TUNGSTEN
material properties and alloys

1

Tu n g s t e n
Tungsten is considered a refractory metal. It has the highest melting point and lowest vapor pressure of all metallic elements.
The story of Plansee began in 1921 with the production of tungsten. To this day, tungsten has been part of our production range,along with other metals that have high melting points, such as molybdenum, tantalum, and their alloys.
Plansee produces tungsten and tungsten alloys by powder metallurgical processes. An advantage of powder metallurgy compared to other manufacturing methods is the fine grain size of the tungsten powder that is obtained. The fine-grained natureof tungsten manufactured by powder metallurgy simplifies further processing and imparts better mechanical properties to thefinished product.

2

Contents
Tungsten

Page

Production process of semifinished products

4

Material range and chemical specification

5

Basis for material selection

7 – 11DIS CLAIM ER

Properties of tungsten and its alloys
Physical properties

12 – 13

Mechanical properties

14 – 15

Chemical behavior

16 – 20

Machining of tungsten

21 – 23

Joining techniques

24 – 25

Surface treatment of tungsten and its alloys

26 – 27

Available products and standard dimensions

28

Other Plansee high-performance materials

29

Conversion of units

30

The contents of this brochure are for general information purposes only. All information contained in this brochure, e.g. regarding
quality, material properties and purpose of use, are provided only as a courtesy and does not constitute legally binding advice.
Plansee expressly disclaims any warranty, either express or implied, and liability, in particular with respect to the accuracy, completeness or suitability of the information, its freedom from errors or that the information is free and clear of third-party rights.
All rights reserved. Text, images and graphics as well as their arrangement are subject to copyright protection and other protective laws. The content of this brochure may not be copied, distributed, modified or made accessible to third parties forcommercial purposes.

3

Tungsten sheets

Tungsten rods with ground surface

Production process of semifinished products
On average, the Earth’s crust contains around 1.25 g/ton of tungsten.
Along with the minerals Ferberite (FeWO₄), Hubnerite (MnWO₄) and Wolframite ((Fe,Mn)WO₄), Scheelite (CaWO₄) is the mostimportant ore involved in tungsten production. The largest deposits are found in China, Russia, Canada and North America,
although tungsten is also mined in Austria.
The ores are primarily separated from their by-products by crushing and grinding, followed by flotation. Ammonium para­tungstate (APT-(NH₄)₂WO₄) is recovered after several intermediate steps and is converted to tungsten oxide (WO₃) or tungsten blue oxide (WO3-x) by heating to evaporate ammonia.
Tungsten powder is obtained from ammonium para tungstate ((NH4)2WO4), tungsten oxide (WO₃) and tungsten blue oxide (WO3-x )by hydrogen reduction at temperatures ranging from 700 °C to 1100 °C. Various grain sizes can be produced as a function of
the reduction temperature and the hydrogen dew point. Purity of the metal powder is above 99.97%.
In the manufacture of doped or alloyed tungsten products, the doping or alloying elements are either introduced into the raw
materials prior to reduction using the sol-gel process, or they can be added to the metal powder after reduction.
Following the reduction stage, the powder is sieved and homogenized. The initial densification of the powder to various plateand rod geometries takes place predominantly by way of die pressing and cold isostatic pressing.

Schematic flow of the production of semifinished products

Oxide
WO
3-x

Raw material

Reduction
Reduction

MixingMixingAlloying
Alloying

Pressing
Pressing

Sintering
SinteringForming
FormingHeat
Heat
treatment
treatment

The pressed compacts are subsequently sintered at temperatures between 2000 °C and 2500 °C, mostly using furnaces withhydrogen flow. This increases the density and strength of the pressed blanks.
Deformation of the sintered blanks takes place at temperatures up to 1600 °C, using for example rolling, forging and swaging.
Intermediate annealing, leading to recovery and recrystallization, is necessary to main­tain sufficient workability. The working
temperature can be reduced as the degree of deformation increases. In this way, forged parts, sheets and foils are produced.
Wires are manufactured from rods by rolling and drawing.

4

Material range and chemical specification
In addition to tungsten of different purity levels, the alloys listed below are produced.

