Method of manufacture of porous coated metallic substrate assemblies

Abstract

Methods for the fabrication of strongly adherent ceramic (e.g., titanium oxide such as TiO2) coatings on porous metallic substrates includes forming a first coating comprising metal particles on a surface of the porous metallic substrate, followed by forming a second coating comprising ceramic particles on the first coating. A porous coated metallic substrate assembly formed by the method includes a first sinter-bonded coating layer on a surface of a porous metallic substrate, the first sinter-bonded coating layer comprising metal particles from a coating composition, and a second sinter-bonded coating layer on the first porous coating layer, the second sinter-bonded coating layer comprising metal oxide particles from a coating composition.

Description

METHOD OF MANUFACTURE OF POROUS COATED METALLIC SUBSTRATEASSEMBLIESCROSS-REFERENCE TO RELATED APPLICATIONThis application claims priority to U.S. Provisional Application Serial No. 63 / 468,193, filed May 22, 2023, the entire contents of which are herein incorporated by reference.TECHNICAL FIELD

[0001] This disclosure relates to porous coated metallic substrate assemblies wherein both the coatings and the substrates are porous, and related methods of fabrication and use, and more particularly, to methods for fabrication of strongly adherent porous metal, for example porous titania (e.g., TiCU) coatings, on porous metallic substrates and related methods of fabrication, systems for fabrication, and uses thereof.BACKGROUND

[0002] Some coated porous metallic substrate assemblies and related fabrication methods are generally known. For example, a sintered coating for a porous metallic surface is described and disclosed in U.S. Patent No. 4,888,114. However, there remains a continued need for the development of coated porous metallic substrate assemblies and related fabrication methods that are cost-effective or include improved features or structures. These and other inefficiencies and opportunities for improvement are addressed or overcome by the assemblies, systems, and methods of this disclosure.BRIEF DESCRIPTION

[0003] The present disclosure provides improved porous coated metallic substrate assemblies and related methods of fabrication and use. More particularly, the present disclosure provides advantageous methods for the fabrication of strongly adherent porous ceramic, for example titania (e.g., TiO2), coatings on porous metallic substrates, and related methods of fabrication and use.

[0004] In an embodiment, a method for fabricating a porous coated metallic substrate assembly includes applying a first coating composition to a surface of a porous metallic substrate, the first coating composition comprising metal particles; sintering the first coating composition on the porous metallic substrate to fabricate a first porous coating layer on the surface of the porous metallic substrate, the first porous coating layer comprising metal particlesfrom the first coating composition; applying a second coating composition to a surface of the first porous coating layer, the second coating composition comprising ceramic particles; and sintering the second coating composition on the first porous coating layer on the porous metallic substrate to fabricate a second porous coating layer on the first porous coating layer, the second porous coating layer comprising ceramic particles from the second coating composition.

[0005] In another embodiment, a porous coated metallic substrate assembly includes a first sinter-bonded coating layer on a surface of a porous metallic substrate, the first sinter-bonded coating layer comprising metal particles from a first coating composition; and a second sinter-bonded coating layer on the first sinter-bonded porous coating layer, the second sinter-bonded coating layer comprising ceramic particles from a second coating composition.

[0006] The above described and other features are exemplified by the following Figures, Detailed Description, Examples, and Claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The following Figures are exemplary aspects wherein like elements are numbered alike, and wherein elements are not necessarily depicted to scale. The various elements, features, steps, or combinations thereof illustrated in the Figures and described below can be arranged and organized differently to result in aspects that are still within the scope of this disclosure. To assist those of ordinary skill in the art in making and using the assemblies and related methods of fabrication, systems for fabrication, and uses thereof, reference is made to the appended Figures, wherein:

[0008] FIG. 1 shows a partial schematic diagram of an exemplary porous coated metallic substrate assembly according to the present disclosure;

[0009] FIG. 2 is a diagram illustrating an exemplary system for fabricating an exemplary porous coated metallic substrate assembly according to the present disclosure;

[0010] FIG. 3 is an annotated photograph at 40x magnification showing a partial side view of an exemplary porous coated metallic substrate assembly according to the present disclosure;

[0011] FIG. 4 is an image of the top view of the second porous coating layer of the porous coated metallic substrate assembly shown in FIG. 3, generated by scanning electron microscopy;

[0012] FIG. 5 is an image of the porous coated metallic substrate assembly shown in FIG. 3 that was cut down the length of the filter;

[0013] FIG. 6 is an image of the top view of the second porous coating layer in a second embodiment, generated by scanning electron microscopy;

[0014] FIG. 7 is a graph showing results of dust challenge testing and flow recovery after back-pulse cycling of the porous coated metallic substrate assembly shown in FIG. 3;

[0015] FIG. 8 is a graph showing results of dust challenge testing and permeate flux of the porous coated metallic substrate assembly shown in FIG. 3;

[0016] FIG. 9 is an image of process fluid before and after filtration of the porous coated metallic substrate assembly shown in FIG. 3; and

[0017] FIG. 10 is a graph of performance data of filtrate flux of the same process fluid of FIG. 9 through the porous coated metallic substrate assembly shown in FIG. 3.DETAILED DESCRIPTION

[0018] Described herein are porous coated metallic substrate assemblies, and related methods of fabrication, systems for fabrication, and uses thereof. More particularly, the inventors hereof have discovered advantageous methods for the fabrication of strongly adherent porous metal coatings, for exemplary titania (e.g., TiCF) coatings, on porous metallic substrates, and related methods of fabrication. In the method, a first coating composition including metal particles is applied to a surface of a porous metallic substrate, which is then sintered to fabricate a first porous coating layer on the porous metallic substrate. A second coating composition including ceramic, e.g., metal oxide, particles is applied to the first porous coating layer on the porous metallic substrate, which is then sintered to fabricate a second porous coating layer including ceramic, e.g., metal oxide, particles.

[0019] The method provides several advantages. It is cost-effective, easily scalable to a wide variety of substrate geometries, facilitates high filtration rates, and can be carried out in standard equipment used for sintering. The first porous coating layer further aids to increase the bond strength and robustness of the second coating to the porous coated metallic substrate assembly. Coated porous metallic substrate assemblies produced via the method disclosed in U.S. Patent No. 4,888,114 generally experience issues where the TiCF coating sheds off from the surface of the porous metallic substrate when light forces are applied. The porous coated, e.g., multicoated, metallic substrate assemblies and related fabrication methods described herein overcome the issues of the conventional fabrication methods, as discussed further below.

[0020] FIG. 1 is a schematic diagram of an exemplary porous coated metallic substrate assembly 10 made by the methods and systems as described herein. Porous coated metallic substrate assembly 10 (also referred to herein as “assembly 10”) includes a porous metallicsubstrate 12 having a surface 14 and an opposite surface 16, a first porous coating layer 18 having a surface 20 opposite surface 14, and a second porous coating layer 22 having a surface 24 opposite surface 20 of the first porous coating layer 18.

