Patent Description:
The manufacturing of components requiring different mechanical, corrosive or physical properties in different areas is often complicated. There are several ways that different properties can be achieved including weld overlay, mechanically attaching different materials together, differential heat treatment by induction hardening, flame hardening, or selective salt bath quenching. All these methods have different drawbacks, and it can be very difficult, if possible, to achieve drastically different materials properties within a component, using these methods.

Methods of making a composite component by hot isostatic pressing from two different alloys joined together by diffusion bonding at the interface, as well as the components, have previously been described in <CIT> as well as in <NPL>). <CIT> describes a method for providing lining on walls or cavities of bodies using hot isostatic pressing.

Various features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying figures in which like characters represent like parts throughout the figures, wherein:.

These described embodiments are only exemplary of the present disclosure. Additionally, in an effort to provide a concise description of these exemplary embodiments, all features of an actual implementation may not be described in the specification.

Present embodiments are generally directed to systems and methods for the hot isostatic pressing (HIP) fabrication of components for use in the oil field services industry, which may relate generally to any activities (e.g., drilling, producing, monitoring, and/or maintaining) that facilitate access to and/or extraction of natural resources (e.g., hydrocarbons) from the earth. The components may be any of a variety of components for use in equipment, such as pressure-containing and/or pressure-controlling equipment. Present embodiments enable the production of multi-metallic (e.g., bimetallic, trimetallic) components, such as pressure-containing components and/or pressure-controlling components. An example embodiment includes a HIP-fabricated multi-metallic ram of a blowout preventer (BOP). A traditional BOP ram is fabricated using a subtractive manufacturing technique in which a forged block of a particular metal alloy is precisely machined into a complex shape, and then a number of conventional and unconventional heat treatments are performed to impart different material properties to different portions of the part. As used herein, the term metal alloy refers to either a pure metal or a metallic solid solution including a number of different metallic and/or non-metallic chemical elements.

In contrast, present embodiments involve the use of a HIP-fabrication process in which different metal alloys (e.g., different metal alloy powders, different metal alloy boundary layers) are combined and sealed in a canister before being heated and pressurized during a HIP process (e.g., in an autoclave) to form a multi-metallic pressure-controlling component (e.g., a BOP ram). As a result, the different metal alloys are disposed in different portions of the part to impart different material properties to these portions of the part (e.g., higher strength and hardness in a blade area of the ram, higher toughness in the body of the ram). Additionally, a finite (e.g., narrow) diffusion bond forms at the interface between different metal alloys, yielding a dense, seamless pressure-controlling component.

It is presently recognized that the disclosed HIP manufacturing process enables substantially greater freedom of design by enabling the joining of metal alloys that may be chemically incompatible using traditional joining methods (e.g., welding). Additionally, by using different metal alloys in different portions of the part, a greater range of material properties (e.g., strength, toughness, ductility, hardness, corrosion resistance) is available compared to the range of material properties achievable using a traditional, single metal alloy ram with multiple thermal processing steps. Within the HIP manufacturing process, a HIP process chemically bonds powder metal into a solid part under "extreme" temperature and pressure. After the HIP process is complete, the final part may be achieved with reduced processing time, compared with the traditional manufacturing techniques. For example, after the HIP process has been applied to join the metal powders of the multi-metallic part, the final part may be realized with reduced machining time, with little or no welding, and without special heat treatment processes of traditional manufacturing techniques, thereby reducing manufacturing time and cost relative to traditional manufacturing techniques. Furthermore, the disclosed HIP manufacturing process generally provides the capability to efficiently construct pressure-controlling equipment components having a complex shape while avoiding or reducing time-consuming and/or costly complex thermal processing, welding, and/or machining steps.

While the present embodiments are described in the context of a ram of a BOP for a drilling system to facilitate discussion, it should be appreciated that the systems and methods for HIP fabrication of multi-metallic components may be adapted for fabrication of other equipment, such as another component of the BOP for the drilling system and/or another component of another device for any type of system (e.g., drilling system, production system).

The invention provides a multi-metallic component according to claim <NUM> and a manufacturing method thereof according to claim <NUM>.

With the foregoing in mind, <FIG> is a block diagram of an embodiment of a drilling system <NUM> for mineral extraction. The drilling system <NUM> may be configured to drill (e.g., circulate drilling mud and take drilling cuttings up to surface) for the eventual extraction of extract various minerals and natural resources, including hydrocarbons (e.g., oil and/or natural gas), from the earth and/or to inject substances into the earth. The drilling system <NUM> may be a land-based system (e.g., a surface system) or an offshore system (e.g., an offshore platform system).

As shown, a BOP stack <NUM> may be mounted to a wellhead <NUM>, which is coupled to a mineral deposit <NUM> via a wellbore <NUM>. The wellhead <NUM> may include or be coupled to any of a variety of other components such as a spool, a hanger, and a "Christmas" tree. The wellhead <NUM> may return drilling fluid or mud toward a surface during drilling operations, for example. Downhole operations are carried out by a conduit <NUM> (e.g., drill string) that extends through a central bore <NUM> of the BOP stack <NUM>, through the wellhead <NUM>, and into the wellbore <NUM>.

As discussed in more detail below, the BOP stack <NUM> may include one or more BOPs <NUM> (e.g., ram BOPs), and component (e.g., rams) of the one or more BOPs <NUM> may be manufactured using systems and methods for HIP fabrication disclosed herein. To facilitate discussion, the BOP stack <NUM> and its components may be described with reference to a vertical axis or direction <NUM>, an axial axis or direction <NUM>, and/or a lateral axis or direction <NUM>.

<FIG> is a cross-sectional top view of a portion of an embodiment of the BOP <NUM> that may be used in the drilling system <NUM> of <FIG>, in accordance with an embodiment of the present disclosure. As shown, the BOP <NUM> includes opposed rams <NUM>, including upper ram 50A and lower ram 50B, also generally referred to herein as pressure-controlling components <NUM> or multi-metallic pressure-controlling components <NUM> of the BOP <NUM>. In the illustrated embodiment, the opposed rams <NUM> are in an open configuration <NUM> of the BOP <NUM> in which the opposed rams <NUM> are withdrawn from the central bore <NUM>, do not contact the conduit <NUM>, and/or do not contact one another.

