HS 30 is a cast cobalt-base superalloy from the Haynes-Stellite family, cross-referenced to AMS 5380 and DIN designation CoCr26Ni14Mo. 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 commented-out description that called HS 30 "nickel-based" with "57.7% nickel." That text was boilerplate copied across several unrelated cobalt-alloy pages and does not reflect HS 30'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; the old page's table also omitted carbon entirely despite this being a carbide-strengthened cast grade.

As a cast alloy, HS 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.

HS 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.