[0021] Porous metallic substrate 12 includes any metallic material, where “metallic” as used herein is inclusive of materials comprising, consisting essentially of, consisting of a metal or a combination comprising a metal. The porous metallic substrate 12 can include metal oxides, nitrides, sulfides, carbides, and further derivatives of the metal, which can be present in both distinct phases and / or exist in an alloyed state. The metallic material can include a combination of metals, i.e., can be an alloy of two or more metals. The metals are selected depending on the desired properties and intended uses of assembly 10. Exemplary metals include aluminum, cobalt, copper, gold, iron, manganese, molybdenum, nickel, palladium, platinum, silver, titanium, tungsten, and the like. Metal alloys can be used, such as 316L stainless steel, Austenitic 304, Ferritic 430, Martensitic 410, Carbon Steels, AISI 1018, AISI 4140, Maragin 250, alloys with a cast nickel base such as IN 738, a cast cobalt base such as MAR-M509, a wrought nickel base such as Rene 95, a wrought cobalt base such as Haynes alloy No. 188, a wrought iron base such as Discaloy, Hastelloy X, Hastelloy C276, RSR 185, or Incoloy 901, titanium alloys such as ASTM Grade 1 or Ti-6A1-4V, nickel alloys, such as nickel 200 or Monel 400, copper alloys such as C 10100, C 17200, C26000, or C95200, or molybdenum alloys such as TZM, niobium alloys such as FS-85, tantalum alloys such as T-l ll, tungsten alloys such as W-Mo alloys, cemented carbides, e.g., nickel- or cobalt-bonded carbides such as WC-3 to 25 Co, or steel bonded carbides, such as 40-55 vol.% TiC, balance steel, or 10-20% TiC -balance steel.

[0022] A preferred metallic material of porous metallic substrate 12 is aluminum, cobalt, iron, copper, stainless steel, nickel, titanium, or an alloy thereof, for example stainless steel or a Hastelloy such as Hastelloy C276, which has a nominal composition by weight of 15.5% chromium, 2.5% cobalt, 16.0% molybdenum, 3.7% tungsten, 15.0% iron, 1.0% manganese, 1 .0% silicon, 0.03% carbon, 2.0% copper and the balance nickel.

[0023] Porous metallic substrate 12 can be of any geometric shape including regular or irregular portions or overall configurations. The shape is generally determined by the intended use of assembly 10, cost, ease of manufacture, and like considerations. For example, metallic substrate 10 can be in the form of a layer as shown in FIG. 1, where the layer can form a cube, a sphere, a hollow sphere, a cylinder, a hollow cylinder (a tube), a multi-bore hollow cylinder, or the like. In an aspect, porous metallic substrate 12 can take the form of a solid cylinder, or a cylindrical porous tube having a lumen, for example a porous tube having a length of 0.50 to 11feet (0.15 to 3.4 meters), and an outer diameter of 0.1 to 10 inches (0.25 to 25.4 centimeters), or of 0.325 to 1.0 inches (0.83 to 2.54 centimeters), and a lumen diameter of 0.125 to 9.5 inches (0.32 to 24.1 centimeters), or of 0.125 to 0.875 inches (0.32 to 2.22 centimeters).

[0024] Porous metallic substrate 12 has pores, preferably pores that provide passage of a fluid (e.g., gas, vapor, or liquid) between at least two surfaces of porous metallic substrate 12. Preferably, porous metallic substrate 12 has tortuous, interconnected pores between two or more surfaces, e.g., between surfaces 14, 16. Such pores can be provided by sintered particles, and can provide excellent filtration, including good depth filtration. Other surfaces can optionally be sealed. For example, porous metallic substrate 12 comprises at least partially sintered particles having a uniform particle size, a variable particle size, or a bimodal, trimodal, or other distribution of particle sizes. The particle size of porous metallic substrate 12 can be 1 to 200 micrometers, or 10 to 100 micrometers.

[0025] The dimensions of the pores can vary, depending on the intended use of the assembly, for example gas, vapor, or liquid filtration. The pores of porous metallic substrate 12 can have a uniform mean pore size, a variable mean pore size, or a bimodal, trimodal, or other distribution of mean pore sizes. The mean pore diameter can be from 0.05 to 50 micrometers in diameter, for example 0.1 to 10 micrometers in diameter.

[0026] Referring again to FIG. 1, a first (i.e., intermediate) porous coating layer 18 is on, preferably directly on, surface 14 of porous metallic substrate 12. First porous coating layer 18 has a surface 20 opposite surface 14 of the porous metallic substrate 12. First porous coating layer 18 includes sintered particles of a metal, a metal alloy, or a combination thereof (also referred to herein as “metal particles”). The metal, metal alloy, or combination thereof can be the same as described for porous metallic substrate 12. In an aspect, preferred metal particles of first porous coating layer 18 comprise aluminum, cobalt, iron, copper, stainless steel, nickel, titanium, or an alloy thereof, for example stainless steel. In another aspect, the metal particles of the first coating composition have the same composition as the porous metallic substrate 12.

[0027] In an aspect, the first porous coating layer 18 further comprises ceramic particles. The ceramic particles can be an oxide, nitride, sulfide, carbide or other ceramic derivative containing a metal in its chemical formula, of a metal or metal alloy as described for the porous metallic substrate 12. The ceramic particles can include a same metal as is present in the porous metallic substrate, a different metal as is present in the porous metallic substrate, or a combination thereof.

[0028] In an aspect, preferred ceramic particles of first metal coating layer 18 comprise an oxide of aluminum, nickel, or titanium. A particularly preferred ceramic is an oxide oftitanium (also referred to herein as titania), which as used herein is inclusive of various titanium oxides, including titanium dioxide (titanium (IV) oxide, TiCh), titanium monoxide (titanium (II) oxide, TiO), dititanium trioxide (titanium(III) oxide, T12O3), TixOywhere x and y refer to a non- stoichiometric, oxygen deficient titanium oxide, or a combination thereof. In an aspect the ceramic is titanium dioxide.

[0029] The sintered metal particles provide tortuous, interconnected pores between two or more surfaces, e.g., surfaces 14, 20, which can provide good filtration of gases, vapors, or liquids. The dimensions of the pores can vary, again depending on the intended use of the assembly, for example gas, vapor, or liquid filtration. The pores can have a uniform mean pore size, a variable mean pore size, or a bimodal, trimodal, or other distribution of mean pore sizes. The mean pore diameter can be from 0.01 to 400 micrometers, or from 0.01 to 200 micrometers, or from 0.01 to 100 micrometers. The mean pore diameter of the first porous coating layer 18 can be larger, smaller, or the same size as porous metallic substrate 12. In an aspect, the mean pore diameter of first porous coating layer 18 is less than a mean pore diameter of porous metallic substrate 12.

