Stress relief removes residual stress from the build; HIP (hot isostatic pressing) closes internal porosity under heat and ~100 MPa of argon pressure. They are not alternatives solving the same problem — most parts need stress relief, only fatigue-critical ones justify HIP, and specifying HIP where plain stress relief suffices adds cost and lead time for no gain.[1] Here is how we decide which treatment your part actually needs.
What each treatment does
| Stress relief | HIP | |
|---|---|---|
| Mechanism | Furnace cycle below the solution temperature; locked-in thermal stresses relax | ~1,000–1,200 °C + ~100 MPa isostatic argon; internal voids collapse and diffusion-bond shut[2] |
| Primary benefit | Dimensional stability — for machining and service | Fatigue life and ductility; density to near-full |
| When applied | Almost every LPBF part, before supports come off or machining starts | Fatigue-critical, thick-section or safety parts; often combined with the solution cycle |
| Cost & lead | In-house furnace hours — modest | Batch process at a HIP facility; adds meaningful cost and days |
| What it does NOT do | Close porosity | Fix surface-connected defects or replace machining |
The decision we apply on every quote
- Static structural parts, brackets, housings: stress relief alone. The porosity levels a good LPBF process produces (~99.5%+ dense) do not govern static strength.
- Fatigue-loaded or safety parts (rotating, pressure, aerospace primary structure): HIP. Gas porosity is the fatigue-life killer, and HIP is the only post-build route that closes internal voids.[2]
- Precipitation-hardened alloys (17-4PH, IN718): the aging/solution schedule can often run through the HIP cycle in one combined recipe instead of two furnace trips.[3]
- Parts that will be machined heavily: stress relief first, always — otherwise the part moves after machining and the tolerances you paid for walk away.
Where HIP does not help
Three honest limits. HIP closes internal porosity; lack-of-fusion defects that reach a surface, or cracks, are not repaired by pressure. It adds a queue at an external facility, extending lead time. And on well-tuned static parts it buys nothing measurable — which is why we recommend it only when the duty case demands it, and document the cycle record in your data pack when it runs. The treatment route we recommend appears line by line on the quote — see the full sequence on the process page, and how the stages price out in our post-processing cost breakdown.
FAQ
Do all 3D printed metal parts need HIP?
No. HIP is for fatigue-critical, thick-section or safety parts. Most static structural work is properly served by stress relief plus controlled print parameters.[1]
What is the difference between HIP and stress relief?
Stress relief relaxes residual stress in a furnace so the part holds its dimensions; HIP applies ~100 MPa isostatic argon pressure at high temperature to close internal porosity for fatigue life.[2]
Does HIP improve tensile strength?
Modestly — its real payoff is ductility and fatigue life, because internal gas porosity stops acting as crack starters. Static UTS often moves only a few percent.
Can HIP fix any printing defect?
No. It closes internal voids; surface-connected lack-of-fusion and cracks are out of scope, which is why process control matters more than any post-treatment.
Send the part and its duty case — we’ll specify the right treatment →
References
- 3Dnatives. “HIP vs Annealing: Which Heat Treatment Should You Choose?” 2025. Link (accessed August 16, 2026).
- Journal of Materials Research and Technology. “Hot isostatic pressing for powder-based additive manufacturing of metals: state-of-the-art review.” 2025. Link (accessed August 16, 2026).
- Paulo Products. “Powder Bed Fusion HIP & Heat Treatment: Inconel 718.” paulo.com. Link (accessed August 16, 2026).
- Baker Hughes. “The case for CT inspection in additive manufacturing” (white paper). Link (accessed August 16, 2026).