Metal-to-glass or metal-to-ceramic sealing applications (e.g., cathode ray tubes and light bulbs), photo-etching components, and applications requiring high resistance to thermal shock.
Kovar Composition detail
Al (aluminum)
0
–
0.01
%
C (carbon)
0
–
0.05
%
Co (cobalt)
16
–
18
%
Cr (chromium)
0
–
0.2
%
Cu (copper)
0
–
0.2
%
Fe (iron)
50.5
–
56
%
Mg (magnesium)
0
–
0.01
%
Mn (manganese)
0
–
0.5
%
Mo (molybdenum)
0
–
0.2
%
Ni (nickel)
28
–
30
%
P (phosphorus)
0
–
0.03
%
S (sulfur)
0
–
0.03
%
Si (silicon)
0
–
0.2
%
Ti (titanium)
0
–
0.01
%
Zr (zirconium)
0
–
0.01
%
Kovar Physical properties
Density
8.32
–
8.4
g/cm3
Kovar Mechanical properties
Young’s modulus
135
–
141
GPa
Specific stiffness
16.1
–
16.9
MN.m/kg
Yield strength (elastic limit)
345
–
410
MPa
Tensile strength
517
–
621
MPa
Specific strength
41.3
–
49.1
kN.m/kg
Elongation
25
–
42
% strain
Compressive modulus
135
–
141
GPa
Compressive strength
345
–
410
MPa
Flexural modulus
135
–
141
GPa
Flexural strength (modulus of rupture)
321
–
385
MPa
Shear modulus
50.4
–
53
GPa
Shear strength
388
–
466
MPa
Bulk modulus
123
–
129
GPa
Poisson’s ratio
0.312
–
0.322
Shape factor
43
Hardness – Vickers
127
–
180
HV
Hardness – Rockwell B
68
–
82
HRB
Hardness – Brinell
120
–
170
HB
Elastic stored energy (springs)
434
–
606
kJ/m3
Fatigue strength at 10^7 cycles
267
–
311
MPa
Fatigue strength model (stress range) Parameters: Stress Ratio = -1, Number of Cycles = 1e7cycles
235
–
354
MPa
Kovar Impact & fracture properties
Fracture toughness
307
–
371
MPa.m0.5
Toughness (G)
688
–
990
kJ/m2
Kovar Thermal properties
Melting point
1440
–
1460
°C
Maximum service temperature
468
–
488
°C
Minimum service temperature
-273
°C
Thermal conductivity
17
–
17.6
W/m.°C
Specific heat capacity
431
–
448
J/kg.°C
Thermal expansion coefficient
4.6
–
5.5
µstrain/°C
Thermal shock resistance
479
–
613
°C
Thermal distortion resistance
3.14
–
3.77
MW/m
Latent heat of fusion
268
kJ/kg
Kovar Electrical properties
Electrical resistivity
46.7
–
51.4
µohm.cm
Electrical conductivity
3.35
–
3.69
%IACS
Galvanic potential
-0.47
–
-0.39
V
Kovar Magnetic properties
Magnetic type
Magnetic
Kovar Optical, aesthetic and acoustic properties
Transparency
Opaque
Acoustic velocity
4020
–
4110
m/s
Mechanical loss coefficient (tan delta)
3e-4
–
5e-4
Kovar Processing properties
Metal casting
Unsuitable
Metal cold forming
Excellent
Metal hot forming
Excellent
Metal press forming
Excellent
Metal deep drawing
Unsuitable
Machining speed
8.23 m/min
Weldability Notes: Preheating and post weld heat treatments may be required
Excellent
Kovar Durability
Water (fresh)
Excellent
Water (salt)
Excellent
Weak acids
Excellent
Strong acids
Acceptable
Weak alkalis
Excellent
Strong alkalis
Excellent
Organic solvents
Excellent
Oxidation at 500C
Excellent
UV radiation (sunlight)
Excellent
Galling resistance (adhesive wear)
Limited use
Flammability
Non-flammable
Kovar Corrosion resistance of metals
Pitting and crevice corrosion
Low (<20)
Stress corrosion cracking Note: Rated in chloride; Other susceptible environments: Hydrogen sulfide
