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Picking a metal for CNC machining is straightforward: choose the alloy, machine to print, done. With metal 3D printing materials, especially those used in laser powder bed fusion (LPBF), material selection becomes part of the manufacturing process itself. The alloy dictates laser parameters, support strategy, post-processing sequence, and ultimately whether the part succeeds.
This guide covers eight SLM-compatible alloys, a five-step selection framework, and the post-processing that turns an as-printed part into a finished component.
The 5-Step Material Selection Framework
Before comparing alloys, work through these five steps. They help prevent a common metal AM mistake: selecting an alloy for its familiar datasheet properties without checking how it behaves in the printing process.
Step 1: Define the dominant requirement. Pick one or two non-negotiable properties. Corrosion resistance? High-temperature strength? Weight reduction? Electrical conductivity? A part rarely needs everything simultaneously. If the dominant requirement is “must survive 500°C exhaust gas,” Inconel 718 is on the shortlist and aluminum is off it.
Step 2: Map to a material family. Each material family has a distinct profile that helps eliminate options quickly. Map the dominant requirement from Step 1 to the right family before picking a specific grade:
- Stainless steels (316L, 17-4PH): corrosion resistance as baseline. Choose between high ductility (316L) and high strength after aging (17-4PH).
- Aluminum alloys (AlSi10Mg, 6061): weight reduction at lower cost than titanium. Cast-alloy properties (AlSi10Mg) differ from wrought (6061); don’t assume interchangeability.
- Titanium (Ti-6Al-4V): strength-to-weight ratio unmatched, biocompatible. Higher material cost; justify by weight savings or application requirements.
- Nickel superalloys (Inconel 718): maintains strength above 650°C. Expensive powder plus mandatory solution + aging cycle. Use only when temperature or corrosion demands rule out stainless.
- Tool steel (1.2709): extreme hardness after aging, approaching 2,000 MPa UTS. Niche application: conformal-cooled injection molds and high-wear tooling.
- Copper alloys (CuCrZr): thermal and electrical conductivity far above any other SLM alloy. Difficult to print; only worth the effort when conductivity is the dominant requirement.
Narrow to one family, then use the comparison table below to pick the specific grade.
Step 3: Check process compatibility. Not every alloy prints equally well by SLM. 316L and AlSi10Mg are mature, high-success-rate options. 6061 aluminum and copper alloys demand specialized parameters and are not plug-and-play. If your team is new to metal AM, start with a proven material and expand to difficult alloys after the process is stable.
Step 4: Plan post-processing. As-printed properties are rarely the final properties. 17-4PH needs H900 aging to reach its rated strength. Fatigue-critical Ti-6Al-4V parts often require HIP. Most parts need CNC post-machining on critical features.
Step 5: Validate with a test build. Metal AM batch-to-batch variation exceeds CNC. Run a single test piece, request a CMM inspection report and material test certificate (MTR), and verify the data before committing to production quantities. This validation approach is consistent with metal AM part qualification practice.
Eight Metal 3D Printing Materials Compared at a Glance
The table below covers eight alloys commonly requested for SLM metal 3D printing.
| Material | Dominant Strength | Best For | Watch Out For |
| 316L Stainless | Corrosion resistance, high ductility | Fluid systems, marine hardware, chemical processing, medical devices | Lower tensile strength than 17-4PH |
| 17-4PH Stainless | High strength + hardness after H900 aging | Aerospace brackets, tooling, oil & gas components | Lower ductility than 316L; requires solution treatment + aging |
| AlSi10Mg | Lightweight, good thermal conductivity | Housings, brackets, heat exchangers, non-structural prototypes | Cast-alloy properties; not a direct substitute for 6061-T6 wrought |
| 6061 Aluminum | Familiar to CNC engineers, good post-print machinability | Transition parts from CNC to AM, lightweight structural components | Difficult to SLM print; laser reflection and hot-cracking risk. See callout below. |
| Ti-6Al-4V (Grade 5) | Best strength-to-weight ratio, biocompatible | Aerospace structural, medical implants, lightweight performance parts | Higher powder cost; HIP recommended for fatigue-critical applications |
| Inconel 718 | Maintains strength above 650°C | Turbine components, exhaust systems, high-temperature tooling | Expensive powder; mandatory solution + aging cycle |
| Maraging Steel (1.2709) | Ultra-high strength after aging (~2,000 MPa UTS) | Injection mold inserts with conformal cooling, high-wear tooling | Brittle if over-aged; high material cost |
| CuCrZr Copper | Highest thermal + electrical conductivity | Heat sinks, induction coils, welding electrodes | Very high laser reflectance; requires optimized parameters |
Why 6061 Is Difficult and How to Print It
6061 aluminum is the most familiar alloy to CNC machinists, and one of the most challenging for SLM. Its high laser reflectivity and wide solidification range produce a strong hot-cracking tendency. Recommended approach:
- Optimized laser parameters: higher energy input, controlled power, scan speed, and hatch spacing to ensure full melting.