Chemical composition(information given in weight %)Material designation
W (pure)> 99.97% W

W-UHP (ultra high purity)> 99.9999% W

WVM

30 – 70 μg/g K

WVMW

15 – 40 μg/g K

WL

WL05

0.5% La₂O₃

WL10

1.0% La₂O₃

WL15

1.5% La₂O₃

WL20

2.0% La₂O₃

WC20
WRe

2.0% CeO₂
WRe05

5.0% ReWRe26

26.0% ReWCu*
W heavy metal alloy
with a high density*

10 – 40% Cu
Densimet®

1.5% – 10% Ni, Fe, Mo

Inermet5% – 10% Ni, Cu

Denal

®

®

2.5% – 10% Ni, Fe, Co

Detailed information on our tungsten-based metal matrix composites and WCu can be found in our W-MMC brochure.

5Chemical specification of solid metallic tungsten (more elements on request)

Main and minor
components
W

EU-Directive

PlanseeMin. content [%]99.99% b)

RoHS a)99.97% b)

Max. values[µg/g]

Impurities
TypicalGuaranteed

Al

1

15

Cr

3

20

Cu

1

10

Fe

8

30

K

1

10

Mo

12

100

Ni

2

20

Si

1

20

C

6

30

H

Max. values[µg/g]

5

N

1

5

O

2

20

Cd

1

5

100

1

1000

5

1000

Hg c)
Pb

1

1000

Cr (VI)
Organic
impurities(e.g. PBB. PBDE.
PFOS. PFOA)a)

The presence of Cr (VI) and organic impurities can be excluded
as a result of the production process (multiple heat treatment
steps at temperatures above 1000 °C in H2 atmosphere).

1000

2015/863/EU, 2011/65/EU and 2000/53/EC b) Metallic purity without Mo c) Initial value

The chemical composition is continuously checked by means of random sampling. The sampling inspection plan, analysis andevaluation methods are outlined in the internal instruction PSE-020-WI-003. The application of the measured values to the chemical analysis is defined in PSE-680-WI-001.
Remarks: The specified physical and chemical characteristics are disclosed without regard to measurement accuracy.

6

Basis for material selection
Correct material selection requires knowledge of the application. Important criteria may be:	Physical properties(e.g., melting point, density, electrical	Chemical properties(corrosion resistance, etching behavior)conductivity, thermal conductivity,
thermal expansion, electron work function)

	Workability(machinability, formability, welding suitability)	Mechanical properties(e.g., strength, creep behavior, ductility)

Recrystallization behavior
		(recrystallization temperature)

Tungsten (W):
Tungsten exhibits the following properties:	High melting point of 3420 °C

	High density	Low vapor pressure	High absorption capacity forionizing radiation

	High hot strength	High corrosion resistance against acids
	Low thermal expansion	High thermal conductivity

and molten metals
	Recrystallization temperature between
1100 °C and 1400 °C

	High Young’s modulus

At around 2900 °C, tungsten exhibits the highest operating temperature of all metals. Pure tungsten is used in few application
fields, such as in the coating industry for crucibles and sputtering targets and in high-temperature furnace construction forheating elements and heat shields. Additionally, tungsten that has a defined residual porosity of up to 35 volume percent is
produced for special applications.
Commonly, tungsten is used as a doped metal. Its properties can be varied widely by using suitable alloy compositions andproduction processes. Plansee therefore developed various grades of tungsten for different applications. They are used in thelighting industry, electronics, medical applications and thin-film technology as well as for welding electrodes and in the construction of high-temperature furnaces. Additionally, tungsten is the main component of tungsten-rhenium alloys, composite materials(tungsten-copper) and high-density heavy-metal alloys (Densimet® and Inermet®)

7

W-UHP (Ultra High Purity Tungsten)
By using tungsten powder with a purity of 99.9999%, out
gassing of impurities can be avoided. This material quality isused for electrodes in HID lamps and, due to its high purity,
ensures consistent lamp quality and an increased service life.

WVM (Tungsten Vacuum Metallizing)
WVM is almost pure tungsten doped with only a tiny amountof potassium. We primarily supply our WVM in rod and wire

Tungsten wires

form. The material is employed for evaporation coils or heating filaments as well as for the production of components for
epitaxial processes. Additionally, it can be used as a sheet
in the form of an evaporation boat. We use doping as wellas proper thermomechanical treatment to create a stacked
structure, which results in increased dimensional stability athigh temperatures.

WVMW (WVM Tungsten)
WVMW and S-WVMW were developed for use as anode materials for short arc lamps with diameters greater than 15 mm.

