Austenitic Stainless Steel 316L (UNS S31603)

Material Profile: Austenitic Stainless Steel 316L (UNS S31603) for Direct Metal Laser Sintering

SLS Engineering Material Technical Report Series

Compiled from manufacturer technical datasheets and peer-reviewed literature

Abstract—316L is the standard low-carbon austenitic chromium-nickel-molybdenum stainless steel — the workhorse corrosion-resistant alloy of the metal additive-manufacturing industry alongside AlSi10Mg and Ti-6Al-4V. The 'L' designation (≤ 0.030 wt% C) suppresses chromium-carbide precipitation at grain boundaries during slow cooling, eliminating intergranular corrosion susceptibility — particularly relevant for AM, where the part experiences many thermal cycles during build and is often welded or post-processed. The 2–3 wt% molybdenum addition over standard 304/304L significantly improves pitting and crevice corrosion resistance in chloride environments (seawater, body fluids, food-processing chlorinated cleaners). DMLS-built 316L achieves as-built UTS ≈ 640 MPa and yield ≈ 530 MPa — substantially higher than wrought 316L (UTS ~ 580 MPa, yield ~ 290 MPa) due to the fine cellular dendritic microstructure produced by laser rapid solidification. Solution annealing per ASTM A403 reduces strength to wrought-equivalent levels but improves elongation from ~40 % to ~50 %. The alloy is ASTM-A403-compliant in the as-built state and meets ASTM A276 / ASTM F138 requirements with appropriate post-processing.

Index Terms—additive manufacturing, DMLS, SLM, stainless steel, 316L, austenitic, corrosion resistance, AISI 316L, UNS S31603.

I.  MATERIAL IDENTIFICATION

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

A.  Designation

Trade names: EOS StainlessSteel 316L (the dominant industrial powder); 3D Systems LaserForm 316L; SLM Solutions 316L; Renishaw SS316L-0405. Wrought / cast equivalent: ASTM A276 / A479 / A480 (UNS S31603), AISI 316L, EN 1.4404 (X2CrNiMo17-12-2), W.Nr. 1.4404. For AM medical implants: ASTM F138 (wrought) is the underlying standard; AM-specific F3184 covers powder-bed fusion 316L.

B.  Full Chemical Name

Low-carbon austenitic FCC chromium-nickel-molybdenum stainless steel. Composition (wt%): Fe — balance, Cr 17.0–19.0, Ni 13.0–15.0, Mo 2.25–3.0, Mn ≤ 2.0, Si ≤ 0.75, P ≤ 0.025, S ≤ 0.010, N ≤ 0.10, C ≤ 0.030 (the 'L' = low-carbon).

C.  Aliases and Alternative Designations

II.  COMPOSITION AND MOLECULAR STRUCTURE

A.  Empirical Chemical Formula

Fe(balance) — Cr(17–19%) — Ni(13–15%) — Mo(2.25–3.0%) — Mn(≤2%) — Si(≤0.75%) — C(≤0.03%, the 'L' = low-carbon) — N(≤0.10%) — P(≤0.025%) — S(≤0.010%). Single-phase austenite (γ-Fe FCC) at room temperature; non-magnetic.

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 STAINLESS STEEL 316L (EOS STAINLESSSTEEL 316L) (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 (in-plane). For polymer SLS this is typically the stronger orientation due to better neck formation between particles within a single layer; for metal DMLS/SLM, columnar β / α-grain growth perpendicular to the build direction also yields different anisotropy that is partially relieved by post-build heat treatment (e.g. stress-relief, HIP).

TABLE II
 MECHANICAL PROPERTIES — XY ORIENTATION (STAINLESS STEEL 316L (EOS STAINLESSSTEEL 316L))

IV.  MECHANICAL PROPERTIES — Z BUILD DIRECTION (VERTICAL)

In the Z orientation the tensile load is applied perpendicular to the powder layers; failure occurs across inter-layer fusion bonds. For polymer SLS the Z properties are typically 70–90 % of XY; for metal LPBF (laser powder-bed fusion) processes Z elongation is often higher due to the columnar grain structure but UTS / yield can be slightly lower in the as-built state. Heat treatment (anneal, HIP) reduces the anisotropy substantially.

