Carburized high-strength steel part

Abstract

Example components (114, 120, 122, 130, 132, 134, 136) of a machine (100) include a core layer (504) and an outer layer (502) that encapsulates the core layer (504). The outer layer (502) has a greater carbon concentration and hardness than the core layer (504). The outer layer (502) can also be under compressive stress while the core layer (504) can have tensile stress. The stress and / or hardness profile of the component can enhance its resistance to cracking, particularly in applications where the component (114, 120, 122, 130, 132, 134, 136) is impacted by other objects and / or operates at high temperatures. The component (114, 120, 122, 130, 132, 134, 136), such as a portion of a fuel injector, can be formed by rough forming the component, carburizing the component, quenching the component, subzero treating the component, and then performing a tempering process. The component (114, 120, 122, 130, 132, 134, 136) can have a relatively sharp transition from the high carbon outer layer (502) to the low carbon core layer (504). Additionally, the component (114, 120, 122, 130, 132, 134, 136) has a relatively high resistance to tempering when used in relatively high temperature environments.

Description

Technical Field

[0001] This disclosure relates to the formation of steel components. More specifically, this disclosure relates to fuel injector nozzle tips and other components formed from high-strength steel to achieve improved crack resistance and improved service life. Background Technology

[0002] The machines are widely used in construction, mining, paving, forestry, and other similar industries. These machines are powered by any suitable fuel, such as diesel, gasoline, biodiesel, liquefied natural gas (LNG), compressed natural gas (CNG), any kind of petroleum distillate, and / or other hydrocarbons. The flow of these fuels into the internal combustion engine of the machine is typically controlled using fuel injectors. Fuel injectors typically have a moving part that operates at a relatively high temperature to control the delivery of fuel to the combustion cylinders of the internal combustion engine. For example, a diesel fuel injector may include a moving nozzle valve that controls the flow of fuel through an orifice through the nozzle tip of the fuel injector. In such a configuration, the nozzle valve can provide fuel flow control by moving and selectively contacting the nozzle tip of the fuel injector to selectively open or block the orifice through the nozzle tip. Due to the thermal operating environment during engine operation and the repeated contact between parts of the fuel injector, cracking may occur in the nozzle tip, nozzle valve, and / or other components of the fuel injector, or in other components of the engine.

[0003] Besides the internal combustion engines of these machines, whose components operate in harsh environments (e.g., impact-induced, hot environments), machines typically include hydraulic systems, such as those used to move or transport materials (e.g., dirt, gravel, etc.). These hydraulic systems may include components that can operate under high pressure and sometimes overheating, such as cylinders and pistons. Therefore, these hydraulic components operating under harsh conditions may also develop cracks and / or other defects during operation, which can reduce the lifespan of these components and involve costly on-site downtime and maintenance.

[0004] Furthermore, in some cases, the chassis of such a machine can utilize track assemblies instead of wheels to provide ground engagement propulsion. Such track assemblies may be preferred in environments where generating sufficient traction is problematic, such as those frequently encountered in the industries mentioned above. Specifically, instead of relying on wheels to roll across the work surface, tracked machines utilize one or more track assemblies comprising annular rings of coupled track links that define an outer surface supporting ground engagement track plates and an inner surface traveling around one or more rotatable track engagement elements (e.g., drive sprockets, idler pulleys, tensioners, and rollers). Such track chain assemblies can operate in extremely adverse environments where the track joint may be exposed to various abrasive mixtures of water, mud, sand, rock, or other mineral or chemical elements. Therefore, components of the track chain assembly may wear, and cracks and / or other defects may form in the various components of the track chain (e.g., bushings, sprockets, idler pulleys, etc.). Additionally, the machine may have other components that may be prone to cracking and / or other defects due to harsh operating conditions, such as working edges.

[0005] An example of producing parts with a relatively high level of surface hardness is described in Chinese Patent No. 10,973,579 (hereinafter referred to as the '579 Patent'). As pointed out in the '579 Patent, in the heat treatment process of steel for surface hardening, the steel part can undergo carburizing, followed by quenching and cryogenic treatment. However, the process described in the '579 Patent also requires several additional steps, and the disclosed process does not maximize the surface carbon content provided to the steel part. In addition, in the steel hardening process described in the '579 reference, the metallurgical composition of the steel does not produce the desired surface hardness or the desired stress distribution.

[0006] The exemplary embodiments disclosed herein aim to overcome the above-mentioned deficiencies. Summary of the Invention

[0007] In an example of this disclosure, a component includes an outer layer having a hardness and compressive stress of at least about 55 Rockwell hardness grade C (HRC), and the outer layer having a vanadium content of at least about 0.1% by weight. The component also includes a core layer encapsulated by the outer layer, the core layer having a hardness and tensile stress of less than about 55 HRC, wherein the thickness of the outer layer is at least 250 micrometers (μm), and wherein after the component is exposed to a temperature of at least about 300°C for at least about 3 hours, the outer layer has a first hardness of at least 59 HRC at a depth of at least 250 μm.

[0008] In another embodiment of this disclosure, the machine includes one or more components. At least one component includes an outer layer having an outer surface having a first hardness and compressive stress of at least about 55 HRC. The at least one component also includes a core layer encapsulated by the outer layer having a second hardness and tensile stress of less than about 55 HRC, wherein after the component is exposed to a temperature of at least about 300°C for at least about 3 hours, a third hardness at a first depth of about 250 micrometers (μm) from the outer surface is at least about 59 HRC, and a fourth hardness at a second depth of about 600 μm is less than about 53 HRC.

[0009] In another example of this disclosure, a method of manufacturing a machine part includes: forming a rough part from steel with a carbon content of less than about 0.5% by weight and a vanadium content of at least about 0.1% by weight; and carburizing the rough part at a carburizing temperature of at least about 900°C to form a carburized outer layer of the machine part. The method further includes: quenching the carburized rough part directly at the carburizing temperature; performing a sub-zero treatment on the quenched rough part; and tempering the sub-zero treated rough part to form the machine part. Attached Figure Description

[0010] Figure 1 It is a schematic diagram of an example machine having one or more components formed according to an example of this disclosure.

[0011] Figure 2 Examples based on this disclosure, such as Figure 1 A schematic diagram of an example portion of the fuel injector of the machine depicted in the image.

