U.S. patent application number 09/988666 was filed with the patent office on 2003-05-29 for surface coatings.
Invention is credited to Hallen, Hans, Nilsson, Lars Ake.
Application Number | 20030098090 09/988666 |
Document ID | / |
Family ID | 25534381 |
Filed Date | 2003-05-29 |
United States Patent
Application |
20030098090 |
Kind Code |
A1 |
Hallen, Hans ; et
al. |
May 29, 2003 |
Surface coatings
Abstract
The invention concerns a nickel based powdered metallic material
comprising in addition to nickel 0-4.5 wt % of copper, 0-5.0% by
weight of iron, whereby the total amount of copper and iron is at
least 2.5% by weight, 0.05-5.0% by weight of a carbide forming
element 0.5-2.0% by weight of boron, 1.0-4.0% by weight of silicon,
0.5-4.0% by weight of phosphorus, 0.01-0.5% by weight of C and less
than 2% by weight of inevitable impurities.
Inventors: |
Hallen, Hans; (Waterloo,
BE) ; Nilsson, Lars Ake; (Hoganas, SE) |
Correspondence
Address: |
Benton S. Duffett, Jr.
BURNS, DOANE, SWECKER & MATHIS, L.L.P.
P.O. Box 1404
Alexandria
VA
22313-1404
US
|
Family ID: |
25534381 |
Appl. No.: |
09/988666 |
Filed: |
November 20, 2001 |
Current U.S.
Class: |
148/242 ;
148/240; 75/252 |
Current CPC
Class: |
C22C 1/0433 20130101;
C23C 24/10 20130101; C23C 26/02 20130101; C22C 32/0052 20130101;
C23C 8/64 20130101 |
Class at
Publication: |
148/242 ;
148/240; 75/252 |
International
Class: |
C23C 022/70 |
Claims
1. A nickel based powdered metallic material comprising in addition
to nickel 0-4.5% by weight of copper, 0-5.0% by weight of iron,
whereby the total amount of copper and iron is at least 2.5% by
weight, 0.05-5.0% by weight of a carbide forming element, 0.5-2.0%
by weight of boron, 1.0-4.0% by weight of silicon, 0.5-4.0% by
weight of phosphorus, 0.01-0.5% by weight of C and less than 2% by
weight of inevitable impurities.
2. Material according to claim 1, including copper in an amount of
2.5-4.5% by weight
3. Material according to claim 1 or 2 claim, wherein the powdered
metallic material comprises less than 3.0 wt % iron.
4. Material according to claim 1 wherein the carbide forming
element is selected from the group consisting of chromium,
tungsten, molybdenum, vanadium, tantalum, niobium, titanium and
zirconium.
5. Material according to any of the preceding claims, wherein the
powdered metallic material preferably comprises 0.05-1.0% by weight
of a carbide forming element.
6. Material according to any of the preceding claims, wherein the
powdered metallic material preferably comprises 1.0-5.0% by weight
of carbide forming element.
7. Material according to any of the preceding claims, wherein the
powdered metallic material preferably comprises 0.6-1.6% boron and
1.6-3.5% silicon.
8. Material according to any of the preceding claims, wherein the
powdered metallic material preferably comprises 1.5-3.0 wt %
phosphorous.
9. Material according to any of the preceding claims, wherein the
powdered metallic material preferably comprises 0.01-0.5% by weight
of carbon and preferably less than 0.3% by weight.
10. Material according to any of the preceding claims, wherein the
powdered metallic material is a homogenous alloy.
11. Material according to any of the preceding claims, wherein the
powdered metallic material is a gas atomized powder or a water
atomized powder.
12. A method of forming a wear resistant surface coating on a cast
iron substrate, comprising the steps of providing a nickel based
powdered metallic material comprising in addition to nickel 0-4.5%
by weight of copper, 0-5.0% by weight of iron, whereby the total
amount of copper and iron is at least 2.5% by weight, 0.05-5.0% by
weight of a carbide forming element, 0.5-2.0% by weight of boron,
1.0-4.0% by weight of silicon, 0.5-4.0% by weight of phosphorus,
0.01-0.5% by weight of C and less than 2% by weight of inevitable
impurities, optionally preheating the substrate to a temperature in
the range of 300-800.degree. C.; and applying and melting at least
one layer of the powdered metallic material onto the substrate by
means of thermal coating, whereby formation of carbide occurs on
the surface of the substrate.
