Alloy 6B wrought base-cobalt alloys No. 6B and 6K have been used successfully for many years in applications involving severe conditions of wear or wear combined with corrosion and/or high temperature. They are particularly for shaft sleeves, bushings, valve parts, pump plungers, doctor blades, feed screws, knives, wear plates, and bearings.
Alloys No. 6B and 6K are
cobalt-base alloys with outstanding resistance to most types of wear.
Their wear resistance is inherent. It is a "built-in"
characteristic and not the result of heat-treatment, plating,
nitriding, or other methods used to produce a superficial hardness on
metal parts.
Half bushings and haft sleeves made of alloy No. 6B
can be used in locations where abrasive particles like fly ash, coke,
metal powder, shale, or cement dust tend to collect in bearing
surfaces. The ability of these parts to withstand the wearing effects
of hard, sharp particles makes them especially useful in screw
conveyors, rock crushing rollers, tile-making machines, and cement
and steel-mill equipment.
Alloy No. 6B is resistant ot the
effects of seizing or galling. In many cases, its low coefficient of
friction allows sliding contact with other metals without damage by
metal pick-up.
Alloy No. 6B has been used in equipment
where no lubricants were used because of the nature of the product
being handled. Sleeves made of alloy No. 6B move smoothly, with a
minimum of resistance, even when operating in contact with other
metal parts. They have been useful in inaccessible areas where
efficient lubrication is impossible. Sleeves and bushings have
resisted seizing even when lubricants were diluted by gasoline,
cleaning fluids, and other liquids that wash out an oil film. They
have operated at peak efficiency even when lubricants decomposed
under heat, or were destroyed by abrasive particles.
Parts made of alloy No. 6B have had long service life - even under constant erosive conditions. It has outstanding resistance to cavitation-erosion. Alloy No. 6B used for steam turbine erosion shields has protected the blades of one turbine for over 19 years of continuous service.
Alloy No. 6B combines wear and corrosion resistance with good impact strength and resistance to thermal stock.
High temperatures have little effect on the hardness, toughness, and dimensional stability of these alloys. They are highly resistant to atmospheric oxidation at ordinary temperatures, and have good resistance to oxidation at elevated temperatures.
Alloy 6B wrought, cobalt-base alloy No. 6B retains high hardness even at red heat. Once cooled back to room temperature, it recovers it's full original hardness.
In addition to its wear-resistance,
alloy No. 6B has good resistance to a variety of corrosive
media. This combination of properties makes alloy No. 6B particularly
useful in such applications as food handling machinery, chemical
equipment, and others where both wear - and corrosion-resistance are
necessary.
Where extraordinary resistance to corrosion is
required, one of the Hastelloy nickel-base alloys may prove more
suitable.
Alloy No. 6B and No. 6K are available in the form of sheet, plate, and fabricated shapes. Alloy No. 6B is also available as bar.
Wrought forms of alloy No. 6B and No. 6K are supplied in the solution heat-treated condition unless otherwise specified. The standard heat-treatment is at 2250°F (1232°C) followed by air cooling.
The properties listed in this page are typical or average values based on laboratory tests conducted by the manufacturer. They are indicative only of the results obtained in such tests and should not be considered as guaranteed maximums or minimums. Materials must be tested under actual service conditions to determine their suitability for a particular purpose. All data represent the average of four or less tests unless otherwise noted. The secondary units (metric) used in this page are those of the SI system.
|
Alloy |
Cobalt |
Nickel |
Silicon |
Iron |
Manganese |
Chromium |
Molybdenum |
Tungsten |
Carbon |
|
No. 6B |
Bal |
3.00 max |
2.00 max |
3.00 max |
2.00 max |
28.00- |
1.50 max |
3.50- |
0.90- |
|
No. 6K |
Bal |
3.00 max |
2.00 max |
3.00 max |
2.00 max |
28.00 |
1.50 max |
3.50- |
1.40- |
|
Physical Properties |
Temp., |
Metric
Units |
Temp., |
British
Units |
|
No. 6B / No. 6K |
No. 6B / No. 6K |
|||
|
Density |
22 |
kg/cubic m |
72 |
lb./cubic in. |
|
Melting Range |
1265 to 1354°C |
2310 to 2470°F |
||
|
Electrical Resistivity |
22 |
Microhm-m |
72 |
Microhm-in. |
|
Thermal Conductivity |
22 |
W/m-K |
72 |
Btu-in./sq. ft.-hr.