[0030] Referring still to FIG. 1, a second porous coating layer 22 is on, preferably directly on, surface 20 of first porous coating layer 18. Second porous coating layer 22 has a surface 24 opposite surface 14 of the porous metallic substrate 12. The second porous coating layer 22 includes sintered ceramic particles. The second porous coating layer 22 can include sintered ceramic particles including more than one ceramic, e.g., first ceramic particles including a first ceramic and second ceramic particles including a second ceramic. The ceramic particles, or combination of ceramic particles, forming the second porous coating layer 22 can be the same as or different from the optional ceramics of the first metal coating layer 18.

[0031] The ceramic particles forming the second porous coating layer 22 can include a same metal as is present in the porous metallic substrate 12, a different metal as is present in the porous metallic substrate 12, or a combination thereof. The ceramic particles of the second coating composition can include a metal oxide, nitride, sulfide, carbide, or other ceramic derivative of the metal, for example titania, preferably TiO2. In an aspect, preferred metal particles of porous metallic substrate 12 comprise aluminum, cobalt, iron, copper, stainless steel, nickel, titanium, or an alloy thereof. In an aspect, preferred ceramic particles of second porous coating layer 22 comprise an oxide of aluminum, nickel, or titanium. A particularly preferred ceramic for the ceramic particles forming the second porous coating layer 22 is an oxide of titanium (inclusive of various titanium oxides, such as titanium dioxide (titanium(IV) oxide, TiC ), titanium monoxide (titanium (II) oxide, TiO), dititanium trioxide (titanium(III) oxide,T12O3), TixOywhere x and y refer to a non-stoichiometric, oxygen deficient titanium oxide, or a combination thereof. In an aspect the ceramic of second porous coating layer 22 comprises, consists essentially of, or consists of, titanium dioxide.

[0032] The sintered ceramic particles provide tortuous, interconnected pores between two or more surfaces, e.g., surfaces 20, 24, which can provide good filtration of fluids such as gases, vapors, or liquids. The dimensions of the pores can vary, again depending on the intended use of the assembly, for example gas, vapor, or liquid filtration. The pores of the second porous layer 22 can have a uniform mean pore size, a variable mean pore size, or a bimodal, trimodal, or other distribution of mean pore sizes. The mean pore diameter of the second porous layer 22 can be 0.01 to 40 micrometers, or 0.01 to 20 micrometers, preferably 0.5 to 5 micrometers or 0.05 to 1 micrometer. The mean pore diameter of second porous coating layer 22 can be larger, smaller, or the same size as porous metallic substrate 12 or first porous coating layer 18. In an aspect, the mean pore diameter of second porous coating layer 22 is smaller than the mean pore diameter of porous metallic substrate 12. The second coating composition can be formulated and formed under conditions that provide a mean pore diameter of 0.50 micrometers, or 0.20 micrometers, or 0.02 micrometers,

[0033] The porous coated metallic substrate assembly 10 includes a porous metallic substrate 12, a first porous coating layer 18, e.g., including metal, and a second porous coating layer 20, e.g., including ceramic, as disclosed herein in connection with FIG. 1. Porous coating layers 18, 22 can be on, or directly on an inner surface of a porous tube or disk having a lumen, which are further described below. Alternatively, porous coating layers 18, 22 can be on, or directly on, an outer surface of the porous tube or disk having a lumen, or on, or directly on, both an inner and an outer surface of the porous tube or disk having a lumen.

[0034] Methods and systems for the manufacture of the porous coated metallic substrate assemblies, for example the porous coated metallic substrate assemblies 10 of FIG. 1 is described next.

[0035] An exemplary method includes coating a surface, e.g., surface 14 of a porous metallic substrate 12 with a first coating composition, followed by sintering the first coating composition to form first porous coating layer 18 on, or directly on a surface, e.g., surface 14 of the porous metallic substrate 12. All or a portion of the surface of the porous metallic substrate can be coated. The first coating composition comprises metal particles as described above in connection with the first porous coating layer 18. The size of the metal particles and the sintering conditions (compaction force, sintering time, and sintering temperature) are selected to provide the desired degree of porosity, including the desired mean pore size. The metal particlescan have an average particle size of, for example, 0.01 to 40 micrometers, 0.05 to 20 micrometers, or 0.5 to 10 micrometers. Particle size as used herein refers to a particle diameter measured along the longest axis passing from one side of a particle to the other side and also passing through the particle center. Particle shapes can be regular, for example substantially spherical, or irregular.

[0036] In an aspect the first coating composition can be a slurry of the metal particles in a liquid carrier, for example water, an alcohol such as isopropanol, ethanol or methanol, or a combination thereof. The liquid carrier can include other components, e.g., an organic binder such as a gel, a viscosity enhancer, a surfactant, or the like. In an aspect, the liquid carrier is water and a surfactant, or water substantially free of, or with no, other components. A concentration of particles can be from 1 to 200 grams per liter (g / L) in the carrier fluid, for example 100 g / L or 5 to 50 g / L.

[0037] Coating can be facilitated by a variety of methods, such as dip-coating, spray coating, or the like. Coating methods are described, for example in U.S. Patent No. 9,149,750 to Steele et al.

[0038] For example, the first coating composition is a slurry applied to an inner surface 14 of porous metallic substrate 12 in the form of a tube or a hollow disk. In an aspect, the slurry can be applied via a pressure gradient from a pressure vessel to force the first coating slurry through the length of the lumen while simultaneously forcing the slurry through the porous volume of the porous metal tube.

[0039] Alternatively, the application of the first coating composition, e.g., in the form of a slurry, can be at a differential pressure by mechanical deformation of the first coating composition, for example by applying a force to a layer of the first coating composition, e.g., the form of a slurry, against a surface, e.g., surface 14, of porous metallic substrate 12 (e.g., compressing the unsintered coating layer). Application of mechanical pressure can be used in addition to dip-coating, or the differential pressure as described above.

[0040] The inner surface 14 of the porous metallic substrate 12 retains a portion of the metal (and optionally ceramic) particles from the first coating slurry to thereby fabricate first porous coating layer 18 on the inner surface 14 of porous metallic substrate 12 via subsequent sintering.

[0041] Another method of applying the first porous coating layer to a surface of porous metallic substrate is a dip-coating process. A porous metallic substrate 12, for example a disk or a cylinder, is dipped into the first coating composition in the form of a slurry. The slurry can optionally be agitated at speeds of 50 revolutions per minute (rpm) to 500 rpm. The porousmetallic substrate 12 is slowly removed from the coating slurry, depositing slurry on or directly on all surfaces of the porous metallic substrate 12. This deposited first coating composition is then thermally bonded to the porous metal element via sintering.

