Havar® Foil

Havar® (UNS R30004) is a precipitation-hardenable cobalt-chromium-nickel alloy with additions of tungsten, molybdenum, and manganese. It is inherently non-magnetic — a property it retains throughout cold working and age hardening, unlike austenitic stainless steels that can develop a magnetic response during cold rolling. Its tungsten content provides solid-solution strengthening and elevated-temperature stability that standard stainless steels cannot match at the thin gauges required for beam windows, diaphragms, and hermetic barriers.

Cold rolling is the primary strengthening mechanism for Havar®. The alloy derives its high strength through cold reduction rather than solid-solution strengthening alone, and a minimum of 80% cold work is required before age hardening to develop maximum tensile and fatigue properties. In practice this means the foil arrives ready for use or for age hardening — all forming, cutting, and joining operations must be completed before the heat treatment step, after which the alloy becomes significantly harder and is no longer suitable for forming.

Age hardening is carried out at 538 °C (1,000 °F) and induces the formation of fine intermetallic precipitates within the cobalt-chromium matrix. These precipitates pin dislocation movement and produce a substantial increase in yield and tensile strength. It is the final processing step — all cutting, forming, stamping, and welding must be done beforehand. Once fully hardened, the foil has peak mechanical properties but is brittle relative to the cold-rolled condition and will not tolerate further deformation.

Havar® has been characterised extensively in the scientific literature as the reference window material for medical isotope cyclotron targets. Its combination of high tensile strength, radiation stability, and low outgassing allows it to survive the sustained thermal and mechanical stress of high-current proton beams. It is used as the entrance window for a wide range of isotope targets including ¹⁸F, ⁶⁴Cu, ⁶⁸Ga, ⁸⁹Zr, and ²¹¹At, and its well-characterised nuclear activation cross-section data means it also functions as a beam monitor foil — a dual role no other commercially available thin foil material replicates.

Yes. Havar® has an extremely low outgassing rate, qualifying it for use in synchrotron beamlines, hermetic vacuum barriers, viewports, and plasma physics chamber windows where gas evolution from window materials would contaminate the vacuum environment or degrade analytical sensitivity. It can be joined by electron beam and laser welding to produce hermetic assemblies — the preferred joining methods for vacuum-side components because the minimal heat-affected zone preserves the dimensional stability and mechanical properties of the thin foil around the weld.

Havar® offers dimensional stability from cryogenic temperatures up to 400 °C under load, and retains a significant proportion of its room-temperature strength above 500 °C — considerably better elevated-temperature performance than Elgiloy® or Phynox®, which are generally limited to around 315 °C in service. Good oxidation resistance extends further still, to approximately 800 °C in air, due to the formation of a stable chromia surface layer stabilised by the tungsten addition. This makes Havar® the correct choice wherever the other two cobalt-chromium alloys would be operating near the top of their temperature envelope.

Havar® is biocompatible and non-magnetic, and has been used in MRI-compatible components, precision medical springs, surgical instruments, and sealed radiation source encapsulations. It does not contain beryllium, so it avoids the occupational health concerns associated with Elgiloy® during fabrication and machining. For long-term direct implantation in regulated medical markets, Phynox® carries the most comprehensive biocompatibility characterisation under ISO 10993, and Elgiloy® has an extensive cardiovascular implant track record — Havar®'s primary medical domain is isotope production and MRI-compatible instrumentation rather than implantable devices.

For cold-rolled material prior to age hardening, precision blanking with hardened carbide tooling and controlled punch-to-die clearance produces clean edges. For fully hardened foil, laser cutting is the preferred method — it delivers burr-free edges, tight dimensional tolerances, and a minimal heat-affected zone when parameters are correctly optimised. Both CO₂ and fibre laser systems are applicable depending on thickness and geometry. Electron beam cutting is an alternative where kerf control and minimal mechanical stress on the surrounding material are critical.

Yes, but only before age hardening and with careful process planning. Havar® has a high work-hardening rate in the cold-rolled condition, which demands a more conservative minimum bend radius than Elgiloy® or Phynox®. Stamping and precision cutting should use hardened tooling with close attention to tool clearance and edge quality. Once the alloy is fully age-hardened, it is significantly harder and less ductile and will not tolerate further forming.

Where tight thickness tolerances or surface finish requirements cannot be achieved through rolling alone, grinding and lapping can be applied using diamond or CBN abrasives — the alloy's high hardness makes softer abrasives ineffective. Careful control of grinding parameters is essential to avoid surface burning or residual stress introduction in thin-gauge material. Electro-discharge machining (EDM) is suitable for complex geometries in fully hardened foil, offering non-contact material removal that sidesteps the work-hardening and tool wear issues associated with conventional machining. Wire EDM is particularly effective for precision disc and ring profiles.

All three are cobalt-chromium alloys sharing high strength, non-magnetic behaviour, corrosion resistance, and biocompatibility, but differ in composition and application fit. Havar® achieves the highest peak tensile strength of the three and is the only alloy with validated radiation-stable performance in cyclotron target service. Its tungsten addition provides superior elevated-temperature stability. Elgiloy® and Phynox® contain significantly more molybdenum, giving them better resistance to pitting and crevice corrosion in chloride-rich environments, and are more formable — reflected in their wider use in precision springs, watch components, and implantable coiled devices. Phynox® is the beryllium-free variant of Elgiloy® and is the preferred implantable device specification in European regulated markets. For nuclear physics, ultra-thin foil, UHV, and elevated-temperature applications, Havar® is the correct choice.

Yes. Custom thicknesses, specific cut dimensions, and laser-profiled shapes can be supplied through Goodfellow's precision cutting service. There is no minimum order quantity. Request a quote with your specification and we will confirm availability and lead time.

Choose foil cut pieces when the application requires a flat, low-volume window, barrier, or target in a non-standard or irregular geometry — beam monitor foils, hermetic seals, and vacuum viewports are typical examples. Disc format provides a pre-profiled circular geometry ready for axial mounting in target holders and transducer housings without additional cutting. Coil provides continuous strip for automated stamping, diaphragm blanking, spring winding, and roll-to-roll operations where material length matters.