Dual-layer protective coating for metal parts

Abstract

1. A dual layer protective coating for a metal component, the dual layer protective coating comprising: a bond coating metallurgically fused to a substrate of the metal component, the bond coating comprising one or more rare metals; and a top coating mechanically bonded to the bond coating, the top coating comprising one or more metal oxides or one or more metal carbides.

Description

[Technical Field]

[0001] Field FIELD OF THE INVENTION

[0001] The present invention relates to bi-layer protective coatings for metal components. [Background technology]

[0002] background

[0002] In various industrial processes, metal components, such as but not limited to valves, are exposed to high temperatures and pressures, as well as highly corrosive and erosive environments.

[0003]

[0003] Examples of such processes include, but are not limited to, autoclave processes for pressure oxidation (POX) and high-pressure acid leaching (HPAL) of slurried ores and concentrates. In many processes, maintenance and downtime associated with wear and corrosion damage to metal components can be significant.

[0004]

[0004] Conventional single layer protective coatings for metal components, such as prior art single oxide coatings, provide wear resistance but are highly susceptible to corrosion-induced fracture and delamination. Summary of the Invention [Problem to be solved by the invention]

[0005]

[0005] With this background in mind, there is a need for improved protective coatings for metal components that have high resistance to corrosion, wear, erosion, and delamination. [Means for solving the problem]

[0006] overview

[0006] In accordance with the present invention, there is provided a dual layer protective coating for metal parts comprising: a bond coating metallurgically fused to a substrate of a metal component, the bond coating comprising one or more rare metals; a bond coating, a top coating mechanically bonded to the surface, the top coating comprising one or more metal oxides or one or more metal carbides; A dual layer protective coating is provided, comprising:

[0007]

[0007] The bond coating can be metallurgically fused to the substrate by one or more of chemical vapor deposition, molten salt electrodeposition, and fusion welding.

[0008]

[0008] The bond coating may be full density or substantially full density.

[0009]

[0009] Thermal spraying of nanometer-sized particles and / or micrometer-sized particles can mechanically bond the top coating to the bond coating.

[0010] The bond coating may include one or more rare metals selected from the group consisting of zirconium, vanadium, niobium, and tantalum.

[0011]

[0011] The top coating may comprise one or more metal oxides selected from the group consisting of titanium oxide (TiOx), chromium oxide (CrOx), silicon oxide (SiOx), and titanium oxide-chromium oxide (TiOx-CrOx).

[0012] Alternatively, the top coating may comprise one or more metal carbides selected from the group consisting of tungsten carbide (WC), chromium carbide (CrC), and chromium carbide-tungsten carbide (CrC-WC).

[0013] After being mechanically bonded to the bond coating, the top coating can be densified.

[0014]

[0014] The bond coating can at least partially impart corrosion resistance to the substrate.

[0015]

[0015] The top coating may at least partially impart abrasion and erosion resistance to the bond coating.

[0016] The present invention provides a method for forming a dual layer protective coating on a metal part, comprising: metallurgically fusing a bond coating to a substrate of a metal component, the bond coating comprising one or more rare metals; mechanically bonding a top coating to the bond coating, the top coating comprising one or more metal oxides or one or more metal carbides; Further provided is a method comprising:

[0017]

[0017] The method may further include densifying the top coating after mechanically bonding it to the bond coating.

[0018]

[0018] The present invention further provides a metal part coated with the above-described dual layer protective coating or coated using the above-described method.