[0012] Figure 3 Examples depicting the present disclosure are shown as follows. Figure 1 The diagram depicts the metallurgical composition of examples of machine parts.

[0013] Figure 4 It describes an example of hardening such as according to this disclosure. Figure 1 The flowchart describes the instance method of an instance component of a machine.

[0014] Figure 5 It is a cross-sectional view of the surface of an example component according to an example of this disclosure. Detailed Implementation

[0015] In all the accompanying drawings, the same reference numerals will be used as much as possible to denote the same or similar parts. Figure 1This is a schematic diagram of an example machine 100 having one or more components formed according to an embodiment of this disclosure. Although machine 100 is depicted as a bulldozer, it should be understood that machine 100 can be of any suitable type, such as those used for construction, agriculture, mining, paving, transportation, etc. In other instances, machine 100 can be any suitable machine 100, such as a loader, excavator, tank, backhoe excavator, drilling rig, trencher, combine harvester, or any other on-road or off-road vehicle.

[0016] Machine 100 includes a frame 102 on which other components of machine 100 are mounted. Machine 100 includes a propulsion system 104, such as a track chain assembly, as shown. Alternatively, machine 100 may have any other suitable type of propulsion system 104, such as wheels and tires. Machine 100 also includes an engine 106, such as an internal combustion engine using hydrocarbon fuels. Alternatively, machine 100 may be an electric machine. Machine 100 includes an exhaust system 108 and / or one or more working systems 110 movable by one or more hydraulic systems 112. Machine 100 also includes a transmission system (not shown) mechanically connecting engine 106 to propulsion system 104. According to an example of this disclosure, any component of machine 100, including propulsion system 104, engine 106, exhaust system 108, working system 110, hydraulic system 112, transmission, etc., of any kind, can be formed by the processes disclosed herein. Furthermore, when formed by the processes disclosed herein, any of the aforementioned components of machine 100 may have the structure and, as a result, material properties disclosed herein.

[0017] The working system 110 may include any type of component, such as a cutting edge 114. The cutting edge 114 and / or other components of the working system 110 may be subjected to harsh operating environments involving friction and / or heat, such as in moving gravel, picking up stones, redistributing bitumen, etc. In many cases, the cutting edge 114 is exposed to repeated impacts with hard objects (e.g., rocks), and in some cases, may also be subjected to relatively high temperatures (e.g., when distributing hot bitumen and / or tar, due to frictional heating, etc.). Several aspects of this application enable the formation of a hard and / or high-strength cutting edge 114 and other components in the working system 110. This allows the cutting edge 114 to have a longer service life.

[0018] Engine 106 may include a variety of components that can be subjected to metallurgical compositions and / or processing as disclosed herein to improve the strength and / or lifespan of those components. Engine 106 may include one or more fuel injectors 116, such as diesel injectors, which have improved characteristics when formed according to the disclosure herein. Fuel injector 116 may include housing 118, in which nozzle tip 120 is disposed, and nozzle valve 122 is movably disposed within nozzle tip 120. Nozzle valve 122 is mechanically coupled and / or connected to plunger 124, which is configured to move nozzle valve 122 in the longitudinal direction (e.g., as shown in the image). Figure 1 As depicted, the nozzle valve moves up and down. The solenoid 126 controls the movement of the plunger 124 and, through its extension, controls the movement of the nozzle valve 122. (As shown in the diagram...) Figure 2 In more detail, when the engine 106 is operating, the movement of the nozzle valve 122 relative to the nozzle tip 120 controls the flow of fuel to components of the engine 106 (e.g., cylinders). However, this movement of the nozzle valve 122 causes it to repeatedly impact the nozzle tip 120. Furthermore, during operation of the engine 106, the impacts between the nozzle valve 122 and the nozzle tip 120 occur at relatively high temperatures, such as 200°C or higher, and sometimes 300°C or higher. These operating conditions (e.g., repeated impacts at high temperatures) make the nozzle tip 120 and / or the nozzle valve 122 prone to breakage and / or other defects. The machining mechanisms and material compositions disclosed herein, when applied to the nozzle tip 120, nozzle valve 122, and / or other components of the fuel injector 116, result in more robust components, such as a more durable and less prone-to-cracking, robust nozzle tip 120 and / or nozzle valve 122. Furthermore, in some cases, the processing mechanisms and material compositions disclosed herein, when applied to the nozzle tip 120, nozzle valve 122, and / or other components of the fuel injector 116, produce a favorable stress distribution in these components, thereby enhancing their durability and / or lifespan. Although discussed in the context of the nozzle tip 120 and nozzle valve 122, it should be understood that the metallurgical compositions and processes disclosed herein can be applied to a wide variety of components of the engine 106, such as combustion cylinders, piston heads, intake valves, exhaust valves, etc.

[0019] Hydraulic system 112 may include cylinder 130 and piston 132 movably coupled to cylinder 130. Piston 132 is mechanically coupled to working system 110 to perform work tasks, such as lifting soil or redistributing gravel. Cylinder 130 and / or piston 132 may experience relatively high levels of stress during operation, for example, by pressurized hydraulic fluid. Additionally, piston 132 may impact cylinder 130 during operation of hydraulic system 112. Therefore, due to the conditions of operation of cylinder 130 and piston 132, cylinder and piston are prone to breakage and / or other types of failure. The machining mechanisms and material compositions disclosed herein, when applied to cylinder 130 and / or piston 132, result in more robust components, such as more durable and less prone to cracking, stronger cylinder 130 and / or piston 132.

[0020] The propulsion system may include one or more components, such as track plates 134 and bushings 136, which may be exposed to harsh environments with high levels of stress and friction applied thereon. For example, track plates 134 engage the ground or other surfaces and propel machine 100 thereon. Therefore, track plates 134 bear the weight of the entire machine as machine 100 travels on abrasive surfaces, which may be approximately tens or even hundreds of tons. The abrasive sand, dirt, rock, etc., of track plates 134 can cause cracking and / or other defects. Similarly, bushings 136 abrade other metal components of the propulsion system 104 under extremely high loads. This can lead to various problems such as cracking, abrasion, and / or other defects. The propulsion system 104 in the form of a tracked propulsion system includes other components, such as rolling elements, sprockets, front idler pulleys, rear idler pulleys, track rollers, etc., which operate under harsh conditions with heavy loads and / or high levels of wear applied thereon. Due to the harsh operating environment and the loads applied to the various components of the propulsion system, it is desirable to improve the material properties of the various components of the track chain assembly to increase the service life of those components. According to examples of this disclosure, various components of the propulsion system 104 (such as track plates 134 and bushings 136) can be formed in a manner that improves their wear resistance while maintaining and / or improving their overall toughness.