As shown, the BOP <NUM> includes a bonnet flange <NUM> surrounding the central bore <NUM>. The bonnet flange <NUM> is generally rectangular in the illustrated embodiment, although the bonnet flange <NUM> may have any cross-sectional shape, including any polygonal shape and/or annular shape. Bonnet assemblies <NUM> are mounted on opposite sides of the bonnet flange <NUM> (e.g., via threaded fasteners). Each bonnet assembly <NUM> includes an actuator <NUM>, which may include a piston <NUM> and a connecting rod <NUM>. The actuators <NUM> may drive the opposed rams <NUM> toward one another along the axial axis <NUM> to reach a closed position in which the opposed rams <NUM> are positioned within the central bore <NUM>, contact and/or shear the conduit <NUM> to seal the central bore <NUM>, and/or contact one another to seal the central bore <NUM>.

Each of the opposed rams <NUM> may include a body section <NUM> (e.g., ram body), a leading surface <NUM> (e.g., side, portion, wall) and a rearward surface <NUM> (e.g., side, portion, wall, rearmost surface). The leading surfaces <NUM> may be positioned proximate to the central bore <NUM> and may face one another when the opposed rams <NUM> are installed within the housing <NUM>. The rearward surfaces <NUM> may be positioned distal from the central bore <NUM> and proximate to a respective one of the actuators <NUM> when the opposed rams <NUM> are installed within the housing <NUM>. The leading surfaces <NUM> may be configured to couple to and/or support sealing elements (e.g., elastomer or polymer seals) that are configured to seal the central bore <NUM> in the closed position, and the rearward surfaces <NUM> may include an attachment interface <NUM> (e.g., recess) that is configured to engage with the connecting rod <NUM> of the actuator <NUM>. The body section <NUM> also includes lateral surfaces <NUM> (e.g., walls) that are on opposite lateral sides of the body section <NUM> and that extend along the axial axis <NUM> between the leading surface <NUM> and the rearward surface <NUM>. In <FIG>, the opposed rams <NUM> have a generally rectangular shape to facilitate discussion; however, it should be appreciated that the opposed rams <NUM> may have any of a variety of shapes or features (e.g., curved portions to seal against the conduit <NUM>, edges to shear the conduit <NUM>).

<FIG> is a front isometric view of an embodiment of the upper ram 50A, and <FIG> is a front isometric view of an embodiment of the lower ram 50B, which may be used together as pressure-controlling components <NUM> in the embodiment of BOP <NUM> of <FIG>. As illustrated in <FIG> and <FIG>, the pressure-controlling components <NUM> each include the body section <NUM> and a blade section <NUM>. Each blade section <NUM> includes the leading surface <NUM>, while the body section <NUM> includes the rearward surface <NUM> of the rams <NUM>. Because the rams <NUM> of <FIG> and <FIG> are shear rams, each blade section <NUM> includes a respective edge portion <NUM> that is formed in the leading surface <NUM> and that extends along the lateral axis <NUM> of each of the rams <NUM>. In a closed configuration, the respective edge portions <NUM> of the upper ram 50A and the lower ram 50B are configured to shear the conduit <NUM> and/or support the seal elements that seal against the central bore <NUM> of the BOP illustrated in <FIG>. However, it should be appreciated that the rams <NUM> may have any of a variety of other configurations (e.g., the rams <NUM> may be pipe rams that lack the respective edge portions <NUM>). The blade section <NUM> of each of the rams <NUM> of <FIG> and <FIG> also includes a leading cutout <NUM> formed in the leading surfaces <NUM> (e.g., positioned above and below the respective edge portion <NUM> along the vertical axis <NUM>). The leading surface <NUM>, the rearward surface <NUM>, the lateral surfaces <NUM>, a top surface <NUM> (e.g., top-most surface), and a bottom surface <NUM> (e.g., bottom-most surface) may be considered the respective outer surfaces of the rams <NUM>. For the illustrated rams <NUM>, the outer surfaces include grooves or channels <NUM>. In certain embodiments, at least a portion of these grooves may be sealing grooves designed to receive or interface with a polymeric material (e.g., an elastomeric seal), while a portion of these grooves may be sliding grooves designed to receive a slide along a metallic extension during operation of the BOP.

For the pressure-controlling components <NUM> illustrated in <FIG> and <FIG>, at least the body section <NUM> and the blade section <NUM> have a different metal alloy composition (e.g., a different chemical composition). For example, in certain embodiments, the body section <NUM> of the rams <NUM> may be made of a first metal alloy, while at least a portion of the blade section <NUM> (e.g., an outer surface) is made of a second metal alloy. The various metal alloys of the pressure-controlling components <NUM> may be selected for desirable material properties, including but not limited to: toughness, percent elongation, percent reduction of area, tensile strength, yield strength, impact strength, ductility, hardness, and corrosion resistance. A non-limiting list of example metal alloys includes, but is not limited to: chromium-molybdenum (Cr-Mo) steels (e.g., Unified Numbering System (UNS) G41300, UNS G41400, UNS K21590); chromium-nickel-molybdenum (Cr-Ni-Mo) steels (e.g., UNS G43400); maraging (also known as martensitic-aged) steels (e.g., UNS K91973, UNS K44220, UNS K93120); super martensitic stainless steels (e.g., Euronorm (EN) <NUM>, UNS S41425, UNS S41426, UNS S41427); precipitation-hardened nickel alloys (e.g., UNS N07718, UNS N09946); precipitation-hardened martensitic steels (e.g., UNS S35000, UNS S17400); solution-annealed nickel alloys (e.g., UNS N06625, UNS N08825); tool steels (e.g., UNS T41907, UNS T30402, UNS T20813); cobalt or nickel-bound tungsten-carbides, nickel-cobalt (Ni-Co) alloys (e.g. UNS R30035); and cobalt-chromium (Co-Cr) alloys (e.g. UNS R30006). In certain embodiments, one or more of the metal alloys of the pressure-controlling components <NUM> may be compliant with the National Association of Corrosion Engineers (NACE) MR0175 standard (also referred to as ISO <NUM>), which is a materials standard intended to assess the suitability of materials for oil and gas applications in which where sulfide stress corrosion cracking may be a risk in hydrogen sulfide-rich (sour) environments.

<FIG> is a cross-sectional view of an embodiment of the upper ram 50A illustrated in <FIG>. For the illustrated embodiment, the blade section <NUM> of illustrated upper ram 50A is made of a first metal alloy <NUM>. The body section <NUM> includes a first portion 68A that is made of a second metal alloy <NUM> and a second portion 68B that is made of a third metal alloy <NUM>, resulting in a substantially trimetallic upper ram 50A. In some embodiments, both portions of the body section <NUM> may only include a single metal alloy, resulting in a substantially bimetallic upper ram 50A, in which the blade section <NUM> and the body section <NUM> each are made entirely of a different respective metal alloy.