[0019] BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic cross-sectional view of a metal component illustrating a dual layer protective coating according to one embodiment of the present invention. [Figure 2A] 1 is a photograph of a post-service inspection of one side of the ball of a ball valve coated with a prior art single layer oxide coating. [Figure 2B] 1 is a photograph of a post-service inspection of the opposite side of the ball of a ball valve coated with a prior art single layer oxide coating. [Figure 3A] 2B is a photograph of a post-service inspection of a prior art single layer oxide coated seat on one side of the ball of FIG. 2A. [Figure 3B] 2C is a photograph of a post-service inspection of a valve seat coated with a prior art single layer oxide on the opposite side of the ball of FIG. 2B. [Figure 4] 1 is a post-use SEM micrograph of a cross section of a prior art single layer oxide coating on a ball substrate. [Figure 5] 1 is a post-use optical micrograph of a cross section of a prior art single layer oxide coating showing delamination from the ball substrate. [Figure 6] 1 is a post-application SEM micrograph of the cross-sectional microstructure morphology at the interface between a prior art single layer oxide coating and a ball substrate; [Figure 7A] 1 is a photograph of a post-use inspection of one side of the ball of a ball valve coated with a dual layer coating according to an example of the present invention. [Figure 7B] 1 is a photograph of a post-use inspection of the opposite side of the ball of a ball valve coated with a dual-layer coating according to an example of the present invention. [Figure 8A] 7B is a photograph of a post-use inspection of a dual-layer coated valve seat on one side of the dual-layer coated ball of FIG. 7A. [Figure 8B] 7C is a photograph of a post-use inspection of a dual-layer coated valve seat on the opposite side of the dual-layer coated ball of FIG. 7B. [Figure 9]1 is a post-use SEM photomicrograph at low magnification of the cross-sectional microstructure morphology at the interface between the dual-layer coating and the substrate of a ball coated with the dual-layer, as well as the composition of the bond and top coating layers. [Figure 10] 1 is a high magnification post-use SEM photomicrograph of the cross-sectional microstructure morphology at the interface between the dual-layer coating and the substrate of a ball coated with the dual-layer, as well as the composition of the bond and top coating layers. [Figure 11] 7A and 7B are post-application SEM micrographs of the cross-sectional microstructure morphology in the stem slot region of the dual-layer coated ball of FIGS. 7A and 7B, where only the dual-layer coating bond coat was applied (i.e., no dual-layer coating top coat was applied). DETAILED DESCRIPTION OF THE INVENTION

[0021] Description of the embodiment

[0020] Referring to the drawings, a dual-layer protective coating 10 for a metal part according to one embodiment of the present invention may generally include a bond coating 12 that metallurgically fuses (or metallurgically adheres) to a substrate 14 of the metal part 10 and a top coating 16 that mechanically bonds (or mechanically adheres) to the underlying bond coating 12.

[0022]

[0021] The bond coating 12 may include, for example, one or more rare metals selected from the group consisting of zirconium, vanadium, niobium, and tantalum. Alternative or equivalent rare metals may also be used.

[0023] The bond coating 12 may be metallurgically fused to the substrate 14 by, for example, one or more of chemical vapor deposition, molten salt electrodeposition, and fusion welding. Other alternative or equivalent techniques for metallurgically fusing the bond coating 12 to the substrate 14 may also be used. The microstructure of the bond coating 12 may be fully dense, or substantially fully dense, and may be void and crack-free or substantially void and crack-free to form a uniform, coherent, and hermetic (or hermetic) coating layer on the underlying substrate 14. Full densification (i.e., 0% porosity) or substantially full densification (i.e., about 0% porosity) of the bond coating 12 may be achieved by selectively controlling the process conditions of the above techniques for attaching the bond coating 12 to the underlying substrate 14.

[0024]

[0023] The top coating 16 can include one or more metal oxides or one or more metal carbides. The one or more metal oxides can be selected from the group consisting of, for example, titanium oxide (TiOx), chromium oxide (CrOx), silicon oxide (SiOx), and titanium oxide-chromium oxide (TiOx-CrOx). Alternatively, the one or more metal carbides can be selected from the group consisting of, for example, tungsten carbide (WC), chromium carbide (CrC), and chromium carbide-tungsten carbide (CrC-WC). Another alternative or equivalent wear- and erosion-resistant top coating can also be used.

[0025] For example, the top coating 16 may comprise a selected nanocomposite coating comprising a nanostructured material combined with a metal or metal alloy matrix to provide improved wear and erosion resistance. Examples of suitable nanocomposites in a metal carbide or metal oxide matrix include: nanometer-sized particles of tungsten carbide (WC) in a tungsten carbide-cobalt (WC-Co) matrix; nanometer-sized particles of aluminum-silicon (Al-Si) alloy and carbon nanotubes; and carbon nanotubes in an aluminum oxide (Al2O3) matrix / micrometer-sized powder particles.