WVMW anode

We use high-purity tungsten, which is doped with potassium,for both materials. S-WVMW is particularly suitable for rod
diameters greater than 30 mm. Thanks to the special production process we use to manufacture S-WVMW, we are able toachieve high densities in the rod core.

WL (Tungsten-Lanthanum Oxide)
We mix our tungsten with 0.5, 1.0, 1.5, or 2.0 percent by
weight lanthanum oxide (La₂O₃) in order to improve its creep
resistance and increase the recrystallization temperature.
Our WL is also easier to machine due to the finely distributedoxide particles in its structure. The electron work function oftungsten-lanthanum oxide is significantly lower than that ofpure tungsten. That is why WL is a popular choice for ion
sources and lamp electrodes.

8

Multiple-stranded WVM wireWC20 (Tungsten-Cerium Oxide)
WC20 is used as the welding electrode material. We dopetungsten with two percent by weight cerium oxide to obtaina material that features a lower electron work function,better ignition characteristics, and a longer service life thanpure tungsten.

WRe (Tungsten-Rhenium)
We alloy our tungsten with rhenium to obtain greater ductility

Parts for ion implantation

and a lower brittle-to-ductile transition temperature. In addition, tungsten-rhenium has a higher recrystallization temperature and better creep resistance. We use the WRe standard
compositions – WRe05 and WRe26 – as a thermoelement
material in applications in excess of 2000 °C. This material isalso used in the aviation and aerospace industries.

Sputtering target for microelectronics

9

The following table provides an overview of the properties of the various tungsten alloys in comparison to pure tungsten.

W

WVM

WL

Alloying components(in % by weight)

99.97% W

30 – 70 µg/g K

0.5% La₂O₃
1.0% La₂O₃
1.5% La₂O₃
2.0% La₂O₃

Thermal conductivity

~

~

~

High-temperature stability /Creep resistance

~

++
+

+

Recrystallization temperature

~

++

+

Fine-grained structure

~

+

+

Ductility~++

Workability/formability

~

+

++

Electron work function

~

~

--

~ comparable with pure W + higher than pure W ++ much higher than pure W - lower than pure W -- much lower than pure W

WC20

WRe

WCu

Alloying components(in % by weight)

2% CeO₂

5% / 26%
Re

10 - 40%
Cu

Thermal conductivity

~

-

+

High-temperature stability /Creep resistance

+

+

--

Recrystallization temperature++Fine-grained structure+~

Ductility

+

++

++

Workability/formability

++

+

++

Electron work function--+~ comparable with pure W + higher than pure W ++ much higher than pure W - lower than pure W -- much lower than pure W

10

Properties of tungsten and its alloys
Physical properties

Properties
Atomic number

74

Atomic mass

183.84 [g/mol]

Melting point

3420 °C

Boiling point

5555 °C

Vapor pressure

at 1800 °C

6 × 10−10 N/m²

at 2800 °C

4 × 10−3 N/m²

Atomic volume0.0159 nm³Density at 20 °C

19.25 [g/cm³]

Crystal structure

Body-centered cubic

Lattice constant

317 [pm]

Hardness at 20 °C

stress-relieved> 460 [HV30]

recrystallized~ 360 [HV30]

Young’s modulus at 20 °C

405 [GPa]

Coefficient of linear thermal expansion at 20 °C

4.4 × 10−6 [m/(mK)]

Thermal conductivity at 20 °C

164 [W/(mK)]Specific heat at 20 °C

0.13 [J/(gK)]Electrical conductivity at 20 °C

18.2 × 106 [S/m]Specific electrical resistivity at 20 °C

0.055 [(Ωmm²)/m]

Acoustic velocity at 20 °C

Longitudinal wave

5180 [m/s]Transverse wave

2870 [m/s]Electron work function

4.54 [eV]Thermal neutron capture cross-section

1.92 × 10−27 [m²]11

Vapor pressures of refractory metals

12Linear thermal expansion coefficient of W and Mo
as a function of temperature

Thermal conductivity of W and Mo
as a function of the temperatureSpecific electrical resistance of W and Mo
as a function of the temperatureSpecific heat of W and Mo
as a function of the temperature

Photo: TU-Bergakademie Freiberg

Optical micrograph of a W sheet(stress-relieved)

Optical micrograph of a W sheet(recrystallized)

Scanning electron micrograph of WVM fracturesurface with potassium-filled bubbles

Mechanical properties
We optimize the material purity, determine the type and quantity of alloying components, and modify the microstructure of ourtungsten through targeted thermomechanical treatment, a combination of deforming and heat treatment. This results in custo­
mized mechanical properties for a wide variety of applications. Tungsten has mechanical properties similar to molybdenum. Similarly to molybdenum, these properties are dependent on the testing temperature. At 3420 °C, tungsten has the highest melting
point of all metals. The material's excellent high-temperature stability, coupled with its high modulus of elasticity, give tungsten
its high creep resistance.