The metal alloys of the pressure-controlling component <NUM> (e.g., metal alloys <NUM>, <NUM>, <NUM>) may be selected based on a number of criteria. For example, for the embodiment illustrated in <FIG>, it may be desirable for the blade section <NUM> to have a greater strength (e.g., a tensile and/or yield strength that is at least <NUM> percent greater, at least <NUM> percent greater, at least <NUM> percent greater, <NUM> percent greater, <NUM> percent greater, <NUM> percent greater) than that of the body section <NUM>. Additionally or alternatively, it may be desirable for the body section <NUM> to have a greater toughness (e.g., a percent elongation and/or percent reduction in area that is at least <NUM> percent greater, at least <NUM> percent greater, at least <NUM> percent greater, <NUM> percent greater, <NUM> percent greater, <NUM> percent greater) than that of the blade section <NUM>. This can result in the formation of rams <NUM> having a stronger blade section <NUM>, while also having a tougher, more ductile, and more resilient body section <NUM>.

As such, for the embodiment illustrated in <FIG>, the first metal alloy <NUM> that forms the blade section <NUM> may be selected based on having a suitably higher strength relative to the second metal alloy <NUM> that forms at least a substantial portion of the body section <NUM>. For embodiments that include the second boundary and the third metal alloy <NUM>, the third metal alloy may be selected based on having a higher corrosion resistance relative to the second metal alloy <NUM>. For example, in an example embodiment, the blade section <NUM> may be formed using a high-alloy steel alloy <NUM>, which has relatively higher strength; the first portion 68A of body section <NUM> may be formed using low-alloy steel <NUM>, which has a relatively higher toughness; and the second portion 68B of the body section <NUM> may be formed using a high-chrome or high-nickel steel <NUM>, which has relatively higher corrosion resistance. While corrosion resistance may be desirable when the second portion 68B of the body section <NUM> will contact a elastomer or polymer seal, for embodiments in which the second portion 68B will contact and slide against a metallic surface during operation, the second portion 68B may instead be formed from a metal alloy having a relatively greater hardness (e.g., at least <NUM> percent greater hardness, at least <NUM> percent greater hardness), which can improve sliding against the metallic part (e.g., reducing or preventing galling, reducing wear). Additionally, the selected metal alloys should be compatible with one another for the HIP process. In other words, in certain embodiments, certain material properties of the selected metal alloys (e.g., melting point, sintering point) should be similar (e.g., within a predetermined threshold), such that simultaneous, preferential microstructural develops in each material during a single HIP process, as discussed below.

Additionally, the embodiment of the upper ram 50A illustrated in <FIG> includes planar (e.g., straight, flat) boundaries or interfaces <NUM>, at which the two different metal alloys meet and join via a narrow (e.g., less than <NUM> millimeter, less than <NUM> millimeter, about <NUM> millimeter) diffusion bond, which may also be referred to as the diffusion bond zone. For the embodiment of <FIG>, these boundaries <NUM> include a first boundary 100A disposed between the blade section <NUM> and the first portion 68A of the body section <NUM>, as well as a second boundary 100B disposed between the first portion 68A and the second portion 68B of the body section <NUM>. For the illustrated embodiment, the boundaries <NUM> are aligned with planes oriented in the vertical and lateral directions (e.g., along a plane defined by axes <NUM> and <NUM>). In certain embodiments, as discussed below, a thin boundary layer may be present along the interface <NUM> and be made of a metal alloy that is the same as or different from the metal alloys present on either side of the boundaries <NUM>. For clarity, since the boundary layer contributes little to the overall composition of the upper ram 50A, the upper ram 50A illustrated in <FIG> may be described herein as being "substantially trimetallic," meaning that it predominantly includes only metal alloys <NUM>, <NUM>, and <NUM>, even when boundary layers are used having different compositions relative to the metal alloys <NUM>, <NUM>, and <NUM>.

It may be appreciated that, for certain embodiments of pressure-controlling components <NUM>, it may be desirable for the diffusion bonds at the boundaries <NUM> to demonstrate certain features or material properties. For example, in certain embodiments, the strength (e.g., tensile strength, yield strength) at each interface <NUM> between different metal alloys is greater than the strength of the material that is used to form at least a substantial portion of the body <NUM>. For the embodiment of <FIG>, this would mean that the diffusion bond at the boundary <NUM> between the blade section <NUM> and the body section <NUM> would have a greater strength than that of the metal alloy <NUM> that forms the bulk of the body section <NUM>. It may also be desirable, in certain embodiments, for the sintering of the metal alloys at and/or near the boundary <NUM>, and therefore the resulting grain structure, to be substantially homogenous. In certain embodiments, it may be desirable that the integrity of the body between the different metal alloys to be stable and maintained through any heating and quenching processes used in the fabrication of the pressure-controlling components <NUM>.

In some embodiments, the boundaries <NUM> that define the diffusion bonds between the different metal alloys of the pressure-controlling components <NUM> may not be planar boundaries. For example, <FIG> are cross-sectional views of embodiments of substantially bimetallic lower rams 50B having a curved boundary <NUM> (e.g., a curved diffusion bond) disposed between a first metal alloy <NUM> and a second metal alloy <NUM> that form the lower ram 50B. In <FIG>, the curved boundary <NUM> results in the blade section <NUM> having both the first and the second metal alloys, while the curved boundary in <FIG> results in the body section <NUM> having both the first and the second metal alloys. In certain embodiments, it may be desirable to use the curved boundary <NUM>, as opposed to the planar boundaries discussed above, to reduce the amount of the first alloy <NUM> or the second alloy <NUM> used to make the pressure-controlling component <NUM>. In some embodiments, it may be desirable to include the curved boundary <NUM> increase the surface area of the interface <NUM> (e.g., the surface area of the diffusion bond) between the first and second metal alloys <NUM>, <NUM> to enhance the material properties (e.g., strength, toughness) of the pressure-controlling component <NUM> at the interface <NUM>. Additionally, while regular curved boundaries are illustrated, in some embodiments, the boundaries <NUM> may have substantial irregularity (e.g., ripples, undulations) without departing from the techniques disclosed herein.

