316L as-built
STANDARDPrinted, stress-relieved and support-dressed. Full density, high ductility, matte granular surface. The right starting point for the majority of industrial parts.
480–620 MPaDuctileCost-effective
MATERIAL · STAINLESS STEEL
Stainless Steel 316L — The Corrosion answer That Machines Well
316L is the molybdenum-bearing austenitic stainless: the grade that survives chlorides, seawater, food acids and most process chemicals without pitting. We print it by selective laser melting to ≥99.5 % density, and unlike titanium it stays ductile, welds easily and machines without drama.
7.9 g/cm³Density
480–620 MPaTensile strength
≥99.5 %Printed density
~400 °CService temperature
OVERVIEW
What 316L actually is
316L is an austenitic stainless steel with roughly 16–18 % chromium, 10–14 % nickel and 2–3 % molybdenum. The chromium is what forms the passive oxide film that makes stainless stainless; the molybdenum is what makes 316 the grade that holds up in chloride environments where 304 fails. The L means low carbon — under 0.03 % — which prevents chromium carbide from precipitating at the grain boundaries during welding or heat treatment, and that is the difference between a part that stays corrosion-resistant at a weld and one that rusts along it.
Compared with titanium it is heavier, weaker per kilogram and cheaper by a wide margin. What it buys in return is ductility and predictability: 316L stretches 20–35 % before it breaks, it welds to itself and to dissimilar steels with ordinary methods, it machines like a proper steel, and it takes threads that hold. For a great many industrial parts that combination matters more than the weight.
On the printer, 316L is the most forgiving of the metals we run. It melts cleanly in an inert atmosphere, holds density reliably and tolerates a wider process window than titanium or copper. The quirk worth knowing about is magnetic: as printed, 316L is very slightly ferromagnetic, because rapid solidification traps a small amount of delta-ferrite in the austenite. It is normally imperceptible, but if your part sits next to a magnetic sensor, say so and we will measure it rather than promise.
PROPERTIES
Mechanical, Thermal & Chemical Data
Typical values for 316L printed by SLM. Note how much more ductile this is than titanium — that difference is the main reason 316L gets specified for anything that has to bend instead of break.
Density7.9 – 8.0 g/cm³
Tensile strength480 – 620 MPa as-built, depending on orientation
Yield strength (0.2 % offset)~380 – 500 MPa
Elongation at break20 – 35 % — substantial plastic deformation before failure
Young’s modulus~200 GPa, close to wrought steel
Hardness~180 – 220 HV
Relative density≥ 99.5 %
Service temperature~400 °C continuous; short excursions to 800 °C with scaling but no structural collapse
Thermal conductivity~15 W/m·K — low, similar to other austenitic grades
CTE~16 × 10⁻⁶ /K — higher than titanium; allow for it on long parts and on mixed-material joints
Corrosion resistanceExcellent in chlorides, seawater, food acids and most process chemicals. Vulnerable to hot concentrated chlorides (pitting) and to reducing acids.
Magnetic behaviourSlightly ferromagnetic as printed, because rapid solidification retains a little delta-ferrite. Usually imperceptible; measurable on request.
MachinabilityGood, with the usual austenitic tendency to work-harden. Cut it properly the first time rather than sneaking up on the dimension.
WeldabilityExcellent. Welds to itself, to 304 and to dissimilar steels by TIG, MIG or laser, without post-weld cracking.
As-built surfaceRa 6 – 12 µm matte granular; Ra 1.6 µm or better after machining.
PassivationNitric or citric passivation restores the oxide film after machining or blasting. Standard on food and medical-adjacent work.
GRADES & VARIANTS
316L Conditions & Finishes
All 316L, differing by heat treatment and finishing route. The condition usually decides whether the part is fit for service, not the grade.
316L stress-relieved
STABILITYA governed thermal cycle for parts with large flat sections, thin walls or long unsupported spans, where residual stress would otherwise distort the geometry after printing.
Low distortionLarge flatsThin walls
316L + HIP
FATIGUEHot isostatic pressing closes residual porosity and homogenises the microstructure. Specified for cyclic-loaded parts and for anything that will be pressure-tested.