13. The method according to claim 12, wherein thermal coating
includes the use of powder welding or plasma transferred arc
welding.
14. The method according to claim 1, wherein thermal coating
includes the use of a equipment providing a fusing temperature of
850-910.degree. C.
Description
TECHNICAL FIELD
[0001] The present invention relates to protective coatings.
Specifically the invention concerns hard, ductile, corrosion, wear
and oxidation resistant surface coatings which can applied on
substrates by thermal coating.
BACKGROUND OF THE INVENTION
[0002] It is generally known to provide surfaces subjected to harsh
conditions such as excessive wear, corrosive environment etc with
protective coatings. The coatings are applied in the form of
powdered materials by methods such as thermal spraying and plasma
arc welding etc. Depending on the final use of the coated substrate
a large variety of powdered metallic materials have been
developed.
[0003] The base element of the powdered material is frequently
nickel and a common alloy system used is nickel alloyed with
silicon and boron. In order to make the powder melt at a lower
temperature the powdered material may include phosphorous as is
disclosed in the U.S. Pat. Nos. 4,231,793 and 5,234,510.
[0004] A problem with these powders, especially when it is desired
to apply the coating rapidly using a high energy input, is that the
molten powder, when applied to the substrate, has too low viscosity
which in turn results in difficulties to restrict the melt on a
specific surface area of the substrate. According to the present
invention it has been now found that this problem may be minimized
or even eliminated by adding controlled amounts of copper or iron
to the powdered material which is to be applied on the
substrate.
[0005] The use of copper in connection with protective coatings
intended for copper based substrates is disclosed in U.S. Pat. No.
5,496,391. According to this patent the copper should be added in
amounts above 5% by weight and even up to 30% by weight in order to
avoid problems related to poor wettability of the copper containing
substrate and poor machinability.
[0006] According to the present invention it has been found that
powdered materials including less than 5% have a beneficial effect
on the viscosity of the molten powder whereas copper additions
above 5% by weight markedly deteriorates the appearance of the
surface coating which is unacceptable.
[0007] An essential feature of the present invention is also the
inclusion of carbide forming elements in the powdered material. The
inclusion of small amounts of such elements will make the final
coating more ductile which is believed to depend on a phenomenon
generally referred to as grain size refinement. With higher amounts
of carbide forming element it is also possible to get coatings
having improved hardness.
SUMMARY OF THE INVENTION
[0008] In brief the present invention thus concerns a nickel based
powdered metallic material comprising in addition to nickel, less
than 5% by weight of copper, less than 5.0% by weight of iron, a
carbide forming element, boron, silicon, phosphorus carbon and
inevitable impurities.
DETAILED DESCRIPTION OF THE INVENTION
[0009] Specifically the present invention concerns a nickel based
powdered metallic material comprising, in addition to nickel,
0-4.5% by weight of copper, 0-5.0% by weight of iron, whereby the
total amount of copper and iron is at least 2.5% by weight,
0.05-5.0% by weight of a carbide forming element, 0.5-2.0% by
weight of boron, 1.0-4.0% by weight of silicon, 0.5-4.0% by weight
of phosphorus, 0.01-0.5% by weight of C and less than 2% by weight
of inevitable impurities.
[0010] Effect of Copper and Iron
[0011] It the amount of Cu is less than 2.5 percent effect on the
viscosity has shown to be too low, resulting in great demands on
the skill of the person applying the powder to the substrate. On
the other hand, if the amount of copper is larger than 4.5% the
appearance of the surface coating will deteriorate, which makes it
difficult to apply several layers. If the viscosity is still too
low i.e. with the addition of 4.5% of Cu we have found that iron
may be added in order to increase the viscosity and thus make it
possible to obtain uniform layers without deteriorating the
appearance of the final surface coating layer. In such a case the
amount of iron should be less than 5.0 percent and preferably less
than 3.0 percent. It has also been found that the copper could be
replaced by iron. However the total amount of copper and iron
should not be less than 2.5% in order to reach the beneficial
effects on the viscosity.
