Stellite 188 is Kennametal Stellite's trade name for the same solid-solution-strengthened cobalt-nickel-chromium-tungsten superalloy marketed elsewhere as Haynes 188 (Haynes International) - identical UNS number, identical AMS specifications, identical nominal chemistry. It belongs in the high-temperature structural sub-group of this library alongside S 816, not with the wear-resistant hardfacing Stellites (1, 12, 19, 100, 151): its strength comes from cobalt and tungsten in solid solution within the cobalt-nickel matrix, not from a dense carbide network engineered for abrasion resistance.

The alloy combines strong high-temperature strength with excellent oxidation resistance up to roughly 1095°C/2000°F for prolonged exposure, plus good resistance to sulfate-deposit hot corrosion, thanks in part to a small lanthanum addition that improves oxide-scale adhesion. That combination makes it a standard choice for gas-turbine combustor liners, transition ducts, flame holders, and afterburner components - hot-section hardware where surface stability under extreme, cyclic temperature matters more than raw hardness. See the Haynes 188 page on this site for the identical alloy under its more common trade name.

Stellite 188 machines identically to Haynes 188, since it is the same alloy: cobalt-base superalloys in this solid-solution class present a harder machining challenge than most nickel superalloys of comparable strength. Thermal conductivity is very low even by superalloy standards, so heat generated in the cut has nowhere to escape except into the tool, accelerating crater wear and edge deformation if speeds are not tightly controlled.

The alloy retains hardness and strength at elevated temperature even more persistently than nickel-base grades, so there is essentially no thermal softening to lean on. Combined with rapid work hardening under cutting stress, a light, hesitant, or interrupted cut leaves a hardened surface layer that is dramatically tougher to remove on the next pass - a steady, adequate chip load is not optional. The heavy tungsten content also promotes hard carbide-forming behavior that adds abrasive wear on top of the adhesive and thermal wear mechanisms shared with nickel alloys.

Unlike the wear-resistant Stellite hardfacing grades in this library, Stellite 188's difficulty comes from its solid-solution strength retention and work-hardening rate, not from a dense engineered carbide network - it is demanding for different metallurgical reasons than Stellite 1, 12, 19, 100, or 151, even though all are nominally "cobalt alloys." Sharp, positively-raked coated carbide, rigid low-deflection setups, and generous coolant flow are essential; expect edge life shorter than on Inconel 718 at comparable material-removal rates.