Ferrous weld overlay compositions and methods

Abstract

A method of forming a protective coating on a substrate includes providing a metal in a molten state, the metal having a composition including at least 12 wt.% Cr, at least.5 wt.% Al, at least 2.7 wt.% Mo, at least.3 wt.% Mn, at least.05 wt.% Ce, and less than or equal to 21 wt.% Ni. The method further includes applying the metal in a molten state to a substrate.

Description

FERROUS WELD OVERLAY COMPOSITIONS AND METHODSSTATEMENT REGARDING FEDERALLY SPONSORED RESEARCH ORDEVELOPMENT

[0001] This invention was made with government support under agreement FE0031911 awarded by the U.S. Department of Energy. The U.S. government has certain rights in the invention.BACKGROUNDTECHNICAL FIELD

[0001] Embodiments of the invention relate generally to reducing erosion and / or oxidation of metal substrates, and, more particularly, to chromia and alumina forming ferrous alloys for use as a weld overlay.DISCUSSION OF ART

[0002] Power generation systems typically include metal tubing, and other surfaces, that are exposed to harsh conditions. For example, water wall tubing in industrial power plants may be located proximate to soot blowing equipment which utilizes steam, air, and / or high-pressure water, to remove soot build up. Such soot blowing can, over time, potentially result in tube erosion resulting from, e.g., particles entrained in the soot blower media. In addition, soot blowing may accelerate oxidation (e.g., corrosion) of the tubing. In addition to soot blowing, tubing may be exposed to fly ash erosion and / or corrosion resulting from exposure to sulfur or chlorine. Tubing exposed to such conditions may require repair and / or replacement, as well as frequent monitoring.

[0003] As will be appreciated, if tubing or other equipment surfaces need to be repaired or replaced, this can lead to lost days and weeks of production (i.e., electricity generation, orother industrial processes using steam from the boiler) and capacity if a boiler has to undergo a shutdown. If the boiler is shut down, it may become necessary for the power plant operators to buy replacement power which can be costly especially if the shutdown occurs during periods of high demand. Adding these costs with the expenses associated with performing maintenance to repair the boiler makes a compelling reason why power plant operators have a desire to ensure that tubing and other surfaces that are prone to erosion and / or corrosion are resistant to the same.

[0002] To provide erosion / corrosion resistance, weld overlays have been utilized. Weld overlays are generally applied via welding alloy wire onto a tube or other substrate to create a corrosion and / or wear resistant protective layer. However, known alloys used for weld overlays for corrosion / erosion resistance are predominately Nickel based and contain > 50 wt.% of Ni. While such alloys do provide a degree of protection from corrosion, Ni is relatively expensive and weld overlay wire made from this material is correspondingly expensive.

[0003] Moreover, many known weld overlay alloys are chromia forming, that is they beneficially promote the development of a chromia (C Ch) scale on the substrate which can passivate against corrosion. However, when deployed in the field for extended periods, chromia forming weld overlays may be susceptible to corrosion and cracking due to, for example, poor oxide adhesion and / or grain boundary diffusion. Some chromia forming weld overlays may also be relatively difficult to effectively weld without, for example, ductility dip cracking or solid- state cracking.

[0004] In addition to weld overlays, other potential corrosion / erosion solutions have been developed such as plate shielding, thermal spraying, and the use of composite tubing. However, these potential solutions may be costly, inefficient, and / or maintenance intensive. Additionally, as an alternative, austenitic stainless steel as a base tubing material can be used to addresscorrosion / erosion. As will be appreciated, however, this material is substantially more expensive than, for example, carbon steel, and may be commercially impractical for use in all tubing subject to soot blowing or other harsh conditions in an industrial boiler.

[0005] In view of the above, there is a need for a chromia forming alloy weld overlay that provides superior layering, adhesion, and resistance to cracking, and allows for welding using conventional methods, at a cost that is lower than known Ni based alloys.BRIEF DESCRIPTION

[0006] Certain embodiments commensurate in scope with the originally claimed subject matter are summarized below. These embodiments are not intended to limit the scope of the claimed subject matter, but rather these embodiments are intended only to provide a brief summary of the possible embodiments. Indeed, the disclosure may encompass a variety of forms that may be similar to or different from the embodiments set forth below.

[0007] According to an aspect of the invention, a method of forming a protective coating on a substrate includes providing a metal in a molten state, the metal having a composition including at least 12 wt.% Cr, at least .5 wt.% Al, at least 2.7 wt.% Mo, at least .3 wt.% Mn, at least .05 wt.% Ce, and less than or equal to 21 wt.% Ni. The method further includes applying the metal in a molten state to a substrate.

[0008] In an embodiment, the composition includes from 21 wt.% to 30 wt.% Cr, from .5 wt.% to .7 wt.% Al, from .05 wt.% to .15 wt.% Y, from 2.7 wt.% to 2.9 wt.% Mo, from .9 wt.% to 1.1 wt.% Si, from 2.1 wt.% to 1.9 wt.% Mn, from .4 wt.% to .6 wt.% Ti, from .05 to .15 wt.% Ce, from .05 wt.% to .15 wt.% La, with the balance Fe.

