AISI M2 High-Speed Tool Steel

Material Profile: AISI M2 High-Speed Tool Steel for Binder Jetting

Binder Jetting Engineering Material Technical Report Series

Compiled from manufacturer technical datasheets and peer-reviewed literature

Abstract—AISI M2 (UNS T11302) is the most widely used molybdenum high-speed steel and a customer-qualified material on the Desktop Metal X-Series platform (Innovent / X25Pro / X160Pro). M2's defining feature is its exceptional hot hardness — HRC 62–66 retained at 540 °C and HRC 60+ even at 600 °C — making it the standard cutting-tool material for drills, taps, milling cutters, and form tools. Binder-jet M2 unlocks geometries impossible to grind from billet: complex chip-flute profiles, internal coolant channels routed through the tool body, and patient-specific dental/orthopaedic cutting tools. After triple-temper heat treatment (austenitise 1220 °C, triple-temper 540 °C × 3), binder-jet M2 achieves HRC 64–66 with retained heavy MC carbide loading (~ 10 vol%).

Index Terms—additive manufacturing, binder jetting, M2, high-speed steel, HSS, cutting tools, AISI M2, Desktop Metal X-Series.

I.  MATERIAL IDENTIFICATION

This section establishes the canonical names and commercial designations under which the material is supplied.

A.  Designation

Trade names: Desktop Metal M2 (X-Series customer-qualified); ExOne M2 Tool Steel; Höganäs M2 powder. Wrought equivalents: AISI M2 (UNS T11302), ASTM A600, DIN 1.3343 / S6-5-2C, JIS SKH51. Sometimes called 'Mo-HSS' to distinguish from the older tungsten T-series HSS.

B.  Full Chemical Name

Molybdenum-tungsten-vanadium-chromium high-speed tool steel. Composition (wt%): C 0.78–0.88, Cr 3.75–4.50, V 1.75–2.20, W 5.50–6.75, Mo 4.50–5.50, Mn 0.15–0.40, Si 0.20–0.45, P ≤ 0.030, S ≤ 0.030, Fe — balance. Microstructure: BCT martensite + ~ 10 vol% MC (V₄C₃) carbides + ~ 8 vol% M₆C (Fe-W-Mo) carbides. The MC carbides resist over-aging at high cutting temperatures.

C.  Aliases and Alternative Designations

II.  COMPOSITION AND MOLECULAR STRUCTURE

A.  Empirical Chemical Formula

Fe(balance) — C(0.78–0.88%) — Cr(3.75–4.50%) — V(1.75–2.20%) — W(5.50–6.75%) — Mo(4.50–5.50%) — minor (Mn, Si, P, S). Microstructure: BCT martensite + 10 vol% MC (V₄C₃) + 8 vol% M₆C (Fe-W-Mo) carbides.

Fig. 1.  Repeating unit / structural schematic of the polymer matrix.

Fig. 2.  Schematic of the single-phase polymer (no reinforcement).

B.  Composition Breakdown

TABLE I
 COMPOSITIONAL BREAKDOWN OF M2 HIGH-SPEED STEEL (DESKTOP METAL X-SERIES) (TYPICAL / PER SUPPLIER DATASHEET)

III.  MECHANICAL PROPERTIES — XY BUILD DIRECTION (HORIZONTAL)

In the XY orientation the tensile load is applied parallel to the powder-bed plane. Binder-jetted (BJ) parts in the as-sintered state generally show modest in-plane vs build-axis anisotropy because sintering occurs near the solidus and re-distributes the porosity left by the binder-removal step. For metal BJ, post-sintering treatments (HIP, solution-anneal, age) are commonly applied to bring properties to wrought-equivalent and to eliminate residual closed porosity.

TABLE II
 MECHANICAL PROPERTIES — XY ORIENTATION (M2 HIGH-SPEED STEEL (DESKTOP METAL X-SERIES))

IV.  MECHANICAL PROPERTIES — Z BUILD DIRECTION (VERTICAL)

In the Z orientation the tensile load is applied perpendicular to the printed layers. Binder-jet metal parts typically exhibit Z-direction strength within 5–15 % of XY in the as-sintered state, since the inter-layer interface effectively dissolves during high-temperature sintering. For sand-mould materials, Z-direction strength is dominated by inter-layer binder bonding and is generally 60–90 % of XY in transverse strength.

TABLE III
 MECHANICAL PROPERTIES — Z ORIENTATION (M2 HIGH-SPEED STEEL (DESKTOP METAL X-SERIES))

Binder-jet M2 has near-isotropic hardness and wear performance after triple-temper heat treatment. The carbide volume fraction and distribution is essentially independent of build orientation because sintering and triple-temper heat treatment fully homogenise the carbide network. Tensile testing is limited use for M2 — the alloy is brittle by design (1–2 % elongation), and component performance is governed by hardness, wear, and bend strength, not tensile UTS.

V.  RECOMMENDED PROCESS PARAMETERS

Values summarised below give consensus operating windows from public datasheets (Desktop Metal, ExOne, voxeljet, cprint3d). Specific machines and parameter sets may differ within ±10 %; the supplier's verified parameter sheet always supersedes this table. For metal binder jetting, complete green-state cure (~200 °C) and a high-temperature de-bind / sinter cycle (typically 1 100–1 380 °C in H₂ / Ar / vacuum) are mandatory after print. For sand binder jetting, parts are usable directly after print (with optional microwave or oven post-cure).

TABLE IV
 RECOMMENDED BINDER-JETTING PROCESS PARAMETERS FOR M2 HIGH-SPEED STEEL (DESKTOP METAL X-SERIES)

VI.  GLASS TRANSITION TEMPERATURE (TG)

Reported / typical Tg: Not applicable (metallic alloy).