In some embodiments, the boundaries that define the diffusion bonds between different metal alloys may be complex and correspond to (e.g., follow, match) one or more contours in the outer surface of the pressure-controlling components <NUM>. For example, <FIG> is a cross-sectional view of an embodiment of a substantially trimetallic lower ram 50B having boundaries <NUM> that follow along features defined in the outer surface of the part. In particular, a layer of the first metal alloy <NUM> defines the outer surface of the blade section <NUM> of the part, while the second metal alloy <NUM> fills the interior of the blade section <NUM> and defines the outer surface of the body section <NUM> of the ram 50B. Additionally, for the illustrated embodiment, the third metal alloy <NUM> (e.g., a corrosion resistant alloy) defines the outer surface of a seal region <NUM> in the body section <NUM> of the ram 50B. It should be appreciated that any of the boundaries <NUM> (e.g., planar, curved, complex) may be used in the upper ram 50A, the low ram 50B, or both in any suitable combination (e.g., all planar, all curved, at least one planar and at least one curved).

For certain embodiments of the lower ram 50B illustrated in <FIG>, at least a portion of the first metal alloy <NUM> or the third metal alloy <NUM> may be disposed on the second metal alloy <NUM> to form the outer surfaces of the pressure-controlling components <NUM> using a welding-based deposition process (e.g., an overlay, inlay, or cladding process) after the formation of the remainder of the part using the HIP manufacturing process set forth below. However, in some embodiments, all of the metal alloys (e.g., metal alloys <NUM>, <NUM>, and <NUM>) of the pressure-controlling component <NUM> are joined together during the HIP manufacturing process discussed below. For example, the layer of the first metal alloy <NUM> may have a defined first thickness <NUM> in the blade section <NUM> of the part, while the third metal alloy <NUM> may have a second thickness <NUM> in the seal region <NUM> of the ram 50B. Using the disclosed HIP manufacturing process, the first and second thicknesses <NUM> and <NUM> may be independently controlled to any suitable thickness, such as <NUM> inch (in) (<NUM> centimeter (cm), about <NUM> millimeters (mm)) or greater, <NUM> in (<NUM>, about <NUM>) or greater, <NUM> in (<NUM>, about <NUM>) or greater, between <NUM> in (<NUM>, about <NUM>) and <NUM> in (<NUM>, about <NUM>), between <NUM> in (<NUM>, about <NUM>) and <NUM> in (<NUM>, about <NUM>), <NUM> in (<NUM>, about <NUM>) or greater. As such, it may be appreciated that, for embodiments in which the metal alloys of the pressure-controlling components <NUM> are joined during HIP process in the disclosed HIP manufacturing process, there is an advantageous reduction in manufacturing time and cost by avoiding the welding-based deposition processes, as well as any subsequent post-welding activity (e.g., clean-up, analysis, inspection). By using the disclosed HIP manufacturing process, the thicknesses <NUM> and <NUM> of the metal alloy layers <NUM> and <NUM> can also reach substantially greater thicknesses than can be suitably deposited using welding-based deposition processes. Additionally, since the HIP manufacturing process does not require depositing the metal alloys <NUM> and <NUM> via a welding-based process, metal alloys <NUM>, <NUM>, and <NUM> may be metal alloys that are less conducive or completely incompatible with welding-based processes. Furthermore, by avoiding the welding-based processes, the potential to introduce issues in the part as a side-effect of the welding-based deposition processes (e.g., unintended thermally-induced changes in the grain structure at or near the weld deposit, unintended introduction of stress or strain in the part, unintended imperfections in the fusion zone) can also be advantageously avoided.

<FIG> is a block diagram of an embodiment of a HIP manufacturing system <NUM> that may be used to construct the multi-metallic pressure-controlling component <NUM> (e.g., the upper ram 50A, the lower ram 50B, other components of the BOP <NUM>). For the illustrated embodiment, the HIP manufacturing system <NUM> includes a controller <NUM>, a user interface <NUM>, a canister <NUM>, a heat source <NUM>, and a pressure source <NUM>, which, as discussed below, may be used to carry out the steps of the manufacturing process <NUM> of <FIG> to form the pressure-controlling component <NUM>.

In certain embodiments, the controller <NUM> is an electronic controller having electrical circuitry configured to process data from various components of the system <NUM>, for example. In the illustrated embodiment, the controller <NUM> includes a processor <NUM> and a memory device <NUM>. The controller <NUM> may also include one or more storage devices and/or other suitable components. By way of example, the processor <NUM> may be used to execute software, such as software for controlling the user interface <NUM>, controlling the heat source <NUM>, the pressure source <NUM>, and so forth. Moreover, the processor <NUM> may include multiple microprocessors, one or more "general-purpose" microprocessors, one or more special-purpose microprocessors, and/or one or more application specific integrated circuits (ASICS), or some combination thereof. For example, the processor <NUM> may include one or more reduced instruction set (RISC) processors.

The memory device <NUM> may include a volatile memory, such as random access memory (RAM), and/or a nonvolatile memory, such as read-only memory (ROM). The memory device <NUM> may store a variety of information and may be used for various purposes. For example, the memory device <NUM> may store processor-executable instructions (e.g., firmware or software) for the processor <NUM> to execute, such as instructions for controlling the user interface <NUM>, the heat source <NUM>, the pressure source <NUM>, and so forth. The storage device(s) (e.g., nonvolatile storage) may include read-only memory (ROM), flash memory, a hard drive, or any other suitable optical, magnetic, or solid-state storage medium, or a combination thereof.

The user interface <NUM> may include suitable input and output devices communicatively coupled to the controller <NUM>. The user interface <NUM> is configured to receive user input defining parameters of the HIP manufacturing process (e.g., temperature/pressure programs). The controller <NUM> may store received inputs in the memory device <NUM> until used by the processor <NUM> to perform portions of the HIP manufacturing process. During the HIP manufacturing process, information about the state of the controller <NUM>, the heat source <NUM>, the pressure source <NUM>, and measurements from various sensors (e.g., temperature sensors, pressure sensors, displacement sensors) of the HIP manufacturing system <NUM> may be suitably presented on a display device of the user interface <NUM>.

The canister <NUM> is generally a sacrificial metal alloy (e.g., steel) container that serves as a mold during the HIP processing. As such, the canister <NUM> includes an internal cavity that generally corresponds to the shape of the pressure-controlling component <NUM> being manufactured, although notably larger due to the reduction in volume experienced during HIP process. As discussed below, the canister <NUM> is designed to receive multiple metal alloy powders, and potentially receive metal alloy foil boundary layers (e.g., nickel foil boundary layers) that are disposed between each layer of distinct metal alloy powder. During HIP processing of the canister <NUM>, the pressure provided by the pressure source <NUM> and the heat provided by the heat source <NUM> condenses the materials (e.g., metal alloy powders, boundary layers) within the canister <NUM> into an integral, dense, multi-metallic pressure-controlling component <NUM>. In certain embodiments, the heat source <NUM> and the pressure source <NUM> are integrated into a single element (e.g., an autoclave furnace).

