Hot Isostatic Press (HIP)

HIP & densification · Densification

Hot isostatic pressing applies high-temperature inert gas pressure uniformly to cast, sintered, and metal powder-bed-fusion parts.

3D printing CastingHigh cost $$$$Gas quench (N₂ / He)

Quote a part with HIP Compare hip & densification

Temperature510–1,220 °C950–2,228 °F

HardnessNo target

Case depthThrough section

Cycle time8–24 hVessel heat-up, pressurization, hold, depressurization, and cooling dominate turnaround.

HIP at a glance

Four scores, each 0–100 against every heat treatment in this catalog. Hardness is derived from the HRC target (20 HRC = 0, 70 HRC = 100) — treatments without a hardness target (anneals, stress relief, HIP, cryo) are not rated. Toughness, dimensional stability and cost are FabDigit's engineering assessment.

Hardness achievedNot rated—

Toughness retainedVery good75 / 100

Dimensional stabilityGood65 / 100

Relative costHigh95 / 100

What is HIP?

Hot isostatic pressing applies high-temperature inert gas pressure uniformly to cast, sintered, and metal powder-bed-fusion parts. It closes internal porosity and improves fatigue consistency, but it does not repair open-to-surface defects or replace alloy-specific solution and aging treatments.

How it works

Parts are heated below the alloy solidus in a pressure vessel while argon applies at least 100 MPa in standard AM cycles. Elevated temperature lowers flow stress; gas pressure drives creep and diffusion so isolated pores and internal lack-of-fusion defects shrink or bond. Pressure is isostatic, so sound external geometry changes little, although unsupported thin features can creep. Defects connected to the surface remain gas-filled and generally do not close. The HIP thermal exposure also changes grain size, phases, and residual stress, so titanium, nickel, stainless, cobalt-chrome, and aluminum each require a specific cycle and often a subsequent solution-and-age treatment.

Why specify it

ASTM F3301 AM cycles use at least 100 MPa inert-gas pressure
Can raise qualified PBF density toward 100%
Closes internal pores that reduce fatigue life
Applies pressure uniformly to complex cast and AM geometry
Covers alloy-specific temperatures from about 510 °C for AlSi10Mg to 1220 °C for Co-Cr-Mo

Where it falls short

Does not close defects connected to the external surface
Cannot remove inclusions or restore material missing from lack-of-build
High temperature can coarsen grains and alter precipitation state
Thin unsupported features can creep under pressure
Requires expensive pressure-vessel capacity and material-specific post-HIP heat treatment

The HIP cycle

Typical furnace parameters from the governing specifications and shop practice; the heat treater sets the exact recipe from the alloy, section size and required result.

Temperature	510–1,220 °C (950–2,228 °F) — Material-specific ASTM F3301 envelope: AlSi10Mg 510–520 °C; Ti alloys 895–955 °C; Ni, 316L, and Co-Cr alloys use higher ranges.
Soak	2–5 h — ASTM F3301 cycles are commonly 180 ± 60 min or 240 ± 60 min.
Cooling	Gas quench (N₂ / He)
Atmosphere	High-pressure argon
Door to door	8–24 h — Vessel heat-up, pressurization, hold, depressurization, and cooling dominate turnaround.

Stages

1Clean and inspect for surface-connected defects
2Load and evacuate pressure vessel
3Ramp temperature and argon pressure
4Hold at the alloy-specific qualified condition
5Controlled cool under inert pressure
6Apply solution and age treatment when required

What HIP does to the part

Hardness	No hardness target — the treatment is specified by condition, not by HRC.
Section affected	The whole section transforms.
Toughness	Closing internal porosity usually improves ductility and fatigue scatter; final toughness still depends on alloy, grain structure, and post-HIP heat treatment.
Distortion	Medium risk. Isostatic pressure preserves sound bulk geometry, but thin walls, trapped cavities, and near-solidus exposure can creep or collapse.
Surface after treatment	External as-built roughness remains; argon prevents bulk oxidation, but surface-connected pores remain open.
Machining sequence	Machine datums and critical surfaces after HIP when possible; remove sacrificial supports and allow for required post-HIP solution and aging cycles.

Specifications for HIP

The documents a drawing cites to define this treatment. Each links to a page explaining the standard, its classes and the tests it invokes.

Standard	Role	Classes used	Status
ASTM F3055 Standard Specification for Additive Manufacturing Nickel Alloy (UNS N07718) with Powder Bed Fusion	Governing	UNS N07718	Active
ASTM F3301 Standard for Additive Manufacturing—Post Processing Methods—Standard Specification for Thermal Post-Processing Metal Parts Made Via Powder Bed Fusion	Governing	Condition HIP	Active

Test and related methods: AMS 2750 (Pyrometry).

Drawing call-out

HOT ISOSTATIC PRESS PER ASTM F3301 CONDITION HIP FOR Ti-6Al-4V: 895–955 °C, 100 MPa MIN, 3 ± 1 H; COOL UNDER INERT GAS BELOW 425 °C; CERTIFY TIME, TEMPERATURE, AND PRESSURE

Which alloys take HIP?

Verdict per material family, with the grades that behave differently. Each family links to its datasheets in the material library. Typical grades: Ti-6Al-4V, Ti-6Al-4V ELI, Co-28Cr-6Mo, Inconel 718, Inconel 625, 316L, AlSi10Mg, A356.