[0009] In an embodiment, the composition includes from 12 wt.% to 21 wt.% Cr, from 4.9 wt.% to 5.1 wt.% Al, from .05 wt.% to .15 wt.% Y, from 2.9 wt.% to 3.1 wt.% Mo, from 1.9wt.% to 2.1 wt.% Si, from .3 wt.% to .5 wt.% Mn, from .4 wt.% to .6 wt.% Ti, .05 wt.% to .15 wt.% Ce, with the balance Fe.

[0010] In an embodiment, the composition may include from 24 wt.% to 26 wt.% Cr, from .5 wt.% to .7 wt.% Al, from 2.9 wt.% to 3.1 wt.% Mo, from .9 wt.% to 1.1 wt.% Si, from 7.9 wt.% to 8.1 wt.% Mn, from .9 wt.% to 1.1 wt.% Ti, from .05 to .15 wt.% Ce, from .05 wt.% to .15 wt.% La, from 2 wt.% to 4 wt.% Ta, from 15 wt.% to 17 wt.% Ni, with the balance Fe.

[0011] In an embodiment, the composition may include from 21 wt.% to 23 wt.% Cr, from 3 wt.% to 5 wt.% Al, from 2.7 wt.% to 2.9 wt.% Mo, from .1 wt.% to .3 wt.% Si, from 2 wt.% to 8 wt.% Mn, from .05 to .15 wt.% Ce, from .4 wt.% to .6 wt.% Cu, from .9 wt.% to 1.1 wt.% Ta, from 18 wt.% to 21 wt.% Ni, with the balance Fe.

[0012] In an embodiment, the step of applying the metal in a molten state includes applying the metal to the substrate as a weld overlay utilizing gas metal arc welding, gas tungsten arc welding, tungsten inert gas welding, or laser welding.

[0013] In an embodiment, the metal, prior to being in the molten state, is in the form of a metal core wire having a metallic outer sheath and an inner core containing metallic powder.

[0014] In an embodiment, the substrate includes metal tubing in a superheater, reheater, and / or economizer of a boiler.

[0015] In an embodiment, the metal tubing is formed from a carbon steel or a low alloy steel.

[0016] According to another aspect, a wire utilized in connection with forming a resistant coating on a substrate, the wire including a composition having at least 12 wt.% Cr; at least .5 wt.% Al; at least 2.7 wt.% Mo; at least .3 wt.% Mn; at least .05 Ce; and less than or equal to 21 wt.% Ni.

[0017] In an embodiment, the composition of the wire includes from 21 wt.% to 30 wt.% Cr, from .5 wt.% to .7 wt.% Al, from .05 wt.% to .15 wt.% Y, from 2.7 wt.% to 2.9 wt.% Mo, from .9 wt.% to 1.1 wt.% Si, from 2.1 wt.% to 1.9 wt.% Mn, from .4 wt.% to .6 wt.% Ti, from .05 to .15 wt.% Ce, from .05 wt.% to .15 wt.% La, with the balance Fe.

[0018] In an embodiment, the composition of the wire may include from 12 wt.% to 21 wt.% Cr, from 4.9 wt.% to 5.1 wt.% Al, from .05 wt.% to .15 wt.% Y, from 2.9 wt.% to 3.1 wt.% Mo, from 1.9 wt.% to 2.1 wt.% Si, from .3 wt.% to .5 wt.% Mn, from .4 wt.% to .6 wt.% Ti, .05 wt.% to .15 wt.% Ce, with the balance Fe.

[0019] In an embodiment, the composition of the wire may include from 24 wt.% to 26 wt.% Cr, from .5 wt.% to .7 wt.% Al, from 2.9 wt.% to 3.1 wt.% Mo, from .9 wt.% to 1.1 wt.% Si, from 7.9 wt.% to 8.1 wt.% Mn, from .9 wt.% to 1.1 wt.% Ti, from .05 to .15 wt.% Ce, from .05 wt.% to .15 wt.% La, from 2 wt.% to 4 wt.% Ta, from 15 wt.% to 17 wt.% Ni, with the balance Fe.

[0020] In an embodiment, the composition of the wire may include from 21 wt.% to 23 wt.% Cr, from 3 wt.% to 5 wt.% Al, from 2.7 wt.% to 2.9 wt.% Mo, from .1 wt.% to .3 wt.% Si, from 2 wt.% to 8 wt.% Mn, from .05 to .15 wt.% Ce, from .4 wt.% to .6 wt.% Cu, from .9 wt.% to 1.1 wt.% Ta, from 18 wt.% to 21 wt.% Ni, with the balance Fe.

[0021] In an embodiment, the wire further includes a metallic outer sheath and an inner core containing metallic powder.

[0022] In an embodiment, the powder has a particle size of 44 microns to 250 microns.

[0023] According to another aspect, a substrate containing a protective coating, the protective coating including at least 12 wt.% Cr, at least .5 wt.% Al, at least 2.7 wt.% Mo, at least .3 wt.% Mn, at least .05 Ce, and less than or equal to 21 wt.% Ni.

[0024] In an embodiment, the substrate may be tubing and / or plating manufactured from carbon steel, stainless steel, Grade 91 steel, and / or a nickel alloy.