Young’s modulus of tungsten as a function of the temperature comparedto the refractory metals as molybdenum, tantalum and niobium

Like molybdenum, tungsten has a body-centered cubic lattice and therefore the same characteristic brittle-to-ductile transition. The
brittle-to-ductile transition temperature can be reduced by means of forming and alloying. The strength of the material increases
with increasing deformation. However, unlike other metals, this also increases the ductility of tungsten. The main alloy element used
to improve the overall ductility of tungsten is rhenium.
If you intend to utilize tungsten at high temperatures, you should take the material's recrystallization temperature into account.
When it comes to tungsten materials, ductility in particular, along with the strength of the material, decreases as the recrystallization level rises. Doping with small oxide particles (e.g., lanthanum oxide or cerium oxide) increases the recrystallization
temperature and creep resistance of tungsten. The higher the deformation, the stronger is the effect in terms of the oxide,
which becomes finer as a result of thermomechanical processing.

13

The table shows the recrystallization temperatures of our tungsten-based materials at different levels of deformation:

Material

Temperature °C for 100% recrystallization(annealing time: 1 hour)
ϕ = 90%ϕ = 99.99%

W (pure)

1350

-

WVM

-

2000

WL10

1500

2500

WL15

1550

2600

WRe05

1700

-

WRe26

1750

-

ϕ = degree of deformation

14

Typical 0.2% yield strength for W and Mo sheet material in
the stress-relieved and recrystallized condition, respectively(thickness of the sheet: W = 1 mm / Mo = 2 mm)

Typical 0.2% yield strength for W and Mo rod material in the
stress-relieved and recrystallized condition, respectively(diameter 25 mm)

Typical ultimate tensile strength for W and Mo sheet material in the
stress-relieved and recrystallized condition, respectively(thickness of the sheet: W = 1 mm / Mo = 2 mm)

Typical ultimate tensile strength for W and Mo rod material in the
stress-relieved and recrystallized condition respectively(diameter 25 mm)

Chemical behavior
Tungsten and its alloys all exhibit very similar corrosion behavior (with the exception of tungsten-copper and the high-density alloys).
Tungsten is corrosion-resistant at a relative humidity of under 60%. In moister air, discoloration starts to occur. However, thisis less pronounced than in molybdenum. Even at very high temperatures, glass melts, hydrogen, nitrogen, noble gases, metal
melts, and oxide ceramic melts are largely unaggressive to tungsten, provided these do not also contain oxidants.
The table below shows the corrosion behavior of tungsten. Unless otherwise indicated, the specifications relate to pure solutions
not mixed with air or nitrogen. Tiny concentrations of extraneous chemically active substances can significantly affect corrosion
behavior. If you have any questions regarding complex corrosion-related topics, we would be happy to assist you with our experience and our in-house corrosion laboratory.

Corrosion behavior of tungsten towards water,acids, lyes, halogens, non-metals, gases, melts and furnace construction materials
MediumResistant (+), Non-Resistant (-)

Note

Water
Cold and warm water < 80 °C+

Hot water > 80 °C, deaerated+

Steam up to 700 °C

+

Acids
Hydrofluoric acid, HF+< 100 °C

Hydrochloric acid, HCl+

Phosphoric acid, H₃PO₄+< 270 °C

Sulfuric acid, H₂SO₄+< 70%, < 190 °C

Nitric acid, HNO₃+

Nitro hydrochloric acid, HNO₃ + 3 HCl+

Organic acids+< 30 °C

Lyes
Ammonia solution, NH₄OH+

Potassium hydroxide, KOH+< 50%, < 100 °C

Sodium hydroxide, NaOH+

< 50%, < 100 °C

Halogens
Fluorine, F₂-

Chlorine, Cl₂+< 250 °C

Bromine, Br₂+< 450 °C

Iodine, I₂+< 450 °C

15

Corrosion behavior of tungsten towards water,acids, lyes, halogens, non-metals, gases, melts and furnace construction materials
MediumResistant (+), Non-Resistant (-)

