IN100 is a vacuum-cast, precipitation-hardened nickel-base superalloy built for high-temperature strength rather than fabricability. Combined titanium and aluminum content runs close to 10% by weight (4.7% Ti + 5.5% Al), driving a very high volume fraction of gamma-prime (Ni3(Al,Ti)) precipitate through the matrix. That level of hardening is only practical in a cast product — an alloy this heavily strengthened cannot be reliably hot-worked, which is why IN100 exists as an investment-casting grade rather than a wrought bar or sheet material.

Cobalt (15%) and molybdenum (3%) provide solid-solution strengthening on top of the gamma-prime hardening, while chromium (10%) gives moderate oxidation resistance at service temperature. The combined result is one of the higher-strength cast nickel superalloys, historically used for turbine blades, vanes, and disks in gas turbine hot sections where rupture strength and creep resistance up to roughly 1900°F (1040°C) matter more than ductility or ease of processing.

Correction note: this project previously identified IN100's composition and Werkstoff number (2.4674) mislabeled as "Incoloy 804" on an unrelated page. That was an error on the other page, not a fact about IN100 or Incoloy 804 — the data below is IN100's own verified composition and designation, independently confirmed for this page.

IN100 is one of the more difficult cast superalloys to machine, and the reason is directly tied to why it's used in the first place: a very high gamma-prime volume fraction. The tool is constantly shearing through a dense field of hard, fine precipitate rather than a soft metallic matrix, so cutting forces stay high, edge wear accumulates fast, and the abrasive wear mechanism dominates over the built-up-edge and galling problems that are more typical of solid-solution nickel alloys.

Low thermal conductivity compounds the problem — heat generated at the cutting edge has nowhere to go but into the tool, since the workpiece conducts it away poorly. IN100 also retains substantial strength and hardness at elevated temperature, so the cutting edge stays under heavy mechanical and thermal load throughout the cut rather than benefiting from thermal softening the way carbon steel does at higher speeds. As-cast material can also carry coarser, less uniform grain structure and occasional hard spots compared to wrought stock, adding to the unpredictability of tool wear.

Because parts are typically near-net-shape investment castings, most machining on IN100 is finish work on root forms, platforms, and locating features rather than heavy stock removal. Light, precise cuts with sharp, wear-resistant coated carbide, maximum rigidity, low tool overhang, and generous coolant flow are essential — dwelling or rubbing accelerates work hardening and edge breakdown quickly on this alloy.