[0042] Sintering of the coated (retained) metal particles (and optional ceramic particles) from the first coating composition can be at temperatures of 1,800 to 2,500 °F (982 to 1,371 °C), under pressures ranging from 10 millitorr to 2,000 torr (1.33 Pascals to 267 kiloPascals (kPa)), preferably between 700 to 800 torr (93 to 107 kPa). The sintering can occur in the presence of oxygen, nitrogen, hydrogen, argon, an inert gas, or a combination thereof. The thermal cycle during the sintering operation can last for 0.5 to 24 hours. In some aspects, sintering to fabricate the first porous coating layer, the second porous coating layer, or both can further include cosintering particles from the porous metallic substrate.

[0043] After fabricating first porous coating layer 18 on or directly on a surface of porous metallic substrate 12, a second coating composition comprising ceramic, e.g., metal oxide, particles is deposited on, or directly on, a surface, e.g., surface 20 of first porous coating layer.

[0044] An exemplary method includes coating a surface, e.g., surface 20 of first porous coating layer 18 with a second coating composition, followed by sintering to form second porous coating layer 22, e.g., on surface 20. All or a portion of the surface of the first porous coating layer can be coated. The second coating composition comprises ceramic, preferably metal oxide, more preferably titanium oxide (e.g., T1O2) particles as described above in connection with second porous coating layer 22. The size of the ceramic particles and the sintering conditions (compaction force, sintering time, and sintering temperature) are selected to provide the desired degree of porosity, including the desired mean pore size. The ceramic particles can have an average particle size (e.g., average longest dimension) from, for example, 0.01 to 50 micrometers, 0.01 to 40 micrometers, 0.5 to 20 micrometers, or 0.05 to 5 micrometers. Particle shapes can be regular, for example substantially spherical, or irregular.

[0045] In an aspect the second coating composition can be a slurry of the ceramic particles in a liquid carrier, for example water, an alcohol such as isopropanol, ethanol or methanol, or a combination thereof. The liquid carrier can include other components, e.g., an organic binder such as a gel, a viscosity enhancer, a surfactant, or the like. In an aspect, the liquid carrier is water and a surfactant, or water substantially free of, or with no other, components. The concentration of particles can be from 10 grams per liter to 200 grams per liter in the carrier fluid, for example 50 grams per liter.

[0046] Coating can be by a variety of methods, such as dip-coating, spray coating, or the like, or as described, for example in U.S. Patent No. 9,149,750 to Steele et al.

[0047] For example, the second coating composition is a slurry applied to an inner surface 20 of first porous coating layer 18 that has been applied to an inner surface of porous metallic substrate 12 in the form of a tube or disc having a lumen. In an aspect, the second composition in the form of a slurry can be applied via a pressure gradient from a pressure vessel to force the second coating slurry through the length of the lumen while simultaneously forcing the second coating slurry through the porous volume of the porous metal tube. One end of the lumen may or may not be dead-ended, e.g., capped, to prevent the second coating slurry from flowing out of the lumen of the porous metal tube. The second coating slurry is applied using a pressure gradient ranging from 1 to 200 pounds per square inch (psi) (6.9 to 1,379 kiloPascals (kPa)), 10 to 200 psi (69 to 1,379 kPa), or 30 to 80 psi (207 to 552 kPa). The pressure vessel is pressurized, for example, by using compressed air, to a desired pressure to achieve a slurry discharge pressure gradient. Slurry effluent can be held at atmospheric pressure conditions, but may be pressurized to help control the applied pressure in tandem with the compressed air pressure in the pressure vessel. Alternatively, the application of the second coating composition, e.g., in the form of a slurry, can be at a differential pressure by mechanical deformation of the second coating composition, for example by applying a force to a layer of the second coating composition, e.g., in the form of a slurry, against a surface, e.g., surface 20, of first porous coating layer 18 (e.g., compressing the unsintered coating layer). Application of mechanical pressure can be used in addition to dip-coating, or the differential pressure as described above.

[0048] Another method of applying second porous coating layer 22 to a surface, e.g., surface 20 of first porous coating layer 18 is a dip-coating process. A porous metallic substrate 12, for example a hollow disk or a tube, including the first porous coating layer 18, is dipped into the second coating composition in the form of a slurry. The slurry can optionally be agitated at speeds of 50 rpm to 500 rpm. The porous metallic substrate 12 including first porous coating layer 18 is slowly removed from the coating slurry, depositing slurry on or directly on all surfaces of first porous coating layer 18. This deposited coating composition is then thermally bonded to the porous metal element via sintering.

[0049] Sintering of the coated (retained) ceramic particles from the second coating composition can be facilitated at temperatures of 1,800 to 2,500 °F (982 to 1,371 °C), under pressures ranging from 10 millitorr to 1,000 torr (1.33 Pascals to 133 kiloPascals (kPa)), preferably between 500 to 1,200 millitorr (0.07 to 0.16 kPa). The sintering can occur hydrogen, oxygen, nitrogen, argon, an inert gas, or a combination thereof. The thermal cycle during thesintering operation can last for 0.5 to 24 hours. In some aspects, the porous metallic substrate 12 and / or the metal (and optional ceramic) particles from the first coating composition can co-sinter with the ceramic particles of the second coating slurry to form an intermetallic or non- stoichiometric alloy to help bond the dissimilar materials together.

[0050] In still another exemplary aspect of the method, a surface, e.g., surface 14 of porous metallic, e.g., stainless steel, substrate 12, is coated (e.g., via a pressure vessel, by dip-coating, or otherwise) with a combined coating composition comprising the first coating composition and the second coating composition as described above, i.e., a coating composition including both the metal particles as described above (e.g., metal particles having a size of 0.01 to 40 micrometers, or 0.05 to 20 micrometers), the ceramic particles as described above (e.g., ceramic particles, for example as a metal oxide such as titanium oxide, specifically T1O2, and having a size of 0.01 to 40 micrometers, or 0.05 to 20 micrometers). The combined coating composition can include a carrier and optional additives as described above. After applying the combined coating composition to the surface, e.g., surface 14, the porous coated metallic substrate is sintered (e.g., at temperatures of 1,800 to 2,500 °F (982 to 1,371 °C), with or without pressure) to form a combined porous coating layer including the metal particles and the ceramic particles co-coated and bonded the surface of porous metallic substrate 12.

[0051] Accordingly, in an embodiment, a method for fabricating a porous coated metallic substrate assembly includes applying a combined coating slurry to a surface of a porous metallic substrate, the combined coating slurry comprising (i) metal particles and (ii) ceramic, e.g., metal oxide such as titanium oxide, preferably TiCF particles; sintering the combined coating slurry to fabricate a combined coating layer comprising the metal and ceramic particles from the combined coating slurry.

