Nimocast 90 is the investment-casting grade produced by Henry Wiggin & Co. as the cast counterpart to wrought Nimonic 90 (documented in ASM's Alloy Digest under filing code Ni-101, "Nimocast 90: High-Temperature Casting Alloy," Producer: Henry Wiggin & Co Ltd), useful for creep-resistant service to roughly 870°C. Compared with Nimocast 80, this grade steps chromium and cobalt up substantially - roughly 20% chromium and 18% cobalt against Nimocast 80's ~2% cobalt - which raises hot-strength and creep resistance at the cost of some ductility and machinability. As with the rest of the Nimocast/Nimonic family, strengthening comes from titanium and aluminum gamma-prime formers (nominally around 1.8-3.0% Ti and 0.8-2.0% Al in the wrought Nimonic 90 parent alloy); this record's confirmed composition covers nickel, chromium, iron, and cobalt, and the source data did not include a confirmed titanium/aluminum figure or an equivalent casting-standard callout for this specific grade, so both are omitted here rather than assumed.

Nimocast 90 was used for gas-turbine blades, rings, and other hot-section components requiring higher creep-rupture strength than Nimocast 80 could provide, in an investment-cast, near-net-shape form.

Nimocast 90's higher cobalt and chromium content relative to Nimocast 80 makes it one of the tougher grades in the Nimocast family to machine. Cobalt raises the hot hardness and strength retention of the matrix, so the alloy resists the softening that would otherwise give a tool some relief as cutting temperature rises - the edge stays under full mechanical load even as it heats up. Combined with low thermal conductivity that keeps heat concentrated at the tool-chip interface rather than carrying it away, this drives accelerated crater wear and edge deformation, and the as-cast grain structure adds abrasive, chip-prone high spots that a wrought bar of similar chemistry would not present.

Work hardening is severe: rubbing, dwelling, or light interrupted engagement immediately hardens the surface and every following pass fights a tougher layer than the one before. A constant, adequate chip load is essential. Galling and built-up edge are a persistent risk given the alloy's chemical affinity for common tool materials. Rigid setups, sharp positive-rake coated carbide grades suited to cast, high-cobalt superalloys, cutting speeds at the conservative end of the Nimocast range, and continuous, high-volume coolant delivery are the standard countermeasures - expect this grade to run slower and wear tools faster than Nimocast 80 or 713.