Inconel 672 belongs to a specialized family of nickel-chromium weld-overlay and cladding alloys rather than the general-purpose wrought engineering grades most machinists think of first. Its defining trait is an unusually high chromium content — roughly 45% chromium against roughly 54% nickel — pushed well beyond what's typical even for other high-chromium Inconel grades. That chemistry gives 672 outstanding resistance to hot corrosion, sulfidation, and molten-salt attack, which is why it's supplied primarily as strip or wire for weld-overlay cladding rather than as solid bar stock.

Typical applications protect components exposed to aggressive combustion or process-side chemistry that would rapidly attack ordinary carbon or low-alloy steel — most notably kraft pulp and paper recovery boiler tubes, where molten smelt and flue-gas attack demand this level of corrosion resistance at the exposed surface. Because 672 is a cladding alloy, most of the machining work a shop encounters is light finishing of an already-deposited overlay layer rather than bulk material removal from solid stock, and the resulting deposit typically carries the coarser, dendritic-influenced structure characteristic of weld metal rather than wrought bar. Shops working with 672-clad components should still expect the general machining behavior common to Ni-Cr superalloys — rapid work hardening, low thermal conductivity, and a strong preference for sharp, positive-rake tooling — even though bulk stock removal is rarely the actual objective on this alloy.

Nickel-chromium superalloys like 672 are difficult to machine for a consistent set of reasons: low thermal conductivity keeps heat concentrated at the cutting edge instead of carrying it away in the chip, the material work-hardens rapidly under light or interrupted cuts, and it retains a large share of its strength even at red heat, so cutting forces stay high well into the temperature range where steel would already have softened. Combined with a tendency to gall and weld to the tool face, these traits chew through uncoated or poorly matched tooling quickly.

672 adds a wrinkle most wrought superalloys don't have: it's a weld-overlay/cladding alloy, so the material a shop actually touches is deposited weld metal, not rolled or forged bar. Weld deposits carry a coarser, more dendritic microstructure than wrought material, and can include localized dilution zones where the overlay picked up iron from the substrate during welding — both of which can produce inconsistent hardness and machinability from one pass to the next. Because the goal is almost always finishing an as-deposited overlay to a target thickness or surface finish rather than bulk stock removal, light, controlled cuts with a sharp, positive-rake edge and steady feed are the priority — dwelling or rubbing on this material work-hardens it fast and makes the next pass harder to start cleanly. A grade with good hot hardness and edge toughness, backed by ample coolant to manage heat at the tool-chip interface, is the practical baseline for finishing 672 overlays.