[0052] The fabricated porous coated metallic substrate assembly incudes a first sinter-bonded porous coating layer on a surface of a porous metallic substrate, the first sinter-bonded coating layer including metal particles from a first coating composition; and a second sinter-bonded coating layer on the first sinter-bonded porous coating layer, the second sinter-bonded coating layer including ceramic particles from a second coating composition.

[0053] The porous metallic substrate can be a porous metallic substrate including sintered particles having a size of 1 to 200 micrometers, or 10 to 100 micrometers, and the porous metallic substrate can further include pores having a mean diameter of 0.1 to 10 micrometers. The porous metallic substrate can be a tube having a lumen or a disk having a lumen. The porous metallic substrate can include stainless steel.

[0054] The metal particles of the first coating composition can include the same material composition as the porous metallic substrate. The second porous coating layer can include pores having a mean pore diameter of 0.01 to 40 micrometers, or 0.01 to 20 micrometers, preferably 0.05 to 1 micrometer, specifically a mean pore diameter of 0.50 micrometers, or 0.20 micrometers, or 0.02 micrometers. The first coating composition can further include ceramic particles, and the ceramic particles of the first and second coating compositions can be the same. The first coating composition and the second coating composition can be a combined coating composition.

[0055] Although the porous coated metallic substrate assemblies described herein comprised two porous coating layers 18, 22, other optional layers can be present between porous metallic substrate 12 and first porous coating layer 18, between first porous coating layer 18 and second porous coating layer 22, on a surface, e.g., surface 24 of second porous coating layer 22, or a combination thereof. To provide an additional layer, e.g., on a surface of 24 of second porous coating layer 22, the coating process described above can be repeated with a third coating composition on a surface, e.g., a surface 24 of second porous coating layer 22. In an aspect, no additional layers are present. In another aspect, no additional layers other than a layer that may arise as a result of the method described herein is present.

[0056] A system (i.e., apparatus) to apply the first coating composition including metal particles and / or the second coating composition or the combined coating composition is shown in FIG. 2. In particular, FIG. 2 is a diagram of an exemplary coating system 200 to fabricate a porous coated metallic substrate assembly 10.

[0057] With reference to FIG. 2, a slurry holding tank 210, which can be, for example, a five gallon tank that has an air powered mixer to keep slurry components agitated within the slurry holding tank. While not illustrated, the coating system can include more than one slurry holding tank, for example, a first slurry holding tank holding a first coating composition and a second slurry holding tank holding a second coating composition. In an aspect, the coating system can include a single slurry holding tank, which is first loaded with a first coating composition and later loaded with a second coating composition after use of the first coating composition and cleaning of the slurry holding tank.

[0058] A fluid pump assembly 220 can circulate fluid throughout the system 200, for example, at 1 to 5 meters per second (m / s), depending on the fluid being circulated. A three-way directional fluid valve 230 can open to allow slurry to fill into pressure vessel 240. The three-way directional fluid valve 230 can be closed once a set volume is dispensed. The pressure vessel 240 can be pressurized with an external compressed air source 250.

[0059] The porous metallic substrate, for example, in the form of a tube capped off on one end, can be loaded in a carriage 260, an end 270 of which is fluidically connected to an outlet valve 280 of the pressure vessel 240. The outlet valve 280 of the pressure vessel 240 can be opened, allowing slurry to discharge into the porous metallic substrate. Slurry can flow through the porous wall of the porous metallic substrate, exiting radially. Once slurry is discharged from the porous metallic substrate, compressed air can be flowed through the porous metallic substrate to remove moisture and densify the coating formed from the slurry, help increase homogenization of e a thickness of the coating formed from the slurry, or a combination thereof. The porous metallic substrate can be removed from the carriage and set aside for drying before being placed into a sintering furnace.

[0060] The process can be operated manually or can be automated. For example, an operator can manually load slurry components into the slurry holding tank. An operator can remove the porous metallic substrate from the carriage, set aside the porous metallic substrate for drying, and place the porous metallic substrate into a sintering furnace.

[0061] In an aspect, to form the first porous coating layer, particulates can be dispersed in water to form a first coating slurry, e.g., a first coating slurry containing particulate suspended in water can be homogenized. Once formed, e.g., homogenized, the first coating slurry can be dispensed into pressure vessel 240. A porous metallic substrate in a form of a tube can be connected to an outlet of the pressure vessel 240, with one end of the porous metallic substrate capped off to prevent the first coating slurry from exiting the other end of the porous metallic substrate not connected to the pressure vessel 240. A valve can be opened allowing the pressurized slurry to discharge from the pressure vessel 240 and into the porous metallic substrate. The first coating slurry then can travel through the porous wall of the porous metallic substrate, exiting the porous metallic substrate radially from the diameter of the porous metallic substrate. A portion of the particulate can be retained on the inner diameter of the porous metallic substrate. Once the first coating slurry is fully discharged, pressurized air can be allowed to flow through the porous metallic substrate, compressing retained particulate as well as removing moisture to form a retained particulate layer. The coating, e.g., retained particulate layer, can be allowed to dry, forming a first porous coating layer. The first porous coating layer can then be sintered.

[0062] To apply the second porous coating layer 22, particulates can be dispersed in a solution to form a second coating slurry, e.g., a second coating slurry including rutile-phase titanium dioxide, water, and a surfactant can be homogenized. Once mixed, the second coating slurry can be introduced into the pressure vessel 240 and pressurized. Similar to the applicationof the first porous coating layer 18, the porous metallic substrate with the first porous coating layer 18 sintered on to the inner diameter of the porous metallic substrate can be fluidically attached to the pressure vessel 240. A valve can be opened to allow the pressurized slurry to discharge into the porous coated metallic substrate, filling it. Particulate from the second coating slurry can be retained on the inner surface of the first porous coating layer 18 to form a second porous coating layer 22. Compressed air can then be discharged through the retained particulate, densifying and removing moisture from the retained particles of the second porous coating layer 22. The second porous coating layer 22 can be sintered.

[0063] The methods, systems, and porous coated metallic substrate assemblies described herein have several advantages over prior art methods and assemblies. Using conventional practices, the ceramic (e.g., metal oxide, such as titania, specifically TiOz) particles generally do not bond well to metals such as stainless steel. Bonding of TiCh to stainless steel is particularly difficult. The methods, systems, and porous coated metallic substrate assemblies described herein can improve bonding of the second porous coating layer 22, e.g., a ceramic layer, to a surface of a porous metallic substrate 12 by pre-coating the surface, e.g., surface 14, with the first porous coating layer 18, the first porous coating layer comprising the sintered metal particles).

