Cobalt-Chrome (CoCrMo, ASTM F75)

Material Profile: Cobalt-Chrome (CoCrMo, ASTM F75) for Binder Jetting

Binder Jetting Engineering Material Technical Report Series

Compiled from manufacturer technical datasheets and peer-reviewed literature

Abstract—Cobalt-chromium-molybdenum (CoCrMo, ASTM F75) is a biocompatible, wear-resistant, high-temperature superalloy used predominantly for orthopaedic and dental implants and gas-turbine components. It was qualified on the Desktop Metal Shop System as one of the first medical-targeted binder-jet alloys, enabling cost-effective production of patient-specific implants and dental crowns at much lower cost than laser PBF. The HCP ε-Co matrix provides exceptional wear resistance (the metal-on-metal hip joint baseline), while the 27–30 wt% Cr content provides corrosion resistance superior to even 316L stainless steel in body fluids. As-sintered binder-jet CoCrMo achieves UTS ≈ 900 MPa and yield ≈ 600 MPa; HIP at 1200 °C / 100 MPa is mandatory for fatigue-critical implants, raising UTS to ≈ 1100 MPa.

Index Terms—additive manufacturing, binder jetting, cobalt chrome, CoCrMo, ASTM F75, biomedical, dental, orthopaedic implant.

I.  MATERIAL IDENTIFICATION

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

A.  Designation

Trade names: Desktop Metal Cobalt Chrome (Shop System); ExOne CoCr; Digital Metal DM CoCr. Wrought / cast equivalents: ASTM F75-18 (cast CoCrMo for surgical implants), ASTM F1537 (wrought low-carbon CoCrMo), ASTM F1241 (CoCr for dental). UNS R30075. Common trade names: Vitallium®, Stellite® 21.

B.  Full Chemical Name

Cobalt-chromium-molybdenum HCP/FCC dual-phase superalloy. Composition (wt%, ASTM F75): Cr 27.0–30.0, Mo 5.0–7.0, Ni ≤ 1.0, Fe ≤ 0.75, C 0.35 max (or ≤ 0.05 for low-carbon F1537), Mn ≤ 1.0, Si ≤ 1.0, W ≤ 0.20, P ≤ 0.020, S ≤ 0.010, N ≤ 0.25, Co — balance. Primary phase: HCP ε-Co at room temperature; transforms to FCC γ-Co above ~ 970 °C (martensitic-like transformation on cooling).

C.  Aliases and Alternative Designations

II.  COMPOSITION AND MOLECULAR STRUCTURE

A.  Empirical Chemical Formula

Co(balance, ≈ 60–65%) — Cr(27–30%) — Mo(5–7%) — minor (Ni, Mn, Si, C, Fe, W). Primary phase: HCP ε-Co + FCC γ-Co dual; carbides M₆C (CoMo₂C) and M₂₃C₆ (Cr-rich) at grain boundaries.

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 COBALT-CHROME (DESKTOP METAL SHOP SYSTEM) (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 (COBALT-CHROME (DESKTOP METAL SHOP SYSTEM))