Referring now to the figures, which are exemplary embodiments and wherein like elements are numbered alike:
a)-3(c) schematically illustrate three embodiments of the interior surface coating of the mold plate from
a) and 4(b) schematically illustrate a mold having a composite coating disposed on a surface of the mold, wherein the coating comprises a metallic matrix and particles dispersed in the metallic matrix; and
a)-6(c) schematically illustrate three embodiments of a copper mold plate coated in three different ways with variable coating thicknesses corresponding to respective sections of the mold plate;
Copper-based molds with enhanced surface properties and methods of making and using the same are described. In particular the molds include a mold member and a coating disposed on at least a portion of a surface of the mold member for enhancing the surface properties of the mold. The surface coating can be designed based on achieving physical and mechanical property matches between the coating materials and the copper-based mold. For example, the coating can have a coefficient of thermal expansion (CTE) equivalent to or slightly less than that of copper (i.e. about 10×10−6/° C. to about 16.5×10−6/° C.) and a Vickers Hardiness Number (HV) significantly greater than that of copper (i.e., greater than about 500 and less than about 1200) at a mold surface temperature of less than or equal to about 600° C. This temperature is based on what the mold can be exposed to during a continuous or semi-continuous casting process in a steel mill. The coating can also have higher corrosion resistance, erosion resistance (including sliding wear resistance), and/or higher tensile strength than does copper. The coating can also be capable of promoting uniform heat flow and can act as an inter-diffusion barrier that prevents migration of the copper out of the mold and adjacent materials into the mold. Other desirable properties of the coating include a relatively high thermal conductivity, a relatively high temperature stability, and a relatively high anti-sticking capability. Enhancing the interior surface of a mold in this manner can significantly increase the service lifetime of the mold.
As used herein, the term “mold” refers to any structure used to form a material positioned in an interior of the mold into a desired shape that remains after the material is removed from the mold. Examples of molds include but are not limited to casting molds, dies, inserts, and the like utilized in casting, molding, or extrusion processes. Also, the term “copper” refers to any metallic composition comprising copper such as pure copper, copper alloys and the like. It is understood that the coating design can be adjusted for other types of non-copper containing molds as well.
Turning now to the figures,
One consideration for the surface coating design is based on matching the CTE's of the copper-based mold and the coating materials. Copper has a high CTE of about 16.5×10−6/° C. Alloys such as certain Fe-based alloys, Ni-based alloys, and Co-based alloys have CTE's slightly lower than that of copper (i.e., about 9×10−6/° C. to about 14×10−6/° C.) and are therefore exemplary candidates as coating materials from the viewpoint of a coefficient of thermal expansion match.
Another consideration for the surface coating design is based on the hardness of the coating materials at application temperatures. The hardness of a material can be related to its mechanical properties such as wear resistance and creep strength. The Vickers Hardness Number (HV) values of some materials that might serve as mold coating materials are given in Table I below. At room temperature (R.T.), all of the materials shown in Table I (except copper) have much higher hardness values than copper. However, at 500° C., the plated Cr, Ni—P, Ni—Co, and Fe—Ni materials exhibit a significant reduction in hardness values, whereas the other alloys (e.g., other Ni-based alloys and Co-based alloys) and WC/Co maintain high hardness values at the high temperature. Such alloys are therefore exemplary candidates as coating materials from the viewpoint of hardness.
Additional consideration for the surface coating design are based on the corrosion and erosion resistances (including sliding wear resistance) of the coating materials. Corrosion of the mold surface can be caused by, e.g., oxidation and/or sulfidation of the surface. Table 2 illustrates the corrosion resistance of various coating materials. The corrosion resistance of copper is relatively low. Of the materials shown in Table 2, only the other alloys (e.g., other Ni-based alloys and Co-based alloys) and WC/Co have high corrosion resistance, making them exemplary candidates as coating materials.
Turning now to
Alternatively, the coating 50 can have a higher hardness and a higher corrosion resistance than does copper but not a CTE near that of copper at a temperature less than or equal to about 600° C. Examples of coating materials having these properties include but are not limited to a WC—Co alloy, a WC—CoCr alloy, a Ni—Cr2C3 alloy, a NiCr—Cr2C3 alloy, and combinations comprising at least one of the foregoing.