NoteBoron, B+< 1200 °C

Carbon, C+< 1200 °C

Silicon, Si+< 900 °C

Phosphorus, P+< 800 °C

Sulfur, S+< 500 °C

Non-metals

Gases (Pay special attention to the dew point of the gases. Moisture can lead to oxidation.)
Ammonia, NH₃+< 1000 °C

Carbon monoxide, CO+< 1400 °C

Carbon dioxide, CO₂+< 1200 °C

Hydrocarbons+< 1200 °C

Air and oxygen, O₂+< 50 °C

Inert gases (He, Ar, N₂)+

Hydrogen, H₂+

Water vapor+< 700 °C

Glass melts*+< 1700 °C

Aluminum, Al+< 700 °C

Beryllium, Be-

Bismuth, Bi+< 1400 °C

Cesium, Cs+< 1200 °C

Cer, Ce+< 800 °C

Copper, Cu+< 1300 °C

Europium, Eu+< 800 °C

Gallium, Ga+< 1000 °C

Gold, Au+

< 1100 °C

Melts* Except glasses with oxidizing agents (e.g. lead glass)16

Corrosion behavior of tungsten towards water,acids, lyes, halogens, non-metals, gases, melts and furnace construction materials
MediumResistant (+), Non-Resistant (-)

Note

Melts
Iron, Fe-

Lead, Pb+

< 1100 °C

Lithium, Li+< 1600 °C

Magnesium, Mg+< 1000 °C

Mercury, Hg+< 600 °C

Nickel, Ni-

Plutonium, Pu+< 700 °C

Potassium, K+< 1200 °C

Rubidium, Rb+< 1200 °C

Samarium, Sm+< 800 °C

Scandium, Sc+< 1400 °C

Silver, Ag+

Sodium, Na+< 600 °C

Tin, Sn+< 980 °C

Uranium, U+< 900 °C

Zinc, Zn+

< 750 °C

Aluminum oxide, Al₂O₃+< 1900 °C

Beryllium oxide, BeO+< 2000 °C

Graphite, C+< 1200 °C

Magnesite, MgCO₃+< 1600 °C

Magnesium oxide, MgO+< 1600 °C

Silicon carbide, SiC+< 1300 °C

Zirconium oxide, ZrO₂+

< 1900 °C

Furnace construction materials

800µm

SEM photograph of a tungsten surface with alternating cavity
corrosion and crystal growth caused by high-temperature oxidation / sublimation and re-deposition / reduction

Lapped and cleaned tungsten disc after 168 hours at 40 °C in
moist air17

Machining of tungsten
Knowledge of material properties and observation of the following recommendations are necessary to successfully process
tungsten.

Transition temperature
Tungsten is brittle at room temperature. Like all other body-centered cubic metals, it has a ductile-to-brittle transition temperature that can vary depending on the type of loading, the sample thickness and form, the material condition, and the chemicalcomposition. When heated to above this temperature, tungsten loses its brittleness and becomes ductile. This effect is capitalized on when mechanically working tungsten.

Transition temperature, recrystallization temperature and recommended temperature range forbending and stamping tungsten as a function of the sheet thickness

Recrystallization temperature
In addition to the transition temperature, it is also important to know the recrystallization temperature. Above this point, structuraltransformation begins, leading to the growth of new grains. This alters the mechanical properties of the material, with strengthand hardness values decreasing. The breaking tendency increases because of grain growth and can only be reduced again byfurther deformation of the material, e.g. by rolling, forging or drawing. A high recrystallization temperature is therefore always
desirable.
The degree of deformation and the chemical composition determine the recrystallization temperature. It can be increased significantly by adding small, finely dispersed oxide particles, known as dispersoids, or by adding aluminum potassium silicate.

