Maraging T300 is the higher-strength member of the cobalt-free branch of the 18% nickel maraging steel family, built on the same martensite-plus-aging principle as every other grade in the group but without cobalt's contribution to the aging response. On cooling from solution-annealing temperature, the very low-carbon nickel-molybdenum-titanium chemistry transforms into a soft, workable martensite. A subsequent aging treatment at moderate temperature then precipitates fine intermetallic compounds through that martensite, developing high strength while the alloy relies on elevated titanium content, rather than cobalt, to reach its target strength level.

Cobalt-free T-series grades exist because cobalt is subject to significant price swings and supply-chain risk, and some programs specify T-series alloys specifically to avoid that exposure. T300 is used in similar applications to the cobalt-bearing C-series grades of comparable strength — aerospace structural components, high-performance tooling, and precision shafting — typically where cost predictability or cobalt sourcing outweighs the marginal toughness advantage the cobalt-bearing grades can offer.

No independently verifiable AISI/SAE, DIN, or UNS cross-reference numbers were available for this specific cobalt-free maraging grade in the source data. Confirm designation cross-references against mill certification for critical applications.

T300's machinability follows the same annealed-versus-aged split as the rest of the maraging family. In the solution-annealed (unaged) condition, the low-carbon martensite is soft and machines predictably with standard carbide tooling, similar to a moderately hard alloy steel. This is the condition in which the great majority of rough and semi-finish machining takes place, ahead of the final aging cycle that develops the alloy's full strength.

Once aged, T300 reaches roughly 53.5 HRC, and cutting forces and tool wear both increase noticeably compared with the annealed condition. Post-aging work is generally limited to grinding or light, precision finishing passes rather than significant stock removal. As with the cobalt-bearing grades, the strengthening mechanism is fine intermetallic precipitation rather than a coarse carbide network, so aged T300 is less abrasive than an equally hard conventional tool steel, but the practical machining window still narrows considerably. The cutting speeds below apply to the solution-annealed, pre-aging condition.