Hot Isostatic Pressing (HIP) Providers
Hot Isostatic Pressing applies high temperature and uniform gas pressure to eliminate internal porosity and improve the mechanical properties of metal AM parts. HIP is a mandatory post-processing step for aerospace and medical components printed in titanium, Inconel, and cobalt chrome. Find HIP providers on ForgedLink verified for pressure vessel certification, temperature uniformity, and compliance with AMS and ASTM specifications.
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How Hot Isostatic Pressing densifies AM parts
HIP combines elevated temperature (typically 900–1,250°C, alloy-dependent) with uniform isostatic gas pressure (100–207 MPa, usually argon) inside a sealed pressure vessel. Under these conditions, internal voids — gas porosity from atomised powder, lack-of-fusion defects from imperfect melt overlap — close by plastic deformation and diffusion bonding. The walls of each pore press together and metallurgically bond, taking part density above 99.95% of theoretical and recovering fatigue properties to wrought-equivalent levels.
For laser and electron beam powder bed metals — LPBF, DMLS, SLM, EBM — HIP is the difference between an "as-built" part and a flight-qualified or implant-qualified part. Aerospace specs (AMS 2774, AMS 2774E for nickel and cobalt alloys), titanium specs (ASTM F2924 for Ti-6Al-4V LPBF, F3001 for Ti-6Al-4V ELI), and medical implant specs (ASTM F3091 for CoCrMo, F3056 for IN718) all either require or strongly recommend HIP as a step in the qualification chain. For non-fatigue-critical parts (housings, brackets with ample safety factor, manifolds), HIP is often optional, and stress relief alone is enough.
When HIP is required for AM parts
Aerospace structural and rotating components
Engine brackets, gearbox housings, turbine blades and vanes, fuel-system components — anywhere the design relies on fatigue-life predictions, HIP is typically mandated by the customer flow-down from AS9100D quality systems.
Medical implants and orthopaedic hardware
Ti-6Al-4V ELI hip stems, acetabular cups, spinal cages, dental abutments, and CoCrMo knee components — HIP is mandated by ASTM F3001 / F3091 and equivalent ISO standards for any load-bearing implant.
Rocket and turbine combustion hardware
CuCrZr combustion chambers, IN718 / IN625 turbine components, regeneratively cooled nozzles — HIP closes the gas porosity that would otherwise initiate fatigue cracks under thermal cycling.
Investment castings (traditional + AM-pattern)
HIP has been used to densify investment castings for over forty years — the same furnaces serve AM parts and traditional cast parts under the same AMS 2774 / NADCAP framework.
High-pressure fluid system components
Hydraulic manifolds, valve bodies, and pressure-containing housings — HIP is needed to qualify the part for the pressure rating without internal porosity creating leak paths or burst risk.
EBM titanium parts targeting wrought-equivalent fatigue
EBM's hot vacuum chamber gives lower residual stress than LPBF, but does not close gas porosity — HIP at 920°C / 1,000 bar / 2 hours is the standard cycle for Ti-6Al-4V EBM implants.
AM alloys commonly densified by HIP
Ti-6Al-4V (Grade 5 / Grade 23 ELI)
Standard cycle: 920°C / 100 MPa / 2 hours under argon. Closes residual gas porosity, recovers fatigue properties to wrought-equivalent. ASTM F2924 / F3001 mandate HIP for medical-grade parts.
Inconel 718 / 625
Typical cycle: 1,160°C / 100 MPa / 4 hours, followed by solution + double-age heat treat. Mandatory under AMS 5662 / 5663 for IN718 aerospace flow-downs.
CoCrMo (Cobalt-Chrome)
Cycle: 1,200°C / 100 MPa / 4 hours under argon. Mandated by ASTM F3091 for orthopaedic implants. Often combined with solution annealing in the same cycle.
AlSi10Mg / Aluminium Alloys
Cycle: 500–520°C / 100 MPa / 2 hours, followed by solution + age (T6). HIP is less commonly applied to LPBF aluminium because the as-built density is already very high; specified for fatigue-critical aerospace parts.
Stainless 316L / 17-4 PH
Cycle: 1,150°C / 100 MPa / 4 hours. Less commonly required on stainless than on Ti / Ni — most stainless AM applications can run without HIP, with stress relief and solution annealing only.