With the foregoing in mind, <FIG> is a flow diagram of a process <NUM> for manufacturing the pressure-controlling component <NUM> (e.g., the upper ram 50A, the lower ram 50B, other components of the BOP <NUM>). In particular, the process <NUM> includes steps for constructing the pressure-controlling component <NUM> using the HIP manufacturing system <NUM> illustrated in <FIG>. In certain embodiments, at least a portion of the steps of the process <NUM> (e.g., loading of the canister) may be performed by a human operator, while at least a portion of the steps of the process <NUM> (e.g., HIP processing) may be performed by the controller <NUM> based on instructions stored in the memory device <NUM> and/or input received from the user interface <NUM>. It may be appreciated that the process <NUM> is merely provided as an example, and in some embodiments, the process <NUM> may include additional steps, omitted steps, repeated steps, and so forth, in accordance with the present disclosure.

For the embodiment illustrated in <FIG>, the process <NUM> begins with depositing (block <NUM>) a first metal alloy powder into the canister <NUM>. The first metal alloy may be any of a variety of suitable materials, including those mentioned above. In certain embodiments, the first metal alloy added to the canister <NUM> may correspond to the metal alloy that forms at least a substantial portion of the body section <NUM> of the rams <NUM> (e.g., metal alloy <NUM> in <FIG>). In some embodiments, the first metal alloy powder added into the canister <NUM> may correspond to the metal alloy that will be disposed nearest the rearward surface <NUM> of the part (e.g., metal alloy <NUM> in <FIG>) or nearest the leading surface <NUM> of the part (e.g., metal alloy <NUM> in <FIG>), depending on the orientation of the part in the canister <NUM>. In certain embodiments, adding the first metal alloy powder into the canister <NUM> may include packing or shaping the powder, for example, using vibration, tamping, or other suitable methods. In certain embodiments, the metal alloy powder may be stored under inert atmosphere (e.g., nitrogen, helium, argon, an oxygen-depleted atmosphere) and/or the canister may be loaded under an inert atmosphere to block oxidation of the surface of the metal alloy powder.

Continuing through the embodiment illustrated in <FIG>, the process <NUM> continues with disposing (block <NUM>) a boundary layer on top of the first metal alloy layer in the canister <NUM>. Subsequently, a second metal alloy powder is deposited (block <NUM>) into the canister <NUM>, above the first metal alloy layer in the canister <NUM> and above the boundary layer (when present). In certain embodiments, a boundary layer may not be used and the actions of block <NUM> may be skipped.

As mentioned, the boundary layer is a thin piece of a metal alloy (e.g., a metallic foil, a flat sheet) that may be disposed between layers of different metal alloy powders to prevent mixing of the powders during placement within the canister prior to carrying out the HIP processing and/or in the part after the HIP processing, which may enable a sharp and well-defined boundary between the different metal alloy powders and/or facilitate bonding. In certain embodiments, the boundary layer may have a composition that is the same as, or similar to, one of the metal alloy powders it separates. In some embodiments, the boundary layer may have a composition that is different than the composition of the metal alloy powders separated by the boundary layer. For example, the boundary layer may serve as a "butter layer" to facilitate the formation of a strong bond between the metal alloy powder layers. That is, the boundary layer may be a metal alloy that is more conducive towards bonding with the first and second metal alloy powders than the first and second metal alloy powders are toward bonding directly with each other. In some embodiments, the actions of blocks <NUM> and <NUM> may be repeated to add a third metal alloy, a fourth metal alloy, etc., to the canister <NUM> as desired.

The actions of blocks <NUM>, <NUM>, and <NUM> may be better understood by way of <FIG>. These figures illustrate cross-sectional views of portions of the canister <NUM> loaded with a first layer <NUM> of a first metal alloy powder (as set forth in block <NUM>), a boundary layer <NUM> (as set forth in block <NUM>), and a second layer <NUM> of a second metal alloy powder (as set forth in block <NUM>). As shown in <FIG>, in certain embodiments, the boundary layer <NUM> may provide a substantially flat interface separating the two planar layers of metal alloy powder <NUM> and <NUM>, which results in a flat planar boundary <NUM> in the pressure- controlling component <NUM>, as illustrated and discussed above with respect to <FIG>. As shown in <FIG>, in certain embodiments, the boundary layer <NUM> may provide a curved interface separating the two layers of metal alloy powder <NUM> and <NUM>, which would result in a curved boundary <NUM> in the pressure-controlling component <NUM>, as illustrated and discussed above with respect to <FIG> and <FIG>. As shown in <FIG>, in certain embodiments, the boundary layer <NUM> may have a shape that corresponds to one or more features of the canister <NUM> (and eventually to the features on an outer surface of the pressure-controlling component <NUM>) to provide a complex interface separating the two layers of metal alloy powder <NUM> and <NUM>, which would result in a complex boundary <NUM> in the pressure-controlling component <NUM>, as illustrated and discussed above with respect to <FIG>.

Returning to <FIG>, the process <NUM> continues with sealing the canister <NUM> (block <NUM>). For example, in certain embodiments, the canister <NUM> is placed under vacuum (e.g., to remove ambient oxygen) and then welded closed. Once sealed, heat and pressure are applied (block <NUM>) to the materials (e.g., metal alloy powders, metal alloy boundary layers) disposed within the canister to consolidate the materials to form the pressure-controlling component <NUM> in a HIP process. For example, heat and pressure may be applied to the canister <NUM> via the heat source <NUM> and the pressure source <NUM> (e.g., an autoclave furnace), and the walls of the canister <NUM> impart the desired heat and pressure to the materials within the canister <NUM>. The heat and pressure cause the materials within the canister <NUM> to condense and bond to one another. More specifically, each of the powdered metal alloys may sinter together to form portions of the component <NUM>, while narrow (e.g., <NUM> millimeter or less) diffusion bonds form at the boundaries <NUM> between the different metal alloys. In other words, there is only a limited amount of mixing of the metal alloys of the two metal alloy powders and/or mixing of the metal alloys with the boundary layer at the interfaces <NUM>, and there is no substantial mixing of the metal alloys and/or the boundary layer a short distance (e.g., <NUM> millimeter) outside of each of these boundaries.