[0064] The first porous coating layer formed via coating the porous metallic substrate with the first coating slurry can roughen the surface to which it is applied; the first porous coating layer can increase the specific surface area of this portion of the porous metallic substrate, allowing for greater intimate contact for the ceramic particles of the second coating slurry. With greater surface area of the ceramic particulate in the second coating slurry in contact with the first porous coating layer, the second coating particles can form a stronger bond to the first porous coating layer during sintering. The increase in surface area promotes more diffusion bonding between the two dissimilar materials, allowing for a stronger overall bond. The increase in the interfacial contact area and associated increase in diffusion bond strength allows the second porous coating layer to resist spalling and delamination, increasing the robustness, abrasion resistance, thickness, and maximum allowable thermal stress before delamination of the second porous coating layer.

[0065] In the alternative, or in addition, use of higher sintering temperatures (e.g., 1,800 to about 2,500 °F (982 to about 1,371 °C)), to form porous coating layers 18, 22 provide substantial improvements over the methods and assemblies disclosed in U.S. Patent No. 4,888,114. Still further in the alternative, or in addition, use of pressure, for example as provided by a pressure vessel 240 such is as shown in system 200, to form porous coating layers18, 22, represent and provide substantial improvements over the method / component disclosed and described in U.S. Patent No. 4,888,114. The use of pressure to compact the coated particulate from the coating slurry enables the coating layer to achieve high density and reduces the moisture content / drying time of the unsintered coating. In particular, use of a combination of small particle size in first porous coating layer 18, higher temperature during sintering of the first and / or second compositions, and higher pressure as described above during sintering of the first and / or second compositions can provide denser porous coatings 18 and / or 22.

[0066] In exemplary aspects, the exemplary porous coated metallic substrate assemblies 10 can be used as a coated filter assembly in applications for filtration, for example for the crossflow filtration of solutions having high solids content (e.g., 5 to 40 weight percent (wt%) solids), or solutions having a large proportion (e.g., greater than 1 to 5 wt%) of sub-micron fine particulates. Without limitation, exemplary applications for exemplary porous coated metallic substrate assemblies 10 include filtration and recovery of wastewater (e.g., from agricultural waste streams), or recovery of catalyst (e.g., from petrochemical process streams ).

[0067] The exemplary aspects and embodiments disclosed herein are illustrative of improved methods, porous coated metallic substrate assemblies, and systems as described herein. It should be understood, however, that the disclosed aspects and embodiments are merely examples of the present disclosure, which may be embodied in various forms. Therefore, details disclosed herein with reference to the exemplary porous coated metallic substrate assemblies and associated methods and systems for fabrication or use, including the below Examples, are not to be interpreted as limiting, but merely as the basis for teaching one skilled in the art how to make and use the assemblies or alternative assemblies of the present disclosure.EXAMPLESExample 1

[0068] A porous coated metallic substrate assembly was manufactured by coating a porous metal tube having an outer diameter of 0.75 inches (1.9 centimeters), an inner diameter of 0.625 inches (1.6 centimeters), and a length of 20 inches (50.8 centimeters). The porosity of the porous metal tube prior to the application of the two coating layers is characterized by a normal pore size distribution with a maximum pore size of 15 micrometers and a mean pore size of 1 micrometer.

[0069] To form a first porous coating layer, a first coating slurry containing 316L stainless steel alloy particulate with a mean particle size of 3 micrometers suspended in water ata concentration of 40 grams per liter (g / L) was stirred by hand for 1 minute to disperse the stainless steel alloy particulate, e.g., homogenize the concentration of the stainless steel alloy particulate within the first coating slurry. Once dispersed, e.g., homogenized, the first coating slurry was dispensed into the pressure vessel 240 as depicted in FIG 2. The pressure vessel was pressurized to a differential pressure of 40 pounds per square inch (psi) (276 kiloPascals (kPa). The porous metal tube was connected to the outlet of the pressure vessel, with one end of the porous metal tube capped off to prevent the first coating slurry from exiting the other end of the porous metal tube not connected to the pressure vessel. A valve was opened allowing the pressurized slurry to discharge from the pressure vessel and into the porous metal tube, filling it. The first coating slurry then travelled through the porous wall of the porous metal tube, exiting the porous metal tube radially from the diameter of the porous metal tube. A portion of the stainless steel alloy particulate, about 30 to 60 weight percent (wt%), was retained on the inner diameter of the porous metal tube. Once the first coating slurry was fully discharged, pressurized air at 40 pounds per square inch differentia] (psid) (276 kPa differential) was allowed to flow through the porous metal tube, compressing retained particulate as well as removing moisture to form a retained particulate layer. The coating, e.g., retained particular layer, was allowed to dry until a moisture content less than 5 wt% was present. The first porous coating layer was then sintered in a commercially available vacuum furnace at a temperature of 2,000 °F (1,093 °C) for a dwell time of 75 minutes in an atmosphere containing 95 wt% argon and 5 wt% hydrogen at a pressure between 700 to 1,000 millitorr (0.09 to 0.13 kPa).

[0070] To apply a second porous coating layer, a second coating slurry containing rutilephase titanium dioxide with a mean particle size of 2.5 micrometers at a concentration of 3.52 g / L of water and a surfactant such as ammonium polymethacrylate at a concentration of 3 volume percent (vol%) was mixed by hand for one minute to disperse the rutile-phase titanium dioxide particulate in the solution. Once mixed, the second coating slurry was introduced into the pressure vessel and pressurized to a differential pressure of 40 psi (276 kPa). Similar to the application of the first porous coating layer, the porous metal tube with the first porous coating layer sintered on to the inner diameter of the porous metal tube was fluidically attached to the pressure vessel. A valve was opened to allow the pressurized slurry to discharge into the porous coated metal tube, filling it. Particulate from the second coating slurry was retained on the inner surface of the first porous coating layer to form a second porous coating layer. Compressed air at 40 psid (275 kPa differential) was then discharged through the retained particulate, densifying and removing moisture from the retained particles of the second porous coating layer. The second porous coating layer was sintered in a commercial vacuum furnace at a temperature of2000 °F (1,093 °C) for a dwell time of 75 minutes under an atmosphere of 95 wt% argon and 5 wt% hydrogen at a pressure between 700 to 1,000 millitorr (0.09 to 0.13 kPa).

[0071] Once sintered, the porous coated metallic substrate assembly was cross sectioned to generate the image shown in FIG. 3, which shows a partial side view of the porous coated metallic substrate assembly. The porous coated metallic substrate assembly includes a porous metallic substrate 12, a first metal coating layer 18, and a second ceramic coating layer 22. Porous coating layers 18, 22 are on, e.g., directly on, an inner surface of the porous metal tube.