[0021] While certain components of machine 100 (e.g., nozzle tip 120, nozzle valve 122, exhaust system 108, cylinder 130, etc.) are discussed herein as being formed from the steel composition and / or processes disclosed herein, it should be understood that the disclosure herein for forming high-strength steel components can be applied to any suitable component in connection with machine 100 or in other applications. For example, processes as disclosed herein can be applied to any kind of non-tracked machine 100 components to increase the surface hardness of those components while maintaining a softer core region in those components to provide improved surface abrasion resistance and high toughness. As another example, mechanisms as disclosed herein can be applied to any kind of equipment components in other industries (e.g., aerospace, manufacturing, transportation, other mechanical systems, etc.).

[0022] According to examples of this disclosure, components (e.g., fuel injector nozzle tip 120) can be formed substantially of steel and then subjected to a hardening process that provides a hard outer surface with a high carbon concentration and a softer core region. The resulting component is hard, tough, relatively fracture-resistant, and particularly well-suited for applications involving metal-to-metal contact at relatively high temperatures (e.g., greater than 150°C). Components formed by the mechanisms disclosed herein have a hard outer layer, which in some examples is in the range of approximately 150 micrometers (μm) to approximately 3 millimeters (mm) thick. In other words, the hard outer layer encapsulates the soft core layer of the component manufactured according to the mechanisms discussed herein. In some examples, this hard outer layer can have a hardness in the range of approximately 55 Rockwell hardness grade C (HRC) to approximately 69 HRC, while the softer core region can have a hardness in the range of approximately 39 HRC to approximately 55 HRC. Additionally, in some cases, the hard outer layer can be under compressive stress, while the softer core portion can be under tensile stress.

[0023] It should be understood that the disclosure herein can produce components with a carbon distribution exhibiting a relatively abrupt gradient or decrease in carbon content from a hard outer surface to a softer core region. This relatively abrupt decrease in carbon distribution can allow relatively thin components or portions of components (e.g., nozzle tip 120) to have a hard outer layer 206 while still maintaining a relatively soft core layer 204. This provides a hard outer surface under compressive stress for greater crack resistance, for example, in the event of maximum Hertzian stress, and a softer core for greater toughness. For example, in one hardness distribution, the component may have a hardness of about 59 HRC or higher at a depth of about 250 μm and a hardness of about 55 HRC or less at a depth of about 500 μm. In another example hardness distribution, after exposure to at least 300°C for at least 3 hours, the component may have a hardness of about 59 HRC or higher at a depth of about 250 μm and a hardness of about 54 HRC or less at a depth of about 600 μm. In another example of hardness distribution, after exposure to at least 300°C for at least 3 hours, the component can have a hardness of about 59 HRC or higher at a depth of about 250 μm and a hardness of about 53 HRC or less at a depth of about 600 μm.

[0024] When an impact occurs between two parts (e.g., nozzle valve 122 and nozzle tip 120), the stress caused by the impact force and the resulting material deformation may be greatest at a certain depth from the surface of those parts. For example, in some cases, the maximum Hertzian stress caused by the impact of nozzle valve 122 and nozzle tip 120 can penetrate to a depth of approximately 200 μm into the surface of those parts. By causing the maximum Hertzian stress from the impact to occur within the hard outer surface of the part, the part can be more resistant to cracking caused by the impact force. This crack resistance may be due to the relatively high hardness of the hard outer layer of the part, the static compressive stress on the outer surface, or both. Additionally, the softer core region provides relatively high toughness to the part, even for relatively thin parts. Furthermore, parts as disclosed herein exhibit relatively high resistance to tempering during use at relatively high temperatures. Parts formed through the mechanisms disclosed herein can therefore be more durable and have a longer service life.

[0025] Figure 2 Examples based on this disclosure, such as Figure 1 A schematic diagram of an example portion of the fuel injector 116 of the machine 100 depicted herein. For ease of description, the various layers of the nozzle tip 120 are depicted and discussed. It should be understood that in some cases, the nozzle valve 122 may be formed in a manner similar to the nozzle tip 120 and have layers similar to the nozzle tip 120.

[0026] The nozzle tip 120 may include an orifice 200 defined therethrough by a surface 202 of the nozzle tip 120. This orifice 200 is configured to allow fuel, such as diesel, to pass through it. Fuel can pass through the orifice 200 when the nozzle valve 122 is moved in its longitudinal direction to an upward position or away from the nozzle tip 120. On the other hand, if the nozzle valve 122 is in its downward position or in contact with the nozzle tip 120, the orifice 200 may be blocked and fuel may not be allowed to pass through it. Through repeated movement of the nozzle valve 122 relative to the nozzle tip 120, fuel is controllably supplied to the engine 106 of the machine 100.

[0027] The nozzle tip 120 includes a core layer 204, which may also be referred to as a core region or body region. The nozzle tip 120 also includes an outer layer 206, which may also be referred to as a hard layer, outer layer, or shell layer. The outer layer 206 extends from the surfaces 202, 208 of the nozzle tip 120 to an interface 210 between the core layer 204 and the outer layer 206. Although the interface 210 is depicted as a direct transition from the outer layer 206 to the core layer 204, it should be understood that in some cases, the interface 210 may be a region transitioning from the outer layer 206 of the nozzle tip 120 to the core layer 204. In some cases, this transition may be gradual and / or graded. In other words, the interface 210 may represent a spatial transition region embodying the material properties between the core layer 204 and the outer layer 206. According to an example of this disclosure, the outer layer 206 of the nozzle tip 120 may be a substantially martensitic and / or austenitic crystal structure, and its carbon content is greater than that of the core layer 204.