[0012] Effect of Carbide Forming Elements
[0013] Another essential feature of the powder according to the
present invention is the presence of carbide forming elements.
These carbide forming elements may be selected from the group
consisting of chromium, tungsten, molybdenum, vanadium, tantalum,
niobium, titanium and zirconium and manganese. Without being bound
to any specific theory it is believed that small amounts of these
elements, such as 0.05-1.0% results in grain size refinement of the
structure of the final coating. The key feature of inoculation is
related to the nucleation during solidification. The inoculants
consist of the precipitated carbides. The obtained structure will
be finer which is advantageous as the obtained coating will have a
high ductility. This will also slightly increase the hardness.
Comparatively high additions of carbide forming elements, such as
between 1.0-5.0% by weight, will increase the hardness and wear
resistance but this will also make the machinablity of the applied
surface coating more difficult. Thus the amount of carbide forming
element should vary between 0.05-5.0% by weight.
[0014] In the event that the substrate to be provided with the
surface coating is cast iron, the carbides may be formed in situ,
i.e. the formation of carbides occurs by picking up carbon from the
substrate. Thus, when the powdered metallic material is applied to
the cast iron substrate surface, the carbide forming element reacts
with the carbon in the substrate resulting in the formation of
carbide, by way of example chromium carbide. In this case the
powdered material to be applied on the substrate includes a metal
such as those listed above which have an high affinity to the
carbon of the cast iron substrate. This must be taken into account
when designing the metal powder due to the fact that cast iron is
frequently used and comparatively inexpensive.
[0015] Furthermore, in the case that the substrate is cast iron the
amount and type of carbides formed during the application process
depends on the temperature provided, since the amount of carbon
that is set free during the application depends on the temperature
conditions on the substrate. The higher temperature, the more
carbon is set free, and accordingly a larger amount of carbide is
formed. It should be understood that other parameters also
influencing the carbide formation are, by way of example, the time
that the substrate is being heated during the application and the
distance between the heating source and the substrate surface.
Further, the preferred temperature depends of the carbide forming
element used. By way of example, if chromium is used, the preferred
temperature at the heating source, i.e. the fusing temperature is
850-910.degree. C. Accordingly, it is essential for the invention
that the amount of carbide and thus the hardness of the coating can
be controlled by not only the choice and amount of carbide forming
element but also the fusing temperature provided during the
application.
[0016] Effect of Carbon
[0017] The carbon is used in amounts between 0.01-0.5% by weight.
Carbon together with the carbide forming element precipitates as
carbides in the surface coating. The amount of carbides is related
to the amount of carbon and carbide forming elements.
[0018] Effect of Boron and Silicon
[0019] The addition of boron and silicon is used for increasing the
wettability but also for lowering the melting point. Also, the
combination of boron and silicon works as a fluxing agent. Further
the addition of silicon adds oxidation resistance to the coating.
The amount of boron is 0.5-2.0, preferably 0.6-1.6% by weight of
the composition. The amount of silicon is 1.0-4.0, preferably
1.6-3.5% by weight.
[0020] Effect of Phosphorous
[0021] The amount of phosphorous is 0.5-4.0, more preferably
1.5-3.0 percent. The main purpose of the addition of phosphorous is
lowering the melting point of the powdered metallic material. The
amount is preferably sufficient for achieving a melting temperature
affordable for the coating to be applicable by means of
conventional methods such as powder welding. The present
composition of the powdered metallic material has shown to provide
a melting temperature of around 850.degree. C. which can be
compared with around 1050.degree. C. without phosphorous. Before
applying the powdered material onto the substrate it is preferred
to preheat the substrate to a temperature in the range of
300-800.degree. C.
