Inconel 718 wire- Excellent corrosion resistance and tensile strength

Inconel 718 is an alloy of nickel-chromium-niobium- molybdenum that has high corrosion resistance, strength and excellent fabrication characteristics. This alloy has high tensile strength and excellent yield & creep-rupture properties at high temperatures. This alloy can operate at cryogenic temperatures up to 1200°F. Inconel718 wire has applications in valves, springs, aircraft and land-based turbine engines. This alloy is used by various industries including nuclear, automotive, oil, nuclear, gas, defense and aerospace.

Nickel-based superalloys such as Inconel 718 are used in nuclear, aerospace and chemical industries due to their excellent mechanical and chemical properties at elevated temperatures. Nickel-based superalloys compose over half of the materials used in the aerospace industry, in particular for the hot section of gas turbine engines for components such as blades, turbine disk, combustors etc. Inconel 718 has low thermal conductivity that increases the thermal effects during machining. Inconel 718 often exhibits strong work-hardening behavior, high adhesion characteristic onto the tool face altering cutting process parameters completely when machining. This alloy may contain hard abrasive particles and carbides that create excessive tool wear and hence the surface integrity of the end products can be disappointing.

Electrical discharge machining (EDM) is a competitive alternative process to machine Inconel 718 as compared to mechanical cutting. EDM can machine titanium alloys, hardened steels, cemented carbide and conductive ceramics regardless of their strength and hardness. It allows machining of complex part geometry. The tool electrode does not rotate for material removal, holes with sharp corners and irregular contours can be conveniently machined by EDM unlike mechanical cutting and grinding. The low force nature in the EDM gap also allows the machining of thin and flexible parts, deep grooves and holes that otherwise are difficult to machine by milling. The machining accuracy and surface finish are high especially at trim cutting conditions despite the low machining efficiency of EDM. These unique process characteristics make EDM an enabling technology in aerospace, medical device, tool and automotive industries.

Wire-EDM is widely used as it can be fully automated and flexible in making complex geometrical shapes in one setup. This process capability is particularly essential for aero-engine manufacture. 

High temperature has significant impact on the process-induce surface integrity including microstructure change, microhardness, surface topography, residual stress and element distributions as EDM is a thermal dominant process. The heat affected zone (HAZ) with a white layer is associated with high tensile residual stress, porosity, microcracks, grain growth and alloying from the tool electrode or dielectric fluid. As per a recent study, wire-EDM is highly detrimental to surface integrity compared to hard turning and grinding. However, this is not necessarily true since the degree of thermal damage depends on not only process conditions but also EDM generators. Thermal damage in main cut can be removed or minimized by subsequent multiple trim cuts at reduced discharge energy. Relaxation pulse with low energy has been tried to improve surface quality in EDM of silicon carbide. It has shown that machining sequence with trim cut and polishing technology is necessary to guarantee surface integrity. Thermal damage by EDM may be minimized with the development of low energy generators and EDM strategy.