Material family	Verdict	Notes
Aluminum	Yes	AlSi10Mg and cast aluminum use low-temperature alloy-specific HIP cycles. AlSi10Mg 510–520 °C under ASTM F3301 A356 uses supplier-qualified cycles
Binder Jet	Yes	Sintered binder-jet parts can be further densified if pores are sealed from vessel gas.
Cobalt-Chrome Alloy	Yes	Co-28Cr-6Mo PBF and implant parts have ASTM F3301 HIP requirements. 1185–1220 °C, 100 MPa minimum
DMLS / SLM	Yes	Metal powder-bed-fusion parts are a principal ASTM F3301 application. Ti-6Al-4V, IN718, IN625, 316L, Co-Cr-Mo, AlSi10Mg
Nickel Alloy	Yes	Inconel 718 and 625 are routinely HIP processed before final heat treatment. ASTM F3055 covers PBF UNS N07718
Refractory Metal	Yes	Powder-consolidated refractory metals are established HIP applications. Cycle and capsule design are alloy-specific
Stainless Steel	Yes	316L PBF has an ASTM F3301 HIP window of 1120–1163 °C at 100 MPa minimum. 316L 17-4 PH needs post-HIP aging control
Steel	Yes	Tool, stainless, and alloy-steel cast or powder parts can be densified with alloy-specific cycles. H13 and 316L require different cycles
Titanium	Yes	Ti-6Al-4V and ELI are standard aerospace and medical HIP substrates. ASTM F3301: 895–955 °C, 100 MPa minimum
Tungsten Alloy	Yes	Tungsten heavy-alloy powder compacts can be densified by qualified HIP cycles.
Magnesium Alloy	With care	Possible only with specialized low-temperature cycles and strict safety controls.
Brass	Limited	Possible in powder metallurgy, but zinc vapor pressure and chemistry require specialized control.
Bronze	Limited	Sintered bronze can be densified with a qualified cycle.
Copper Alloy	Limited	Powder and cast copper alloys can be HIP consolidated using proprietary alloy-specific cycles.
Precious Metal	Limited	Powder precious metals can be consolidated, but economics and alloy-specific cycles govern.
Zinc Alloy	No	Low melting and vapor-pressure behavior make conventional metal HIP impractical.

Design rules for HIP

What to decide on the drawing before the part goes to the heat treater.

Seal or remove surface-connected porosity before relying on HIP.Pressurized argon enters an open defect and prevents a closing pressure differential.
Select a material-specific ASTM F3301 cycle.AlSi10Mg uses about 510–520 °C while Co-Cr-Mo uses 1185–1220 °C.
Plan solution and aging treatment after HIP when required.The HIP soak can dissolve or overage strengthening precipitates.
Support thin walls and large flat areas.Hot material can creep even under nominally uniform pressure.
Specify acceptance by density, CT, metallography, or mechanical testing.HIP machine records prove the cycle, not that every original defect closed.
Provide venting strategy for intentional cavities.A sealed cavity can collapse while an open cavity communicates with vessel pressure.

HIP versus the alternatives

Treatments engineers weigh against HIP, and when each wins.

Treatment	Hardness	Toughness	Stability	Cost	Choose it when
HIP this page	—	75	65	$$$$	—
Stress Relief	—	75	95	$	when only residual-stress reduction is needed and internal porosity is acceptable
Solution Anneal	—	90	55	$$$	when phase condition and corrosion properties, not pore closure, are the objective

Cost, lead time and applications

Relative cost

Hot Isostatic Press (HIP) is a high-cost treatment ($$$$) relative to the other heat treatments in this catalog.

Heat treatment is priced per lot with a furnace minimum. The exact figure appears on the instant quote once the part is uploaded.

Lead time

Added lead time	7–21 working days
Furnace time	8–24 h

What HIP is used for

Flight-critical PBF Ti-6Al-4V parts
PBF Inconel 718 turbomachinery
Medical cobalt-chrome implants
316L valve and manifold bodies
AlSi10Mg AM structures
Nickel-superalloy investment castings

HIP — frequently asked

What pressure does HIP use?

ASTM F3301 Condition HIP cycles use inert atmosphere at not less than 100 MPa. Commercial equipment often operates in the 100–200 MPa range, but the drawing must state the alloy-specific requirement.

What temperature does HIP use?

There is no universal temperature: AlSi10Mg uses about 510–520 °C, Ti alloys 895–955 °C, 316L 1120–1163 °C, and Co-Cr-Mo 1185–1220 °C under ASTM F3301. Applying the wrong alloy cycle can damage microstructure or geometry.

How long is a HIP hold?

ASTM F3301 commonly specifies 180 ± 60 minutes for titanium and 240 ± 60 minutes for several nickel, stainless, and cobalt alloys. Total vessel time is longer because heating, pressurization, cooling, and depressurization are included.

Does HIP remove all AM porosity?

It can close isolated internal pores and bring a qualified PBF material toward full density. It generally cannot close defects that remain connected to the external surface because vessel gas reaches both sides.

Does HIP increase hardness?

Not inherently, so this record has no hardness score. Hardness may rise or fall with alloy phase changes, and nickel or precipitation-hardening alloys commonly need solution and aging treatment after HIP.

Will HIP change dimensions?

Sound bulk geometry changes little under isostatic pressure, but porous regions shrink and thin unsupported features can creep. Critical surfaces are commonly machined after HIP.