Tool Steels (H13, M300 maraging)
HIP at 1,150–1,180°C closes porosity in conformal-cooled mould inserts before age-hardening. Improves thermal-fatigue life of inserts subjected to cyclic mould-cooling stresses.
When HIP is mandatory, optional, or unnecessary
Mandatory: any aerospace part flowing down from AS9100D where fatigue or burst pressure is design-critical; any medical implant under ASTM F-spec or ISO 13485 traceability; any rotating or pressure-containing rocket / turbine component. If the customer spec calls out AMS 2774 or an equivalent ASTM F-series HIP requirement, it is mandatory.
Optional but recommended: motorsport hardware, high-end industrial tooling, fatigue-loaded brackets where the cost of HIP is small relative to part value. Specifying HIP as optional gives the design team a path to certify the part later without re-qualifying the print process.
Unnecessary: non-load-bearing housings, prototype parts, jigs and fixtures, and parts with substantial design safety factors over their service stress. As-built LPBF density is already above 99.5% — for many industrial applications the residual porosity is acceptable, and HIP's £200–£800 per part adds cost without functional benefit.
Lead time and cost expectations for HIP
HIP cycles are batch processes — providers typically run the furnace once per week per alloy family, loading multiple customers' parts into a single cycle. Standard turnaround is 1–3 weeks from receipt of parts. Rush single-cycle dedicated runs can be arranged at substantial premium for time-critical aerospace MRO work.
Indicative pricing is per kilogram of charge weight rather than per part, so cost scales with how densely parts can be packed in the furnace. Standard rates run £15–£60 / €18–€70 per kg for common cycles (Ti-6Al-4V, IN718, 316L) — meaning a 1 kg titanium aerospace bracket typically adds £30–£80 / €35–€95 to its total cost. Specialty cycles (high-pressure 207 MPa, very high temperature, controlled cooling for STA) run 2–4× standard rates.
Related processes & materials
Frequently asked questions
What does HIP actually do to an AM part?
It closes internal porosity. Under high temperature and uniform gas pressure, the walls of each internal void plastically deform inward and metallurgically bond. The result is a part at >99.95% of theoretical density, with fatigue properties brought up to wrought-equivalent levels. HIP does not change the part's external dimensions appreciably, and does not affect surface roughness or external geometry.
Do I always need HIP after LPBF or EBM?
No — only if the application requires it. Aerospace fatigue-critical parts and medical implants almost always require HIP, mandated by AMS 2774 or ASTM F-spec flow-downs. For non-fatigue-critical industrial parts (housings, brackets with ample safety factor, low-stress manifolds) HIP is usually optional, and stress relief alone is enough. Specify HIP if the customer flow-down or service environment demands it; otherwise it adds cost without benefit.
Can HIP fix bad printing?
Partly. HIP can close gas porosity and small lack-of-fusion defects, but it cannot fix gross defects — large unfused regions, surface-connected porosity (gas can't pressurise an open path), cracks, or geometric distortion. HIP is a finishing step, not a rescue mechanism for poorly qualified prints. Providers should still produce parts at 99.5%+ as-built density before HIP.
What's the difference between HIP and stress relief?
Stress relief is a relatively low-temperature heat-treatment step (typically 600–900°C in vacuum or inert gas, no pressure) that reduces residual stresses left over from the print process. HIP is a much higher-temperature, high-pressure step that additionally closes internal porosity. Many qualified AM workflows combine them: stress relief on the build plate first to allow safe wire-EDM separation, then HIP for full densification. Some providers run combined HIP-quench cycles that perform both steps in one furnace charge.
How do I verify HIP worked?
Standard verification is <strong>CT scanning</strong> of first-article parts. Industrial CT (typically 225–450 kV) can detect internal voids down to ~0.1 mm in titanium and steel. Density measurement by Archimedes method gives a bulk-density check but cannot localise defects. For aerospace and medical work, CT scanning of the first article (and sometimes every part) is now standard practice, often delivered by the same NDT provider that handles dye penetrant and ultrasonic inspection.
Is HIP an in-house service for AM bureaux, or always outsourced?
A small number of large AM bureaux operate in-house HIP units (notably the largest Ti aerospace and medical-implant houses), but the majority outsource to dedicated HIP providers — Bodycote, Quintus / Pressure Technology Inc., Hauck Heat Treatment, and regional specialists. Outsourcing is standard practice and adds 1–3 weeks of lead time but generally lower per-part cost than in-house operation.