[0026]

[0025] The top coating 16 can be mechanically bonded to the bond coating by thermal spraying of one or both of nanometer-sized particles and micrometer-sized particles. Thermal spraying can include one or more thermal spraying techniques selected from, for example, combustion, electrical discharge, cold spray, and laser. Examples of such techniques include powder flame spraying, air plasma spraying (APS), and high velocity oxygen fuel spraying (HVOF). For example, in the case of nanometer-sized particles, they can be sprayed by solution or suspension plasma spraying. Other alternative or equivalent thermal spraying techniques can also be used.

[0027] After being mechanically bonded to the bond coating 12, the top coating 16 can be densified. For example, the top coating 16 can be densified by applying a sealant onto the thermally sprayed surface to fill the pores and cracks to make the top coating 16 more dense. Other alternative or equivalent densification techniques can also be used.

[0028] The bond coating 12 can have a thickness of, for example, 5 to 100 μm, such as 30 to 70 μm. The top coating 16 can have a thickness of, for example, 100 to 900 μm, such as 200 to 750 μm. The top coating 16 can have a bond strength or shear strength of, for example, 6,000 PSI or greater and a hardness of 700 HV0.5 or greater.

[0029]

[0028] During use, the bond coating 12 can at least partially impart corrosion resistance to the substrate 14, and the top coating 16 can at least partially impart wear and erosion resistance to the bond coating 12.

[0030] The metal component may be used, for example, in an industrial process, such as, but not limited to, an autoclave process, such as, but not limited to, HPAL or POX. The metal component may include, for example, a valve component. However, it will be appreciated that embodiments of the present invention are not limited to metal components such as valve components used in autoclave processes, but may alternatively be implemented to coat any metal component used in any industrial process requiring high resistance to corrosion, wear, and erosion.

[0031]

[0030] The following examples are intended to illustrate the present invention, but are not intended to limit the scope of the invention. [Example]

[0032] Example - Post-service comparison of single and dual layer coated valve trim Prior art single layer oxide coated valve trim In this example, "valve trim" collectively refers to a set of internal metal parts in a ball valve, including a ball with two sides and two valve seats on opposite sides of the ball. Prior to use, a set of valve trim parts was coated with a conventional single-layer oxide coating. The conventional single-layer coated valve trim was then installed for use in a ball valve used in an industrial process at high temperature and pressure, and in highly corrosive and erosive environments. The conventional single-layer oxide coated valve trim was removed and removed from service after 62 days in-line due to a decrease in sealing efficiency. Post-use inspection of the conventional single-layer oxide coated parts was then performed as follows:

[0033] 2A and 2B are photographs of opposite sides of a ball coated with a prior art single-layer oxide coating after post-use inspection. Both sides of the prior art single-layer oxide coated ball are highly corroded. There is a large buildup of corrosion products on the surface of each side, and most of the prior art single-layer oxide coating has spalled from both sides.

[0034] 3A and 3B are photographs of post-service inspections of valve seats coated with a prior art single-layer oxide on opposite sides of the balls of FIGS. 2A and 2B. The prior art single-layer oxide coating has spalled over large areas of each seat. Corrosion is present in large areas of both seats where the prior art single-layer oxide coating has spalled, and corrosion products have accumulated on all surfaces of both seats. Marks in the same direction on the seats indicate the wear pattern caused by the ball as the seats rotate between open and closed positions.

[0035]

[0034] Figure 4 is an SEM photomicrograph of a cross section of a prior art single-layer oxide coating on a ball substrate after use. The application medium contacted the substrate through the pores inherent in the prior art single-layer oxide coating, and corrosion of the substrate was initiated. There is a significant buildup of corrosion products at the interface between the prior art single-layer oxide coating and the ball substrate, resulting in coating spalling.

[0036] 5 is a post-service optical micrograph of a cross section of a prior art single layer oxide coating showing delamination of the prior art single layer oxide coating from the ball substrate. There is significant buildup of corrosion products along the interface between the substrate and the prior art single layer oxide coating, and evidence of substrate material loss (i.e., corrosion), resulting in delamination and failure of the prior art single layer oxide coating.

[0037]

[0036] Figure 6 is a post-service SEM micrograph of the cross-sectional microstructural morphology of the interface between a prior art single layer oxide coating and the underlying ball substrate. There is significant buildup of corrosion products on the substrate, and the prior art single layer oxide coating has delaminated due to loss of mechanical interlock with the corroding substrate.

