GMR 235-D is a variant of GMR 235, the nickel-base precipitation-hardening cast superalloy developed by General Motors Research, cross-referenced under the DIN designation NiCr16MoAl. It belongs to the same investment-cast, gamma/gamma-prime hardened alloy family as standard GMR 235, used for gas turbine and jet engine components and precision-cast automotive turbocharger wheels operating above 1400 degF (760 degC).

The "D" variant carries a reduced iron content relative to standard GMR 235, with chromium, molybdenum, aluminum, and titanium levels essentially unchanged - consistent with the general naming convention used across this alloy family, where variant suffixes typically denote a specific processing route or minor compositional adjustment rather than a fundamentally different alloy system.

Verification note: the composition and DIN cross-reference below are carried forward from this page's earlier FM Carbide version. Unlike standard GMR 235 - whose composition and AISI 686 cross-reference were independently corroborated against third-party alloy references during this rewrite - GMR 235-D's exact figures could not be independently verified against a primary datasheet. They are internally consistent with GMR 235's verified chemistry and are presented as reference values, not as independently confirmed data.

GMR 235-D shares its parent alloy's core machining profile: a cast, precipitation-hardened nickel superalloy combining the abrasive, interrupted-cut demands of investment casting with the retained hot hardness and rapid work hardening of a true gamma-prime strengthened superalloy. Its slightly lower iron content compared with standard GMR 235 does not meaningfully change this behavior - chromium, molybdenum, and the gamma-prime-forming aluminum and titanium, which drive both hot strength and tool wear, are essentially unchanged between the two variants.

As with GMR 235, tool edges face heavy mechanical load throughout the cut because the alloy does not soften significantly at elevated cutting temperature, while low thermal conductivity concentrates that heat at the tool-chip interface. The austenitic nickel matrix work-hardens rapidly under light or interrupted engagement, and as-cast surface conditions add abrasive wear and impact loading beyond what a wrought bar of similar chemistry would present.

Treat GMR 235-D with the same practical approach used for GMR 235: rigid, vibration-resistant setups, sharp positive-rake coated-carbide edges tough enough for interrupted cuts, feed sufficient to cut beneath the work-hardened layer, moderate-low cutting speeds, and generous coolant to manage heat and clear abrasive chips.