Stellite 30 is a cast cobalt-base alloy from the Haynes-Stellite family, cross-referenced in this library to material HS 30, which carries the same nominal chemistry, DIN designation CoCr26Ni14Mo, and AMS 5380 reference. Cobalt forms the majority element by weight, with chromium, nickel, and molybdenum as the principal alloying additions - chromium for oxidation and hot-corrosion resistance, nickel to stabilize the matrix and improve ductility, and molybdenum for solid-solution strengthening and added resistance to certain corrosive media.

Correction: the previous version of this page carried a description calling this alloy "nickel-based" - boilerplate text that was found reused across several unrelated cobalt-alloy pages in the old dataset and does not reflect the alloy's actual chemistry. Cobalt, not nickel, is the base element. The composition table below has been corrected against published reference data for this alloy family; independent web sources for "Stellite 30" converge on the same Cr~26% / Ni~15% / Mo~6% / C~0.5% profile documented for HS 30, confirming that Stellite 30 and Haynes-Stellite 30 refer to the same alloy.

As a cast alloy, Stellite 30 relies on a carbide-dispersed microstructure for its wear and high-temperature strength, which makes it noticeably more abrasive to cut than wrought cobalt or nickel superalloys of similar composition. It is typically specified for cast components running in elevated-temperature, corrosive, or wear-prone service where a fabricable wrought alloy is not required.

Stellite 30 combines two separate machining challenges: it is a cobalt-base superalloy, and it is a cast structure. Cobalt-base alloys generally retain hardness and strength at elevated temperature even better than nickel-base grades, so the softening effect that makes many alloys easier to cut at higher speed largely does not apply - the cutting edge stays under heavy thermal and mechanical load throughout the cut. Cobalt alloys also work-harden aggressively; any hesitation, rubbing, or light/inconsistent feed leaves a hardened layer on the next pass that is measurably tougher to cut.

The cast microstructure adds a second layer of difficulty. Cast cobalt superalloys derive their strength and wear resistance from a network of hard chromium and molybdenum carbides distributed through the matrix. Those carbides are highly abrasive to cutting tools - they behave much like an embedded abrasive grit - and drive rapid flank wear even on grades that hold up well in wrought cobalt or nickel alloys. Casting-related variables (porosity, dendritic segregation, hard skin from the mold) add further inconsistency to the cut.

In practice this means low, conservative cutting speeds, sharp positive-rake carbide edges to minimize work hardening, rigid tooling and workholding to avoid chatter that accelerates carbide-phase chipping, and frequent flank-wear monitoring rather than running to a fixed tool-life target. Generous, consistent coolant flow is essential to control heat at the edge and flush abrasive carbide debris from the cut.