[0025] In an embodiment, the protective coating of the substrate is a weld overlay applied to the substrate utilizing gas metal arc welding, gas tungsten arc welding, tungsten inert gas welding, or laser welding.

[0026] In an embodiment, the protective coating includes from 21 wt.% to 30 wt.% Cr, from .5 wt.% to .7 wt.% Al, from .05 wt.% to .15 wt.% Y, from 2.7 wt.% to 2.9 wt.% Mo, from .9 wt.% to 1.1 wt.% Si, from 2.1 wt.% to 1.9 wt.% Mn, from .4 wt.% to .6 wt.% Ti, from .05 to .15 wt.% Ce, from .05 wt.% to .15 wt.% La, with the balance Fe.BRIEF DESCRIPTION OF THE FIGURES

[0027] The present invention will be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below:

[0028] FIG. 1 is a backscatter electron micrograph of a cross-sectioned sample of a known Ni-Cr based weld overlay alloy composition depicting significant corrosion when subject to corrosion testing.

[0029] FIG. 2 is a backscatter electron micrograph of a cross-sectioned sample of a weld overlay alloy composition according to embodiments of the invention evidencing significantly reduced corrosion when subject to the same corrosion testing, compared to the sample of FIG. 1.

[0030] FIG. 3 is a photograph of a substrate that includes a weld overlay according to an embodiment of the present invention.

[0031] FIG. 4 is an enlarged view of the weld overlay of FIG. 3 providing an example of a structural arrangement of the overlay applied to a substrate.DETAILED DESCRIPTION

[0032] Reference will be made below in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference characters used throughout the drawings refer to the same or like parts.

[0033] While embodiments of the invention are described as for use with industrial power generation equipment, such as tubing used in connection with superheaters, reheaters, and / or economizers of a boiler, the invention is not so limited. Certain embodiments may begenerally suitable for use on metal substrates exposed to conditions that promote oxidation, corrosion, and / or erosion. Embodiments may be utilized in the construction, mining, water treatment, paper, steel, and petrochemical industries, among others.

[0034] Likewise, embodiments are not limited to tubing and other boiler surfaces. To that end “substrate” as used herein is meant encompass metal tubing and all other metal surfaces, e.g., plating, that are potentially prone or subject to oxidation and / or erosion, regardless of shape, size, location, environment, or orientation. While embodiments facilitate the use of a relatively low-cost base metal for tubing, such as carbon steel and low alloy steel, the invention is not limited in this regard and embodiments may potentially be used with other base metals.

[0035] Referring now to Table 1 below, embodiments of the invention provide chromia- forming and / or alumina-forming alloy compositions suitable for weld overlays. Table 1 lists by weight percent the components of several specific embodiments, as well as percent ranges of the components. These compositions provide surprisingly superior layering, adhesion, and resistance to cracking, as well as weldability using conventional methods, at a cost that is lower than known chromia forming weld overlay alloys. The compositions include at least 12 wt.% Cr, at least .5 wt.% Al, at least 2.7 wt.% Mo; at least .3 wt.% Mn, at least .05 wt.% Ce, and less than or equal to 21 wt.% Ni.

[0036] The compositions all feature Ni weight %’s that are significantly lower than commonly used Ni-Cr weld overly alloys, all of which have >50 wt % Ni. Ni is an expensive material and, as will be appreciated, a reduction in the weight percent of the same reduces alloy composition costs. In two preferred embodiments, FC-Delta (FC-5) and FC-Beta (FC-0), the compositions include no Ni for a substantial cost reduction. Indeed, embodiments have been demonstrated to reduce material costs by 64% to 76% compared to known Ni-Cr weld overlaycompositions. As will be appreciated, this results in reduced initial purchase and future maintenance costs to power plant owners.

[0037] In comparison to known Ni-Cr alloys, and as discussed in greater detail below, embodiments also: eliminate cobalt, niobium and tungsten; reduce the amount of molybdenum; increase aluminum, silicon, and manganese; and include rare earth elements yttrium, cerium, and lanthanum.

[0038] The compositions are chromia forming and / or alumina forming, i.e., they promote the formation of chromia scale (i.e., chromium oxide - &2O3), alumina scale (AI2O3), or a non- stochiometric mixture thereof, on the substrate, which can passivate against corrosion. As such, the efficacy of the formed scale is important. To that end, the compositions include at least .5 wt.% Al. The addition of Al was shown to aid in the creation of a layered passivating oxide formation. The multiple layers of the passivating oxide provide superior protection from erosion / corrosion (e.g. hot corrosion) compared to single layer oxide layers that form via the use of conventional known chromia forming weld overlay alloys such as Ni-Cr alloys.

[0039] In addition, the compositions include at least 12 wt.% Cr which provides, e.g., protection against environmental embrittlement which could result in cracking of the overlay. The compositions also include at least 2.7 wt.% Mo to provide grain refinement and mitigate grain boundary diffusion (to increase weldability) and at least .3 wt % Mn for the purpose of forming a rapidly growing Cr-Mn Spinel Oxide in or on the outermost portion of the passivating chromia layer that further separates the metal surface from the corrosive environment.

[0040] In embodiments, the compositions include at least .05 wt % Ce as a getter to scavenge O and S, which reduces the alloy solidification range to 527° F (275° C). As will be appreciated, this provides a beneficial effect on weldability by reducing slag and cracking.

