Patent Application
20080093350
Referring now to the figures, which are exemplary embodiments and wherein like elements are numbered alike:
a)-1(d) are schematic illustrations of various embodiments of cored wires having a core comprising agglomerates of nanoparticles and/or superfine particles;
Described herein are cored wires comprising a metallic sheath at least partially surrounding a core that includes agglomerates of superfine particles, nanoparticles, or a combination comprising at least one of the foregoing particles. As used herein, the term “superfine particles” refers to particles having a grain size of about 100 nanometers (nm) to about 1 micrometer (micron), more specifically about 100 nm to about 0.5 micron, and even more specifically about 100 nm to about 0.3 micron. Moreover, the term “nanoparticles” refers to particles having a grain size of less than about 100 nm, more specifically less than about 50 nm, and even more specifically less than about 20 nm.
The wires can be used in thermal spraying processes, such as electric arc spray, combustion flame spray, and plasma spray, and in overlay welding processes to form coatings on components that exhibit superior resistance to wear, cavitation, erosion, corrosion, high temperature oxidation, hot corrosion, and/or sulphidation. The resultant coatings also can have improved hardness, adhesion, toughness, strength, and lubrication properties. Industrial applications of such coatings include slurry pumps, ball valves, gate valves, drill bits, bear seats, pistons, exhausting fans, chutes, plows, shafts, agitators, mineral and ash-handing equipment, rollers, boiler tubes and fire walls.
Turning now to the Figures,
b) depicts another embodiment similar to the one shown in
c) depicts yet another embodiment similar to the one shown in
d) depicts still another embodiment similar to the one shown in
In an additional embodiment, the core filling described in the foregoing embodiments can include multimodal agglomerates comprising micron-sized particles in addition to the superfine particles and/or nanoparticles. The agglomerates can have an average size of about 10 microns to about 200 microns, more specifically about 10 microns to about 100 microns, and even more specifically about 20 microns to about 60 microns.
An exemplary embodiment of a process for manufacturing the cored wires is illustrated in
The next part of the process involves degreasing, cleansing, and drying a metallic strip, followed by shaping or bending the strip into a U-shaped tube using suitable forming rollers (step 60). Subsequently, the U-shaped tube can be fed to a die, and the agglomerates can be concurrently fed to an interior of the U-shaped tube at a constant feeding rate via a powder feeder and a powder port (step 70). The U-shaped tube can then be closed to form a sheath at least partially surrounding the agglomerates via rotation of a pair of screws disposed at the end of the die (step 80). The rotating screw set can also drive the feeding of the U-Shaped tube through the die. This step can gradually reduce the closed tube to a small diameter accompanying the high density packing of the core filling. The use of an integrated die device can ensure that the sheath is tightly closed just after it is filled and has a smooth surface and even diameter. The use of agglomerated powders as the fill material can provide for steady feeding into the U-shaped tube, thus increasing the packing density of the agglomerates in the cored wire. Finally, the resultant cored wire can be pulled through another die to reduce its diameter to a pre-selected diameter size (step 90). The process disclosed herein is applicable for making various types of cored wires disclosed herein.
To form the embodiment of the cored wire shown in
An exemplary embodiment of an integrated die device for making a cored wire is illustrated in
An electric arc spray process can be performed to form coatings for different applications. In particular, an electric arc can be induced between the tips of two wire electrodes to melt the electrodes, wherein one or both of the electrodes include a cored wire described herein. An air or gas jet can then be directed toward the molten electrodes to blow and atomize them into droplets and transfer the droplets toward a substrate where they can solidify. During the coating process, the sheath can melt and the inert agglomerated particles can become distributed into the metallic sheath matrix. The chemically active agglomerated particles can be thermally decomposed and alloyed with the molten sheath materials. The highly active agglomerated particles can produce exothermal heat during the spray process to promote melting, fluxing, and alloying of the wire materials. For example, flux flattening of the molten droplets on the substrate can be increased to form a less defective and highly bonded coating. The agglomerates can also act as active agents that cleanse and/or wet the substrate surface for creating a strong bond with the substrate surface. The coating that is produced can be further treated to improve its microstructure and properties. For example, it can be heat treated, sealed, re-melted, or subjected to shot peening.