°F |
|
Mean
Coefficient |
|
x 10(-6)m/m-K |
|
microinches/in.-°F |
|
Electrical
Conductivity |
22 |
1.90 / --- |
72 |
109 / -- |
|
Specific
Heat |
Room |
J/kg-K |
Room |
Btu/lb.- °F |
|
Magnetic
Permeability |
22 |
<1.2 / <1.2 |
72 |
<1.2 / <1.2 |
|
Reflecting
Power, |
57-70 / ----- |
57-70 / ---- |
|
Alloy |
Test Temp.,°F (°C) |
Brinell
Hardness at Temperature |
|
No. 6B |
1000(538) |
226 |
|
Alloy |
Form |
Test Temp. |
Average |
|
No.
6B |
1/2-in.
(12.7mm), Plate* |
Room |
347(2392) |
|
Alloy |
Form |
Test Temp. |
Average |
|
No. 6B |
Sheet* |
Room |
338(2360) |
|
Alloy |
Form |
Test Temp. |
Average |
|
No.
6B |
Sheet* |
Room |
30.4(210,000) |
|
Alloy |
Form |
Test Temp. |
Average
Izod |
|
|
ft.lbs. |
J |
|||
|
No. 6B |
1/2-in. (12.7mm), Plate* |
Room |
62 |
84 |
|
Alloy |
Test Temp., °F(°C) |
Type of Test |
Average
|
|
|
Longitudinal |
Transverse |
|||
|
No. 6B |
Room |
Un-notched |
72(98) |
65(88) |
|
1000(538) |
Un-notched |
81(110) |
--- |
|
|
1250(677) |
Un-notched |
116(157) |
--- |
|
|
1500(816) |
Un-notched |
126(171) |
--- |
|
*Solution heat-treated at 2250°F (1232°C), air cooled.
|
Form |
Condition |
Ultimate
Tensile Strength |
Yield
Strength |
Elongation |
Hardness |
|
Sheet 0.040 in. (1.0 mm),thick |
Solution Heat-treated* |
145.0(1000)a |
90.1(621)a |
12a |
36a |
|
Sheet 0.065 in. (1.7 mm),thick |
Solution Heat-treated* |
140.8(971)a |
86.7(598)a |
11a |
36a |
|
Sheet 0.125 in. (3.2 mm),thick |
Solution Heat-treated* |
144.7(998)a |
89.8(619)a |
11a |
37a |
|
Sheet 0.187 in. (4.8 mm),thick |
Solution Heat-treated* |
144.5(996)a |
89.3(616)a |
10a |
37a |
|
Plate 0.312 in. (7.9 mm),thick |
Solution
Heat-treated* |
140.2(967)b |
87.9(606)b |
10b |
37b |
|
Plate 0.437 in. (11.1 mm),thick |
Solution
Heat-treated* |
140.2(967)a |
85.6(590)a |
12a |
37a |
|
Plate 0.625 in. (15.9 mm),thick |
Solution
Heat-treated* |
135.5(935)a |
86.4(596)c |
11a |
36a |
a - Average of 27-31
tests
b - Average of 23 tests
c - Average fo 22-24 tests
d -
Average of 9 tests
*Solution heat-treated at 2250°F (1232°C),
air cooled.
|
Alloy |
Form |
Test |
Ultimate |
Yield |
Elongation |
|
No. 6B |
0.063
in. (1.6 mm), |
Room
|
146.0
(1007) |
91.6
(632) |
11 |
|
1/2-in.
(12.7 mm), |
Room
|
148.0
(1020) |
88.0
(607) |
7 |
|
|
5/8-in.
(15.9 mm), |
Room
|
154.1
(1063) |
92.6
(638) |
17** |
|
|
No. 6K |
0.063 in
(1.6mm), |
Room |
176.5 (1217) |
102.7 (708) |
4 |
|
1/2-in. (12.7
mm) |
Room |
146.2 (1008) |
108.2 (746) |
1** |
* Solution heat-treated
at 2250°F (1232°C), air cooled.
**Elongation, percent in 1
in. (25.4 mm)
***Test bars cut transverse to rolling direction.
|
Alloy |
Test |
Stress, |
Initial |
Life, hrs. |
Time
in Hours |
Elongation |
||
|
0.5 |
1.0 |
2.0 |
||||||
|
No. 6B, |
1000 (538) |
60 (414) |
0.70 |
192.8* |
--- |
--- |
--- |
0.8 |
* Test discontinued
before rupture.