[0041] In embodiments, Ti is added in an amount of from .4 wt. % to .9 wt.% to preferentially form TiC rather than CrC, which provides corrosion resistance. Ta may also be included to increase weldability by reducing ductility dip cracking.

[0042] Moreover, embodiments do not include Co, Nb, and W, which are found in known Ni-Cr weld overlays. This elimination provides cost savings in addition to that afforded by the reduction / elimination of Ni. Moreover, the removal of Nb prevents susceptible grain boundary NbC formation, which reduces potential solid-state cracking.

[0043] In embodiments, microalloyed rare earth elements (Yttrium, Cerium, and Lanthanum) are included to improve oxide adhesion to the underlying substrate and to provide getter corrosive elements.

[0044] Table 1 - Alloy compositions (by wt. %)

[0045] In a preferred embodiment (FC-5 / FC-Delta), the composition includes from 21 wt.% to 30 wt.% Cr, from .5 wt.% to .7 wt.% Al, from .05 wt.% to .15 wt.% Y, from 2.7 wt.% to2.9 wt.% Mo, from .9 wt.% to 1.1 wt.% Si, from 2.1 wt.% to 1.9 wt.% Mn, from .4 wt.% to .6 wt.% Ti, from .05 wt.% to .15 wt.% Ce, from .05 wt.% to .15 wt.% La, with a balance of the composition being Fe.

[0046] In a specific embodiment of FC-5, the composition includes 25.5 wt.% Cr, .6 wt.% Al, .1 wt.% Y, 2.8 wt.% Mo, 1.0 wt.% Si, 2.0 wt.% Mn, .5 wt.% Ti, .1 wt.% Ce, .1 wt.% La, with a balance of the composition being Fe.

[0047] In another embodiment (FC- p / FC-Beta), the composition includes from 12 wt.% to 21 wt.% Cr, from 4.9 wt.% to 5.1 wt.% Al, from .05 wt.% to .15 wt.% Y, from 2.9 wt.% to 3.1 wt.% Mo, from 1.9 wt.% to 2.1 wt.% Si, from .3 wt.% to .5 wt.% Mn, from .4 wt.% to .6 wt.% Ti, .05 wt.% to .15 wt.% Ce, with a balance of the composition being Fe.

[0048] In a specific embodiment of FC- P, the composition includes 16.5 wt.% Cr, 5.0 wt.% Al, .1 wt.% Y, 3.0 wt.% Mo, 2.0 wt.% Si, .4 wt.% Mn, .5 wt.% Ti, .1 wt.% Ce, with a balance of the composition being Fe.

[0049] In yet another embodiment (AC- 5 / AC -Delta), the composition includes from 24 wt.% to 26 wt.% Cr, from .5 wt.% to .7 wt.% Al, from 2.9 wt.% to 3.1 wt.% Mo, from .9 wt.% to 1.1 wt.% Si, from 7.9 wt.% to 8.1 wt.% Mn, from .9 wt.% to 1.1 wt.% Ti, from .05 wt.% to .15 wt.% Ce, from .05 wt.% to .15 wt.% La, from 2 wt.% to 4 wt.% Ta, from 15 wt.% to 17 wt.% Ni, with a balance of the composition being Fe.

[0050] In a specific embodiment of AC- 5, the composition includes 25 wt.% Cr, .6 wt.% Al, 3.0 wt.% Mo, 1.0 wt.% Si, 8.0 wt.% Mn, 1.0 wt.% Ti, .1 wt.% Ce, .1 wt.% La, 3.0 wt.% Ta, 16.0 wt.% Ni, with a balance of the composition being Fe.

[0051] In another embodiment (AC- p / AC-Beta), the composition includes from 21 wt.% to 23 wt.% Cr, from 3 wt.% to 5 wt.% Al, from 2.7 wt.% to 2.9 wt.% Mo, from .1 wt.% to .3 wt.% Si, from 2 wt.% to 8 wt.% Mn, from .05 wt.% to .15 wt.% Ce, from .4 wt.% to .6 wt.% Cu, from .9 wt.% to 1.1 wt.% Ta, from 18 wt.% to 21 wt.% Ni, with a balance of the composition being Fe.

[0052] In a specific embodiment of AC- 0, the composition includes 22 wt.% Cr, 4.0 wt. % Al, 2.8 wt.% Mo, .2 wt.% Si, 5.0 wt.% Mn, .1 wt.% Ce, .5 wt.% Cu, 1.0 wt.% Ta, 19.5 wt.% Ni, with a balance of the composition being Fe.

[0053] Turning now to FIGS. 1 and 2, embodiments of the invention were corrosion tested utilizing cast cylindrical pins of embodiments of the invention, as well as cast pins of known alloys. In particular, the pins were exposed to synthetic ash and flue gas in a temperature controlled 3-zone furnace and then assessed for wastage (metal loss). In a coal fuel simulation, the temperature was set to 1300°F for 500 hours and 2 thermal cycles. For a biomass fuel simulation, the temperature was 1100°F for 500 hours and 2 thermal cycles.