[0028] In the embodiments of this disclosure, the outer layer 206 may be harder than the core layer 204 of the nozzle tip 120. In some cases, the core layer 204 may have a hardness in the range of about 39 HRC to about 55 HRC. In other cases, the core layer 204 may have a hardness in the range of about 42 HRC to about 50 HRC. In still other cases, the core layer 204 may have a hardness in the range of about 44 HRC to about 48 HRC. In some cases, the outer layer 206 may have a hardness in the range of about 55 HRC to about 69 HRC. In other cases, the outer layer 206 may have a hardness in the range of about 58 HRC to about 64 HRC. In still other cases, the outer layer 206 may have a hardness in the range of about 60 HRC to about 62 HRC.

[0029] It should also be understood that the characteristics of the outer layer 206 can be non-uniform across its entire thickness. In some cases, the presence of the outer layer 206 can be detected by measuring the hardness at a threshold depth penetrating the outer layer 206. For example, the hardness at a depth of approximately 150 μm to approximately 300 μm from the surface 208 of the nozzle tip 120 can range from approximately 56 HRC to approximately 67 HRC. In some cases, the hardness at a depth of approximately 200 μm to approximately 300 μm from the surface 208 of the nozzle tip 120 can range from approximately 58 HRC to approximately 65 HRC. In still other cases, the hardness at a depth of approximately 225 μm to approximately 275 μm from the surface 208 of the nozzle tip 120 can range from approximately 58 HRC to approximately 64 HRC. For example, in some cases, the hardness at a depth of 250 μm from the surface 208 of the nozzle tip 120 can be at least approximately 59 HRC. Meanwhile, the hardness at the surface 208 can be at least approximately 60 HRC.

[0030] The outer layer 206 can have any suitable thickness. For example, the outer layer 206 can have a thickness ranging from about 150 μm to about 3 mm. In some other cases, the thickness of the outer layer 206 can range from about 200 μm to about 1.5 mm. In still other cases, the thickness of the outer layer 206 can range from about 250 μm to about 1 mm. For example, the outer layer 206 can have a thickness of about 400 μm. Although certain thicknesses of the outer layer 206 are discussed herein, it should be understood that thicknesses beyond those discussed herein are contemplated. It should also be understood that the thickness of the outer layer 206 can vary based on the component and / or the application of the component. For example, a thicker outer layer for the bushing 136 may be desired compared to the nozzle tip 120.

[0031] In some cases, the outer layer 206 may have a thickness such that the maximum Hertzian stress resulting from the impact between the nozzle tip 120 and the nozzle valve 122 is contained within the outer layer 206. The outer layer 206 is not only harder, but in some cases, it is also under compressive stress while the core layer 204 is under tensile stress. Therefore, by designing this component such that the maximum Hertzian stress from the impact is contained within the compressive stress region (e.g., the outer layer 206), a lower likelihood of cracking can be generated, resulting in greater component durability. In other words, the compressive properties of the outer layer 206 can suppress crack formation and / or crack propagation. In addition to the favorable stress distribution described herein, the enhanced hardness of the outer layer 206 improves its wear resistance and durability against impacts (e.g., impacts at high ambient temperatures). In some instances, the outer layer 206 of the nozzle tip 120 may be approximately 400 μm thick, and the maximum Hertzian stress from the impact between the nozzle valve 122 and the nozzle tip 120 may be located at a surface depth of approximately 200 μm. Therefore, in this example, the maximum Hertzian stress can occur in the relatively hard and compressively stressed outer layer 206 of the nozzle tip 120. The nozzle valve 122, as disclosed herein, can also be manufactured in a manner similar to that depicted for the nozzle tip 120, since the nozzle valve 122 can, in some cases, also have a hard outer layer and a softer core layer. This makes the nozzle tip 120 and / or the nozzle valve 122 more resistant to repeated impacts at high temperatures during operation of the machine 100.

[0032] It should also be understood that the nozzle tip 120 can be relatively thin, and therefore, conventional hardening metallurgy and methods may not be able to form a hard outer layer 206 with a softer core layer 204. For the nozzle tip 120, a relatively abrupt gradient of carbon content from the surfaces 202, 208 to the core layer 204 may be desired to provide both a soft core layer 204 and a harder outer layer 206. As disclosed herein, the carbon distribution of the nozzle tip 120 or other components can have a relatively abrupt gradient or decrease in carbon content from the outer layer 206 to the core layer 204. Thus, this relatively abrupt decrease in carbon distribution allows relatively thin components or portions of components (e.g., the nozzle tip 120) to have a hard outer layer 206 while still maintaining a relatively soft core layer 204. This provides a hard outer surface under compressive stress for greater crack resistance, for example, in cases where maximum Hertzian stress may be encountered, and a softer core for greater toughness. For example, in one hardness distribution, the component can have a hardness of about 59 HRC or higher at a depth of about 250 μm and a hardness of about 55 HRC or less at a depth of about 500 μm. Additionally, the nozzle tip 120, nozzle valve 122, or other components can be relatively resistant to tempering during use at relatively high temperatures. In other words, the outer layer 206 can be relatively resistant to softening during high-temperature use. In one instance, even after use at a temperature of about 300°C for about 3 hours or more, the component can maintain a hardness of 59 HRC at a depth of 250 μm. The abrupt hardness distribution allows the component to have a hardness of less than 53 HRC at a depth of 600 μm from surfaces 202, 208 after exposure to an environment of at least 300°C for at least 3 hours. This makes the nozzle tip 120 and / or nozzle valve 122 more resistant to cracking and more durable at high temperatures during operation of the machine 100.

[0033] Figure 3 It describes an example according to this disclosure, such as Figure 1 Figures 300 and 302 illustrate the metallurgical composition of components of the machine 100 depicted herein. Components of the machine 100 as described herein (e.g., nozzle tip 120) can be crudely formed from steel having the composition described herein, followed by further heat treatment to achieve bonding. Figure 2 The desired layered structure is described. As used herein, rough forming refers to the shaping of a part prior to subsequent strengthening via heat treatment (such as annealing, quenching, carburizing, etc.).