Cyclic loadPressure-tightLonger lead time
Machined interfaces
TIGHT FITBores, sealing faces, bearing seats and threads cut from the printed blank. This is what turns a printed shape into a component that assembles with real hardware.
Sealing facesThreadsBearing seats
Electro-polished & passivated
HYGIENEElectro-polishing removes the surface layer and levels the micro-texture, then passivation restores the oxide film. The usual finish for food-contact, pharmaceutical and clean-service parts.
Food contactClean serviceLow Ra
Bead-blasted
COSMETICUniform matte grey and a clean edge break. The general-purpose finish when the part is visible but does not need to be polished.
Uniform matteEdge break
Inconel 718 and CoCr are available on request. Stainless powder is available in bulk for your own machines — see powder supply.
FINISHING
Finishing 316L
Stainless steel is the easiest of our metals to finish, and the finishing is often what decides whether the part passes inspection.
Support removal & dressing
Supports are cut from the plate and dressed by hand. Stresses are planned so that witness marks land on non-functional faces.
Stress relief
Relaxes the residual stress from the melt cycle. Essential on large flat plates, thin-walled ducts and anything that has to stay flat after machining.
Hot isostatic pressing
Closes residual porosity for fatigue-loaded or pressure-containing parts. Ask for it at enquiry stage rather than after a leak test.
CNC machining
Mating faces, bores, O-ring grooves and threads are machined from printed stock. Add machining stock on the model and we will cut to the drawing.
Wire EDM
Clean removal of the part from its base plate, with a flat witness face and no heat-affected zone to clean up afterwards.
Bead blasting & shot peening
Blasting gives a uniform matte surface; peening raises fatigue life by putting the surface into compression.
Electro-polishing
Removes the surface layer, drops the roughness and de-burrs internal channels that cannot be reached by hand.
Passivation
Nitric or citric passivation re-forms the passive oxide film after machining, blasting or handling. Standard on food and medical-adjacent parts.
Tumbling
Mass finishing for small parts in quantity, where per-part hand work would dominate the cost.
WHERE IT FITS
Where 316L Is the Right Answer
316L is the workhorse of printed metal. It is rarely the lightest or the strongest — it is usually the one that survives contact with reality and industry.
Strengths
- Genuinely corrosion resistant in chlorides, seawater, food acids and process chemistry
- Very ductile — it yields and bends before it fails, which forgives imperfect load estimates
- Welds reliably to itself and to dissimilar steels with standard processes
- Machines and threads properly, unlike titanium
- Holds ≥99.5 % density with a wide, forgiving process window
- Costs a fraction of titanium and copper per part
- Passivates and electro-polishes to food and pharmaceutical hygiene standards
- Available in bulk as powder for your own machines, with batch traceability
Limits to know
- Heavy: 7.9 g/cm³ is nearly twice aluminium and 78 % more than titanium
- Not a lightweight structural material — if mass matters, look at AlSi10Mg or Ti-6Al-4V
- Low thermal conductivity (~15 W/m·K): not a heat-sink material
- Slightly ferromagnetic as printed, which can matter next to magnetic sensors
- Pitting risk in hot, concentrated chlorides despite the molybdenum content
- High thermal expansion needs allowance on long parts and mixed-material assemblies
- Supports are required and leave witness marks on downward faces
Fluid manifolds and valve bodies
Consolidated manifolds that replace a brazed or welded assembly of tubes and fittings, removing every joint as a potential leak path. HIP and passivate, then pressure-test.
Food and dairy processing hardware
Nozzles, dies, guides, sprockets and change parts. Electro-polished and passivated for hygiene, in a grade that does not pit on food acids.
Marine and offshore fittings
Deck hardware, instrument housings and brackets that live in salt spray and cannot be maintained. The reason 316L exists commercially.
Chemical and pharmaceutical process parts
Impellers, valve internals, static mixers and custom spargers in geometries that machining cannot reach. Confirm the specific medium with us first.