**Specimens were solution heat-treated at 2250°F
(1232°C) and air cooled prior to testing.
|
Alloy |
Test |
Weight loss, mg |
|
Alloy No. 6B |
100 |
42.3 |
|
Alloy |
Condition |
Volume |
Hardness, |
Wear |
|
Alloy No. 6B |
Mill
annealed |
8.2 |
C-38 |
0.471
x 10(-3) |
|
Alloy |
Condition |
Ring Alloy |
Volume |
Wear |
|
Alloy No. 6B |
Mill
annealed |
4620
Steel |
0.293 |
3.70
x 10(-3) |
|
Material Against |
Alloy No. 6B |
Cast Iron |
Bronze |
Aluminum |
Lead |
|
Alloy No. 6B |
0.119 |
0.123 |
0.125 |
0.138 |
0.119 |
Coefficient represents
tangent of angle of repose. Tests made on dry surfaces having better
than 120 grit finishes. All Value based on averages and are to be
used comparatively and not as absolute values.
**Average of two or
more tests against a case-hardened SAE 4620 steel ring (Rockwell
C-63)
*The wear coefficient (K) was calculated using the equation:
V= KPL/3h
where V= Wear Volume (mm(3))
P = Load (kg)
L =
Sliding distance (mm)
h = Diamond pyramid hardness
A
combination of a low wear coefficient and a high hardness is
desirable for good wear resistance.
Alloys No. 6B and 6K can be welded by
gas tungsten-arc (TIG) with an argon flow of 25 CFH, gas metal-arc
(MIG), shielded metal-arc (coated electrode), and oxy-acetylene in
this order of preference. The oxy-acetylene method should be used
with discretion and care in that alloys No. 6B and 6K will "boil"
during welding which may cause porosity. Use a 3X reducting flame to
minimize oxidation, penetration and inter-alloying.
Alloy 6B and 6K should be preheated and maintained at 1000°F (538°C)
minimum to prevent cracking during welding and then will air cooled.
Fixturing which would chill the weld rapidly should not be used.
Standard weld joints are recommended. Haynes alloy No. 25 or
Hastelloy alloy W filler metals are recommended for joining alloy No.
6B to softer materials such as carbon steel or stainless steel, while
the harder cobalt-base filler metals such as Alloy 6, No.
6B, and No. 21 are recommended for joining alloy No. 6B to itself,
especially if wear resistance is required in the weld areas. In the
latter case, Haynes No. 25 or Hastelloy alloy W may be used for the
root passes and then be overlayed with the harder materials. Gas
shielding of the root side of the gas tungsten-arc weldments is not
mandatory but it is recommended in order to improve weld penetration.
Alloys No. 6B and 6K are readily
joined to other materials by brazing. All forms of surface dirt such
as paint, ink, oil, chemical residues, ect., must be removed from the
mating parts by etching, solvent scrubbing, degreasing, or other
means. In addition, fluxing will be required during torch brazing
operations when using silver brazing filler metal, to help clean the
joint and allow the filler metal to flow more freely over the mating
surfaces. Brush joining areas generously with brazing filler metal
melts, the source of heat should be removed and the parts positioned.
The assembly should then be pressed together to squeeze out the
excess flux and still air-cooled. The part should not be
quenched.
Other brazing filler metals (i.e., gold, palladium, or
nickel-base alloys) are satisfactory for joining alloys No. 6B and
6K. Brazing filler metal selection depends on the service conditions
expected.
A close fit of the mating surfaces is recommended. The
finished joints will have greater strength if the filler metal is
very thin, generally 0.001-0.005" (0.03-0.14 mm) thick.
Brazing,
with high-temperature filler materials, is generally performed in a
furnace. Induction and resistance heating with salt-bath and
metal-bath dip brazing have limited application. Vacuum furnaces held
at less than one micron pressure or controlled atmosphere furnaces,
having adequate moisture control at brazing temperatures (less than
-60°F (-51°C) dew point), produce the most satisfatory
results. Controlled atmospheres such as hydrogen or cracked ammonia
are suitable for brazing alloys No. 6B and 6K base materials.
Alloys No. 6B and 6K are machined
with tungsten-carbide tools. Carbide inserts are used with a 5-degree
(0.09 rad.) negative tool holder and a 30-degree (0.52 rad.) or
45-degree (0.79 rad.) lead angle. Tools for facing or boring are
essentially the same except for greater clearances where needed. For
best results in drilling, the drill web should be kept thin. Screw
machine length, carbide tipped drills should be used. In reaming, a
45-degree (0.79 rad.) cutting lead angle should be used. High speed
tabs are not recommended for alloys No. 6B and 6K, but threads can be
produced by EDM techniques. For better surface finish, these alloys
should be ground.