In certain embodiments, the materials sealed within the canister <NUM> may be heated to approximately <NUM> to <NUM> degrees Celsius, and the hydrostatic pressure within the canister may be approximately <NUM> to <NUM> Megapascals. However, any suitable temperature and/or pressure may be utilized to cause formation of the pressure-controlling component <NUM>. For example, in some embodiments, the temperature may be between approximately <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM> degrees Celsius and/or the pressure may be approximately <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM> Megapascals. In certain embodiments, the temperature and/or the pressure may be varied at different times during HIP processing as part of a temperature/pressure program, for example, with various ramps to increase or decrease the temperature and/or pressure over predefined time windows, and with various holds times during which the temperature and/or pressure are held substantially constant. It may be appreciated that the particular temperatures and pressures used in the HIP process of block <NUM> may be selected based on the material properties (e.g., melting point, sintering point) of the powder metal alloys and boundary layers disposed within the canister <NUM>. It may be noted that there is a substantial reduction in volume (e.g., between <NUM> percent and <NUM> percent, about <NUM> percent) of the materials disposed within the canister <NUM> during this HIP process. Upon completion of the HIP process of block <NUM>, the pressure-controlling component <NUM> is subsequently removed from the canister <NUM>. The resulting pressure-controlling component <NUM> may have a substantially uniform density (e.g., plus or minus <NUM> percent, plus or minus <NUM> percent) and/or the various regions of the component <NUM> with different metal alloys may be coupled to one another via narrow diffusion bonds. In certain embodiments, the pressure-controlling component <NUM> may undergo additional processing steps (e.g., machining, welding overlays, thermal treatment) to yield the final part.

The disclosed techniques enable the HIP fabrication of multi-metallic (e.g., bimetallic, trimetallic) pressure-controlling components for pressure-controlling equipment used in oil and gas applications. The disclosed HIP manufacturing process enables multiple, distinct metal alloys to be used to form particular portions of a pressure-controlling component, wherein the different metal alloys can be joined using a single HIP process. Compared with traditional subtractive manufacturing techniques, the disclosed HIP manufacturing process reduces the manufacturing time and cost, enables greater freedom of design in the selection of metal alloys, and enables a broader range of different material properties (e.g., strength, toughness, corrosion resistance) in different portions of the pressure-controlling component. Additionally, the disclosed HIP manufacturing technique can enable the formation of surface layers of metal alloy at thicknesses not achievable using weld-based processes (e.g., inlaying, overlaying, cladding) and using metal alloys that are not conducive to welding-based processes.

In an embodiment the multi-metallic component is a cutting or shearing tool having a cutting edge requiring high hardness, very high strength, and toughness, and a main body requiring high strength, high toughness, and good corrosion resistance, in particular in view of sulfide stress cracking.

Preferably the cutting edge fulfilling at least one of the following conditions:.

and an elongation of at least <NUM>%, preferably above <NUM>%.

Preferably, the main body fulfilling at least one of the following conditions:.

Each requirement cannot be met with a single steel. For a multi steel component, the bond between the steels needs to be strong, preferably such that the component will break in the main body before it breaks at the interface between the steels.

By using HIP diffusion bonding to join a super martensitic stainless steel (SMSS) as the first metal alloy and a tool steel (TOS) as the second metal alloy it is possible to manufacture a multi-metallic component that can provide a cutting or shearing tool meeting the requirements of the cutting edge and the main body. At least one of the steels, the first metal alloy or the second metal alloy, is a PM steel. Preferably both are PM steels. Preferably the component is a Near Net Shape component.

According to the invention, the SMSS comprises (in weight %):.

The impurities of the SMSS can be limited as follows:.

The SMSS may contain <NUM>-<NUM> Cu to improve corrosion resistance.

The first metal alloy (SMSS) is preferably a PM steel, more preferably a gas atomized PM steel. The atomization gas can e.g., be argon or nitrogen, preferably nitrogen.

The preferred Charpy Impact test requirements of the first metal alloy (SMSS ) according to ASTM370 at -<NUM>, Charpy V-notch, is a minimum average energy of 27J. The minimum average energy is preferably at least <NUM> J, and is typically within the range of <NUM>-<NUM> J.

Preferred requirements of the first metal alloy (SMSS) according to Tensile test at room temperature in accordance with ASTM A370 are as follows:.

Different strengths of the first metal alloy (SMSS) can be produced by controlling the composition and the heat treatment. For instance, the following ranges of yield strength could be desirable for different applications, each level having different Yield strength:.

Certain applications require the base material, here the first metal alloy (SMSS), to be approved according to NACE in certain environments. The testing evaluates the susceptibility of Sulfide Stress Cracking at a given stress level and environment consisting of e.g., water, H2S, chlorides and CO2. In general, the lower the strength of the SMSS for a given composition, the more likely the material will pass the testing and be approved for use at that given environment. Hence, a level X material is more likely to pass a more severe NACE test than a level X+<NUM> material.

It may be difficult to reach the desired yield strength of the first metal alloy (SMSS) through heat treatment while meeting the minimum strength requirement of the second metal alloy (TOS), since the strength of the second metal alloy (TOS) is also affected by the heat treatment. The negative effect on the strength of the second metal alloy (TOS) can however be mitigated by insulation of the second metal alloy (TOS) section of the component during one of the <NUM> alternatively <NUM> tempering cycles performed.

The first metal alloy (SMSS) is homogeneous apart from the bond region at the interface between the two steels. It is free of cracks and porosity. In particular, the micro porosity determined according to ASTM A988 can be made less than <NUM>%. The microstructure at grain boundaries is further free from deleterious carbides, nitrides, and intermetallic phases. The first metal alloy (SMSS) is martensitic with <NUM>-<NUM> vol% retained austenite. It may contain up to <NUM> vol% ferrite. The grain size of the first metal alloy (SMSS) is between ASTM <NUM> and ASTM <NUM>, preferably between <NUM> and <NUM>.

In an embodiment, the SMSS is limited to have a composition consisting of in weight %:.

This embodiment of the first metal alloy (SMSS) can be combined with the broadest definition of the second metal alloy (TOS), as well as any one of the other proposed example compositions of the second metal alloy (TOS).

In another embodiment, the SMSS is limited to have a composition consisting of in weight %:.

This embodiment of the first metal alloy (SMSS) can be combined with the broadest definition of second metal alloy (TOS), as well as any one of the other proposed compositions of the second metal alloy (TOS).