[0034] Rough-formed components, such as nozzle tips 120, can be formed from low- to medium-carbon (C) steel, wherein the C content ranges from about 0.17% by weight to about 0.5% by weight. The steel used for rough-formed components can have any suitable crystal structure, such as ferrite, pearlite, cementite, bainite, martensite, and / or austenite. The initial low- or medium-carbon steel can be relatively soft and ductile, thereby allowing for easier rough-formation of components, such as nozzle tips and / or nozzle valves 122. For example, the steel can have an initial hardness in the range of about 38 HRC to about 50 HRC. In other cases, steels with higher C contents can also be used. The steel can contain a variety of other impurities and / or additives. For example, components of machine 100 may be formed of steel, which may also contain other elements such as manganese (Mn), phosphorus (P), sulfur (S), silicon (Si), chromium (Cr), boron (B), cobalt (Co), molybdenum (Mo), nickel (Ni), titanium (Ti), tungsten (W), niobium (Nb), vanadium (V), and combinations thereof. It should also be noted that the composition of the steel may remain relatively homogeneous until any carburizing, hardening, sub-zeroing, and / or tempering treatments are performed.

[0035] As shown in Table 300, the steel used to form the component, as discussed herein, may contain Mn in the range of about 0.2 wt% to about 1 wt%, Si in the range of about 0 wt% to about 0.3 wt%, P in the range of about 0 wt% to about 0.3 wt%, S in the range of about 0 wt% to about 0.01 wt%, Ni in the range of about 0 wt% to about 0.3 wt%, Cr in the range of about 1.5 wt% to about 2 wt%, Mo in the range of about 1.7 wt% to about 2.4 wt%, and V in the range of about 0.1 wt% to about 1 wt%. As shown in Table 302, a particular composition of the steel that can be used for rough forming parts (e.g., nozzle tip 120) may contain about 0.3 wt% C, about 0.5 wt% Mn, about 0.13 wt% Si, 0.013 wt% P, about 0.001 wt% S, about 0.2 wt% Ni, about 1.7 wt% Cr, about 2 wt% Mo and about 0.5 wt% V.

[0036] As shown in Tables 300 and 302, the concentrations of additives and / or impurities in the steel may allow for the formation of bonds such as Figure 2 The structure of the discussion. For example, the metallurgical concentration discussed here is well-suited for forming, as for... Figure 2The nozzle tip 120 depicts the outer layer 206 and the core layer 204. In other words, as discussed herein, the chemical concentration of steel can be used to form a relatively hard outer layer 206 under compressive stress, having a relatively soft core layer 204 under tensile stress. However, other metallurgical compositions, different from those discussed in Figures 300, 302 (where the single-element composition is greater than or less than those listed or has additional or fewer elemental additives), can also provide a similar combination. Figure 2 The structures discussed herein, as disclosed above, demonstrate that the configuration of a softer core layer 204 encapsulated by a harder outer layer 206, achieved through the chemical composition disclosed herein, provides a relatively high level of durability and thus a longer lifespan for components subjected to harsh operating conditions. In some cases, the metallurgical composition disclosed herein may be relatively more cost-effective (e.g., cheaper) compared to other alloy steel compositions that can be used to form components with the desired hardness characteristics and / or hardness distribution.

[0037] Figure 4 It describes an example of hardening such as according to this disclosure. Figure 1 The flowchart illustrates an example method 400 for an example component of machine 100. Method 400 can be performed using low-carbon steel, medium-carbon steel, etc., as discussed herein. In examples of this disclosure, the starting steel can have, for example, the bonding... Figure 3 The composition of the composition is discussed. Alternatively, higher carbon steel can be used. In some cases, if the initial low-carbon or medium-carbon steel is not in a ferritic structure, a tempering process can optionally be performed before starting method 400.

[0038] At box 402, the component is formed of steel. This is a rough formation of a component (e.g., nozzle tip 120, nozzle valve 122, cylinder 130, etc.) prior to subsequent processing. The component can be formed by any suitable mechanism, such as any suitable thermal forming mechanism and / or machining technique. For example, any type of casting, rolling, hot rolling, cold rolling, extrusion, or combinations thereof can be used to form the rough component. Alternatively or concurrently, the rough component can be formed by any kind of machining technique suitable for forming the component, such as any type of forming, turning, milling, drilling, grinding, gouging, lathe machining, and / or other machining techniques.

[0039] During roughing, the component can have any suitable crystal structure, such as ferrite, pearlite, bainite, cementite, martensite, and / or austenite. In some cases, the starting steel can have a relatively high level of relatively soft ferrite and / or pearlite crystal structure. The initial low-carbon or medium-carbon steel can be relatively soft and ductile, thereby allowing for easier formation of roughed components, such as roughed nozzle tips. For example, the initial hardness of the steel can be in the range of about 80 Rockwell hardness grade B (HRB) to about 100 HRB. In other cases, the steel can have an initial hardness in the range of about 30 HRC to about 40 HRC. The hardness ranges described herein and throughout this disclosure are examples, and shorter or longer hardness ranges may be used according to examples of this disclosure.

[0040] At box 404, the component can be carburized. The carburizing process may involve diffusion processes and / or cycles of diffusion processes, wherein the component is held at a carburizing temperature in a carbon-rich environment. For example, the component may be held in a furnace at a high temperature while carbon-containing gases flow through the furnace. The carburizing process selectively introduces a relatively high concentration of C near the surfaces 202, 208 of the component. These regions with relatively high carbon concentrations form the outer layer 206, while regions further away from the surfaces 202, 208 do not have a significant amount of C diffused therein from the carburizing process, and those regions far from the surfaces 202, 208 form the core layer 204 of the component. In some cases, the carburizing process may be a vacuum carburizing process, wherein the carburizing process can be performed in a partially vacuum environment within the furnace. Alternatively, the carburizing process may be performed in an atmospheric pressure environment, a nitrogen environment, an argon environment, a combination thereof, etc. In some alternative instances, a nitrocarburizing process or other similar variations of the carburizing process may be performed instead of the carburizing process.

[0041] It should be understood that a partial vacuum carburizing process can provide advantages in carburized surfaces 202, 208, which are shielded from the carbonaceous reactants in the carburizing environment. For example, as in the case of nozzle tip 120, it may be difficult to carburize surfaces at the bottom of relatively high aspect ratio holes and / or trenches using atmospheric carburizing techniques. This difficulty may be due to the relatively short path length of the carbonaceous reactants (due to scattering in relatively high aspect ratio holes and / or trenches). However, in a partial vacuum environment used for carburizing, the relatively reduced gas scattering can produce a relatively long path length for the carbonaceous reactants, thereby allowing the carbonaceous reactants to be transported to the bottom of relatively deep holes and trenches. Therefore, surface carburizing processes (e.g., diffusion, etc.) at the bottom of relatively deep holes and / or trenches can continue due to the availability of carbonaceous reactants at those surfaces.