Tooling and mould inserts
Conformal-cooled cores and cavity inserts where drilling straight lines would leave hot spots and long cycle times.
Pressure-containing components
With HIP and machining, parts that have to hold pressure rather than just hold shape. Tell us the test regime at enquiry stage.
Brackets and fixtures
General industrial brackets where ductility and corrosion resistance matter more than weight, and where a printed part avoids a machining setup.
Surgical instruments and non-implant devices
Retractors, guides, handles and housings. Passivated and, where required, electro-polished. Implant-grade supply is a separate chain — ask first.
COMPARISON
How 316L Compares
Against its neighbours: lighter than titanium on cost, heavier than aluminium on the scale, and tougher than both in terms of ductility.
| Material | Process | Density | Strength | Heat | Pick it when |
|---|---|---|---|---|---|
| Ti-6Al-4V | SLM | 4.43 g/cm³ | 900–1100 MPa | ~400 °C | Strength per gram, or biocompatibility |
| 316L stainless | SLM | 7.9 g/cm³ | 480–620 MPa | ~400 °C | Corrosion resistance, ductility, machinability |
| AlSi10Mg | SLM | 2.67 g/cm³ | 330–400 MPa | ~170 °C | Light, thermally conductive, machinable |
| Copper & Cu alloys | SLM | 8.9 g/cm³ | 210–400 MPa | ~200 °C | Electrical or thermal conductivity |
| PA12 nylon | SLS | 1.01 g/cm³ | 48–50 MPa | ~120 °C | Tough, complex geometry, no supports |
| Photopolymer resins | SLA | ~1.1–1.2 g/cm³ | 40–70 MPa | ~80 °C | Detail, smoothness, transparency |
The usual comparison is 316L against AlSi10Mg. Aluminium is a third of the weight and conducts heat ten times better; 316L is stronger, far more ductile, and indifferent to salt water. Which one you want depends entirely on whether the part is fighting mass or fighting corrosion.
FAQ
316L — Common Questions
Is printed 316L as corrosion resistant as wrought 316L?
Yes, provided the surface is finished properly. The alloy chemistry is the same and we hold ≥99.5 % density, so there is no connected porosity for the medium to track through. The two things that can degrade a printed part are trapped loose powder in internal channels and an unpassivated machined surface; we clear the first and passivate the second.
Why is my 316L part slightly magnetic?
Rapid solidification during printing retains a small amount of delta-ferrite in the austenitic matrix, and that is mildly ferromagnetic. It is a normal characteristic of printed austenitic stainless, not contamination or a wrong alloy. If the part sits next to a magnetic sensor or a reed switch, tell us at enquiry stage and we will measure a coupon instead of assuming.
Can you print a watertight part?
Yes, with the right process route. Printed 316L at ≥99.5 % density is pressure-tight by itself for most purposes, and we specify HIP when the part will actually be pressure-tested. Add machining stock on sealing faces so O-ring grooves and flanges can be cut rather than printed.
Can I get my part electro-polished?
Yes, and for food, pharmaceutical or clean-service parts it is usually the right finish. Electro-polishing removes the surface layer, drops the roughness and de-burrs internal channels that no tool can reach. Passivation afterwards restores the oxide film that the polishing removed.
Should I choose 316L or titanium?
If mass is the constraint and the cost can carry it, titanium. If corrosion resistance, ductility, machinability or cost is the constraint, 316L. Practically: titanium for things that fly, walk or get carried by a person; 316L for things that sit in a plant, a food line or on a boat deck.
What is the largest 316L part you can print?
We print in sections and weld when a part exceeds the machine envelope, then re-machine the joint, so the practical limit is set by how many joints you are willing to accept rather than by the machine. Send the assembly drawing and we will tell you where we would split it.
Related reading
GET STARTED
Steel Parts, Printed and Finished
Send the drawing, the medium the part will see and the environment it will live in. We will confirm the grade, the heat treatment and the finishing route, and quote it with the alternates beside it.
Built for global product teams · Worldwide shipping via DHL / FedEx / UPS