According to the invention, the TOS comprises (in weight %):.

The second metal alloy (TOS) is preferably a PM steel, more preferably a gas atomized PM steel. The atomization gas can e.g., be argon or nitrogen, preferably nitrogen.

Requirements of the second metal alloy (TOS) according to tensile test at room temperature in accordance with ASTM A370.

The surface hardness of the second metal alloy (TOS) according to ASTM E10 is <NUM>-<NUM> HRC, preferably <NUM>-<NUM> HRC.

The microstructure of the second metal alloy (TOS) is homogeneous apart from the bond zone between the first metal alloy (SMSS) and the second metal alloy (TOS). It is free of cracks and porosity. In particular, the micro porosity determined according to ASTM A988 shall be less than <NUM>%. The second metal alloy (TOS) is martensitic and may contain up to <NUM> vol% retained austenite. However, normally the microstructure is free of retained austenite. The grain size of the second metal alloy (TOS) is between ASTM <NUM> and ASTM <NUM>, preferably between <NUM> and <NUM>.

In an embodiment the TOS is limited to have a composition consisting of in weight %:.

This composition of second metal alloy (TOS) can be combined with any one of the proposed first metal alloy (SMSS) compositions.

In another embodiment, the TOS is limited to have a composition consisting of in weight %:.

This example composition of second metal alloy (TOS) can be combined with any one of the proposed first metal alloy (SMSS) compositions.

The bond of the steel is preferably tested by performing a tensile test of a specimen crossing the interface between the first metal alloy (SMSS) and the second metal alloy (TOS). The tensile strength should be higher in the interface than that of the material with the lowest yield strength, i.e. the first metal alloy (SMSS). Breakage in a tensile test according to ASTM A370 should occur in the first metal alloy (SMSS) and not in the interface. The microstructure of the bond shall be free from any lamination, cracks, porosity, or insufficient sintering.

An example of the HIP process for producing a multi-metallic component comprising of the first metal alloy (SMSS) and the second metal alloy (TOS) will now be described.

The multi-metallic component of the invention is produced by the method comprising the steps of:.

The HIP process is preferably a near net shape (NNS) HIP process. Hence, the multi-metallic component in step f) is preferably a NNS component.

The pressure in step f) is preferably above <NUM> bar.

The temperature in step f) is preferably within the range of <NUM>-<NUM>.

An example of the heat treatment process of the multi-metallic component will now be described.

The multi-metallic component is preferably austenitized at a temperature of <NUM>-<NUM>, normally <NUM>-<NUM>. Hold time is preferably <NUM> to <NUM> minutes. Quench rate is not critical for this steel but some geometries may be susceptible to cracking of quench rate is too high. The quenching is normally done in air or oil but other methods can be used e.g. gas or polymer quenching.

Tempering is performed at temperatures above <NUM>. Normal tempering temperature for the first metal alloy (SMSS) is within the range of <NUM>-<NUM>. The second metal alloy (TOS) should preferably be tempered at ≤ <NUM>.

The tempering can be performed in multiple cycles top optimize the properties of the first metal alloy (SMSS) and the second metal alloy (TOS). Preferably, at least <NUM> tempering steps, more preferably at least <NUM> tempering steps. Preferably, at least one of the tempering steps includes insulating the second metal alloy (TOS).

In a specific example the tempering process is as follows:.

The first tempering is preferably done immediately after the quenching by heating the multi metal component to a temperature of <NUM>- <NUM>, more preferably <NUM>-<NUM>, at a holding time of <NUM> to <NUM> hours. The multi metal component is thereafter cooled to room temperature, preferably by air cooling.

Before a second tempering, the portion of the multi metal component comprising the second metal alloy (TOS) is insulated. The insulation preferably covering the interface between the two steel grades. In the second tempering the multi metal component is loaded to a furnace preheated to a temperature above <NUM> Temperature of the HIP component is monitored such that the second metal alloy (TOS) part does not exceed <NUM>-<NUM> depending on strength requirements of the second metal alloy (TOS), while the first metal alloy (SMSS) can be tempered at temperatures up to <NUM>. Preferably the multi metal component is air cooled to room temperature and the insulation is preferably removed as soon as air cooling commence.

A third tempering is preferably done by heating the multi metal component without insulation to a temperature of <NUM>-<NUM>, more preferably <NUM>-<NUM> at a holding time of <NUM>-<NUM> hours. The purpose of the third tempering is to adjust the hardness of the second metal alloy (TOS) to a target hardness in the range of <NUM>-<NUM> HRC. The tempering time and temperature of the third tempering can be adjusted by measuring the hardness of the second metal alloy (TOS) after the second tempering.

Several investigating examples will now be described.

The purpose of Example <NUM> was to investigate the interface between a super martensitic stainless steel (SMSS) and a tool steel (TOS) joined by HIP solid state diffusion bonding.

A SMSS powder of grade UNS S41425 and a TOS powder of grade UNS T20813 were provided as nitrogen gas atomized powders.

The chemical requirements of the SMSS powder were:.

The chemical requirements of the TOS powder were:.

Powders were produced according to the specifications.

The SMSS has a very low C-content and <NUM> - <NUM>% Cr and <NUM>-<NUM>% Mo, both of which are strong carbide formers. The TOS contain <NUM>-<NUM>% C which will diffuse in to the SMSS and could cause issues with excessive carbide precipitation through reaction with Cr and Mo. Furthermore, the SMSS contain <NUM>-<NUM>% N which could react with the V in the TOS to form nitride or carbonitride precipitation in the interface between the two steels. To investigate the effect of this and find a way to control the diffusion of C and N tests was made using a <NUM> diffusion barrier of Ni that has in other applications proven stop or at least drastically slow down the diffusion of C and N.

A first canister was filed with a base of the SMSS powder and on top of the SMSS powder, the TOS powder. The canister was thereafter sealed, and air was evacuated (<<NUM> mBar). The canister material was a low carbon sheet metal of grade DC04.

A second canister was filed with a base of the SMSS powder and on top of the SMSS powder, a <NUM> diffusion barrier foil of Ni was placed and on top of the diffusion barrier the TOS powder. The canister was thereafter sealed, and air was evacuated (<<NUM> mBar).

The sealed canister was loaded to a Hot Isostatic Press where it was subjected to pressure of <NUM> MPa at a temperature of about <NUM> for a duration of three hours. The Hot Isostatic Press used argon gas as pressurizing medium.

