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Abstract Inconel 718 is a nickel-based superalloy widely used in the aerospace industry, nuclear plants and gas turbines due to the exceptional mechanical properties and resistance to corrosion at elevated temperature. For these reasons Inconel 718 have a low machinability due to the high temperatures that appear in the cutting area in addition to the wear caused in the tools as abrasion, chemical affinity, diffusion, flank and notch wear. Carbide and recently Polycrystalline Cubic Boron Nitride (PCBN), are the cutting tool materials used in finishing operations of nickel-based superalloys. This paper focuses on the comparative analysis of carbide and PCBN tools in finishing operations on Inconel 718 using cutting fluid at conventional pressure (7.5 bar). Experimental tests were performed at different cutting speeds, feed rate and depths of cut depending of the cutting tool. PCBN tools were used at speeds within the range of 250-300 m/min, feed between 0.1 and 0.15 mm/rev and depth of 0.15mm. Carbide tools are not used at such speeds because of their lower hardness at high temperature. Speeds five times lower than those were used for PCBN (50-70 m/min), the same feeds (between 0.1 and 0.15 mm/rev) and a depth of 0.25 mm were used. Tool life and machined surface has been analyzed with the aim of studying the viability of these tools in finishing conditions of Inconel 718. The results indicate that PCBN tools have a shorter life in minutes than carbide tools; however, the machined surface by cutting edge is larger at higher cutting speeds, so PCBN tools are an interesting alternative in this type of machining. [ABSTRACT FROM AUTHOR]

Inconel 718 is a Ni superalloy widely used in high responsibility components requiring excellent mechanical properties at high temperature and elevated corrosion resistance. Inconel 718 is a difficult to cut material due to the elevated temperature generated during cutting, its low thermal conductivity, and the strong abrasive tool wear during cutting process. Finishing operations should ensure surface integrity of the component commonly requiring the use of hard metal tools with sharp tool edges and moderate cutting speeds. Polycrystalline cubic boron nitride (PCBN) tools recently developed an enhanced toughness suitable for these final operations. This paper focuses on the study of PCBN tools performance in finishing turning of Inconel 718. Several inserts representative of different manufacturers were tested and compared to a reference carbide tool. The evolution of tool wear, surface roughness, and cutting forces was analyzed and discussed. PCBN tools demonstrated their suitability for finishing operations, presenting reasonable removal rates and surface quality. [ABSTRACT FROM AUTHOR]

Inconel 718 is a superalloy, considered one of the least machinable materials. Tools must withstand a high level of temperatures and pressures in a very localized area, the abrasiveness of the hard carbides contained in the Inconel 718 microstructure and the adhesion tendency during its machining. Mechanical properties along with the low thermal conductivity become an important issue for the tool wear. The finishing operations for Inconel 718 are usually performed after solution heat treatment and age hardening of the material to give the superalloy a higher level of hardness. Carbide tools, cutting fluid (at normal or high pressures) and low cutting speed are the main recommendations for finish turning of Inconel 718. However, dry machining is preferable to the use of cutting fluids, because of its lower environmental impact and cost. Previous research has concluded that the elimination of cutting fluid in these processes is feasible when using hard carbide tools. Recent development of new kPCBN (Polycrystalline Cubic Boron Nitride) grades for cutting tools with higher tenacity has allowed the application of these tool grades in the finishing operations of Inconel 718. This work studies the performance of commercial PCBN tools from four different tool manufacturers as well as an additional grade with equivalent performance during finish turning of Inconel 718 under dry conditions. Wear tests were carried out with different cutting conditions, determining the evolution of machining forces, surface roughness and tool wear. It is concluded that it is not industrially viable the high-speed finishing of Inconel 718 in a dry environment. [ABSTRACT FROM AUTHOR]

Despite the interest of industry in nickel-based superalloys and its main features (high temperatures resistance, hardness, low thermal conductivity, among others), even today they are still materials that are difficult to cut. Cutting tools withstand both high pressures and temperatures highly localized at the cutting area because of the elevated work hardening of the alloy and the problems for the cutting fluid to access the region, with the consequent strong tool wear. The use of cutting fluids at high pressures improves coolant access and heat removal. This paper analyzed the machining of Haynes 282 alloy by means of coated carbide tools under high-pressure cutting fluids at finishing conditions. Tests were developed at different cutting speeds and feeds quantifying the machining forces, surface roughness, tool wear, and tool life. Values of 45.9 min and Ra between 2 µm and 1 µm were obtained in this study for tool life and roughness, respectively, for the combination of cutting speed 50 m/min and feed 0.1 mm/rev. Likewise, a comparative analysis is included with the results obtained in previous works developed by the authors relating to the finishing turning of Haynes 282 and Inconel 718 under conventional pressure cooling. The comparative analysis with Inconel 718 is included in the study due to its importance within the nickel base superalloys being widely used in industry and widely analyzed in scientific literature. [ABSTRACT FROM AUTHOR]