M300 Tool Steel (18Ni-300 Maraging Steel)

metal

maraging steel — tooling grade (ultra-high-strength, precipitation-hardened)

EOS M30018Ni-300DIN 1.2709UNS K93120Maraging 300Vascomax 300 (wrought ref.)AMS 6514 (wrought ref.)

M300 Tool Steel (18Ni-300 Maraging Steel) 3D printed component

Density

8.00 g/cm³

YS (LPBF as-built (XY) — soft martensite)

900–1100 MPa

UTS (LPBF as-built (XY) — soft martensite)

1000–1200 MPa

Elongation (LPBF as-built (XY) — soft martensite)

8.0–16.0 %

Elastic modulus

170–190 GPa

Thermal conductivity

16.0–18.5 W/m·K

Composition — DIN 1.2709 / UNS K93120 / AMS 6514

Element	Min %	Max %	Notes
Ni	17.00	19.000	High Ni for martensite transformation (no carbon hardening). Ni content controls martensite start temperature (Ms ~155°C for 18Ni-300)
Co	8.50	9.500	Promotes Mo precipitation on ageing by reducing Mo solubility in γ matrix; lowers Ms temperature slightly
Mo	4.50	5.200	Primary age-hardening precipitate Ni₃Mo; also Ni₄Mo. Controls ultimate hardness — 4.5–5.2% Mo is the 18Ni-300 specification
Ti	0.50	0.800	Forms Ni₃Ti precipitates; secondary contribution to peak hardness. Interacts with Al to form ordered Ni₃(Al,Ti)
Al	0.05

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Mechanical & thermal properties — 4 conditions

Property	LPBF as-built (XY) — soft martensite	LPBF aged 490°C/6h (XY) — tooling condition	LPBF aged 490°C/6h (Z)	LPBF aged + nitrided surface (tooling production)
Elastic modulus	170–190 GPa	—	—	—
Yield strength (0.2%)	900–1100 MPa	1900–2080 MPa	1740–1960 MPa	—
Ultimate tensile strength	1000–1200 MPa	1960–2150 MPa	1830–2050 MPa	—
Elongation at break	8.0–16.0 %	2.0–6.0 %	1.5–5.0 %	—
Hardness (HV)	—	530–600 HV10	—	900–1150 HV0.1
Fatigue strength	—	700–900 MPa	—	—
Density	7.95–8.05 g/cm³	—	—	—
Thermal conductivity	16.0–18.5 W/m·K	—	—	—
CTE	10.2–11.2 µm/m·K	—	—	—

Values shown as min–max where a spread is reported, otherwise as typical ± unit. Ranges reflect inter-source variation, not single-sample scatter. All values are for AM-processed specimens unless noted.

Engineering considerations

Ageing protocol for tooling: 490°C / 4–6h in vacuum furnace or nitrogen atmosphere. Peak hardness typically achieved at 5h. Do not exceed 500°C — hardness drops 2–3 HRC per 10°C over-temperature. Verify hardness with calibrated hardness tester on a coupon run with the tool batch.
Sequence for tooling manufacture: LPBF → stress-relieve (300°C/1h, reduces distortion) → EDM/CNC machine cavity to within 0.1–0.2 mm of final dimension → age (490°C/5h) → finish grind/polish/EDM to final dimension → surface treat if required (nitriding, PVD).
Conformal cooling channel design: minimum printable channel diameter 1.5 mm; standard tooling channel 3–6 mm. Minimum wall thickness between channel and cavity surface: 1.5–2 mm (verify by FEA at peak injection pressure). Spirolift, baffle, and turbulator geometries are printable — use optimisation to maximise flow turbulence and heat transfer coefficient.
Distinguishing from Maraging MS1: when specifying for tooling vs. aerospace, explicitly state 'M300 (EOS tooling grade, 490°C/6h ageing)' rather than 'maraging steel' or '18Ni300' to ensure the correct material and heat treatment protocol is applied. The hardness target (50–54 HRC for M300 vs. 53–55 HRC for MS1) confirms the correct batch.
Dimensional change on ageing: typical linear shrinkage 0.05–0.10% — account for this in pre-age final machining allowance when tolerances are ±0.01 mm or tighter.
Surface finish for mould cavities: as-built M300 Ra 8–15 µm. Typical finishing sequence: coarse EDM → fine EDM (Ra ~1 µm) → hand polishing or abrasive blasting → final polish to Ra <0.1 µm (SPI A1 grade) for optical surfaces.
Wear resistance for abrasive resins: glass-filled (GF) and talc-filled polymers cause accelerated cavity wear on uncoated steel. For >20% GF content, apply plasma nitriding (0.2 mm case depth, ~1050 HV) or PVD TiAlN coating (4–6 µm, 3200 HV). Both are compatible with M300.
Fatigue life in high-cycle tooling: typical injection mould tool sees 10⁷–10⁸ cycles over lifetime. Design to <30% of endurance limit (~800 MPa) at gate/runner stress concentration points. Use FEA to verify cavity face stresses during peak injection. Gate area is the primary fatigue initiation site.