[0072] The porous coated metallic substrate assembly shown in FIG. 3 has a maximum pore size of 3.25 micrometers and a mean pore size of 0.5 micrometers as determined by capillary flow porometry testing. FIG. 4 is a top view of the second porous coating layer. The sintered titanium oxide and surrounding pores are shown in FIG. 4. The porous coated metallic substrate assembly was cut in half down the length of the filter and shown in FIG. 5. The black surface revealed on the inner diameter of the porous metal tube shows the ceramic of the second porous coating layer. The gray outer diameter shown in FIG. 5 is the uncoated outer surface of the porous metal tube.Example 2

[0073] Using the same process as Example 1, a porous metal tube of same geometry was coated using the same first coating slurry at a lower concentration of 10 g / L and at a pressure vessel discharge pressure of 80 psi (552 kPa). The first porous coating layer was sintered using the same sintering parameters as in Example 1. For the second porous coating layer, a slurry including rutile-phase titanium dioxide particulate of mean particle size between 0. 1 to 0.3 micrometers at a concentration of 2.3 g / L and a surfactant at a concentration of 3 vol% was discharged from the pressure vessel through the porous coated metal tube at a differential pressure of 50 psid (345 kPa). Compressed air at 50 psid (345 kPa differential) was then flowed through the porous coated metallic substrate assembly to densify and dry the second porous coating layer. The second porous coating layer was then sintered using the same thermal cycle as in Example 1 for the second porous coating layer. The resulting porous coated metallic substrate assembly had a maximum pore size of 1.29 micrometers and a mean pore size of 0.08 micrometers. A top view of the second porous coating layer is shown in FIG. 6, which shows a tighter density and smaller porosity than the second porous coating layer of Example 1 , shown in FIG. 4.Performance Evaluation

[0074] The performance of the porous coated metallic substrate assembly of Example 1 shown in FIG. 2 was evaluated. The porous coated metallic substrate assembly was set up in a traditional crossflow filtration scheme, in which a process fluid containing 1 ,000 parts per million by weight (ppm) of dust with a bimodal particle size distribution centered around 0.44 micrometers and 26 micrometers was flowed through the inner diameter of the porous coated metallic substrate assembly at an inlet velocity of 8 feet per second (ft / s) (2.44 meters per second (m / s)). The slurry, e.g., process fluid, was discharged from a holding tank by use of a pump, entering the porous coated metallic substrate assembly at a pressure of 25 psid (172 kPa differential). The slurry, e.g., process fluid, was allowed to exit throughout the length of the porous coated metallic substrate assembly at 15 psid (103 kPa differential) and return into the holding tank. Due to the differential pressure between the inner and outer diameter of the porous coated metallic substrate assembly, slurry could be filtered through the wall of the porous coated metallic substrate assembly to produce a clean effluent free of dust. Specifically, the effluent showed a reduction in turbidity of 99.90% after 20 minutes of operation. The flowrate of the effluent over time was measured. In addition, the filter was “back pulsed” or subject to a reverse flow of clean effluent flowing through the outer diameter of the filter through the inner diameter of the filter at a gradient of 60 psi (414 kPa). The back pulse cycle was periodically performed to remove a thin layer of captured dust particulate on the inner diameter of the filter. By removing the layer of captured dust particulate, which has a lower permeability than the porous region of the filter, the effluent flowrate is improved and is closer to the original flowrate of the system prior to conditioning / build-up of the dust particulate on the inner diameter. Back pulse cycles were performed to determine the comparative performance of a porous coated metallic substrate assembly against an uncoated filter of equivalent porosity as shown in FIG. 7, which is a graph of percent of initial flow versus elapsed time (minutes (min)) showing flow recovery after back-pulse cycling, and FIG. 8, which is a graph of permeate flux (liters per minute per square meters (LPM7m2)) at 12 ft / s (3.66 m / s) crossflow velocity and 45 psi (310 kPa) transmembrane pressure with 1 backwash recovery cycle versus time (min).

[0075] The performance of the porous coated metallic substrate assembly of Example 1 shown in FIG. 2 was tested in a crossflow filtration system for efficacy in filtering a byproduct process stream, specifically the bottoms portion of a distillation column, in the distillation process for whisky. The process fluid included 5 to 10 wt% of solids, primarily yeast, with fiber, plant matter, and dissolved sugar. The filter was challenged with this fluid at a crossflow inlet velocity of 12 ft / s (3.66 m / s) at a temperature of 150 °F (66 °C) at a differential pressure of20 psi (138 kPa). The turbidity of the filtrate, shown in FIG. 9, in which the feed byproduct process stream is shown on the left and the filtrate is shown on the right, was reduced by greater than 99.5%. The filtrate flux through the filter as a function of permeate recovery is shown in FIG. 10, which is a graph of flux (gallons per square feet per day (Gals / ft2 per day) versus permeate recovery (percent (%)), or the portion of the initial process volume that has been filtered, for multiple runs. The data indicates similar performance between runs indicating that the process fluid did not permanently foul the filter.

[0076] The above results show that the exemplary porous coated metallic substrate assemblies 10 described herein showed improved performance with respect to permeability for a given pore size, and in strength (i.e., resistance to erosion and / or chipping) compared to porous assemblies fabricated by conventional T1O2 coating technology.

[0077] As used herein, a “particle” is inclusive of particulates, as well as agglomerates of individual particles that function as an individual particle (e.g., retaining is agglomerated form upon sintering).

[0078] When an element such as a layer is referred to as being “on” another element, it can be directly on the other element or intervening elements can be present. For example, when the first porous layer is on a surface of the substrate, or the second porous layer is on a surface of the first porous layer, a thin intervening layer, for example a metal oxide can be located between the two layers. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.

[0079] The ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other (e.g., ranges of “up to 25 wt.%, or, more specifically, 5 wt.% to 20 wt.%”, is inclusive of the endpoints and all intermediate values of the ranges of “5 wt.% to 25 wt.%,” etc.). “Combinations” is inclusive of blends, mixtures, alloys, reaction products, and the like. The terms “first,” “second,” and the like, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “a” and “an” and “the” do not denote a limitation of quantity and are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Thus, reference to “an” element in a claim followed by reference to “the” element is inclusive of one element and a plurality of the elements. “Or” means “and / or” unless clearly stated otherwise.

[0080] Reference throughout the specification to “some aspects”, “an aspect”, and so forth, means that a particular element described in connection with the aspect is included in at least one aspect described herein, and may or may not be present in other aspects. In addition, itis to be understood that the described elements may be combined in any suitable manner in the various aspects. A “combination thereof’ is open and includes any combination comprising at least one of the listed components or properties optionally together with a like or equivalent component or property not listed.

[0081] 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 application belongs. All cited patents and patent applications are incorporated herein by reference in their entirety. However, if a term in the present application contradicts or conflicts with a term in the incorporated reference, the term from the present application takes precedence over the conflicting term from the incorporated reference.

