To choose a metal 3D printing alloy, work down five questions in order: does it run hot, does it need to resist corrosion, does weight dominate, how strong must it be, and what is the budget. The answer at the first hard constraint usually names the alloy — AlSi10Mg for light and cheap, Ti-6Al-4V for high strength-to-weight, 316L for corrosion, 17-4 PH for hardness, and Inconel for heat. At Layer X, this is the exact conversation we have on every DMLS enquiry before a single powder lot is loaded, and this guide turns it into a tree you can walk yourself.
Why alloy choice comes before anything else
The alloy decides more than the finished mechanical properties. It sets the powder cost, the build time, the support strategy, the post-processing and often whether a part is even worth printing versus machining from billet. Get it wrong and you either over-pay for Inconel where 316L would have served, or you under-spec an aluminium bracket that fatigues in service. Our DMLS line is certified to five alloy families — 316L stainless, 17-4 PH stainless, H13 tool steel, Ti-6Al-4V titanium, and Inconel 625/718 — and we also print AlSi10Mg aluminium for lightweight structural work. This guide is a buyer's selector across that range, and each branch links to the deeper per-alloy and per-application writing we have already published.
Two things stay constant whichever alloy you land on. Every part on our DMLS metal 3D printing line holds ±0.1mm dimensional tolerance as standard, with critical surfaces post-machined below ±0.05mm, and every order ships with a CMM dimensional report — not as an optional extra. The build envelope is 250×250×325mm, lead time is 5–7 days, and pricing starts from ₹5,000 per part.
The decision tree at a glance
Read the branches top to bottom and stop at your first non-negotiable constraint. If two constraints tie — say heat and corrosion — the higher branch wins, because thermal survival is harder to engineer around than surface protection.
- Does the part run above ~500°C or see hot corrosive gas? → Inconel 625 or 718.
- Does it live in seawater, chemicals, or a medical/food environment? → 316L stainless steel.
- Is strength-to-weight the whole point (aerospace, motorsport, implants)? → Ti-6Al-4V.
- Do you need high hardness and strength at low cost, with corrosion resistance a bonus? → 17-4 PH stainless steel.
- Is it a light, geometrically complex, cost-sensitive structural part? → AlSi10Mg aluminium.
The five alloys compared
The table below is the same one we sketch on a whiteboard during a quote review. Treat the property columns as relative positioning between these five alloys, not absolute datasheet values — the exact figures depend on build orientation, heat treatment and the specific powder lot, all of which we document per order.
| Alloy | Best for | Strength | Max service heat | Corrosion resistance | Relative weight | Relative cost |
|---|---|---|---|---|---|---|
| AlSi10Mg | Light structural, heatsinks, complex geometry | Moderate | Low | Moderate | Lowest (≈1/3 of steel) | Lowest |
| Ti-6Al-4V | Aerospace, motorsport, implants | Very high (per unit mass) | Moderate–high | Excellent | Low | Highest |
| 316L SS | Marine, chemical, medical, food-grade | Moderate | Moderate | Excellent | High | Low–moderate |
| 17-4 PH SS | Hard, strong, defence and tooling | High (heat-treatable) | Moderate | Good | High | Moderate |
| Inconel 625/718 | Turbines, combustion, exhaust | High (retained hot) | Very high | Excellent (hot) | Highest | High |
Walking the five branches
Each branch below explains the alloy the tree points to, when to override it, and the linked reading that goes deeper. Work them in order and commit at the first hard constraint.
Branch 1 — Heat: Inconel 625 and 718
If the part sees combustion gas, exhaust temperatures, or sustained high heat, the tree stops here. Nickel-based superalloys retain their strength where stainless and titanium soften, which is why Inconel dominates turbine, combustor and heat-exchanger work. Choose 625 for the best hot corrosion resistance and weldability; choose 718 when you need higher room-and-elevated-temperature strength, since it is precipitation-hardenable. The trade is cost and machinability — Inconel is the most expensive powder we run and the slowest to post-machine, so reserve it for parts that genuinely need it. A common mistake is reaching for Inconel because a datasheet mentions "high temperature" when the part actually sees only intermittent warmth well within a stainless steel's envelope; that over-specification can double the part cost for no engineering gain, which is why the heat branch asks about a specific threshold rather than a vague thermal worry. We walk through a real example in our Inconel 625 combustion nozzle part-consolidation case study, where DMLS collapsed a multi-piece assembly into one printed component and removed several potential leak paths in the process.