In
In another embodiment, a graded compositional or multi-layered coating can be disposed on an interior surface of the mold 10. The HV, the creep strength, the corrosion resistance, the erosion resistance, and/or the wear resistance of a coating comprising a graded composition can increase with distance from the surface. Similarly, the HV, the creep strength, the corrosion resistance, the erosion resistance, and/or the wear resistance of a coating comprising two or more layers can increase from one layer to the next in a direction away from the surface. For example, as shown in
a) and 4(b) illustrate another embodiment of the coatings shown in
The addition of the particles 80 is also expected to bring an effect of dispersion strengthening to the matrix 90. The particles 80 can have a higher thermal conductivity, a higher lubricity, and/or a higher hardness than that of the matrix 90. For example, the particles 80 can include a lubricating additive, a thermally conductive additive, a hard additive, or a combination comprising at least one of the foregoing additives. The addition of thermally conductive additives is expected to improve heat flow uniformity and cooling efficiency, and the addition of lubricating additives and hard additives is expected to improve surface resistance to erosion and sticking. Examples of suitable lubricating additives include but are not limited to BN, MoSi2, FeS, CaF2, graphite, B4C, and combinations comprising at least one of the foregoing. Examples of suitable thermally conductive additives include but are not limited to WC, TiN, AlN, Si3N4, and combinations comprising at least one of the foregoing. Examples of suitable hard additives include but are not limited to WC, Cr2C3, TiC, SiC, TiB2, ZrB2, and combinations comprising at least one of the foregoing.
a)-6(c) illustrate three additional embodiments of a plate of a copper-based mold 10. In
The foregoing copper-based mold can be made in accordance with the exemplary process illustrated in
In an exemplary embodiment, thermal spraying technology can be utilized to form the surface coating in step 180. Examples of thermal spray processes include electric arc spray, combustion flame spray, detonation spray, plasma spray, high velocity oxygen (air) fuel (HVOF) spray, cold spray, and the like. Plasma spraying and HVOF spraying can advantageously produce high quality coatings having high adhesion and cohesion strengths, high density, and less oxide inclusions. These processes involve forming a feedstock comprising solid particles or an agglomeration of particles (e.g., superfine particles and/or nanoparticles) and feeding the feedstock into a high velocity flame, such as a plasma arc or HVOF flame, generated by the ionization or combustion of a mixture of gases, respectively. As a result, the feedstock melts and impacts on the target substrate to form a coating thereon. Modified plasma spray and HVOF spray processes can also be used to form the coating. For example, plasma spraying and HVOF spraying using liquid suspensions comprising fine particles of INCONEL® 625 NiCrMo alloy and self-flux NiCrSiB alloy (commercially available from powder vendors such as Praxair Surface Technology) can produce highly bonded and fine-grained coatings as shown in the examples below. Additional disclosure related to modified HVOF spray processes can be found in concurrently owned U.S. Patent Application Ser. No. 60/826,663 to Ma et al., filed on Sep. 22, 2006, which is incorporated by reference herein. With thermal spraying techniques, coatings of large thicknesses (e.g., greater than 1 mm) can be built at a relatively high deposition rate. In principle, thermal spraying has no limit in the dimension of the coated area and is therefore suitable for coating large molds.
The thermally sprayed coatings can be exposed to post treatments as described above in step 190. For example, a thermally sprayed NiCrSiB self-fluxing alloy coating can be refused at a temperature of about 1000° C. in a vacuum or inert gas filled chamber. The refusing treatment can result in a fully dense coating and a strong metallurgical bond between the coating and the substrate. Also, open pores and micron-sized cracks in the thermally sprayed coatings can be sealed with suitable sealants, such as Al, Cr phosphates, colloided SiO2 and sodium silicate, applied to the pores and cracks in solution form. After the evaporation or thermal decomposition of the sealant solution at a high temperature, the sealant material most likely will fill the pores and cracks. The corrosion resistance, strength, and likely the anti-sticking property of the sealant can be improved. Further, as indicated in step 200, the thermally sprayed coating can be machined to a desired surface roughness, configuration, and coating thickness by, e.g., cutting, grinding, honing, and polishing.
In another exemplary embodiment, PVD can be utilized to form the surface coating in step 180. PVD processes such as sputtering can produce high quality coatings having a high bonding strength, a high density, and a smooth surface. With a multi-source/target setup, PVD can readily produce multi-layered or graded coating structures. However, technically and economically, the use of PVD can be limited by a small processing chamber relative to the dimension of the mold to be coated and low coating thickening rates.