[0054] The results of this testing, as observed via backscatter electron microscopy, revealed that the compositions according to embodiments of the invention (FC-Delta and FC- Beta) had surprisingly low wastage rates (.11 mm / year and .07 mm / year, respectively) compared to known alloys (such as, for example, commercially available Alloy 72 (~60Ni-49Cr)), whose wastage rates ranged from .28 to 3.68 mm / year. Indeed, alloys according to embodiments of the invention, such as FC-Delta and FC-Beta, were shown to provide an 81% to 91% reduction in wastage while eliminating costly Ni and Co. Embodiments have been determined to result in a 64% to 76% reduction in raw material costs.

[0055] In this regard, compositions according to embodiments of the invention may allow for the use of less expensive base tube metals compared to austenitic stainless steel. These include carbon steel and low alloy steels. As will be appreciated, this potentially provides a significant cost savings. That said, embodiments may be applied to a variety of base metals including ferritic-martensitic steel or austenitic stainless steel.

[0056] As shown in FIG. 1, which is a backscater electron micrograph of a crosssectioned sample coupon 10 of a known Ni-Cr based weld overlay composition (Alloy 800HT) depicting significant corrosion 12 when subject to the corrosion testing regime described above. FIG. 2 is a micrograph of a cross-sectioned sample coupon 20 of a composition according to embodiments of the invention (FC-Delta, with 30 wt.% Cr), evidencing significantly and surprisingly reduced corrosion 22 when subject to this same testing.

[0057] Embodiments of the above compositions have been deposited via various conventional welding methods onto a variety of substrates (tubing and plating). For example, the FC-Delta, FC-Beta, and AC-Delta compositions have been successfully applied to carbon steel (210, A516, A36), 300 series stainless steel (304, 304FI, 347), Grade 91 steel, and Alloy 800H (Nickel-Iron-Chromium Alloy). The compositions have been applied using Gas Metal Arc Welding, Gas Tungsten Arc Welding, Tungsten Inert Gas (stick) welding, and laser welding.

[0058] The compositions were successfully deposited onto substrates that include tubing and plating of varying sizes and dimensions. In particular, the compositions were deposited onto tubing that ranged from 5.08cm to 10.16cm (2in to 4in) inside diameter and ,635cm to 1.27cm (,25in to ,5in) thick plate.

[0059] Referring now to FIG. 3 a substrate 100 (tube) with a weld overlay 102 according to a specific embodiment is depicted. In the depicted embodiment, the substrate 100 is a 304H stainless steel tube with an inside diameter of 5.715cm (2.25in). To this substrate, FC-Delta composition was applied via Gas Metal Arc Welding. Though FIG. 3 depicts a specific weld overlay pattern, embodiments of the invention are not limited to the depicted patern.

[0060] Referring to FIG. 4 an enlarged view of a section of the weld overlay 102 of FIG.3 is depicted. As shown, the weld overlay 102, when applied to a substrate and exposed to acorrosive environment, may have an outer passivating oxide layer 104 enriched in Mn. Below the outer layer 104 is a layer enriched in Cr 106, followed by one enriched in Si 108, and one enriched in Al 110. As shown, Mo is also present at 112, as well as Cr at 114. As will be appreciated, FIG. 4 shows an exemplary application and structure of an embodiment composition as applied to a substrate and the thickness, size, and shape of the various layer is not meant to limit the scope of the invention.

[0061] As will be appreciated, the above substrates and welding techniques are exemplary and are not meant to be inclusive. In certain embodiments, other substrate materials and welding processes may potentially be utilized without departing from the scope of the invention.

[0062] Compositions may be formed into wire suitable for welding to a substrate as an overlay using known techniques. For example, the wire may be formed as a solid wire or as a metal core wire having a metallic outer sheath and an inner core containing a metallic powder. In an embodiment, the wire is formed as a folded core wire with an outer sheath and an inner core containing a powder.

[0063] In this embodiment, the wire is formed utilizing known processes in which an alloy strip material is bent or folded to create a substantially U-shape channel using rolling equipment. The channel is then continuously filled with the composition as a metallic powder. The U-shaped channel is then closed to create a tube shaped metallic outer sheath with an inner core, and then rolled / drawn to create the final diameter of the wire. In a specific embodiment, a .1143cm (,045in) diameter folded core wire was formed which is suitable for use as a weld overlay.

[0064] As mentioned, the wire has an inner core containing the composition as a powder. In embodiments, the powder has a particle size of 44 microns to 250 microns, which, among other things, facilitates manufacture of the wire using the above-described process. In an embodiment, the outer sheath is formed from 400-series stainless steel, 300-series stainless steel, or very low carbon steel. Of course, other materials may be utilized for the outer sheath without departing from the scope of the invention. In embodiments where the wire is formed as a metal core wire, the compositions set forth in Table 1 may be the sum of the metal outer sheath and the metallic powders in the inner core.

[0065] In certain embodiments, wire may be formed as a solid wire from billets using, for example, known swaging techniques. These include hot and cold swaging processes.Regardless of the method of forming the wire, it is contemplated that commercially available metallic powders are utilized to form compositions, weld overlay wires, and overlay containing substrates pursuant to embodiments of the invention. In certain instances, powders that are byproducts of other industrial processes, e.g., rare earth elements bonded to Si, may be utilized.