18

Bending, forming, stamping, punching and cutting
The graph shows the temperature ranges for bending and punching tungsten as a function of the sheet thickness.
Due to the preferred orientation of the grains from rolling in the longitudinal direction, thin, intensely worked sheets and foils havepronounced fibrous structures. Their bending properties, parallel and transversely to the rolling direction, differ considerably.
Generally, we recommend bending tungsten sheet only transversely to the rolling direction. If bending along the longitudinal
direction is unavoidable, the working temperature must be increased considerably. The minimum bend radius is usually approximately the same as the sheet thickness.
At high temperatures, tungsten can also be worked by spinning, flow turning or forging.
Stamping of tungsten is also possible if the temperature of the sheet and tools is accordingly high.
Tungsten can be punched and sheared at elevated temperatures. However, cracks and laminations can be caused by blunt
cutting edges on tools and shears, by excessive tool clearance, and by an insufficiently high cutting temperature.

MachiningTungsten can only be machined with difficulty. However, alloying with either CeO₂ or La₂O₃ notably improves the machinability.
Additionally, high-density tungsten alloys have significantly better machining properties than pure tungsten. Generally, very hightool wear is to be expected. Robust machine tools and consistent machining conditions are essential. It is important to machinefrom the edges into the material, otherwise chips and cracks can occur.

19

Recommended machining conditions for tungsten and its alloys
Turning
Tools

CERATIZIT Maxilock-S (Catalog No.: 183)

Indexable carbide inserts

Use with Code 27 and 25, Carbide grade H 216 T / H 210 T

Cutting speed [m/min]vc = 80 – 100

Feed [mm/rev]

f = 0.05 – 0.20

Depth of cut [mm]ap = 0.5 – 4.0 (acc. to type of insert)

Coolant

Emulsion
Milling

Tools

Insert XDHT 11T325FR-27P H 216 T (Catalog No.: 126)

Rake angle γ~ 10 °C

Inclination angle

0 – 10 °C

Carbide grade

H 216 T

Cutting speed [m/min]vc = 30 – 40

Feed [mm/tooth]f = 0.05 – 0.20

Coolant

Emulsion
Drilling

Drill

HSS

Solid carbide drill (micrograin)

Cutting speed [m/min]vc = 10 – 20

20 – 30

Feed [mm/rev]

f = 0.05 – 0.20

0.01 – 0.03

Coolant

dry

Emulsion
Grinding

20

Grinding wheel

Silicon carbide, for example
TYROLIT C I20 L5 V15

Diamond, for example
TYROLIT D126 C75 B 52

Cutting speed [m/sec]

16 – 25

16 – 18

Sufficient coolant

Emulsion

Emulsion

Joining techniques
Various joining techniques are available for producing complex components from tungsten. Highly stressed parts should only bejoined by rivets or threaded fasteners because tungsten has limited suitability for welding. Depending on the operating conditions,brazing can also be used as a joining process.

Mechanical fastening
Riveting
Tungsten parts can be joined economically to similar parts made of tungsten or other metals by riveting. Button head and countersunk rivets are available in a range of sizes. Various fixation forms can be achieved by radial riveting (countersunk or buttonhead). The thickness of sheet sections to be riveted should, at a minimum, correspond to the rivet diameter. Rivet holes must be
deburred after drilling. Both the rivet and the riveting tool should be warmed in advance to optimize joint strength.
In principle, it is not possible to achieve a water-tight or gas-tight joint. In certain applications, gas tightness can be improved byflame spraying with molybdenum.
Countersunk and button head rivets are available in the Plansee Online Shop.

Fastening
Machine screws with various thread forms are available. However, screws are expensive to manufacture, and screwed joints areused predominantly for repair work. When choosing this joining technique, remember that, after high-temperature use, it is
no longer possible to remove a screw without breaking it.

Welding
Options for welding tungsten are limited. Because of recrystallization and grain growth in the heat-affected zone, welded joints
exhibit low strength and toughness. The associated tendency to brittle fracture must be taken into account at the design stage.
If possible, seam welding should be avoided or restricted to low stress areas.
Additionally, tungsten is highly sensitive to impurities. Even the smallest concentrations of oxygen, nitrogen and carbon increase
the ductile-to-brittle transition temperature and increase the danger of fracture at lower temperatures. Any parts to be welded
must be carefully cleaned in advance. The weld area must be as finely ground as possible and cleaned by pickling with acid.
Welding should always be carried out under a controlled shield gas atmosphere (Ar, He) or in vacuum.
GTAW (Gas Tungsten Arc Welding) welding is possible, but should be carried out in a glove box. Welding procedures withconcentrated heat input, such as EBW (Electron Beam Welding) or LBW (Laser Beam Welding), lead to small weld zones andfavorable weld properties. In this regard, EBW is advantageous since it takes place in vacuum. Tungsten rhenium alloys arerecommended as filler materials for tungsten fusion welding. Parts to be joined should always be pre-heated before welding tominimize cooling rates and welding stresses.