In still another exemplary embodiment, the surface coating can be fortified in step 180 by composite electroplating. In comparison to a current electroplating process, a composite electroplating process is capable of incorporating superfine particles and nanoparticles (metal, alloy, ceramic, or metal-ceramic composite particles) into a metallic matrix layer to form coatings like those shown in
The invention is further illustrated by the following non-limiting examples.
In this example, HVOF spraying was used to deposit a single layered coating of INCONEL® 625 particles onto a copper substrate. HVOF process parameters for the coating are given below:
The coating properties are listed below:
Coating porosity: <2%
In this example, HVOF spraying was used to deposit a single layered coating of a self-flux alloy onto a copper substrate. The HVOF process parameters for the coating are given below:
The coating properties are listed below:
Coating porosity: <1%
In this example, HVOF spraying was used to deposit a single layered coating of WC/Co onto a copper substrate. The as-sprayed coating was ground and polished to reduce its surface roughness from about 4.5 microns to about 1.0 micron. It was then sealed with a sodium silicate solution comprising BN at a temperature of about 550° C. The HVOF process parameters for the coating are given below:
The coating properties are listed below:
Coating porosity: <1%
In this example, modified HVOF spraying of a liquid suspension comprising INCONEL® 625 particles of less than 11 microns in size was used to deposit a single layered coating onto a copper substrate along with AlN dispersed therein. The HVOF process parameters for the coating are given below:
The coating properties are listed below:
Coating porosity: <1%
In this example, HVOF spraying was used to deposit a double layered coating comprising a bondcoat of Al and a topcoat of INCONEL® 625 onto a copper substrate. The HVOF process parameters for the coating are given below:
The properties of the bondcoat and topcoat are listed below:
Coating porosity: <1%
Coating porosity: <2%
In this example, HVOF spraying was used to deposit a double layered coating comprising a bondcoat of Al and a topcoat of a self-flux alloy onto a copper substrate. The HVOF process parameters for the coating are given below:
The properties of the topcoat are listed below:
Coating porosity: <1%
In this example, HVOF thermal spraying was used to deposit a double layered coating comprising a bondcoat layer of Ni and a topcoat layer of a self-flux alloy onto a copper substrate.
The properties of the bondcoat and topcoat are listed below:
Coating porosity: <1%
Coating porosity: <1%
In this example, HVOF spraying was used to deposit a double layered coating comprising a bondcoat of Ni and a topcoat of a self-flux alloy and WC/Co onto a copper substrate. The HVOF process parameters for the coating are given below:
The properties of the composite topcoat are listed below:
Coating porosity: <1%
In this example, electroplating was used to deposit a double layered coating comprising a bondcoat of Ni and a topcoat of a Ni/WC composite onto a Cu substrate.
The Cu substrate was sand blasted, degreased, neutralized, and activated. After activation, the Cu substrate was immersed into a nickel sulphamate bath where the anode was Ni and the cathode was the Cu substrate. An electrodeposition current was applied to the bath and monitored using an amperometer with an accuracy of 0.1 milliAmpere (mA) under a controlled temperature and acid concentration. The deposition parameters included: a plating ply of 2.7, a machine unit stirring value of 60, and a current density of 20 amperes/foot squared (A/ft2). The plating was performed at 20 to 50 A/ft2. The thickness of the coating depended on the plating time.
After the first Ni layer was plated, the sample was quickly transferred into a Ni/WC plating bath. The sample was transferred when everything was ready to start plating (i.e., electrolyte up to temperature, stirrer on and out of the way of where the sample will be, hooks/suspension clips ready to receive the sample, power supply on and turned to a low value such as about 10% of the estimated plating current, etc.). A film of nickel electrolyte on the sample was maintained during the transfer to prevent air oxidation of the sample surface. The sample was immersed in the plating bath (i.e., electrolyte) such that all surfaces to be plated were below the electrolyte surface. The sample was kept well covered with electrolyte, and a good flow of electrolyte at and by the sample was maintained.
Once the sample was positioned satisfactorily, the plating current was slowly raised to as high as possible to help the electrophoresis effect on the WC nanoparticles that are deposited. The current was raised over a period of 15 to 30 seconds to the desired plating current. The plating time depended on the desired thickness of the plated layer. After plating, the current was reduced to about zero. The sample was then removed, washed, and inspected.