Critical thermal limits: austenitisation 1220 °C (very narrow window — risk of incipient melting at 1240 °C); martensite start Ms ≈ 200 °C; tempering peak (secondary hardening) at 540 °C; service-temperature limit ≈ 600 °C (cutting-tool peak); melting range 1330–1410 °C (only ~ 100 °C above austenitisation — process must be carefully controlled).

VII.  HEAT DEFLECTION TEMPERATURE (HDT)

Heat deflection temperature is the temperature at which a standard bar deflects 0.25 mm under a specified flexural load (ASTM D648 / ISO 75).

TABLE V
 HEAT DEFLECTION TEMPERATURE OF M2 HIGH-SPEED STEEL (DESKTOP METAL X-SERIES) UNDER STANDARD TEST LOADS

VIII.  DISTINGUISHING CHARACTERISTICS AND STANDARDS

A.  Highest hot hardness in BJ portfolio

M2 retains HRC 60+ at 540 °C and HRC 56 at 600 °C — the highest hot hardness of any binder-jettable metal. This is what makes high-speed cutting (cutting speeds 30–200 m/min, where the chip-tool interface reaches 500–700 °C) possible. Without M2's hot hardness, the cutting edge would be plastically deformed by the chip after seconds.

B.  Geometric freedom for advanced cutting tools

BJ enables internal coolant channels routed directly to the cutting edge, complex chip-flute geometries optimised by CFD, and conformal-rake-angle face-mill inserts impossible to grind. Documented case studies (Sandvik, Iscar, Kennametal) show 30–50 % tool-life increase for AM cutting tools with internal coolant routing vs ground equivalents.

C.  Heavy carbide loading — extreme wear resistance

~ 18 vol% combined MC + M₆C carbides give M2 the highest carbide loading of any binder-jet steel. Wear rate in pin-on-disc tests is ~ 1/100 of 4140 and ~ 1/50 of 17-4PH — the reason M2 is the dominant cutting-tool steel globally despite being more difficult to process than carbide tooling.

D.  Brittle — impact loading must be avoided

M2 has only 1–2 % elongation at break — by design. It must be used only in components subjected to compressive loading (cutting tools, dies, punches). Avoid impact loading or tensile fatigue applications. Tool design must include generous radii to avoid stress concentrations.

E.  Narrow process window — careful sintering required

Austenitisation at 1220 °C is only 110 °C below the 1330 °C solidus. Sintering must be done with tight temperature control (± 5 °C) to avoid incipient melting at grain boundaries. This is why M2 is customer-qualified rather than fully Desktop-Metal-qualified — process robustness depends on furnace calibration and operator expertise.

IX.  REPRESENTATIVE APPLICATIONS

M2 High-Speed Steel (Desktop Metal X-Series) is typically deployed in the following applications:

1)  High-speed cutting tools: Drills, end mills, taps, broaches with optimised flute geometries and internal coolant channels.

2)  Punches and dies (cold work): Punches and dies for stamping, blanking, coining — leveraging hot hardness retention during the brief plastic deformation cycle.

3)  Custom dental and surgical drills: Patient-specific bone drills and dental burs leveraging AM geometry (e.g. tapered profile matched to specific cavity geometry).

4)  Cold-heading dies: Bolt and screw cold-heading dies — long tool life from M2's high hardness.

5)  Plastic injection-mould inserts (high-wear): Wear-prone runner inserts and gating points where filled / glass-reinforced plastics would erode H13 too rapidly.

X.  REFERENCES

[1]  ASTM A600-92a(2021), “Standard Specification for Tool Steel High Speed,” ASTM International, 2021.

[2]  DIN EN ISO 4957:2018, “Tool steels,” European Committee for Standardization.

[3]  Böhler Edelstahl, “S600 — High-Speed Steel (M2 equivalent),” Technical bulletin.

[4]  Crucible Industries, “M2 Tool Steel Data Sheet,” 2020.

[5]  ExOne, “M2 Tool Steel for ExOne InnoventPro Material Profile,” 2022.

[6]  ASTM E8/E8M-22, “Standard Test Methods for Tension Testing of Metallic Materials,” ASTM International, 2022.

[7]  ASTM B962-17, “Standard Test Methods for Density of Compacted or Sintered Powder Metallurgy (PM) Products Using Archimedes' Principle,” ASTM International, 2017.

[8]  ASTM E18-22, “Standard Test Methods for Rockwell Hardness of Metallic Materials,” ASTM International, 2022.

[9]  ASTM F3318-22, “Standard for Additive Manufacturing — Finished Part Properties — Specification for AlSi10Mg with Powder Bed Fusion — Laser Beam,” ASTM International, 2022.

[10]  ISO/ASTM 52900:2021, “Additive manufacturing — General principles — Fundamentals and vocabulary,” ISO, 2021.

[11]  ISO/ASTM 52904:2024, “Additive manufacturing — Process characteristics and performance — Practice for metal powder bed fusion process to meet critical applications,” ISO, 2024.

[12]  MPIF Standard 35-MIM, “Materials Standards for Metal Injection Molded Parts,” Metal Powder Industries Federation, 2022 ed.

[13]  Desktop Metal, “Material Properties of Binder Jet Parts,” Desktop Metal Technical White Paper. [Online]. Available: https://www.desktopmetal.com/resources/material-properties-of-binder-jet-parts

[14]  Desktop Metal, “Why Binder Jetting?” Desktop Metal Application Note. [Online]. Available: https://www.desktopmetal.com/resources/why-binder-jetting-1

[15]  Desktop Metal, “Materials portfolio overview,” Desktop Metal product page. [Online]. Available: https://www.desktopmetal.com/materials/

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