[0066] Embodiments of the invention also contemplate methods of forming a protective coating, e.g., a corrosion / erosion resistant weld overlay, on a substrate. In embodiments, a method involves providing a metal in a molten state, the metal having a composition including at least 12 wt.% Cr, at least .5 wt.% Al, at least 2.7 wt.% Mo, at least .3 wt.% Mn, at least .05 wt.% Ce; and less than or equal to 21 wt.% Ni. The method further includes applying the metal in a molten state to a substrate.

[0067] Embodiments of the invention may be further understood in view of the following clauses:

[0068] Clause 1. A method of forming a protective coating on a substrate, the method including providing a metal in a molten state, the metal having a composition having at least 12 wt.% Cr, at least .5 wt.% Al, at least 2.7 wt.% Mo, at least .3 wt.% Mn, at least .05 wt.% Ce; and less than or equal to 21 wt.% Ni; and the method includes applying the metal in a molten state to a substrate.

[0069] Clause 2. The method of clause 1 wherein the composition includes from 21 wt.% to 30 wt.% Cr, from .5 wt.% to .7 wt.% Al, from .05 wt.% to .15 wt.% Y, from 2.7 wt.% to 2.9 wt.% Mo, from .9 wt.% to 1.1 wt.% Si, from 2.1 wt.% to 1.9 wt.% Mn, from .4 wt.% to .6 wt.% Ti, from .05 wt.% to .15 wt.% Ce, from .05 wt.% to .15 wt.% La, with a balance of the composition being Fe.

[0070] Clause 3. The method of clause 1 wherein the composition includes from 12 wt.% to 21 wt.% Cr, from 4.9 wt.% to 5.1 wt.% Al, from .05 wt.% to .15 wt.% Y, from 2.9 wt.% to 3.1 wt.% Mo, from 1.9 wt.% to 2.1 wt.% Si, from .3 wt.% to .5 wt.% Mn, from .4 wt.% to .6 wt.% Ti, .05 wt.% to .15 wt.% Ce, with a balance of the composition being Fe.

[0071] Clause 4. The method of clause 1 wherein the composition includes from 24 wt.% to 26 wt.% Cr, from .5 wt.% to .7 wt.% Al, from 2.9 wt.% to 3.1 wt.% Mo, from .9 wt.% to 1.1 wt.% Si, from 7.9 wt.% to 8.1 wt.% Mn, from .9 wt.% to 1.1 wt.% Ti, from .05 wt.% to .15 wt.% Ce, from .05 wt.% to .15 wt.% La, from 2 wt.% to 4 wt.% Ta, from 15 wt.% to 17 wt.% Ni, with a balance of the composition being Fe.

[0072] Clause 5. The method of clause 1 wherein the composition includes from 21 wt.% to 23 wt.% Cr, from 3 wt.% to 5 wt.% Al, from 2.7 wt.% to 2.9 wt.% Mo, from .1 wt.% to .3 wt.% Si, from 2 wt.% to 8 wt.% Mn, from .05 wt.% to .15 wt.% Ce, from .4 wt.% to .6 wt.%Cu, from .9 wt.% to 1.1 wt.% Ta, from 18 wt.% to 21 wt.% Ni, with a balance of the composition being Fe.

[0073] Clause 6. The method of any of the preceding clauses wherein applying the metal in a molten state comprises applying the metal to the substrate as a weld overlay utilizing gas metal arc welding, gas tungsten arc welding, tungsten inert gas welding, or laser welding.

[0074] Clause 7. The method of any of the preceding clauses wherein the metal, prior to being in the molten state, is a metal core wire having a metallic outer sheath and an inner core containing metallic powder.

[0075] Clause 8. The method of any of the preceding clauses wherein the substrate includes metal tubing in a superheater, reheater, and / or economizer of a boiler.

[0076] Clause 9. The method of clause 8 wherein the metal tubing is formed from a carbon steel or a low alloy steel.

[0077] Clause 10. A wire utilized in connection with forming a resistant coating on a substrate, the wire including a composition including at least 12 wt.% Cr, at least .5 wt.% Al, at least 2.7 wt.% Mo, at least .3 wt.% Mn, at least .05 wt. % Ce; and less than or equal to 21 wt.% Ni.

[0078] Clause 11. The wire of clause 10 wherein the composition includes from 21 wt.% to 30 wt.% Cr, from .5 wt.% to .7 wt.% Al, from .05 wt.% to .15 wt.% Y, from 2.7 wt.% to 2.9 wt.% Mo, from .9 wt.% to 1.1 wt.% Si, from 2.1 wt.% to 1.9 wt.% Mn, from .4 wt.% to .6 wt.% Ti, from .05 wt.% to .15 wt.% Ce, from .05 wt.% to .15 wt.% La, with a balance of the composition being Fe.

[0079] Clause 12. The wire of clause 10 wherein the composition includes from 12 wt.% to 21 wt.% Cr, from 4.9 wt.% to 5.1 wt.% Al, from .05 wt.% to .15 wt.% Y, from 2.9 wt.%to 3.1 wt.% Mo, from 1.9 wt.% to 2.1 wt.% Si, from .3 wt.% to .5 wt.% Mn, from .4 wt.% to .6 wt.% Ti, .05 wt.% to .15 wt.% Ce, with a balance of the composition being Fe.