The table which follows gives some general
information which may be used as a guide in machining alloys No. 6B
and No. 6K.
|
Operation |
Speed |
Roughing |
Finishing |
||
|
Feed per rev. |
Depth of cut |
Feed per rev. |
Depth of cut |
||
|
Turning* |
50- (0.25-) |
0.008- (0.20-) |
0.050- (1.27-) |
0.002- (0.05-) |
0.025- (0.63-) |
|
Facing* |
50- (0.25-) |
0.008- (0.20-) |
0.050- (1.27-) |
0.006- (0.15-) |
0.025 (0.63) |
|
Boring* |
|
Depends on bar and
size of tool |
|
|
|
|
Drilling** |
|
--- |
--- |
Depends on size of
drills |
--- |
|
Reaming*** |
40- (0.20-) |
0.001- (0.03-) |
0.015- (0.38-) |
0.001- (0.03-) |
0.007- (0.18-) |
|
Threading |
Using single point C-3 tungsten carbide tools. |
||||
*Use C-3 tungsten
carbide tools. Coolant-water base fluid diluted 15 parts water to one
part fluid. Tools for facing and boring are basically the same as
turning tools except for greater clearance where needed.
**C-2
tungsten carbide twist drills with drill web kept as thin as
possible. Coolant - same as item * above
***C-2 tungsten carbide
tools. Reamers should have a 45-degree (0.79 rad.) side cutting edge
angle. Coolant - same as item * above.
Whenever close tolerances are
required, grinding is recommended for finishing Alloys No.
6B and 6K. Honing can be used to finish inside diameters. Recommended
wheels and coolants are listed in the table on the following page.
For convenience, the manufacturers of grinding wheels are also
listed; however, similar wheels of other brands can also be used if
desired.
Grinding speeds should be kept between 2800 and 6000
s.f.p.m (14-31 m/s). Alloys being ground dry should not be quenched,
because this may cause surface checking.
|
Types of Grinding |
Wheels |
Wheel Manufacturer |
Type of Work |
Coolant |
|
CYLINDRICAL
GRINDING |
A54-M5-V |
Precision |
Sharp corners
and |
Emulsifying Oil |
|
Form Work,
Single-Wheel |
19A60-J-V |
Norton |
Removing stock |
Emulsifying Oil |
|
Form Work,
Crush-Roll |
19A220-L9-VG |
Norton |
------------------------- |
"Sultan" B-6** |
|
Centerless |
ZA60-K9-V1 |
Sterling |
Thin-walled
material |
1 gal. "Argon"
No. 4* |
|
INTERNAL
GRINDING |
GA605-J5-V1 |
Carborundum |
Small
holes |
1 gal. "Argon"
No. 4* |
|
SURFACE
GRINDING |
38Z46-I-V |
Norton |
Angles, Radii Forms |
Emulsifying
Oil |
|
Reciprocating Type |
38A46-I-V |
Norton |
Surface, angles, forms |
1 part "Vantrol"
523* |
|
Double-Opposed |
87A46-G12-BV |
Gardner |
Through-feed work |
1 gal. "Argon"
No. 4* |
|
Disk Type |
87A46-G12-BW |
Gardner |
Ferris-wheel work |
1 gal. "Argon"
No. 4* |
|
Cylinder
or |
29A46-F10V6 |
Macklin |
Thin work |
1 lb. Sal Soda to
50 |
|
Profile Work,
Single-Wheel |
A
100-L7-V |
Norton |
--- |
Dry |
|
Profile Work,
Crush-Roll |
A 200-K-V |
Norton |
--- |
"Sultan" B-6** |
|
THREAD
GRINDING |
A 120-W2-B7 |
Macklin |
Test Bars |
"Vantrol" 5299-M oil |
|
HONING |
IC-220-M12-VL2F |
Bay State |
|
"Vantrol" 5299-A oil |
|
ROUGH
GRINDING |
A24-S10-BKRS |
Sterling |
Gates |
Dry |
|
Snagging |
A162-M10-2893 |
Sterling |
Welds |
Dry |
|
TA36-N5-V1 |
Simonds |
--- |
Dry |
|
|
LAPPING |
39C180-J9-V |
Norton |
Flat work |
Mixed with kerosene |
|
Silicon
Carbide |
--- |
Flat work |
--- |
|
|
H-40 Coarse |
Carborundum |
Small holes |
--- |
|
|
TUMBLING |
Aluminum oxide tumbling abrasive mixed with water and soap |
|||
*Or any good grade of
water soluble oil
**Or any good grade of sulfur-base cutting oil