[0042] The furnace process for carburized surfaces can be performed at any suitable temperature and for any duration. For example, the furnace process can be performed at a temperature between about 850°C and about 1200°C for a duration of about 1 hour to about 24 hours. In some instances, the furnace process can be performed at a temperature range of about 900°C to about 1100°C for a duration of about 14 hours to about 18 hours. In other instances, the furnace process can be performed at a temperature range of about 950°C to about 1000°C. The carburizing process may involve pulsed and paused processing, with interruptions between the carbon-containing gas streams. In some instances, the total pulse time can range from about 30 seconds to about 5 minutes. In other cases, the total pulse time can range from about 1 minute to about 2 minutes. In some cases, the carburizing process can be a batch process, where more than one part of machine 100 can be carburized simultaneously.

[0043] During the furnace process, carbon-containing gases can flow into the furnace to provide a carbon-rich environment, from which carbon diffuses to the surface areas of the roughened part. For example, acetylene can flow into the furnace at a suitable flow rate to carburize the surface areas of the roughened part. In other examples, liquefied petroleum gas (LPG) can flow into the furnace at a suitable flow rate to carburize the surface areas of the roughened part. Other carbon sources may include, but are not limited to, carbon dioxide, carbon monoxide, methane, ethane, propane, butane, pentane, other carbon-containing molecules, combinations thereof, etc.

[0044] As discussed here, the carburizing process can be a diffusion-limited process. For example, the carburizing process can be a Fickian process (e.g., defined by Fick's second law), where the process is essentially self-limiting, making the formation of a carbon-rich layer beyond a certain thickness (e.g., from about 3 mm to about 6 mm) thermally and / or temporally inefficient. Therefore, due to the self-limiting nature of the carburizing process, it may be difficult to form a relatively thick shell region on the part being carburized. Thus, the carburizing process may be particularly useful in applications where a hard outer layer of less than about 3 mm is required. While a hardened martensitic carbon-rich steel shell provides high wear resistance and compressive stress, it is generally brittle and lacks ductility. Therefore, limiting the hardened carbon-rich steel to a shell on the surface of the part provides benefits from a cracking point of view, while the softer internal portion of the part allows for toughness and fatigue resistance.

[0045] It should also be noted that, since carburizing is a diffusion process (e.g., carbon diffuses into low-carbon or medium-carbon steel), the carbon content may decrease with distance from the surface of the carburized part. For example, the carbon concentration may be highest at the surface of the part and gradually decrease with distance from said surface. The carbon concentration at the surface of the part can range from about 0.7 wt% to about 1.6 wt%, and can decrease monotonically with distance from the surface of the part until the carbon concentration is substantially similar to the bulk carbon concentration of the part. This bulk carbon concentration of the part can be substantially similar to the initial carbon concentration of low-carbon or medium-carbon steel.

[0046] Following the carburizing process, a carbon-rich surface region can be formed on the roughed part, for example, an outer layer 206 in the case of nozzle tip 120. After the remainder of method 400, the carbon-rich surface region can have a hardened martensite and / or austenite crystal structure. In other words, the roughed part can have a hardened shell on its surface region due to the relatively high carbon content near its surface (due to the carburizing process). Due to the carburizing process, after the remainder of method 400, the hardness of the surface region can range from about 55 HRC to about 69 HRC.

[0047] At box 406, the component is quenched directly at the carburizing temperature. After the furnace process, the rough component (e.g., nozzle tip 120 or bushing 136) can be quenched, for example, in a nitrogen atmosphere. Alternatively, the quenching process can be performed in any suitable medium, such as a salt bath, water, air, and / or oil. In some instances, the component can be cooled at a rate between approximately 1 °C / s (or 60 °C / min) and approximately 10 °C / s (or 600 °C / min). In other instances, the component can be cooled at a rate between approximately 2 °C / s (or 120 °C / min) and approximately 6 °C / s (or 360 °C / min). During the quenching process, the component can be cooled from the carburizing temperature to near room temperature. Due to the carburizing process at box 404, the quenching process can produce a relatively high level of martensite in regions with relatively high carbon content. This martensite structure causes hardening in those relatively carbon-rich regions near the outer surface of the component. Carbon bonding in the carbon-rich region relative to the main body of the component can induce compressive stress in the carbon-rich region.

[0048] At box 408, the component undergoes a sub-zero process. This process can be performed using liquid nitrogen or other cryogenic fluids to cool the component to sub-zero temperatures. For example, a sub-zero process can cool the component to a range of approximately -100°C to approximately -175°C for approximately 2 hours (hr) to approximately 4 hours. These temperatures and times are examples, and it should be understood that other temperatures and times, greater than or less than those listed, can be used during a sub-zero process. This sub-zero process can transform more carbon-rich surface areas into a martensitic crystal structure, exceeding the martensitic composition achieved after quenching, thereby further hardening those areas. This sub-zero process can also contribute to compressive stress in the outer layer 206.

[0049] At box 410, the component is tempered. The tempering process can be carried out in a furnace with a non-oxidizing and / or reducing environment (e.g., a nitrogen environment, an argon environment, etc.). In embodiments of this disclosure, the tempering process can be carried out at a specific temperature (e.g., about 350°C) for annealing for several hours. In some cases, steel can be held at a temperature range between about 150°C and about 600°C for about 1 to 10 hours to temper steel components (e.g., nozzle tip 120 or cutting edge 114). In other cases, steel can be held at a temperature range between about 250°C and about 450°C for about 1 to 10 hours to temper steel components (e.g., nozzle valve 122 or piston 132). In still other cases, steel can be held at a temperature range between about 300°C and about 400°C for about 1 to 10 hours to temper steel components (e.g., track plate 134 or cylinder 130). The tempering process allows both the core layer 204 and the outer layer to have a martensitic crystal structure. Due to the carburizing process of the box 404, the outer layer 206 has a higher carbon content than the core layer 204. Because of the higher carbon content of the outer layer 206 compared to the core layer 204, the outer layer 206 has a higher hardness than the core layer 204.