Advantages

Near-zero dimensional change on ageing (<0.1% linear): machine cavity to tight tolerance in soft as-built state (~32 HRC), then age to 50–54 HRC — eliminates distortion risk of H13 quench-and-temper
Achieves injection mould specification hardness (50–54 HRC) without the complex thermal management required for H13 through-hardening
LPBF enables conformal cooling channels impossible in machined H13/P20 tooling: can reduce injection moulding cycle time 20–40%
Uniform hardness through section thickness — superior to H13 which has through-hardening gradients in sections >100 mm
Highest strength of any standard LPBF metal in tooling condition: UTS ~2050 MPa — withstands injection pressures up to 200 MPa without plastic deformation
Good machinability in as-built state (32 HRC): conventional carbide machining and excellent EDM machinability enable finishing of complex cavity geometry
Can be nitrided after ageing for enhanced wear resistance against abrasive-filled polymers (surface hardness up to 1100 HV)
Laser micro-weld repair with matching maraging filler wire — enables cavity repair without full tooling replacement

Limitations

Very low ductility after ageing (2–6%) — not suitable for impact-loaded structures; only for tooling predominantly under compressive or low-tensile stress
Ageing is mandatory for tooling use — as-built 32 HRC is insufficient for production injection moulding
High raw powder cost: M300 powder is 4–6× more expensive per kg than H13 tool steel powder. Cost-justified only for complex conformal cooling geometries where cooling efficiency improvements outweigh the material cost
Over-ageing above 510°C causes hardness reduction via precipitate coarsening — temperature control to ±5°C is critical; record and verify every oven batch
Susceptible to hydrogen embrittlement: avoid acid pickling without pre-bake at 200°C/4h; prohibit electroless nickel plating without special HE relief procedures
Limited corrosion resistance vs. stainless — suitable for dry conditions; for humid or chemical environments, apply PVD TiN or CrN surface coating
M300 is frequently confused with Maraging MS1 in quotation and procurement: both are 18Ni-300, but M300 has a tooling-specific data package and is distinguished by its ageing optimisation (490°C vs. 480°C). Always specify by EOS material code to avoid mix-up
Limited fracture toughness data: unlike aerospace alloys, standardised KIC values for LPBF M300 are sparse — use wrought 18Ni-300 data (KIC ~70–80 MPa√m aged) as conservative estimate

Typical applications

Injection mould inserts with conformal cooling channels (automotive, consumer goods)Die-casting tooling for aluminium and zinc alloy casting insertsHigh-pressure press forming dies and deep-drawing toolsInjection mould hot-runner manifold componentsPrecision jigs, fixtures, and gauges requiring high dimensional stabilityMotorsport gear and drivetrain components requiring extreme strengthAerospace structural brackets and fasteners (ultra-high-strength, non-fracture-critical)Textile machinery and packaging equipment tooling (wear-resistant)

Standards & certifications

ASTM-E8established

Tensile test method for acceptance testing of AM M300 steel

toolingaerospaceindustrial

ASTM-E18established

Rockwell hardness testing — primary acceptance criterion for tooling inserts (50–54 HRC specification)

tooling

ISO-52904established

Process quality assurance for safety-critical LPBF metal parts

aerospacedefence

M300 Tool Steel (18Ni-300 Maraging Steel)

Composition — DIN 1.2709 / UNS K93120 / AMS 6514

Mechanical & thermal properties — 4 conditions

Engineering considerations

Advantages

Limitations

Typical applications

Industries

Standards & certifications

Compatible AM processes (3)

Other metal materials

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