[0038] Dual-layer coated valve trim Another set of identical valve trim components, prior to use, was coated with a dual-layer coating comprising the bond coating and top coating of the present invention. The dual-layer coated valve trim was then tested in a ball valve used in the same industrial process as the valve trim coated with the prior art single-layer oxide. The dual-layer coated valve trim was subjected to the same severe service conditions as the valve trim coated with the prior art single-layer oxide. The dual-layer coated valve trim was removed after 310 days in-line for post-service testing to evaluate the success of the test and to compare the service performance of the dual-layer coated valve trim with that of the prior art single-layer oxide. Post-service testing of the dual-layer coated components was then performed as follows:

[0039] 7A and 7B are photographs of opposite side post-use inspections of a ball coated with the dual-layer coating of the present invention. No corrosion is observed on the sealing surfaces on either side of the ball. The top oxide coating of the dual-layer coating is intact, with only minor deposits present on the top coating of the dual-layer coating.

[0040] 8A and 8B are photographs of post-service inspection of dual-layer coated valve seats on opposite sides of the dual-layer coated ball of FIGS. 7A and 7B. The top coating of the dual-layer coating remained in excellent condition, with only minor coating spalling at the outer edge of the sealing surface of the valve seat.

[0041] 9 and 10 are low- and high-magnification post-treatment SEM micrographs, respectively, of the cross-sectional microstructural morphology and composition of the bond and top coating layers at the interface between the dual-layer coating and the substrate of a dual-layer coated ball. The metallurgical bond between the bond coating of the dual-layer coating and the underlying substrate remained without signs of substrate corrosion, and the top oxide coating of the dual-layer coating remained intact and bonded to the underlying bond coating.

[0042]

[0041] Figure 11 is a post-service SEM micrograph of the cross-sectional microstructure morphology in the stem slot region of the dual-layer coated ball of Figures 7A and 7B, where only the bond coat of the dual-layer coating was applied (i.e., no top coat of the dual-layer coating was applied). The bond coat alone was easily fractured when mechanical force or load was applied. Extensive corrosion of the substrate occurred, as evidenced by the accumulation of corrosion products between the substrate and the bond coat, and extensive intergranular and transgranular cracking in the substrate.

[0043]

[0042] The above post-service comparison of the prior art single layer coated valve trim and dual layer coated valve trim demonstrates an unexpected synergistic effect between the dual layer coated bond coating and top coating of the present invention, as shown by the dual layer coated valve trim's higher resistance to corrosion, wear, erosion, and coating delamination when compared to the prior art single layer oxide coated valve trim or the dual layer coated bond coating alone (i.e., no dual layer coating top coating).

[0044]

[0043] Embodiments of the present invention provide dual layer protective coatings that are useful both specifically and generally for providing metal parts with simultaneous resistance to corrosion, wear, and erosion.

[0045]

[0044] For purposes of this specification, the word "comprising" means "including but not limited to" and the word "comprises" has a corresponding meaning.

[0046]

[0045] The above embodiments have been described by way of example only and modifications are possible within the scope of the following claims.

Claims

1. A metal part, a bond coating metallurgically fused or adhered to the substrate of the metal component by one or more of chemical vapor deposition, molten salt electrodeposition, and fusion welding, the bond coating comprising one or more of zirconium, vanadium, niobium, and tantalum; a top coating mechanically bonded to the bond coating by thermal spraying, the top coating comprising one or more oxides of titanium, chromium, or silicon, or one or more carbides of tungsten or chromium; Including, The metal component comprises a valve trim component of a metal ball valve.

2. The metal component of claim 1 , wherein the valve trim component comprises one or both of a ball or a seat ring of the metal ball valve.

3. 2. The metal part of claim 1, wherein the one or more oxides of titanium, chromium, or silicon are selected from the group consisting of titanium oxide, chromium oxide, silicon oxide, and titanium oxide-chromium oxide.

4. 2. The metal component of claim 1, wherein the one or more carbides of tungsten or chromium are selected from the group consisting of tungsten carbide, chromium carbide, and chromium carbide-tungsten carbide.

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