Coating method and coated substrate

Abstract

A metal substrate ( 71 ) is coated with an enamel or other coating material ( 72 ) by irradiating the coating material ( 72 ) and substrate ( 71 ) with electromagnetic radiation to melt an underlying surface of the metal substrate ( 71 ) before melting the coating material ( 72 ) to create, after cooling, a fusion bond between the solidified substrate and coating material, whereby the fusion bonded interface ( 73 ) has an intermeshing irregular tongue and groove like microstructure profile shown in FIG. 7 . The electromagnetic radiation may be unfocussed, circulinear or focussed at a point located within the metal substrate ( 71 ) to first melt the substrate ( 71 ).

1 . A method for coating a metal substrate, the method comprising the steps of:
 depositing a coating material on an underlying surface of the metal substrate, the coating material having a coating melting temperature which exceeds the substrate melting temperature;   irradiating the metal substrate and coating material with electromagnetic radiation to melt the coating material and the underlying surface of the metal substrate; and   cooling the metal substrate and coating material to create a solidified coated metal substrate;   characterized in that the underlying surface of the metal substrate is molten before melting the coating material to generate a fusion bond between the solidified metal substrate and coating material.   
     
     
         2 . The method of  claim 1 , the step of irradiating the coating material comprising focussing the electromagnetic radiation to a point of focus located below the underlying surface of and within the metal substrate thereby melting the underlying surface of the metal substrate before melting the coating material. 
     
     
         3 . The method of  claim 1  or  2 , wherein the coating material comprising enamel, the step of irradiating the substrate and coating material providing a fusion bonded enamelled metal substrate. 
     
     
         4 . The method of  claim 3 , wherein the coating material comprises weight fractions comprising one or more of: SiO 2  1 to 50 weight %, B 2 O 3  0 to 20%, Na 2 O 4 to 20%, Al 2 O 3  0.5 to 15%, K 2 O, 0.2 to 8%, CaO 0.1 to 3%, CaF 2  0 to 15%, ZrO 2  0-16%, MnQO 2  0 to 4%, NiO 0 to 2%, CoO 0 to 2%, Cu 2 O 3  0 to 8%, Zn- 2 O 3  0 to 4%, Cr 2 O 3  0 to 4%, Fe 2 O 3  1 to 40%. 
     
     
         5 . The method of  claim 3 , wherein the enamel comprises a mixture of silica and alumina. 
     
     
         6 . The method of  claim 1 , wherein the electromagnetic radiation is visible laser light. 
     
     
         7 . The method of  claim 1 , wherein the step of irradiating the coating material comprises substantially completely defocusing the electromagnetic radiation. 
     
     
         8 . The method of  claim 1 , wherein the metal substrate forms part of at least one of the group consisting of a downhole well casing, a liner, a production tubing, a surface tubular, and a surface vessel; used in the hydrocarbon production and/or conversion industry. 
     
     
         9 . The method of  claim 8 , the surface being at least one of the group consisting of an inner surface of the casing, a liner, another other tubular, and another vessel. 
     
     
         10 . The method of  claim 9 , the step of irradiating the coating material comprising the steps of:
 providing optical projection means for transforming a linear laser beam into a circulinear laser beam; and   moving the optical projection means in axial direction through the pipe section to irradiate the coating material on the inner surface of the pipe section with the circulinear laser beam.   
     
     
         11 . The method of  claim 1 , the step of depositing the coating material comprising depositing the coating material using thermal spraying, electroplating, brushing, and dipping. 
     
     
         12 . A coated substrate made in accordance with the method of  claim 1 , comprising:
 a metal substrate having a surface;   a layer of molten coating material provided on said surface; and   an interface layer interposed between the surface and the layer of molten coating material, the interface layer comprising coating material and molten metal entangled in a fusion bond.   
     
     
         13 . The coated substrate of  claim 12 , the metal substrate forming part of at least one of the group consisting of a downhole well casing, a liner, a production tubing, a surface tubular, and a surface vessel; used in the hydrocarbon production and/or conversion industry. 
     
     
         14 . The coated substrate of  claim 13 , wherein the coating material comprises weight fractions comprising one or more of: SiO 2  1 to 50 weight %, B 2 O 3  0 to 20 weight %, Na 2 O 4 to 20 weight %, Al 2 O 3  0.5 to 15 weight %, K 2 O 0.2 to 8 weight %, CaO 0.1 to 3 weight %, CaF 2  0 to 15 weight %, ZrO 2  0-16 weight %, MnO 2  0 to 4 weight %, NiO 0 to 2 weight %, CoO 0 to 2 weight %, Cu 2 O 3  0 to 8 weight %, Zn- 2 O 3  0 to 4 weight %, Cr 2 O 3  0 to 4 weight %, Fe 2 O 3  1 to 40 weight %. 
     
     
         15 . The coated substrate of  claim 1 , wherein the coated substrate comprises a fusion bonded interface with an irregular tongue and groove like microstructure between the solidified coating material and metal substrate. 
     
     
         16 . The method of  claim 2  and creating and metal a fusion bonded interface with an irregular tongue and groove like microstructure between the solidified coating material and metal substrate.