TABLE III
 MECHANICAL PROPERTIES — Z ORIENTATION (STAINLESS STEEL 316L (EOS STAINLESSSTEEL 316L))

316L DMLS shows ~15 % UTS anisotropy as-built (XY higher than Z), but Z elongation is typically higher (~50 %) than XY (~40 %) due to columnar austenite grains aligned along the build direction. Solution annealing per ASTM A403 (1 050 °C / 1 h, water quench) recrystallises the cellular sub-grain structure, dropping UTS to wrought-equivalent (~580 MPa) but raising elongation to ~50 % and substantially reducing anisotropy. EOS specifically notes the as-built mechanical properties already meet ASTM A403 — solution annealing is optional unless the part will operate in the 427–816 °C 'sensitisation window' where intergranular Cr-carbide precipitation must be prevented.

V.  RECOMMENDED PROCESS PARAMETERS

Values summarised below give consensus operating windows from public datasheets (EOS, 3D Systems, BASF Forward AM, SLM Solutions). Specific machines and parameter sets may differ within ±10 %; the supplier's verified parameter sheet always supersedes this table.

TABLE IV
 RECOMMENDED LASER POWDER-BED-FUSION PROCESS PARAMETERS FOR STAINLESS STEEL 316L (EOS STAINLESSSTEEL 316L)

VI.  GLASS TRANSITION TEMPERATURE (TG)

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

Austenitic FCC iron alloys do not exhibit a glass transition. The closest analogue is the austenite-to-ferrite transformation, but 316L is fully austenitic at all service temperatures up to ~ 1 400 °C. Critical thermal limits: sensitisation window 427–816 °C (chromium-carbide precipitation at grain boundaries — avoid sustained exposure unless solution-annealed); creep limit ~ 800 °C; melting range 1 380–1 400 °C.

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 STAINLESS STEEL 316L (EOS STAINLESSSTEEL 316L) UNDER STANDARD TEST LOADS

VIII.  DISTINGUISHING CHARACTERISTICS AND STANDARDS

A.  Outstanding corrosion resistance

316L's 17–19 % Cr forms a passive Cr₂O₃ surface layer; the 2–3 % Mo provides best-in-class pitting and crevice corrosion resistance in chloride media (seawater, sweat, biological fluids, food-grade chlorinated cleaners). PREN (Pitting Resistance Equivalent Number) ≈ 26–28, vs ~18 for 304L. Excellent in oxidising acids; limited in reducing acids (use Hastelloy / Inconel for those).

B.  Biocompatibility — short-term implants and surgical instruments

316L meets ASTM F138 wrought medical-grade requirements and is widely used for non-permanent orthopaedic implants (bone screws, fracture-fixation plates, dental crowns). For permanent implants Ti-6Al-4V ELI is preferred (lower modulus, no Ni allergy concern). 316L is the standard for surgical instruments — corrosion resistance combined with sterilizability (autoclave, gamma).

C.  As-built strength exceeds wrought 316L

Laser rapid solidification produces a fine cellular sub-grain austenite microstructure (cell size 0.5–1 µm) with high dislocation density. As-built yield strength (~530 MPa) is nearly twice wrought 316L (~290 MPa), at equivalent or better elongation. Solution annealing recovers wrought-equivalent properties — required for code-stamped pressure-vessel applications, optional otherwise.

D.  Welds and machines like wrought 316L

DMLS 316L parts can be TIG / MIG welded using ER316L filler (no special procedure), wire-EDM cut, machined with conventional carbide tooling, and electropolished or passivated (per ASTM A967) for hygienic-design applications. Surface roughness in the as-built state is Ra 6–10 µm; electropolished surfaces achieve Ra < 0.4 µm — relevant for biomedical, semiconductor, and aseptic-process applications.