[0080] Clause 13. The wire of clause 10 wherein the composition includes from 24 wt.% to 26 wt.% Cr, from .5 wt.% to .7 wt.% Al, from 2.9 wt.% to 3.1 wt.% Mo, from .9 wt.% to 1.1 wt.% Si, from 7.9 wt.% to 8.1 wt.% Mn, from .9 wt.% to 1.1 wt.% Ti, from .05 wt.% to .15 wt.% Ce, from .05 wt.% to .15 wt.% La, from 2 wt.% to 4 wt.% Ta, from 15 wt.% to 17 wt.% Ni, with a balance of the composition being Fe.

[0081] Clause 14. The wire of clause 10 wherein the composition includes from 21 wt.% to 23 wt.% Cr, from 3 wt.% to 5 wt.% Al, from 2.7 wt.% to 2.9 wt.% Mo, from .1 wt.% to .3 wt.% Si, from 2 wt.% to 8 wt.% Mn, from .05 wt.% to .15 wt.% Ce, from .4 wt.% to .6 wt.% Cu, from .9 wt.% to 1.1 wt.% Ta, from 18 wt.% to 21 wt.% Ni, with a balance of the composition being Fe.

[0082] Clause 15. The wire of any of the preceding clauses further including a metallic outer sheath and an inner core containing metallic powder.

[0083] Clause 16. The wire of clause 15 wherein the powder has a particle size of 44 microns to 250 microns.

[0084] Clause 17. A substrate containing a protective coating, the protective coating including at least 12 wt.% Cr; at least .5 wt.% Al; at least 2.7 wt.% Mo; at least .3 wt.% Mn; at least .05 wt.% Ce; and less than or equal to 21 wt.% Ni.

[0085] Clause 18. The substrate of any of the preceding clauses wherein the substrate is tubing and / or plating manufactured from carbon steel, stainless steel, Grade 91 steel, and / or a nickel alloy.

[0086] Clause 19. The substrate of any of the preceding clauses wherein the protective coating is a weld overlay applied to the substrate utilizing gas metal arc welding, gas tungsten arc welding, tungsten inert gas welding, or laser welding.

[0087] Clause 20. The substrate of clause 17 wherein the protective coating includes from 21 wt.% to 30 wt.% Cr, from .5 wt.% to .7 wt.% Al, from .05 wt.% to .15 wt.% Y, from 2.7 wt.% to 2.9 wt.% Mo, from .9 wt.% to 1.1 wt.% Si, from 2.1 wt.% to 1.9 wt.% Mn, from .4 wt.% to .6 wt.% Ti, from .05 wt.% to .15 wt.% Ce, from .05 wt.% to .15 wt.% La, with a balance of the protective coating being Fe.

[0088] As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property.

[0089] While the dimensions and types of materials described herein are intended to define the parameters of the invention, they are by no means limiting and are exemplary embodiments. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description.

[0090] The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.”

[0091] Moreover, in the following claims, terms such as “upper,” “lower,” “bottom,” “top,” etc. are used merely as labels, and are not intended to impose numerical or positional requirements on their layers or objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted as such, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.

[0092] This written description uses examples to disclose several embodiments of the invention, including the best mode, and also to enable one of ordinary skill in the art to practice the embodiments of invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to one of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

CLAIMS:

1. A method of forming a protective coating on a substrate, the method comprising: providing a metal in a molten state, the metal having a composition comprising: at least 12 wt.% Cr; at least .5 wt.% Al; at least 2.7 wt.% Mo; at least .3 wt.% Mn; at least .05 wt.% Ce; and less than or equal to 21 wt.% Ni; and applying the metal in a molten state to a substrate.

2. The method of claim 1 wherein the composition comprises. from 21 wt.% to 30 wt.% Cr, from .5 wt.% to .7 wt.% Al, from .05 wt.% to .15 wt.% Y, from 2.7 wt.% to 2.9 wt.% Mo, from .9 wt.% to 1.1 wt.% Si, from 2.1 wt.% to 1.9 wt.% Mn, from .4 wt.% to .6 wt.% Ti, from .05 wt.% to .15 wt.% Ce, from .05 wt.% to .15 wt.% La, with a balance of the composition being Fe.

3. The method of claim 1 wherein the composition comprises. from 12 wt.% to 21 wt.% Cr, from 4.9 wt.% to 5.1 wt.% Al, from .05 wt.% to .15 wt.% Y, from 2.9 wt.% to 3.1 wt.% Mo, from 1.9 wt.% to 2.1 wt.% Si, from .3 wt.% to .5 wt.% Mn, from .4 wt.% to .6 wt.% Ti, .05 wt.% to .15 wt.% Ce, with a balance of the composition being Fe.

4. The method of claim 1 wherein the composition comprises. from 24 wt.% to 26 wt.% Cr, from .5 wt.% to .7 wt.% Al, from 2.9 wt.% to 3.1 wt.% Mo, from .9 wt.% to 1.1 wt.% Si, from 7.9 wt.% to 8.1 wt.% Mn, from .9 wt.% to 1.1 wt.% Ti, from .05 wt.% to .15 wt.% Ce, from .05 wt.% to .15 wt.% La, from 2 wt.% to 4 wt.% Ta, from 15 wt.% to 17 wt.% Ni, with a balance of the composition being Fe.