The resulting coating had a thickness ranging from a few microns to a few hundred microns and a coating hardness ranging from 400 to 900 HV. The volume fraction of the WC phase depended on the amount of WC particles dispersed into the bath at a given volume. It ranged from 10 g/L to 100 g/L concentration.
In this example, electroplating was used to deposit a double layered coating comprising a bondcoat of Ni and a topcoat of a Ni/Cr2O3 composite onto a Cu substrate.
The Cu substrate was sand blasted, degreased, neutralized, and activated. After activation, the Cu substrate was immersed into a nickel sulphamate bath where the anode was Ni and the cathode was the Cu substrate. An electrodeposition current was applied to the bath and monitored using an amperometer with an accuracy of 0.1 mA, under a controlled temperature and acid concentration. The deposition parameters included: a plating pH of 2.7, a machine unit stirring value of 60, and a current density of 20 A/ft2. The plating was performed at 20 to 50 A/ft2. The thickness of the coating depended on the plating time.
After the first Ni layer was plated, the sample was quickly transferred into a Ni/Cr2O3 plating bath. The sample was transferred when everything was ready to start plating (i.e., electrolyte up to temperature, stirrer on and out of the way of where the sample will be, hooks/suspension clips ready to receive the sample, power supply on and turned to a low value such as about 10% of the estimated plating current, etc.). A film of nickel electrolyte on the sample was maintained during the transfer to prevent air oxidation of the sample surface. The sample was immersed in the plating bath such that all surfaces to be plated were below the electrolyte surface. The sample was kept well covered with electrolyte, and a good flow of electrolyte at and by the sample was maintained.
Once the sample was positioned satisfactorily, the plating current was slowly raised to as high as possible to help the electrophoresis effect on the Cr2O3 nanoparticles that are deposited. The current was raised over a period of 15 to 30 seconds to the desired plating current. The plating time depended on the desired thickness of the plated layer. After plating, the current was reduced to about zero. The sample was then removed, washed, and inspected.
The topcoat layer was a composite coating of Ni/Cr2O3. The resulting had a thickness ranging from a few microns to a few hundred microns and a coating hardness ranging from 400 to 900 HV. The volume fraction of the Cr2O3 phase depended on the amount of Cr2O3 particles dispersed into the bath at a given volume. It ranged from 10 g/L to 100 g/L concentration.
In this example, electroplating was used to deposit a double layered coating comprising a bondcoat of Ni and a topcoat comprising BN particles dispersed in a Ni/Cr2O3 matrix onto a Cu substrate.
The Cu substrate was sand blasted, degreased, neutralized, and activated. After activation, the Cu substrate was immersed into a nickel sulphamate bath where the anode was Ni and the cathode was the Cu substrate. An electrodeposition current was applied to the bath and monitored using an amperometer with an accuracy of 0.1 mA, under a controlled temperature and acid concentration. The deposition parameters included: a plating pH of 2.7, a machine unit stirring value of 60, and a current density of 20 A/ft2. The plating was performed at 20 to 50 A/ft2. The thickness of the coating depended on the plating time.
After the first Ni layer was plated, the sample was quickly transferred into a BN/Cr2O3/Ni plating solution. The sample was transferred when everything was ready to start plating (i.e., electrolyte up to temperature, stirrer on and out of the way of where the sample will be, hooks/suspension clips ready to receive the sample, power supply on and turned to a low value such as about 10% of the estimated plating current, etc.). A film of nickel electrolyte on the sample was maintained during the transfer to prevent air oxidation of the sample surface. The sample was immersed in the plating bath such that all surfaces to be plated were below the electrolyte surface. The sample was kept well covered with electrolyte, and a good flow of electrolyte at and by the sample was maintained.
Once the sample was positioned satisfactorily, the plating current was slowly raised to as high as possible to help the electrophoresis effect on the Cr2O3 and BN nanoparticles. The current was raised over a period of 15 to 30 seconds to the desired plating current. The plating time depended on the desired thickness of the plated layer. After plating, the current was reduced to about zero. The sample was then removed, washed, and inspected.
The resulting coating had a thickness ranging from a few microns to a few hundred microns and a coating hardness ranging from 400 to 700 HV. The volume fraction of the BN+Cr2O3 phase depended on the amount of BN+Cr2O3 particles dispersed into the bath at a given volume. It ranged from 10 g/L to 100 g/L concentration.
