatly improved, about 3 times of dry cutting. Observed by scanning electronic microscope (SEM) and energy disperse spectrum (EDS), the worn surface morphology of tool and its abrasion mechanism are studied. The results show that the failure modes are rake wear, flake wear, flaking and chipping and the main failure mechanisms of tool are adhesive wear, abration wear, oxidation wear, diffusive wear and so on.Experiment of the friction and wear properties of Inconel 718/ carbide tool show that the friction coefficient is decreased with the increase of load and increased with the increase of sliding velocity. The wear mechanisms are mainly adhesive wear, abration wear and oxidation wear.Finite element simulation results show that cutting force increases linearly at first, and then stabilized. The cutting force showed a downward trend with the cutting speed increases. The highest cutting temperature point is always at face near the cutting edge. The maximum cutting temperature increases with the increase in cutting speed. The maximum tool effective stress is located in the flank face near cutting edge and the shear deformation zone on the workpiece. Shear angle increases with the increase in cutting speed.