Heat Treatment Providers
Heat treatment encompasses stress relief, solution annealing, ageing, and hardening processes that optimise the microstructure and mechanical properties of metal AM parts. Proper heat treatment is critical for achieving target tensile strength, ductility, and fatigue life. Find heat treatment providers on ForgedLink verified for furnace calibration, atmosphere control, and compliance with material-specific treatment specifications.
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Why heat treatment is essential for metal AM parts
Metal AM builds parts under steep thermal gradients — laser or electron beam energy melts powder against a relatively cool substrate or previous layer, and the molten pool solidifies in milliseconds. The resulting microstructure is far from equilibrium: residual stresses sit locked into the part, grain structure is columnar and anisotropic, and precipitation-hardening alloys (17-4 PH, IN718, maraging steel, Ti-6Al-4V STA) have not yet developed the secondary phases that give them their target strength. Without post-print heat treatment, an AM part has the wrong mechanical properties for almost any structural application.
A typical AM heat-treatment chain runs three or four stages: stress relief on the build plate (to allow safe wire-EDM separation without warpage), solution annealing (to homogenise microstructure and dissolve unwanted phases), optional HIP (to close porosity), and ageing or quench-and-temper (to develop target strength and hardness). Each stage runs to a material-specific recipe — temperature ramps, hold times, atmosphere, and cooling rates are governed by AMS, ASTM, and customer specifications. AM-specific protocols often differ from the wrought equivalents because the as-built microstructure is finer, the residual stress is higher, and the alloy chemistry can drift slightly between powder lots.
Common heat-treatment cycles for AM parts
Stress relief on the build plate
Typically 600–900°C for 1–4 hours under inert gas or vacuum, performed before wire-EDM separation. Reduces residual stresses by 60–90% and prevents distortion or cracking during separation. Mandatory for nearly every metal AM part.
Solution annealing + double age (Inconel 718)
Solution at 980°C for 1 hour under argon, water quench, then double age (720°C / 8 hr → furnace cool to 620°C / 8 hr). Standard AMS 5662 cycle to develop γ' and γ'' precipitates that give IN718 its high-temperature strength.
STA / mill anneal on Ti-6Al-4V
Solution at 940°C for 1 hour, water quench, age at 540°C for 4 hours. Develops target tensile strength and ductility. Mill anneal alone (730°C / 2 hr) is the standard for medical implants under ASTM F3001.
H900 / H1025 ageing (17-4 PH stainless)
Solution at 1,040°C, water quench, then age at 480°C (H900) or 552°C (H1025). H900 reaches ~40 HRC with high strength but lower toughness; H1025 is the balance grade for most AM applications.
T6 cycle (AlSi10Mg and aluminium)
Solution at 540°C for 1–6 hours, water quench, age at 160–180°C for 4–10 hours. Develops Mg₂Si precipitates and lifts AlSi10Mg from ~250 MPa as-built to ~400 MPa after T6.
Maraging steel age hardening
Single-step age at 490°C for 6 hours under argon takes maraging M300 / 1.2709 from ~30 HRC as-built to 50–55 HRC age-hardened — without distortion or dimensional change beyond ~0.1%, which is why maraging dominates conformal-cooled mould inserts.
Heat treatment by AM alloy family
Ti-6Al-4V (Grade 5 / Grade 23)
Stress relief at 600–800°C is universal. Mill anneal (730°C / 2 hr) is standard for medical implants under F3001 / F2924. STA cycle (940°C solution + 540°C age) for higher-strength aerospace structurals.
Inconel 718 / 625
IN718: solution + double age (AMS 5662 / 5663). IN625: solution annealing only at 1,150°C — IN625 is solution-strengthened, not precipitation-hardened. Both require argon or vacuum atmospheres.
Stainless 17-4 PH / 15-5 PH
Solution + age. H900 for highest strength (~40 HRC, ~1,400 MPa UTS), H1025 for balance, H1150 for toughness. Vacuum or hydrogen-bearing atmospheres preferred to avoid surface oxidation.
Stainless 316L
Solution annealing at 1,050–1,080°C followed by water quench restores corrosion resistance and homogenises the as-built columnar grain structure. Mostly run for marine, food-contact, and chemical applications where pitting resistance matters.
AlSi10Mg / Aluminium Alloys
T5 (artificial age only) or T6 (solution + age) cycles. AM AlSi10Mg responds differently to heat treatment than cast — the fine cellular structure can coarsen aggressively, so AM-tuned T6 cycles are usually shorter and lower-temperature than the cast equivalent.
Maraging Steel (M300 / 1.2709)
Single-step age at 490°C for 6 hours. Minimal dimensional change, isotropic property development. Standard for tooling and conformal-cooled mould inserts.