As described previously, coatings formed using the foregoing cored wires have superior properties. The coatings can have a different composition, a different phase structured, and/or a different microstructure from the sheath and the core of the cored wire. For example, the coating can include a primary metallic phase and a secondary metallic-rich phase structure. It can also include, for example, a microstructure comprising a metallic phase matrix with superfine particles, nanoparticles, and/or other core particles. Different compositions of the coatings can be formed based on the properties desired. For better corrosion resistance, coatings including Fe, Co, or Ni-based alloys with high Cr, Al, Ti, Zn, Mo, Si, and/or B contents can be formed. For better wear resistance, coatings including Fe, Co, or Ni-based alloys with high Cr, W, Mo, Mn, and/or oxide contents can be formed. For better erosion resistance, coatings including Fe, Co, or Ni-based alloys with high oxide, carbide, and/or nitride contents can be formed. For better high temperature oxidation resistance, coatings including Fe, Ni, or Co-based alloys with high Cr, Al, Si, and/or Y contents can be formed. For better lubricity, coatings including Fe, Co, or Ni-based alloys with high Cr, Mn, Mo, B, FeS, MoSi2, and/or BN contents can be formed.
The invention is further illustrated by the following non-limiting examples.
A cored wire having an alloy sheath and a core comprising WC/Co agglomerates of superfine particles was prepared. This wire would be suitable for electric arc spraying high temperature (up to about 500° C.) wear resistant coatings. The size of the WC phase in the cermet (i.e., ceramic-metal) composite was in the range of 50 to 500 nm. In preparing the cored wire, as-synthesized WC/Co particles were agglomerated into spherical granules with a size of 20 to 60 microns in a reconstitution process of spray drying. An INCONEL® 625 Ni—Cr—Mo alloy strip was used to form the sheath. First, the strip was bent into a U-shaped tube through forming rollers and fed into a die. A powder feeder system was integrated with the die, and WC/Co granules were fed into the U-shape tube via a powder port. A screw-driven mechanism at the exit of the die closed the tube into a round sheath. Finally, the wire was pulled through a die to reduce its diameter to 1.6 to 2 millimeters (mm). The end and side views of the resultant cored wire are shown in
A cored wire having an alloy sheath and a composite core comprising WC/Co agglomerates of superfine particles and micron-sized Ni3Al particles was prepared. This wire would be suitable for electric arc spraying high-temperature oxidation resistant coatings. The size of the WC phase in the cermet composite was in the range of 50 to 500 nm. In preparing the cored wire, as-synthesized WC/Co particles were agglomerated into spherical granules with a size of 20 to 60 microns in a reconstitution process of spray drying. Ni3Al particles with a grain size of 10 to 50 microns were mechanically mixed with the WC/Co agglomerates. A Fe-20Cr alloy strip was used to form the sheath. First, the strip was bent into a U-shape tube through forming rollers and fed into a die. A powder feeder system was integrated with the die, and the mixture of WC/Co agglomerates and Ni3Al powder were fed into the U-shape tube via a powder port. A screw-driven mechanism at the exit of the die closed the tube into a round sheath. Finally, the wire was pulled through a die to reduce its diameter to 1.6 to 2 mm. The resultant cored wire was smooth, even in diameter, and had sufficient ductility and strength to be wound into a spool or a coil. The volume percentage of WC/Co and Ni3Al in the core of the wire is 60 to 70% and 30 to 40%, respectively. The microstructure cross-section of an electric arc sprayed coating 250 formed on a substrate 240 using the cored wire is shown in
Cored wires having an alloy sheath and a composite core comprising oxide agglomerates of nanoparticles and WC/Co agglomerates of superfine particles were prepared. Sequentially, the cored wires were made into coatings using an electric arc spray system sold by Praxair, Inc. Table I below lists the types of cored wires prepared and the process parameters for making them. The compositions are presented as weight percentages (wt. %). The oxide nanoparticles had a size range of about 20 to 50 nm, and the WC/Co superfine particles had a size range of about 100 to 300 nm. The electric arc spray parameters were determined by the shell/core materials and resultant coatings in terms of primarily coating porosity and bond strength. These parameters include voltage (V), current in amperes (A), spray distance (S.D.) in millimeters (mm), air pressure in pounds per squared inch (psi), and air flow rate in cubic feet per minute (cfm). The resultant coatings had a thickness of about 200 to 300 microns.
