Machining
Inconel is a difficult metal to shape and machine using traditional techniques due to rapid work hardening. After the first machining pass, work hardening tends to plastically deform either the workpiece or the tool on subsequent passes. For this reason, age-hardened Inconels such as 718 are machined using an aggressive but slow cut with a hard tool, minimizing the number of passes required. Alternatively, the majority of the machining can be performed with the workpiece in a solutionized form, with only the final steps being performed after age-hardening. External threads are machined using a lathe to "single point" the threads, or by rolling the threads using a screw machine. Holes with internal threads are made by welding or brazing threaded inserts made of stainless steel. Internal threads can also be formed using EDM machining.
Cutting of a plate is often done with a waterjet cutter. Internal threads can also be cut by the single point method on a lathe, or by threadmilling on a machining center. New whisker reinforced ceramic cutters are also used to machine nickel alloys. They remove material at a rate typically eight times faster than carbide cutters. 718 Inconel can also be roll threaded after full aging by using induction heat to 1300°F without increasing the grain size. Apart from these methods, Inconel parts can also be manufactured by selective laser melting.
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