Branch 2 — Corrosion: 316L stainless steel
Not hot, but wet, salty, acidic, or destined for a body or a kitchen? 316L is the workhorse. Its molybdenum content gives strong resistance to chlorides and pitting, and its low carbon suppresses the carbide precipitation that would otherwise sensitise welds. That combination makes it the default for marine hardware, chemical-process parts, food-contact components and many medical devices. Strength is only moderate, so if you also need hardness look at 17-4 PH instead. 316L frequently replaces investment castings, as we detail in our 316L pump impeller casting-replacement case study, where printing removed tooling lead time entirely.
Branch 3 — Weight: Ti-6Al-4V (and AlSi10Mg)
Two alloys answer "weight matters", and the split is about how much strength you need per gram. Ti-6Al-4V has an outstanding strength-to-weight ratio, excellent corrosion resistance and biocompatibility, which is why it is the standard for aerospace structures, motorsport and orthopaedic implants — the additive grade is covered by standards such as ASTM F2924 and, for the extra-low-interstitial medical variant, ASTM F3001. It is the most expensive of the two by a wide margin. AlSi10Mg gives you roughly a third of steel's density at the lowest cost in the range, ideal where the load case is moderate and geometry is complex — brackets, housings, heatsinks. Our AlSi10Mg antenna-bracket case study shows topology optimisation on aluminium, and the weight-reduction design guide covers the lattice and shelling moves that make either alloy lighter still.
Branch 4 — Strength and hardness at low cost: 17-4 PH
When you need high strength and hardness, some corrosion resistance, and you are cost-sensitive, 17-4 PH precipitation-hardening stainless is the pragmatic pick. It heat-treats to a range of tempers (H900 for maximum hardness through to overaged conditions for toughness), so one alloy covers a spread of duty. It is a staple for defence components, tool holders and structural brackets where Ti-6Al-4V would be overkill on budget and Inconel unnecessary on heat. It is denser than titanium and aluminium, so it is the wrong answer the moment weight becomes the constraint — which is exactly why weight sits above strength in the tree. In practice, 17-4 PH is where a lot of over-titanium projects land once the numbers are checked: if the part is stiff enough and mass is not on the drawing as a requirement, the precipitation-hardening stainless delivers comparable static strength at a fraction of the powder cost. Specify the target temper up front, because heat treatment is not a free retrofit — the H900 condition that gives you maximum hardness also gives you the lowest toughness, and picking that by default has cracked more than one bracket that would have been fine in an overaged temper.
Branch 5 — Cost and complexity: AlSi10Mg
If nothing above forced your hand — no extreme heat, no aggressive corrosion, no strict weight or hardness target — you are optimising for cost and manufacturability, and AlSi10Mg is usually the answer. It prints quickly, supports fine features, machines and anodises well, and is the least expensive powder we run. It is the right default for prototypes, jigs, fixtures and short-run structural parts that simply need to be metal, complex, and affordable.
What the tree can't decide for you
Two design factors sit underneath every branch. First, orientation and support strategy change residual stress and achievable geometry more than most buyers expect — we cover this in our DMLS thermal and residual-stress design guide. Second, wall thickness, overhang angles and self-supporting features differ by alloy; the metal AM design-rules guide is the companion read before you finalise a model. If part count is high or geometry is simple, it is also worth checking whether hybrid injection tooling beats printing on unit cost at volume — the alloy that wins for one-off DMLS is not always the right route to a thousand parts.
Underpinning all of it is process control. Our DMLS work runs under AS9100 Rev D, ISO 9001:2015 and ISO 13485:2016, all governed by the AM terminology and process framework of ISO/ASTM 52900, with material certifications and lot traceability supplied on every order. That is what lets us stand behind the alloy recommendation, not just the print.
Still unsure? Send us the part
A decision tree gets you to the right shortlist in minutes; a real load case, environment and budget get you to the right alloy. Upload your CAD file for a 24-hour quote and we will confirm the alloy, tolerance and finish against your actual application before you commit.