21

Stress-relief annealing after welding is recommended. Thick-walled weld designs as well as large differences in sections of theparts should be avoided. Small parts may be welded by RSW (Resistance Spot Welding) in a protective atmosphere with andwithout filler metal. The use of filler metals made of iron-based or nickel-based alloys or of platinum or other refractory metals withlow melting points can be advantageous.

Brazing
Where the design permits, brazed joints that have good strength properties can be produced from similar and dissimilar materials (e.g., other refractory metals, steels, non-ferrous metals, graphite, ceramics, etc.). Because tungsten is sensitive to oxidation, brazing is carried out in a protective atmosphere, under hydrogen or in vacuum. Brazing procedures involving exposure to
the atmosphere, such as autogenous flame brazing, are not suitable. Furnace brazing is the standard technique for joining large
flat parts, while induction brazing equipment is recommened for joining small parts.
Components to be joined must be free from grease, oils, oxides and other impurities in order to ensure acceptable wetting withbraze material. Depending on the operating conditions and the material combinations, the following brazing alloys can be used:	Silver-based and copper-based alloys for temperatures up to 1000 °C
	Nickel-containing and precious metal-containing alloys for temperatures up to 1400 °C
	Titanium-based, zirconium-based and platinum-based alloys for high-temperature brazing up to 2000 °C

22

S u r f a c e t rea t m en t o f tung ste n an d its alloys
No significant differences are found in the behavior of tungsten and its alloys (except tungsten-copper and the high-density
alloys), and as a result they are not treated separately in this section.

Cleaning
Ultrasonic cleaning in strongly alkaline, aqueous solutions containing detergents is highly suitable. Subsequent rinsing in highpurity water (conductivity σ ≤ 10 μS/cm), followed by warm air drying, results in a clean, blemish-free surface.

Storage
Humid conditions and large fluctuations in temperature can cause surface oxidation. Tungsten should therefore always be stored under dry conditions (humidity less than 60%) at an even temperature. Surface oxidation can be prevented by storing thematerial in sealed containers filled with inert gas.

Pickling
Heavily oxidized tungsten can be cleaned in molten sodium hydroxide containing a small percentage of oxidizing agent (e.g.,
sodium nitrate) in the temperature range of 400 °C to 450 °C.
To start with, the material must be dry to avoid the danger of the melt splashing. After cooling, any remaining pickling residues
are removed by immersion in warm water. Pickled or lightly oxidized tungsten parts can be etched in acid to achieve a brightfinish.
A suitable solution contains 4.5 parts by volume nitric acid (52 weight %), 2.5 parts by volume sulfuric acid (73 weight %) and
3.0 parts by volume water. Thorough rinsing in cold water removes acid residues, and final rinsing with high-purity water, followed by warm air drying, leads to a bright, metallic finish. Lightly oxidized tungsten can also be cleaned and bright annealed inhydrogen at approximately 1000 °C.

23

Surface roughening
Surface roughening can be achieved by pickling (ten-point height of irregularities Rz ≈ 5 μm), or shot blasting e.g. with alumina(ten-point height of irregularities Rz ≈ 20 μm).

ElectropolishingTungsten can be anodically electropolished in an aqueous alkaline solution consisting of 40 g/l potassium chlorate, 40 g/l potassium
carbonate, and 2 g/l potassium hydroxide. The electrolyte temperature should be around 50 °C, with the voltage ranging from 10 to 15 V.

Coating
Provided the surface is clean, tungsten can be coated by a variety of methods. On request, Plansee can supply coated semi-finished products or components:	For protection against atmospheric corrosion and as a surface layer to assist brazing operations: nickel, chromium andnoble metal-based coatings
For wear protection: carburizing
As a diffusion barrier: oxide coatings
The typical coating thickness is in the range of 0.1 to 200 µm, depending on conditions of use. Flame spraying, atmosphericplasma spraying (APS), vacuum plasma spraying (VPS), physical vapor deposition (PVD), slurry coating, gas hardening and packcementation are all processes employed by Plansee.