The canisters were cooled to room temperature and the produced HIP components were separated from the canisters. The HIP components were austenitized at temperature of <NUM> and at a holding time of <NUM> and followed by twice tempering at <NUM> at <NUM>+<NUM>.

Test specimens were extracted from the different portions of the HIP component, including specimens from the SMSS part, the TOS part and specimens crossing the interface between the SMSS and TOS. Table <NUM> below show the properties of each steel as well as the interface between the two, with and without a Diffusion Barrier (DB).

The yield strength using a diffusion barrier is higher. This is likely explained by the formation of austenite in the SMSS caused by precipitation of carbides. Surprisingly, the overall strength of the interface is higher when not using a diffusion barrier and most importantly the ductility is much higher which is very positive from a material integrity standpoint. The reason for the lower overall strength and ductility when using a diffusion barrier of Ni is likely the fact that it produces a sharper interface between the two steels and when one steel starts to yield and neck the resulting stresses in the interface becomes higher locally. The fact that we use two PM steels and some intermixing between the two is unavoidable. This produces a more gradual interface between the two steels and surprisingly any carbide precipitation here seems not to have a too detrimental effect on the bond.

From this experiment it was determined that the multi-metallic steel preferably is produced without a diffusion barrier between the SMSS and TOS.

A SMSS powder of grade UNS S41425 and a TOS powder of grade UNS T20813 were provided as nitrogen gas atomized powders. The specifications of the powders were the same as in example <NUM>.

A canister was filled with a base of the SMSS powder and on top of the SMSS powder, the TOS powder. The canister was thereafter sealed, and air was evacuated (<<NUM> mBar). The canister material was a low carbon sheet metal of grade DC04.

The process is a solid-state diffusion bonding process providing a multi-metallic component comprising the SMSS and the TOS joined by diffusion bonding, where the SMSS and the TOS are free from porosity and has apart from the region around the border between the steels a respective homogenous microstructure. A near net shape multi-metallic component is a result from the HIP process.

The produced HIP component was thereafter cooled at a rate of about <NUM>/min to room temperature.

To finalize the properties, the HIP component was subjected to a heat treatment process including austenitizing followed by oil quenching and triple tempering. The aim in this example was to control the strength level of the SMSS to a yield strength of <NUM>-<NUM> MPa.

During austenitizing The HIP component was heated to a temperature of <NUM> and held there for <NUM>. The austenitized HIP component was thereafter oil quenched in warm oil at about <NUM> to a final part temperature of around <NUM>.

A first tempering was performed immediately after the quenching by heating the HIP component to <NUM>, where it was held at a holding time of <NUM> hours. The HIP component was thereafter air cooled to room temperature.

Before a second tempering the portion of the HIP component comprising the TOS was insulated. The insulation was also covering the interface between the two steel grades. In the second tempering the HIP component was loaded to a furnace at a temperature of <NUM>. Temperature of the HIP component was monitored such that the SMSS was tempered around <NUM> until a control surface of the insulated TOS reached <NUM>, after which the HIP component was air cooled to room temperature. The insulation was removed as soon as air cooling commenced.

A third tempering was done by heating the HIP component without insulation to a temperature of <NUM>, where it was a held time for <NUM> hours. The purpose of the third tempering is to adjust the hardness of the TOS to a target hardness in the range of <NUM>-<NUM> HRC. The tempering time and temperature of the third tempering can be adjusted by measuring the hardness of the TOS after the second tempering.

Test specimens were extracted from the HIP component at different positions to measure the properties of the SMSS, the TOS and the interface between the SMSS and the TOS. The results from the tests are shown in Table <NUM>.

All the requirements of the TOS and the SMSS were met. Specifically, the yield strength of the SMSS was <NUM> MPa and <NUM> MPa for the TOS.

A tensile test of a specimen crossing the interface between SMSS and TOS was performed. Break occurred in the SMSS, which was the desired result.

A SMSS specimen was further subjected to a Charpy Impact test according to ASTM370 at at -<NUM>, Charpy V-notch. The test showed that the impact toughness <NUM> J.

The hardness of the TOS was tested, and it was found out to be in the desired range <NUM>-<NUM> HRC. The method used followed ASTM E10.

The microstructure of the SMSS, TOS and the interface between the SMSS and TOS was metallographic studied at a magnification of 400X. The TOS, the SMSS, and the interface were all free of laminations, cracks, porosity, and insufficient sintering. The micro porosity determined according to ASTM A988 were less than <NUM>% for TOS and SMSS.

The TOS and SMSS was further evaluated for non-metallic inclusions according to ASTM E45. The steels contained no type A, B, C inclusions. Type D showed inclusions at <NUM> and <NUM>, but not at <NUM>, for both thin and heavy.

The grain sizes of the SMSS and TOS were analyzed to be between ASTM <NUM> to ASTM <NUM> in the SMSS, and between ASTM7 to ASTM <NUM> in the TOS.

Specimens from the SMSS was further tested according to NACE TM0177 method A, solution B, that simulates the conditions in an oil well. Test duration <NUM> hours. The test condition was a sustainable load of <NUM>% of the yield strength of the SMSS for a duration of <NUM> hours. The test solution contained <NUM><NUM> ppm CI and pH was adjusted to <NUM>. The gas mixture contained <NUM>. 5mbar H2S balance CO2. The specimen survived the test. Hence, the SMSS showed sulphide stress cracking resistance in the given environment.

In a third example the several more test cases were done. The steel and the manufacturing of the multi-metallic component was the same. The difference in relation to Example <NUM> was that the tempering time and temperatures was adjusted to modify the tensile strength and yield strength of the SMSS and the TOS. Particularly, specimens from the SMSS were tested according to NACE TM0177. The higher the SMSS yield strength is, the more difficult it is to pass the NACE test. Case <NUM> and Case <NUM> survived the NACE test. However, Case <NUM> failed the NACE test. Therefore, it was concluded that the maximum yield strength of the SMSS should be below <NUM> MPa.

Specimens from the TOS and the SMSS, respectively. The test results from example <NUM> are shown in table <NUM>.

Claim 1:
A multi-metallic component comprising:
a first metal alloy that forms a first portion of the multi-metallic component;
a second metal alloy that forms a second portion of the multi-metallic component; and
a diffusion bond disposed at an interface between the first metal alloy and the second metal alloy that joins the first metal alloy to the second metal alloy within the multi-metallic component;
wherein the first metal alloy comprising in weight %:

<TAB>

balance Fe apart from impurities; and
the second metal alloy comprising in weight %:

<TAB>

balance Fe apart from impurities.