UGI® PHYNOX®: Premium Austenitic Cobalt Alloy for High-Performance Applications

UGI® PHYNOX® is an austenitic cobalt basis alloy with high yield strength which offer multiple properties:

Age hardening by heat treatment after cold forming without any distortion,

Excellent corrosion resistance in several medias, stress corrosion cracking and absence of hydrogen embrittle-ment,

Excellent fatigue resistance without any relaxation,

Non magnetic in all temper : annealed, cold drawn or aged,

Can be used in a wide range of temperature :from liquid helium to 500°C,

Perfectly biocompatible, it has been used for more than twenty five years in surgical implants

Cleanliness conforms to standards AFNOR NF S 90 - 403 and ISO 5832/7: Sulfides: 1, Aluminates: 3, Silicates: 1, Globular Oxides: 3

Properties

General

Property	Value
Density	8.3 g/cm³

Mechanical

Property	Value	Comment
Elastic modulus	182 GPa
Shear modulus	75 GPa
Tensile strength	1550.0 - 2250.0 MPa	depending on the cold drawing degree

Thermal

Property	Value	Comment
Coefficient of thermal expansion	0.0000125 1/K	20 to 100°C
Melting point	1450.0 - 1460.0 °C
Specific heat capacity	430 J/(kg·K)

Electrical

Property	Value
Electrical resistivity	9.5e-07 Ω·m

Magnetic

Property	Value	Comment
Relative magnetic permeability	1.0002 [-]	500 / 1000 Oe

Chemical properties

Property	Value	Comment
Carbon	0.15	max.
Chromium	19.0 - 21.0 %
Cobalt	39.0 - 41.0 %
Manganese	1.5 - 2.5 %
Molybdenum	6.5 - 7.5 %
Nickel	15.0 - 18.0 %
Other	1.0	max.
Phosphorus	0.015	max.
Silicon	1.2	max.
Sulfur	0.015	max.

Technological properties

Property

Corrosion properties

The UGI® PHYNOX® is not attacked by the organic acids. It resists the salt spray perfectly and its behavior with the mineral acids is definitely higher than that of the best stainless steels In addition, its perfect passivity in con-tact with human tissues, explains why UGI PHYNOX has been used for more than twenty five years in surgical implants. Examples of corrosion resistance:

A: <0.05 mm/y

B: 0.05 to 0.25 mm/y

C: 0.25 to 0.50 mm/y

D: 0.50 to 1.25 mm/y

E: >1.25 mm/y

Media	Concentration	°C	Indice		Media	Concentration	°C	Indice
Acetic acid Chlorhydric acid Chlorhydric acid Sulfuric acid Calcium chloride Ferric chloride	50 % Concentrated 50 % 50 % 10 % 10 %	100 110 110 150 100 25	A E E E A A		Citric acid Lactic acid Nitric acid Nitric acid Phosphoric acid Sodium chloride	10 % 10 % 50 % 10 % 50 % 10 %	100 100 100 100 120 100	A A B B C A
Stress corrosion as per NACE STANDARD TM.01.07 aqueous Solution NaCl 50 g/l + CH₃C00H 5 g/l, saturated in H₂S under 1 atmosphere (pH = 3). Temperature : 24-26.8°C Tensile strength: 90% of yield strength Test piece as per TM.01.07 with: UTS >= 1600 N/mm2 YS 0.2% >= 1130 N/mm2					Minimum guaranteed time :720 hours without failure Result : no failure after 720 hours. Complementary test: Increase in the temperature with 150°C Increase in the pressure Result: no rupture, nor cracking after 1370 hours. Test stopped

General machinability

The high mechanical properties in the as drawn condition and the ability of cold hardening during machining, need to take particular precautions for machining:

Robust and rigid machines

moderate Cutting speeds

Carbides tools, or brazed pastilles, with large rake angles

Cutting fluid with high performances of cooling and lubrication

Heat Treatment

520°C / 3 hours – Air cooled:

The heat treatment is performed after cold forming or machining without any deformation of the treated part.

This treatment must be realized preferably in a vacuum furnace(10-5 Torr) or under protective atmos-phere (Argon)

Processing in open air doesn’t affect the mechanical properties of the material, but alters its aspect.

The influence of the treatment on annealed material is negligible but become very important on cold drawn products.

Cleaning of parts

3 methods for removing the lubricating film and pickling after heat treatment

1. Phosphoric Acid 6% at 70°C

Immersion 15 to 20 minutes

Rinsing hot or cold water & drying

2. Acid nitric 30% with 40°C

Immersion 2 to 3 minutes

Rinsing hot or cold water & drying

3. Acid hydrochloric 40% + Acid nitric 5% at room temp

Nitric passivation (40%) at room temp

Rinsing hot or cold water

Other

Available in wire (coil form) and in straightened ground bars (minimum diameter: 1 mm)

Annealed condition: ø 0,60 mm up to 18 mm

Hard condition : ø 0,012 mm up to 15 mm

Other options: contact the supplier

Surface Treatment

Pickling and polishing: Apart from mechanical descaling, the oxyde film formed during heating in air can be removed by immersing the parts in a boiling aqueous solution containing 5% hydrofluoric acid and 12% nitric acid.

UGI® PHYNOX® can be electro chemically polished with products used for dental alloys cobalt basis

Welding

UGI® PHYNOX® can be readily welded: resistance spot welding, electron beam welding, laser, argon arc welding. It can also be brazed. However, since age hardening can only obtained in cold worked area, this must be taken into account by placing the weld or braze joint in positions where it is not heavily loaded or by using a discontinu-ous joint

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