Photograph of a tungsten disc coated with ZrO₂ - CaO

24Section of a Mo spray coating on W after several weeks ofusage at high temperatureAvailable products and standard dimensions
Overview of semifinished products made of tungsten and tungsten alloys:
Materials
W

Sheets and plates[thickness]Rods[diameter]Wires[diameter]

0.025 – 20 mm

0.3 – 90 mm

0.025 – 1.50 mm

0.3 – 12.99 mm

0.050 – 1.50 mm

W-UHP

Upon request

WVM

0.05 – 5 mm

13 – 45 mm

WVMW
WL05/WL10/WL15

Upon request

0.3 – 90 mm

WC20Upon request

WRe05/WRe26

Upon request

0.4 – 1.50 mm

Please contact us if you have any questions about the above dimensions or should you be interested in semifinished products
made of other materials, such as WCu or Inermet®.

25

Other Plansee high-performance materials
Based on our many years of experience in the field of powder metallurgy, we supply a wide range of products made from highperformance materials. In addition to tungsten and its alloys, Plansee is also a leading producer of:	Molybdenum and Mo alloys
	Tantalum and Ta alloys
	Niobium and Nb alloys
	Tungsten-based metallic matrix composites (W-MMC)
Sputter materials for hard coating

Selection of Plansee products made of high-performance materials:

26

Sputtering targets

Semiconductor base plates

CuCr contacts

Glass melting electrodes

Wires for the lighting industry

Various finish types of X-ray rotary anodes

Conversion of units
Property

SI UnitAreamDensitykg/mConversation factor

2

3

J = N•m= W•sEnergyForce

N = kg • m/s2

Length

m

Mass

kg

Power

W = J/s

Pressure (Stress)

Pa = N/m2

Specific Heatby Mass

J (kg • K)

1 in²

= 6.4516 • 10-4 m²

1 ft²= 9.2903 • 10-2 m²

1 lb/in³= 2.76799 • 104 kg/m³

1 lb/ft³= 16.0185 kg/m³

1 Btu= 1.05506 • 103 J

1 cal= 4.184 J

1 eV= 1.6022 • 10-19 J

1 lbf= 4.4482 N

1 in= 2.54 • 10-2 m

1 ft= 3.048 • 10-1 m

1 lb= 4.5359 • 10-1 kg

1 Btu/hr= 2.93071 • 10-1 W

1 hp= 7.457 • 102 W

1 atm= 1.01325 • 105 Pa

1 lbf/in² (psi)= 6.89476 • 103 Pa

1 lbf/ft²= 47.8803 Pa

1 mbar= 102 Pa

1 N/mm² (MPa)= 106 Pa

1 torr

= 1.33322 • 102 Pa

1 cal/(g • °C)= 4.1868 • 10³ J/(kg • K)

1 Btu/(lb • °F)= 4.1868 • 103 J/(kg • K)

x °C = (x + 273.15) K
y °F = (y • 0.5556 + 255.37) K
Temperature

K (Kelvin)°F in °C: (°F – 32) • 5/9 = °C
°C in °F: (°C • 9/5) + 32 = °F

Thermal Conductivity

W/(m • K)

Volume

m3

°F 32

200

400

°C 0

100

200

600
300

800
400

1000
500

1 kcal/(m • hr • °C)= 1.163 W/(m • K)

1 Btu/(ft • hr • °F)= 1.73073 W/(m • K)

1 in³

= 1.63871 • 10-5 m³

1 ft³= 2.83168 • 10-2 m³

1200
600

1400
700

800

1600
900

1800
1000

2000

2200

1100

1200

2400
1300

2600
1400

1500

27

Close to the customer – our global network
Plansee manufactures and markets its products worldwide. Production sites in Europe, the USA, Japan, India, China, and Korea
as well as a global network of sales subsidiaries and sales partners enable outstanding customer service and product quality
delivered by local teams. Stronger than any alliance and more diversified than single producers, Plansee is the most reliable
source for high-performance components made of refractory metals.

For more information and local contacts, please visit our website:www.plansee.com

Plansee SE
Metallwerk-Plansee-Str. 71
6600 Reutte
Austria
Telephone: +43 5672 600 0
E-Mail: info@plansee.com
We reserve the right to make technical changes for improvement of the product.
Edition: 08.2023

Part of the Plansee GroupQM1 / HPM-070-TD-025 / part 000 / Version 01