CoCrMo (Cobalt-Chrome)
Solution annealing at 1,150–1,200°C for medical implants under F3091. Often performed in the same furnace cycle as HIP for dental and orthopaedic work.
Tool Steels (H13, M2, D2)
Quench-and-temper cycles for hardness development. AM tool steels are typically tempered at slightly lower temperatures than wrought equivalents to preserve the fine as-built grain structure.
How to specify heat-treatment for AM parts
Always specify stress relief as the first step for any metal AM part — it is non-negotiable for safe build-plate separation. The cycle is alloy-specific but inexpensive (£50–£150 per part typical) and prevents most distortion and cracking issues in subsequent processing.
Reference the controlling spec, not the cycle in customer-facing documentation. "Heat treat per AMS 5662 (IN718 solution + double age)" is more specific than describing temperatures and times — it ties the part to a published, NADCAP-auditable procedure that any AS9100 heat-treatment provider can execute consistently.
Combine HIP and solution annealing where possible. Many providers offer combined HIP-solution cycles that run densification and homogenisation in a single furnace charge — saving 2–4 days of handling and one quench-cool cycle. Specify combined cycles in the part PO if your provider supports them.
Verify AMS 2750 furnace class. Aerospace and medical heat-treatment work requires AMS 2750 Class 2 furnaces (±6°C uniformity) at minimum, often Class 1 (±3°C) for critical alloys. Ask the provider for their TUS (Temperature Uniformity Survey) records and SAT (System Accuracy Test) certification — both are NADCAP audit requirements.
Lead time and cost expectations for AM heat treatment
Standard heat-treatment cycles deliver in 1–3 weeks from receipt of parts, with most providers running specific alloy cycles 1–3 times per week. Combined HIP-solution cycles take similar wall-clock time. Rush single-charge runs are available at premium for urgent aerospace MRO work.
Indicative pricing is per kilogram of charge weight, with surcharges for atmosphere class. Standard rates run £8–£35 / €10–€42 per kg for common cycles — meaning a 1 kg titanium aerospace bracket typically adds £15–£60 / €18–€70 to its total cost across stress relief + solution + age. Vacuum atmospheres add ~30%; AMS 2750 Class 1 furnaces add another ~20–40% over Class 2.
Related processes & materials
Frequently asked questions
Why do AM parts need different heat treatment than wrought equivalents?
AM parts come out of the printer with a finer cellular grain structure, higher residual stresses, and potentially different precipitate distributions than the wrought equivalents the standard heat-treatment specs were originally written for. Many AM-specific protocols (Ti-6Al-4V mill anneal, AlSi10Mg T6 with shorter solution times) deviate from cast / wrought cycles to preserve the fine as-built microstructure that contributes to AM's mechanical advantages.
What is AMS 2750 and why does it matter?
AMS 2750 (currently revision F) is the SAE aerospace pyrometry specification that governs furnace temperature uniformity, instrumentation calibration, and Temperature Uniformity Surveys (TUS). NADCAP-accredited heat-treatment providers must hold AMS 2750-compliant furnaces with documented TUS records. For any aerospace or medical AM work, AMS 2750 compliance is a baseline requirement — not a nice-to-have.
Can I skip stress relief for non-critical parts?
Sometimes — for very small parts, low-stress geometries, or short-lived prototypes that are coming straight off the build plate by careful EDM. But stress relief is genuinely cheap (£50–£150 per part typical) and prevents the most common AM failure mode (build-plate separation cracking or post-EDM warpage). For nearly all production work, skip it only with explicit provider agreement.
Should heat treatment happen before or after HIP?
Typical order is: stress relief → wire-EDM separation → HIP → solution annealing → ageing. Many providers combine HIP and solution annealing in a single furnace cycle (the gas pressure is released after the HIP hold and the cycle continues into solution and controlled cooling). Combined cycles save 2–4 days and one quench step. Final ageing is almost always run separately because age temperatures are below typical HIP operating ranges.
What atmosphere should AM parts be heat-treated in?
Vacuum (10⁻⁴ to 10⁻⁶ mbar) is preferred for most reactive alloys — Ti, IN718, IN625, 17-4 PH, maraging — because it eliminates oxidation and decarburisation. Argon backfill is used for cooling cycles where vacuum cooling would be too slow. Atmospheric heat treatment in air is acceptable for simple stress relief on stainless and low-alloy steels, but not for any aerospace or medical-grade work.
How do I verify the heat treatment was done correctly?
Three layers of verification: (1) <strong>process records</strong> — the heat-treatment provider should supply a chart recording showing actual temperature profile vs target, signed by the operator and the quality manager; (2) <strong>hardness testing</strong> on a sample part or coupon, verifying the alloy reached its target hardness band; (3) <strong>tensile testing</strong> of an as-built witness coupon for first-article qualification, demonstrating UTS, yield, and elongation meet the specification.