[0050] Although certain processes are discussed with respect to method 400, it should be understood that other processes may be performed besides those listed here. For example, if volumetric material expansion is expected due to the carburizing process and the resulting carbon bonding to the surface of the part, undercutting or other machining processes may be performed before or after method 400 to compensate for any expected dimensional changes. Additionally, in some applications, it may be advantageous to have a thicker hard outer layer compared to what is provided by the carburizing process. In these cases, other processes, such as surface hardening, may be used to provide a thicker outer layer. In practice, any suitable process may be performed before or after the processes of method 400.

[0051] It should be understood that after performing method 400, the outer layer of the component (e.g., the outer layer 206 of the nozzle tip 120) can be a substantially martensitic and / or austenitic crystal structure with a relatively high carbon content compared to the core layer. It should also be understood that method 400 can produce a carbon distribution that produces a relatively high level of carbon at, for example, the outer layer 206, while the carbon content at the core layer 204 exhibits a relatively sharp gradient or decrease. This relatively sharp decrease in carbon distribution can allow a relatively thin component or portion of the component (e.g., the nozzle tip 120) to have a hard outer layer 206 while still maintaining a relatively soft core layer 204. Thus, as disclosed herein, the outer layer can be harder than the core layer of the component. It should also be understood that a favorable hardness distribution and / or carbon distribution can be achieved without having to perform additional machining and / or removal processes after the component is formed. Furthermore, the outer layer of the component can be under compressive stress while the core layer can be under tensile stress. Moreover, method 400 allows the component to be used at relatively high temperatures and substantially maintains its hardness distribution. For example, a nozzle tip 120 exposed to temperatures of 300°C or higher during use can still have a hardness of approximately 59 HRC or greater at a depth of approximately 250 μm. Therefore, method 400, alone or in combination... Figure 3 The described metallurgical composition allows for the formation of favorable structures (such as bonds). Figure 2 (as described), thereby enhancing the durability and lifespan of the components.

[0052] It should be noted that some operations of method 400 may not be performed in the order shown, may have additional elements and / or may not have some elements. Some operations of method 400 may also be performed substantially simultaneously, and therefore may end in a different order than the order of operations shown above.

[0053] Figure 5 This is a cross-sectional view of an example component surface 500 according to an embodiment of the present disclosure. As disclosed herein, the component may have an outer layer 502 and a core layer 504. The component having the example component surface 500 can be formed by means of, as in, combining Figure 3 The steel composition described and / or as combined Figure 4 The described material processing method 400 is implemented. The discussion herein can be applied to combinations such as... Figure 1 Any part of the machine 100 described, as well as parts manufactured for other applications and / or industries.

[0054] As discussed here, the outer layer 502 may also be referred to as a hard layer, outer layer, or shell layer. Similarly, the core layer 504 may also be referred to as the core region or body region. Although the outer layer 502 and the core layer 504 are depicted as having an abrupt transition, it should be understood that in some cases, the transition from the outer layer 502 to the core layer 504 may be graded and / or gradual. In other words, there may be spatial transition regions that embody material properties intermediate between the core layer 504 and the outer layer 502.

[0055] According to embodiments of this disclosure, the outer layer 502 and the core layer 504 may be substantially martensitic and / or austenitic crystal structures, wherein the outer layer 502 has a relatively larger carbon content compared to the core layer 504. Therefore, the outer layer 502 may be harder than the core layer 504 of the component. In some cases, the core layer 504 may have a hardness in the range of about 39 HRC to about 55 HRC. In other cases, the core layer 504 may have a hardness in the range of about 42 HRC to about 50 HRC. In still other cases, the core layer 504 may have a hardness in the range of about 44 HRC to about 48 HRC. In some cases, the outer layer 502 may have a hardness in the range of about 55 HRC to about 69 HRC. In other cases, the outer layer 502 may have a hardness in the range of about 58 HRC to about 64 HRC. In still other cases, the outer layer 502 may have a hardness in the range of about 60 HRC to about 62 HRC.

[0056] It should also be understood that the characteristics of the outer layer 502 can be non-uniform across its entire thickness. In some cases, the presence of the outer layer 502 can be detected by measuring the hardness at a threshold depth penetrating the outer layer 502. For example, the hardness at a depth of approximately 250 μm into the outer layer 502 can range from approximately 56 HRC to approximately 67 HRC. In some cases, the hardness at a depth of approximately 250 μm into the outer layer 502 can range from approximately 58 HRC to approximately 65 HRC. In still other cases, the hardness at a depth of approximately 250 μm into the outer layer 502 can range from approximately 58 HRC to approximately 64 HRC. For example, in some cases, the hardness at a depth of 250 μm into the outer layer 502 can be as low as approximately 59 HRC.

[0057] The outer layer 502 can have any suitable thickness. For example, the outer layer 502 can have a thickness ranging from about 150 μm to about 3 mm. In some other cases, the thickness of the outer layer 502 can range from about 200 μm to about 1.7 mm. In still other cases, the thickness of the outer layer 206 can range from about 300 μm to about 1 mm. For example, the outer layer 206 can have a thickness of about 500 μm. Although certain thicknesses of the outer layer 502 are discussed herein, it should be understood that thicknesses beyond those discussed herein are contemplated. It should also be understood that the thickness of the outer layer 502 can vary at least in part based on the component and / or the application of the component. For example, a thicker outer layer of the track plate 134 may be desired compared to the nozzle valve 122.

[0058] In some cases, the outer layer 502 can have a thickness such that the maximum Hertzian stress resulting from an impact between the component and one or more other objects is contained within the outer layer 502. The outer layer 502 is not only harder, but in some cases, it is also under compressive stress, while the core layer 504 is under tensile stress. Therefore, by designing the component such that the maximum Hertzian stress from the impact is in the compressive stress region (e.g., the outer layer 502), a lower likelihood of cracking can be achieved, resulting in greater component durability. In addition to the favorable stress distribution described herein, the increased hardness of the outer layer 502 improves its durability against impacts, such as impacts at high ambient temperatures. In some instances, the outer layer 502 of the component can be approximately 500 μm thick, and the maximum Hertzian stress from an impact with the component can be located at a surface depth of approximately 300 μm. Therefore, in this example, the maximum Hertzian stress can occur in the relatively hard and compressively stressed outer layer 502.