E.  Non-magnetic

316L is non-magnetic in the fully austenitic state, useful for MRI-compatible medical devices, sensitive scientific instruments, and electronic shielding. Mild cold-work or rapid solidification can introduce trace ferromagnetic phases — typically < 1 % volume fraction in as-built DMLS 316L; controlled by parameter selection and confirmed by feritscope measurement when required.

IX.  REPRESENTATIVE APPLICATIONS

Stainless Steel 316L (EOS StainlessSteel 316L) is typically deployed in the following applications:

1)  Surgical instruments and short-term implants: Customised retractors, bone screws, fracture-fixation plates, and surgical drill guides — leverages biocompatibility (ASTM F138), sterilizability, and AM's ability to produce patient-specific geometry.

2)  Food and pharmaceutical processing equipment: Custom valves, flow distributors, and cleanable manifolds for aseptic process lines, leveraging electropolishability and chloride-cleaner resistance.

3)  Marine and offshore hardware: Pump impellers, valve bodies, and fittings exposed to seawater — pitting / crevice resistance combined with weldability for repair.

4)  Heat exchangers and process intensification: Compact lattice / micro-channel heat exchangers for chemical and pharmaceutical processes — trades the higher conductivity of AlSi10Mg for chemical inertness.

5)  Mould inserts with conformal cooling: Injection-mould inserts with internal cooling channels following the part geometry — comparable to AlSi10Mg but preferred when mould-cleaning chemicals would corrode aluminium.

X.  REFERENCES

[1]  EOS GmbH, “EOS StainlessSteel 316L — Material data sheet,” EOS Metal Solutions, 2022. [Online]. Available: https://www.eos.info/var/assets/05-datasheet-images/Assets_MDS_Metal/EOS_StainlessSteel_316l/material_datasheet_eos_stainlesssteel_316l_en_web.pdf

[2]  EOS GmbH, “Material data sheet — EOS StainlessSteel 316L (FlexLine, M 100),” 2022. [Online]. Available: https://www.eos.info/var/assets/03-system-related-assets/material-related-contents/metal-materials-and-examples/metal-material-datasheet/stainlesssteel/ss-316l_9011-0032_m100_material_data_sheet_flexline_06-22_en.pdf

[3]  ASTM International, “A276 / A276M-17: Standard Specification for Stainless Steel Bars and Shapes,” 2017.

[4]  ASTM International, “A403 / A403M-22: Standard Specification for Wrought Austenitic Stainless Steel Piping Fittings,” 2022.

[5]  ASTM International, “F138-19: Standard Specification for Wrought 18Chromium-14Nickel-2.5Molybdenum Stainless Steel Bar and Wire for Surgical Implants,” 2019.

[6]  ISO 6892-1:2019, “Metallic materials — Tensile testing — Part 1: Method of test at room temperature,” ISO, 2019.

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

[8]  ASTM F3001-14, “Standard Specification for Additive Manufacturing Titanium-6 Aluminum-4 Vanadium ELI (Extra Low Interstitial) with Powder Bed Fusion,” ASTM International, 2014.

[9]  ASTM F3122-14, “Standard Guide for Evaluating Mechanical Properties of Metal Materials Made via Additive Manufacturing Processes,” ASTM International, 2014.

[10]  ASTM F3055-14a, “Standard Specification for Additive Manufacturing Nickel Alloy (UNS N07718) with Powder Bed Fusion,” ASTM International, 2014.

[11]  K. Saeidi et al., “Hardened austenite steel with columnar sub-grain structure formed by laser melting,” Materials Science and Engineering: A, vol. 625, pp. 221–229, 2015.

[12]  EN 10088-3:2014, “Stainless steels — Part 3: Technical delivery conditions for semi-finished products, bars, rods, wire, sections and bright products of corrosion resisting steels for general purposes,” CEN.

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