Haynes 75 is a trade name for the 80/20 nickel-chromium solid-solution alloy also widely known as Nimonic 75 — the two names refer to essentially the same material. Like Haynes 600, it relies on solid-solution strengthening rather than gamma-prime hardening, but Haynes 75 carries no significant iron or molybdenum addition; it is a comparatively simple nickel-chromium alloy with small, controlled additions of titanium and carbon to refine grain structure and stabilize carbides.

The result is a moderate-strength alloy (usable to roughly 1200°F / 650°C) with excellent oxidation and scaling resistance and very good fabricability — it forms, welds, and machines more predictably than higher-alloyed superalloys. It is most commonly supplied and used as sheet for fabricated components: combustion chambers, flame tubes, furnace fixtures, heat-treatment equipment, and other parts that need to hold up to repeated thermal cycling in oxidizing atmospheres without carrying heavy mechanical load.

Haynes 75 is among the more machinable alloys in the nickel superalloy family, since it carries no gamma-prime hardening and only a modest 20% chromium content — there is no abrasive precipitate structure and comparatively little solid-solution hardening compared to higher-chromium grades like Haynes 690. Even so, it shares the fundamental nickel-alloy machining constraints: thermal conductivity is low, so cutting heat concentrates at the tool edge rather than dissipating into the chip, and the alloy work-hardens under mechanical deformation from the cutting action itself.

Because the alloy is soft, tough, and ductile in its typical mill-annealed sheet condition, chip control and built-up edge are often the more practical challenges rather than raw tool wear — long, stringy chips and galling against the cutting edge are common if speeds or feeds are mismatched to the tool geometry. Sharp, positive-rake cutting edges, consistent chip loads to avoid dwelling in the deformation zone, and adequate coolant are the standard approach, with somewhat more latitude on speed than the higher-alloyed, higher-chromium grades in this family.