- Substrate preheating: reduced thermal gradient minimizes residual stress and crack risk.
- Island scanning strategy: partitioned layers scanned in rotating patterns for improved heat distribution.
- Post-build HIP + heat treatment: closes residual porosity and recovers mechanical properties.
If your design can accept AlSi10Mg, use it. If 6061 is non-negotiable, budget for additional process control and post-processing.
Post-Processing: From As-Printed to Ready to Use
An as-printed metal part is an intermediate step. Final mechanical properties and dimensional accuracy depend on what happens after the build plate cools.
HIP (Hot Isostatic Pressing). High-pressure argon at elevated temperature collapses internal porosity. Essential for fatigue-critical and pressure-containing parts. In one FastPreci project, a 316L nozzle bend underwent HIP and solution treatment to reduce internal porosity and stabilize its material condition. Slurry honing then finished a complex internal channel, inaccessible to cutting tools, to Ra 3.2.
Heat treatment. Stress relief stabilizes dimensions for any metal AM part. Solution treatment plus aging unlocks full strength for precipitation-hardening grades: 17-4PH reaches approximately 1,300 MPa UTS after H900, roughly 30% higher than the as-printed condition. Inconel 718 requires solution + aging per AMS 5663 to deliver rated high-temperature performance.
CNC post-machining. SLM dimensional tolerance is typically ±0.1 to 0.2 mm. CNC machining on critical features brings this to ±0.005 mm. A hybrid workflow delivers the best of both: print the complex geometry, machine only the surfaces that need precision.
Surface finishing. Bead blasting as standard. Polishing, nickel plating, and passivation for stainless steels are available. Specify the function before choosing the finish: lower roughness may be needed on sealing faces, mating surfaces, or fluid passages; cosmetic surfaces may only need uniform bead blasting; corrosion-exposed aluminum may need plating or anodizing. Features that require a controlled Ra value or a flat sealing face should be CNC machined before finishing. For a full list of surface finishing options, see our capabilities page.
Three Selection Mistakes That Cost Time and Money
These patterns show up repeatedly in metal AM projects. All three are avoidable if addressed during material selection.
Material-process mismatch. Selecting a material based on its wrought properties without checking SLM printability. 6061 aluminum is the textbook example: standard in every CNC shop, notoriously difficult in laser powder bed fusion. Before locking in a material, verify it is mature and well-characterized on your target AM process.
Grade over-spec. Specifying Inconel 718 when 316L meets the corrosion and temperature requirements. The cost difference extends beyond powder price. Inconel demands tighter process control, more aggressive support structures, and mandatory solution + aging. Total part cost can land three to five times higher than an equivalent 316L part.
Ignoring post-processing in the initial budget. The print is one line item. HIP, heat treatment, CNC finishing, and surface treatment are separate operations with their own lead times and costs. For nickel and titanium alloys, post-processing can exceed the printing cost.
Metal 3D Printing Materials FAQ
What is the strongest 3D-printed metal?
Maraging steel (1.2709) after aging reaches approximately 2,000 MPa UTS, the highest among common SLM alloys. For high-temperature strength, Inconel 718 holds properties above 650°C. For general high-strength applications, 17-4PH H900 offers the best balance of strength and cost.
Can aluminum 6061 be 3D printed?
Yes, with optimized laser parameters, substrate preheating, and post-build HIP. AlSi10Mg is the standard SLM aluminum and should be the first choice unless 6061 is specifically required by the application. See the callout in Section 2 for process details.
Is HIP necessary for every metal AM part?
No. HIP is needed for fatigue-critical structural parts and pressure-containing components where internal porosity is unacceptable. For brackets, housings, and non-structural parts, stress relief alone is often sufficient. Discuss the application requirements with your manufacturer.
What tolerances can metal 3D printing achieve?
SLM typically delivers ±0.1 to 0.2 mm on general dimensions, subject to part size, geometry, orientation, and post-processing. Design critical holes, threads, datum surfaces, and sealing faces with machining allowance, then CNC machine them to the required tolerance.
When is metal 3D printing more cost-effective than CNC machining?
Metal AM is most competitive when the part has internal channels, lattice structures, consolidated assemblies, or geometry that requires multiple CNC setups. For simple prismatic parts or higher-volume production with no AM-specific geometry, CNC machining is usually the lower-cost route. Compare the finished-part cost, including post-processing, rather than the print cost alone.
Start With the Right Material
Choosing an alloy for metal 3D printing starts from the part’s actual service conditions. The right material prints reliably, matches the application environment, and leaves enough budget margin for the post-processing that turns an as-printed blank into a finished component.
Upload your CAD file for a free DFM review with material recommendation. We’ll tell you which alloy fits, what post-processing is needed, and what the total timeline looks like.