[0082] The assemblies, systems, and methods described herein have been described with reference to exemplary aspects thereof, the present disclosure is not limited to such exemplary aspects or uses. Rather, the assemblies, systems and methods of the present disclosure are susceptible to many implementations and applications, as will be readily apparent to persons skilled in the art from the disclosure hereof. The present disclosure expressly encompasses such modifications, enhancements and / or variations of the disclosed aspects. Since many changes could be made in the above construction and many widely different aspects of this disclosure could be made without departing from the scope thereof, it is intended that all matter contained in the drawings and specification shall be interpreted as illustrative and not in a limiting sense. Additional modifications, changes, and substitutions are intended in the foregoing disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the disclosure.

Claims

CLAIMSWhat is claimed is:

1. A method for fabricating a porous coated metallic substrate assembly, the method comprising: applying a first coating composition to a surface of a porous metallic substrate, the first coating composition comprising metal particles; sintering the first coating composition on the porous metallic substrate to fabricate a first porous coating layer on the surface of the porous metallic substrate, the first porous coating layer comprising metal particles from the first coating composition; applying a second coating composition to a surface of the first porous coating layer, the second coating composition comprising ceramic particles; and sintering the second coating composition on the first porous coating layer on the porous metallic substrate to fabricate a second porous coating layer on the first porous coating layer, the second porous coating layer comprising ceramic particles from the second coating composition.

2. The method of claim 1, wherein applying the first coating composition to the surface of the porous metallic substrate comprises applying the first coating composition to an inner surface of a porous metal tube having a lumen or a porous metal disk having a lumen.

3. The method of claim 1 or claim 2, wherein applying the second coating composition to a surface of the porous metallic substrate comprises applying the second coating composition to an outer surface of a porous metal tube having a lumen or a porous metal disk having a lumen.

4. The method of any one of claims 1 to 3, wherein the metal particles of the first coating composition have an average size of 0.01 to 40 micrometers, or 0.5 to 10 micrometers; the ceramic particles of the second coating composition have an average size of 0.01 to 40 micrometers, or 0.05 to 5 micrometers; and the ceramic particles of the second coating composition comprise a metal oxide, nitride, sulfide, carbide, or other ceramic derivative of the metal, for example titania, preferably TiCX5. The method of any one of claims 1 to 4, wherein sintering the first coating composition to fabricate the first porous coating layer comprises sintering at temperatures between 1,800 to 2,500 °F (982 to 1,371 °C); and sintering the second coating composition to fabricate the second porous coating layer comprises sintering at temperatures between 1,800 to 2,500 °F (982 to 1,371 °C).

6. The method of any one of claims 1 to 5, wherein applying the first coating composition to an inner or outer surface of the porous metallic substrate comprises applying the first coating composition to the inner or outer surface via a pressure gradient, using a differential pressure of 10 to 200 pounds per square inch (69 to 1,379 kiloPascals); or applying the second coating composition to the sintered first porous coating layer comprises applying the second coating composition to the first porous coating layer via a pressure gradient and using differential pressure of 10 to 200 pounds per square inch (69 to 1,379 kiloPascals); or both.

7. The method of any one of claims 1 to 6, wherein applying the first coating composition to the inner surface of the porous metallic substrate comprises dipping the porous metallic substrate into the first coating composition, which is agitated at 50 to 500 revolutions per minute, then removing the dipped porous metallic substrate from the first coating composition to deposit metal particles from the first coating composition, forming the first porous coating layer; or applying the second coating composition to the sintered first porous coating layer comprises dipping the porous metallic substrate with the sintered first porous coating layer into the second coating composition, which is agitated at 50 to 500 revolutions per minute, then removing the dipped porous metallic substrate from the second coating composition to deposit the ceramic particles from the second coating composition to form the second porous coating layer.

8. The method of any one of claims 1 to 7, wherein the porous metallic substrate is a porous metallic substrate comprising sintered particles having a size of 1 to 200 micrometers, or 10 to 100 micrometers, the porous metallic substrate further comprising pores having a mean diameter of 0. 1 to 10 micrometers.

9. The method of claim 8, wherein sintering to fabricate the first porous coating layer, the second porous coating layer, or both further comprises co-sintering particles from the porous metallic substrate.

10. The method of any one of claims 1 to 9, wherein the porous metallic substrate comprises stainless steel.

11. The method of any one of claims 1 to 10, wherein the metal particles of the first coating composition comprise the same material composition as the porous metallic substrate.

12. The method of any one of claims 1 to 11, wherein the second porous coating layer comprises pores having a mean pore diameter of 0.01 to 40 micrometers, or 0.01 to 20 micrometers, preferably 0.05 to 1 micrometer, specifically a mean pore diameter of 0.50 micrometers, or 0.20 micrometers, or 0.02 micrometers .

13. The method of any one of claims 1 to 12, wherein the first coating composition further comprises ceramic particles, wherein the ceramic particles of the first and second coating compositions are the same.

14. The method of any one of claims 1 to 13, wherein the first coating composition and the second coating composition is a combined coating composition applied to a surface of the porous metallic substrate; and the combined coating composition is sintered to form a combined first and second porous coating layer on the surface of the porous metallic substrate.

15. A porous coated metallic substrate assembly comprising: a first sinter-bonded porous coating layer on a surface of a porous metallic substrate, the first sinter-bonded coating layer comprising metal particles from a first coating composition; and a second sinter-bonded coating layer on the first sinter-bonded porous coating layer, the second sinter-bonded coating layer comprising ceramic particles from a second coating composition.

16. The porous coated metallic substrate assembly of claim 15, wherein the porous metallic substrate is a porous metallic substrate comprising sintered particles having a size of 1 to 200 micrometers, or 10 to 100 micrometers, the porous metallic substrate further comprising pores having a mean diameter of 0.1 to 10 micrometers.

17. The porous coated metallic substrate assembly of claim 15 or claim 16, wherein the porous metallic substrate is a tube having a lumen or a disk having a lumen.

18. The porous coated metallic substrate assembly of any one of claims 15 to 17, wherein the porous metallic substrate comprises stainless steel.

19. The porous coated metallic substrate assembly of any one of claims 15 to 18, wherein the metal particles of the first coating composition comprise the same material composition as the porous metallic substrate.

20. The porous coated metallic substrate assembly of any one of claims 15 to 19, wherein the second porous coating layer comprises pores having a mean pore diameter of 0.01 to 40 micrometers, or 0.01 to 20 micrometers, preferably 0.05 to 1 micrometer, specifically a mean pore diameter of 0.50 micrometers, or 0.20 micrometers, or 0.02 micrometers.

21. The porous coated metallic substrate assembly of any one of claims 15 to 20, wherein the first coating composition further comprises ceramic particles, wherein the ceramic particles of the first and second coating compositions are the same.

22. The porous coated metallic substrate assembly of any one of claims 15 to 21, wherein the first coating composition and the second coating composition is a combined coating composition.

Images