Optimization Of Process Parameters In High-speed Milling Inconel 718

Nickel-based superalloys play an important role in the field of high-temprature alloys. Inconel 718, as the most widely used category of superalloys, combines corrosion resistance, high strength with outstanding weldability and excellent creep-rupture strength at elevated temperatures, and it is widely used in gas turbines, rocket motors, spacecraft, nuclear reactors, and pumps, etc. However, Inconel 718 is a well-known difficult-to-cut material due to its unique characteristics. Its low thermal conductivity and volume specific heat result in high cutting temperature near the cutting zone. Good mechanical properties together with its severe work-hardening tendency lead to large cutting force. Some hard carbide particles included in Inconel 718 greatly increase abrasive wears of the cutting tools. As a result, the cutting tool wears rapidly during machining. Accordingly, severe tool injury usually occurs during cutting this material, which deteriorates surface accuracy and finish, increases production cost and reduces machining efficiency.Milling process which can obtain complex surface and high productivity is widely used in machining Inconel 718 components. With the rapid development of coating technology, the application of coated carbide cutting tools is becoming more and more popular for advantages like the better toughness, wear resistance, thermal conductivity, higher surface quality in finish and rough milling.With the popularization and application of high speed cutting technologies, high speed end-milling Incnonel 718 with coated carbided tools has become the challenging research, undoubtedly. Inconel 718 was selected to be the research material and the cutting forces in high speed milling with the PVD coated cemented carbide tools, workpiece machined surface roughness, tool wear morphologies and wear mechanisms were studied. Analysis of milling parameters (cutting speed, feed per tooth, radial depth of cut and axial depth of cut) on the effects of different targets (milling forces, surface roughness and tool wears) were made using the experimental data, and the empirical models of cutting forces and surface roughness were built then verified, the optimized combination of process parameters were obtained. In the meanwhile, contrast experiment study of the cutting condition impact on tool life in air and cold air MQL was carried out. The conclusions of the above studies could be used as the reference in the actual production process design of milling Inconel 718 material.By analysis of these orthogonal experiments, single factor experiments and the same metal removal rates experiments, it can be known that the effect of milling parameters on cutting forces depends on the metal removal rate of milling parameters combination used and the higher the rate is, the greater the cutting force; orthogonal and signal to noise ratio analysis show that good surface roughness can be obtained taking high-speed milling speed, with low feed, the lower axial and radial depth of cut; scanning electron microscopy SEM and energy dispersive spectroscopy EDS scanning analysis showed that the tool wear mechanisms are abrasion, adhesion wear, oxidation, diffusion wear and coatings wear, even tipping. These types of wear are not alone, but rather influence each other, leading to tool failure.Contrast experiment on the tool life in dry and cold air MQL environment proved that with cold and cutting oil mist cooling and lubricating effect, tool life has been improved significantly.The work is sponsored by the National Key Science & Technology Specific Projects " Milling-lathe Machining Center " (2009ZX04001-032).