Jethete X20 corresponds to one of the most widely used steam turbine blading and rotor steels ever produced: 12% chromium-molybdenum-vanadium martensitic creep-resisting steel, standardized as X20CrMoV12-1, Wnr. 1.4922. The closely related grade X22CrMoV12-1 (Wnr. 1.4923) carries a slightly higher carbon content and is easy to confuse with X20 in supplier literature and cross-reference tables — always confirm which of the two is actually specified on the drawing, since they are not identical.

Molybdenum raises the recrystallization temperature and suppresses temper embrittlement, while vanadium forms fine, stable carbide/carbonitride precipitates that pin grain boundaries and resist dislocation movement at temperature — the metallurgical basis for this grade's creep resistance. Supplied and machined in the hardened-and-tempered condition, X20 has been the workhorse material for steam turbine rotor blading, rotor forgings, and high-temperature bolting in fossil and combined-cycle power plants operating up to roughly 600°C (1110°F) for decades.

Nominal composition per DIN/EN for grade 1.4922 / X20CrMoV12-1.

X20 is machined almost exclusively in the hardened-and-tempered condition, and its vanadium- and molybdenum-alloyed carbide structure is markedly more abrasive than a plain 12Cr martensitic stainless of the same nominal hardness. Expect elevated cutting forces, faster flank wear, and a real need to keep the edge sharp — a dull tool on this alloy generates heat and work-hardens the surface quickly, compounding wear on the next pass.

Given that this grade is frequently machined into large rotor forgings and blading with tight dimensional tolerances, rigidity of both the machine and the setup matters as much as tool selection. Sharp, positive geometries, steady feed rates that stay below any hardened surface layer, and consistent coolant delivery are the standard approach. Confirm actual tempered hardness before finalizing speeds, since X20 stock is supplied across a range of tempering conditions depending on the target mechanical properties.

Turning

Parting / Grooving

Milling