A cored wire having a bi-layered alloy sheath and a composite core comprising WC/Co agglomerates of superfine particles and lubricating particles was prepared. The size of the WC phase in the cermet composite was in the range of 50 to 500 nm. In preparing the cored wire, as-synthesized WC/Co particles were mechanically mixed with BN particles, and then the mixture was agglomerated into spherical granules with a size of 20 to 60 microns in a reconstitution process of spray drying. Ni3Al particles with a grain size of 10 to 50 microns were mechanically mixed with the WC/Co+BN agglomerates. An Al strip was used to form an inner sheath. First, the strip was bent into a U-shaped tube through forming rollers and fed into a die. A powder feeder system was integrated with the die, and the composite WC/Co+BN agglomerates were fed into the U-shaped Al tube via a powder port. A screw-driven mechanism at the exit of the die applied compression force to close the tube into a round shell. A Ni-20Cr strip was bent into a U-shaped tube, and then the Al-shelled wire was positioned in the center of the U-shaped tube. Next, the U-shaped alloy tube was closed through forming rollers and wrapped to form a bi-layered sheath wire. Finally, the wire was pulled through a die to reduce its diameter to 1.6 to 2 mm. The resultant cored wire was smooth, even in diameter, and had sufficient ductility and strength to be wound into a spool or a coil.
A cored wire having an alloy sheath and a composite core comprising WC/Co agglomerates of superfine particles and a fine wire was prepared. This wire would be suitable for electric arc spraying coatings that are resistant to high temperature oxidation and wear. The size of the WC phase in the cermet composite was in the range of 50 to 500 nm. In preparing the cored wire, as-synthesized WC/Co particles were agglomerated into spherical granules with a size of 20 to 60 microns in a reconstitution process of spray drying. A Ni-20Cr strip was used to form a sheath. First, the strip was bent into a U-shaped tube through forming rollers and fed into a die. Then, a fine Al wire having a diameter of 0.5 mm was positioned relative to the central line of the U-shaped tube. A powder feeder system was integrated with the die, and the WC/Co agglomerates were fed into the U-shaped tube with a central wire via a powder port. A screw-driven mechanism at the exit of the die applied a compression force to close the tube into a round sheath. Finally, the wire was pulled through a die to reduce its diameter to 1.6 to 2 mm. The resultant cored wire was smooth, even in diameter, and had sufficient ductility and strength to be wound into a spool or a coil.
As used herein, the terms “a” and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. Moreover, the endpoints of all ranges directed to the same component or property are inclusive of the endpoint and independently combinable (e.g., “about 5 wt % to about 20 wt %,” is inclusive of the endpoints and all intermediate values of the ranges of about 5 wt % to about 20 wt %). Reference throughout the specification to “one embodiment”, “another embodiment”, “an embodiment”, and so forth means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and might or might not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments. Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this invention belongs.
While the disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this disclosure, but that the disclosure will include all embodiments falling within the scope of the appended claims.
This application claims the benefit of U.S. Provisional Patent Application No. 60/862,039 filed Oct. 18, 2006, which is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60862039 | Oct 2006 | US |