In this example, electroplating was used to deposit a double layered coating comprising a bondcoat of Ni and a topcoat of a SiC/Ni composite onto a Cu substrate.
The Cu substrate was sand blasted, degreased, neutralized, and activated. After activation, the Cu substrate was immersed into a nickel sulphamate bath where the anode was Ni and the cathode was the CLl substrate. An electrodeposition current was applied to the bath and monitored using an amperometer with an accuracy of 0.1 mA, under a controlled temperature and acid concentration. The deposition parameters included: a plating pH of 2.7, a machine unit stirring value of 60, and a current density of 20 amp/ft2. The plating was performed at 20 to 50 A/ft2. The thickness of the coating depended on the plating time.
After the first Ni layer was plated, the sample was quickly transferred into a SiC/Ni plating solution to deposit a SiC/Ni composite layer on the Ni bondcoat layer. The sample was transferred when everything was ready to start plating (i.e., electrolyte up to temperature, stirrer on and out of the way of where the sample will be, hooks/suspension clips ready to receive the sample, power supply on and turned to a low value such as about 10% of the estimated plating current, etc.). A film of nickel electrolyte on the sample was maintained during the transfer to prevent air oxidation of the sample surface. The sample was immersed in the plating bath such that all surfaces to be plated were below the electrolyte surface. The sample was kept well covered with electrolyte, and a good flow of electrolyte at and by the sample was maintained.
Once the sample was positioned satisfactorily, the plating current was slowly raised to as high as possible to help the electrophoresis effect on the SiC nanoparticles. The current was raised over a period of 15 to 30 seconds to the desired plating current. The plating time depended oil the desired thickness of the plated layer. After plating, the current was reduced to about zero. The sample was then removed, washed, and inspected.
The resulting coating had a thickness ranging from a few microns to a few hundred microns and a coating hardness ranging from 400 to 900 HV. The volume traction of the SiC phase depended on the amount of SiC particles dispersed into the bath at a given volume. It ranged from 10 g/L to 100 g/L concentration.
In this example, electroplating was used to deposit a double layered coating comprising a bondcoat of Ni and a topcoat of a B4C/Ni composite onto a Cu substrate.
The Cu substrate was sand blasted, degreased, neutralized, and activated. After activation, the Cu substrate was immersed into a nickel sulphamate bath where the anode was Ni and the cathode was the Cu substrate. An electrodeposition current was applied to the bath and monitored using an amperometer with an accuracy of 0.1 mA, under a controlled temperature and acid concentration. The deposition parameters included: a plating pH of 2.7, a machine unit stirring value of 60, and a current density of 20 A/ft2. The plating was performed at 20 to 50 A/ft2. The thickness of the coating depended on the plating time.
After the first Ni layer was plated, the sample was quickly transferred into a B4C/Ni plating solution to deposit a B4C/Ni composite layer on the Ni bondcoat layer. The sample was transferred when everything was ready to start plating (i.e., electrolyte up to temperature, stirrer on and out of the way of where the sample will be, hooks/suspension clips ready to receive the sample, power supply on and turned to a low value such as about 10% of the estimated plating current, etc.). A film of nickel electrolyte on the sample was maintained during the transfer to prevent air oxidation of the sample surface. The sample was immersed in the plating bath such that all surfaces to be plated were below the electrolyte surface. The sample was kept well covered with electrolyte, and a good flow of electrolyte at and by the sample was maintained.
Once the sample was positioned satisfactorily, the plating current was slowly raised to as high as possible to help the electrophoresis effect on the B4C particles. The current was raised over a period of 15 to 30 seconds to the desired plating current. The plating time depended on the desired thickness of the plated layer. After plating, the current was reduced to about zero. The sample was then removed, washed, and inspected.
The resulting coating had a thickness ranging from a few microns to a few hundred microns and a coating hardness ranging from 400 to 900 HV. The volume fraction of the B4C phase depended on the amount of B4C particles dispersed into the bath at a given volume. It ranged from 10 g/L to 100 g/L concentration.
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. 60/862,040 filed Oct. 18, 2006, which is incorporated by reference herein in its entirety.
Number | Date | Country | |
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60862040 | Oct 2006 | US |