5. The method of claim 1 wherein the composition comprisesfrom 21 wt.% to 23 wt.% Cr, from 3 wt.% to 5 wt.% Al, from 2.7 wt.% to 2.9 wt.% Mo, from .1 wt.% to .3 wt.% Si, from 2 wt.% to 8 wt.% Mn, from .05 wt.% to .15 wt.% Ce, from .4 wt.% to .6 wt.% Cu, from .9 wt.% to 1.1 wt.% Ta, from 18 wt.% to 21 wt.% Ni, with a balance of the composition being Fe.

6. The method of claim 1 wherein applying the metal in a molten state comprises applying the metal to the substrate as a weld overlay utilizing gas metal arc welding, gas tungsten arc welding, tungsten inert gas welding, or laser welding.

7. The method of claim 1 wherein the metal, prior to being in the molten state, is a metal core wire having a metallic outer sheath and an inner core containing metallic powder.

8. The method of claim 1 wherein the substrate includes metal tubing in a superheater, reheater, and / or economizer of a boiler.

9. The method of claim 8 wherein the metal tubing is formed from a carbon steel or a low alloy steel.

10. A wire utilized in connection with forming a resistant coating on a substrate, the wire including a composition comprising: at least 12 wt.% Cr; at least .5 wt.% Al; at least 2.7 wt.% Mo; at least .3 wt.% Mn; at least .05 wt. % Ce; and less than or equal to 21 wt.% Ni.

11. The wire of claim 10 wherein the composition comprises: from 21 wt.% to 30 wt.% Cr, from .5 wt.% to .7 wt.% Al, from .05 wt.% to .15 wt.% Y, from 2.7 wt.% to 2.9 wt.% Mo, from .9 wt.% to 1.1 wt.% Si, from 2.1 wt.% to 1.9 wt.% Mn,from .4 wt.% to .6 wt.% Ti, from .05 wt.% to .15 wt.% Ce, from .05 wt.% to .15 wt.% La, with a balance of the composition being Fe.

12. The wire of claim 10 wherein the composition comprises: from 12 wt.% to 21 wt.% Cr, from 4.9 wt.% to 5.1 wt.% Al, from .05 wt.% to .15 wt.% Y, from 2.9 wt.% to 3.1 wt.% Mo, from 1.9 wt.% to 2.1 wt.% Si, from .3 wt.% to .5 wt.% Mn, from .4 wt.% to .6 wt.% Ti, .05 wt.% to .15 wt.% Ce, with a balance of the composition being13. The wire of claim 10 wherein the composition comprises: from 24 wt.% to 26 wt.% Cr, from .5 wt.% to .7 wt.% Al, from 2.9 wt.% to 3.1 wt.% Mo, from .9 wt.% to 1.1 wt.% Si, from 7.9 wt.% to 8.1 wt.% Mn, from .9 wt.% to 1.1 wt.% Ti, from .05 wt.% to .15 wt.% Ce, from .05 wt.% to .15 wt.% La, from 2 wt.% to 4 wt.% Ta, from 15 wt.% to 17 wt.% Ni, with a balance of the composition being Fe.

14. The wire of claim 10 wherein the composition comprises: from 21 wt.% to 23 wt.% Cr, from 3 wt.% to 5 wt.% Al, from 2.7 wt.% to 2.9 wt.% Mo, from .1 wt.% to .3 wt.% Si, from 2 wt.% to 8 wt.% Mn, from .05 wt.% to .15 wt.% Ce, from .4 wt.% to .6 wt.% Cu, from .9 wt.% to 1.1 wt.% Ta, from 18 wt.% to 21 wt.% Ni, with a balance of the composition being Fe.

15. The wire of claim 10 further comprising: a metallic outer sheath and an inner core containing metallic powder.

16. The wire of claim 15 wherein the powder has a particle size of 44 microns to 250 microns.

17. A substrate containing a protective coating, the protective coating comprising: at least 12 wt.% Cr; at least .5 wt.% Al; at least 2.7 wt.% Mo;at least .3 wt.% Mn; at least .05 wt.% Ce; and less than or equal to 21 wt.% Ni.

18. The substrate of claim 17 wherein the substrate is tubing and / or plating manufactured from carbon steel, stainless steel, Grade 91 steel, and / or a nickel alloy.

19. The substrate of claim 17 wherein the protective coating is a weld overlay applied to the substrate utilizing gas metal arc welding, gas tungsten arc welding, tungsten inert gas welding, or laser welding.

20. The substrate of claim 17 wherein the protective coating comprises (FC-Delta): from 21 wt.% to 30 wt.% Cr, from .5 wt.% to .7 wt.% Al, from .05 wt.% to .15 wt.% Y, from 2.7 wt.% to 2.9 wt.% Mo, from .9 wt.% to 1.1 wt.% Si, from 2.1 wt.% to 1.9 wt.% Mn, from .4 wt.% to .6 wt.% Ti, from .05 wt.% to .15 wt.% Ce, from .05 wt.% to .15 wt.% La, with a balance of the protective coating being Fe.

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