[0022] The surface coatings are generally applied to the substrate
on a specific wear exposed area or over an entire surface. The
coating is thereafter machined for supplying a true gauge surface
or a desired texture. Thus, it is of great importance that the
coating although providing the desired hardness can be machined
using conventional equipment.
[0023] The application of the surface coating can be performed
manually or be automatized, and irrespective of method chosen it is
a generally known problem that there sometimes are problems when
building layers of large thickness as the viscosity in the weld
pool might be to low. The low viscosity results in dripping effects
which makes high demands on the skill of the person performing the
application. On the other hand, if the viscosity in the weld pool
is too high it is difficult applying even layers.
[0024] The melting temperature of the used powdered metallic
material must in addition not be too high, since the available
maximum fusing temperature with conventional equipment is limited
and the melting temperature of the substrate must also be taken
into account. The melting temperature is also important since a
reasonable melting temperature provides the possibility of speeding
up the application process.
[0025] When the carbide forming element is present in the upper
part of the above range a coating that is machinable but still
provides sufficient hardness to withstand the harsh conditions
prevailing in e.g. glass moulds.
[0026] The powder composition also includes carbon. The amount of
carbon is decided by the required properties of the final coating.
Thus if the substrate is cast iron carbon from this substrate may
diffuse from the cast iron into the coating and the prealloyed
carbon will be set lower.
[0027] The powdered metallic material is manufactured by
conventional methods such as water atomization or gas atomization.
The particle size is adapted to the application method being used.
By way of example, if the powder is applied by powder welding the
particle size is often in the range of 20-106 .mu.m. On the other
hand, if the powder is applied by PTA, the particle size is often
in the range of 45-150 .mu.m.
[0028] To enhance the wettability and to better control the
formation of carbides the substrate is preheated before application
of the powdered material. The preheating is preferably uniform
throughout the thickness of the substrate and is thus suitable
performed in an oven. The temperature can be varied depending on
e.g. the purpose of the coating and available equipment. Generally
the temperature interval is 300-800.degree. C. The preheating
reduces the affordable application time since the melting of the
applied powder on the substrate surface occurs faster. On the other
hand, the affordable time can also be reduced by e.g. increasing
the fusing temperature.
EXAMPLES
[0029] The invention is further illustrated by, but should not be
limited to, the following preparations and examples.
Example 1
[0030] A powdered metallic material of the composition according to
table 1 below was prepared by gas atomization and applied on a cast
iron substrate containing 3.2% by weight of carbon and also on a
substrate of mild steel having a carbon content of about 0.1% by
weight. The hardness KV30 of the coating on the cast iron substrate
was 299, whereas the hardness of the coating on the mild steel
substrate was 280. The higher hardness of the coating on the cast
iron substrate results from the carbon pick up from the cast
iron.
1 TABLE 1 Composition % by weight Cu 3.9 Fe 0.1 Cr 0.2 B 0.9 Si 2.2
P 2.1 C 0.03 Ni Bal Impurities <1.0
[0031] Additionally the powdered material having the above
composition could be applied at high temperature without problems
because of the relatively high viscosity. The wettablilty to the
substrates, cast iron and mild iron, was without remark. Also the
appearance of the final coatings was acceptable.
Example 2
[0032] A powdered material having the composition according to
table 2 was prepared.
2 TABLE 2 Composition % by weight Cu 1.7 Fe 1.5 Cr 4.9 B 1.2 Si 3.1
P 1.9 C 0.17 Ni Bal. Impurities <1
[0033] Also this powder was prepared by gas atomization. The
hardness HV30 of the coating on the cast iron substrate was 402,
whereas the hardness of the coating on the mild steel substrate was
380. Thus also in this case an effect of the pick up of carbon from
the cast iron substrate could be observed. Furthermore, as in the
previous example, the powder was applied at high temperature and
the viscosity was sufficiently high for applying the coating
without problems. The wettablity to both the substrates was quite
acceptable as was the machinability of the coatings.
* * * * *