Incoloy 800 is the baseline alloy of the 800-series iron-nickel-chromium superalloys, balancing roughly equal parts nickel and iron against 19-23% chromium. That iron content is what separates it from a solid nickel-base superalloy: it keeps raw material cost down while still giving the alloy strong resistance to oxidation and carburization at temperatures that would quickly degrade ordinary stainless steel. Small controlled additions of aluminum and titanium (roughly 0.15-0.60% each) form fine intermetallic precipitates that add a useful margin of strength without pushing the alloy into the cost or difficulty bracket of a true nickel-base material.

Incoloy 800 is the alloy the rest of the family branches from — 800H and 800HT tighten the carbon range and control grain size for better creep strength, 801 adds extra titanium for strength and resistance to polythionic acid cracking, 802 and 803 raise carbon content for carburizing resistance, and DS leans on silicon instead of the standard 800 chemistry. In its own right, 800 is a workhorse for furnace muffles, radiant tubes, heat-treating baskets and fixtures, and other equipment that spends its life at high temperature without demanding the creep performance of the H or HT variants. It is normally supplied and used in the annealed condition.

Nickel-iron-chromium superalloys like Incoloy 800 are demanding to machine for a consistent set of reasons: low thermal conductivity concentrates the heat generated by the cut right at the tool edge instead of carrying it away in the chip, the alloy work-hardens noticeably wherever a previous pass rubbed instead of cut, and it holds onto its strength at elevated temperature rather than softening the way steel does as the cutting zone heats up. Together these push cutting forces, edge temperature, and abrasive wear well above what a similarly hard steel would produce.

The good news is that 800's substantial iron content dilutes the tough nickel-chromium matrix that makes solid nickel-base alloys like Inconel or Hastelloy so punishing on tooling, so it machines somewhat more forgivingly than those grades even though it is still firmly in the \"difficult\" category. Chips tend to be tough and stringy rather than brittle, so chip control and evacuation deserve real attention alongside tool wear.

A rigid setup is essential — any flex or vibration burnishes the surface and work-hardens it before the next pass, making things progressively worse. Use sharp, positive-rake carbide with a coating built for heat-resistant alloys, run at moderate-to-low cutting speeds, and keep feed rates high enough that the edge consistently cuts beneath the hardened layer left by the prior pass instead of skating across it.