[0059] It should be understood that, such as Figure 5 The structure of the component surface 500 depicted herein can be manufactured using the material composition and / or processes disclosed herein. The manufactured component surface 500 can provide enhanced resistance to cracking and / or fracture, particularly due to impact with other objects at high ambient temperatures. In some cases, crack initiation and / or propagation can be suppressed due to compressive stress in the outer layer 502. Therefore, the hardness distribution and / or stress distribution of the component surface 500 can provide overall improved durability and lifespan of the component.

[0060] Industrial applicability This disclosure describes systems, structures, and methods for reducing crack initiation and / or crack propagation while increasing the wear tolerance, fatigue resistance, and / or toughness of components, such as those used in machine 100. These improved components may include fuel injector nozzle tips 120, fuel injector nozzle valves 122, track plates 134, bushings 136, cutting edges 114, hydraulic cylinders 130, hydraulic pistons 132, or any other structure or component including hardened, crack-resistant, and / or wear-resistant surfaces. As disclosed herein, the components may have hard, wear-resistant surface portions and soft core portions. During operation, the soft core portion provides a high level of toughness to the component, while the hard surface portion provides a high level of wear resistance. Additionally, the surface portions may be under compressive stress, thereby inhibiting crack initiation and / or crack propagation. Although components (such as nozzle tip 120) and the procedures for forming the components are discussed in the context of machine 100, it should be understood that the mechanisms for forming said components are applicable to a wide variety of mechanical systems, such as any mechanical system that can benefit from the improved fracture tolerance and / or wear resistance of various components.

[0061] Due to the systems, equipment, and methods described herein, components of machine 100 (e.g., fuel injector 116) can have a longer lifespan. For example, the fuel injector 116 described herein can have a longer lifespan than conventional fuel injectors not formed through the mechanisms described herein. In some cases, components (e.g., bushing 136) can allow for a significant improvement in the wear life of components of machine 100. This reduces on-site downtime, decreases the frequency of repairs and maintenance, and overall reduces the cost of heavy equipment such as machine 100. Improved reliability and reduced on-site downtime also improve the user experience, allowing machine 100 to be dedicated to its intended purpose for longer periods and a larger percentage of its overall lifespan. Improved machine 100 uptime and reduced planned maintenance can allow for more efficient resource deployment (e.g., fewer but more reliable machines 100 on the construction site). Therefore, the techniques disclosed herein improve the efficiency of project resources (e.g., construction resources, mining resources, etc.), provide longer uptime for project resources, and improve the financial performance of project resources.

[0062] While aspects of this disclosure have been specifically shown and described with reference to the foregoing embodiments, those skilled in the art will understand that various other embodiments can be conceived through modifications to the disclosed machines, systems, and methods without departing from the spirit and scope of the disclosure. Such embodiments should be understood to fall within the scope of this disclosure as defined by the claims and any equivalents.

[0063] Unless otherwise indicated herein, the description of value ranges herein is intended only as a shorthand method for referring to each independent value falling within the range, and each independent value is incorporated into the specification as if described separately herein. All methods described herein may be performed in any suitable order unless otherwise specified herein.

Claims

1. A fuel injector (116), comprising: Casing (118); A nozzle tip (120) is disposed within the housing (118), the nozzle tip (120) comprising a body through which fuel is delivered, the body comprising: A first outer layer, located on or near the outer surface of the body, has a hardness of at least 55 Rockwell hardness grade C (HRC), and the first outer layer also has compressive stress. The first outer layer has a vanadium content of at least 0.1% by weight and a first carbon content in the range of 0.7% by weight to 1.6% by weight. The second outer layer, having a Rockwell hardness rating of at least 55 C (HRC) and compressive stress, having a vanadium content of at least 0.1 wt% and a second carbon content in the range of 0.7 wt% to 1.6 wt%, is positioned on the inner surface of the body. A core layer (204), encapsulated by a first outer layer and a second outer layer, the core layer (204) having a third carbon content in the range of 0.17% to 0.5% by weight, a hardness of less than 55 HRC, and a tensile stress, wherein the carbon content decreases from the first outer layer to the core layer; and The outer layer has a thickness of at least 250 micrometers (μm), and Wherein, after the fuel injector (116) is exposed to a temperature of at least 300°C in the operating environment for at least 3 hours, the first outer layer maintains a first hardness of at least 59 HRC at a depth of at least 250 μm.

2. The fuel injector (116) according to claim 1, wherein the core layer (204) comprises manganese in the range of 0.2 wt% to 1 wt%, silicon in the range of 0 wt% to 0.3 wt%, phosphorus in the range of 0 wt% to 0.3 wt%, sulfur in the range of 0 wt% to 0.01 wt%, nickel in the range of 0 wt% to 0.3 wt%, chromium in the range of 1.5 wt% to 2 wt%, molybdenum in the range of 1.7 wt% to 2.4 wt%, and vanadium in the range of 0.1 wt% to 1 wt%.

3. The fuel injector (116) according to claim 1, wherein after the fuel injector (116) is exposed to a temperature of at least 300°C for at least 3 hours, the first outer layer has a first hardness of at least 60 HRC at a depth of at least 200 μm.

4. The fuel injector (116) according to claim 1, wherein after the fuel injector (116) is exposed to a temperature of at least 300°C in an operating environment for at least 3 hours, the first outer layer has a first hardness of at least 59 HRC at a depth of 250 μm from the outer surface and a second hardness of less than 53 HRC at a depth of 600 μm from the outer surface.

5. A method for manufacturing a machine part, comprising: Rough parts are formed from steel with a carbon content of less than 0.5% by weight and a vanadium content of at least 0.1% by weight; The rough part is carburized at a carburizing temperature of at least 900°C to form a carburized outer layer of the machine part; The rough carburized parts are quenched directly at the carburizing temperature; Perform sub-zero treatment on the hardened, rough-made parts; as well as The crudely manufactured parts, which have been treated to freezing temperatures, are tempered to form the machine parts. The carburized outer layer comprises a first hardness and compressive stress of at least 55 Rockwell hardness grade C (HRC), and the carburized outer layer has a first carbon content in a first range of 0.7% to 1.6% by weight and has a thickness of at least 300 micrometers (μm). The machine component includes a core layer encapsulated by the carburized outer layer, the core layer having a second hardness of less than 55 HRC, a second carbon content in a second range of 0.17 wt% to 0.5 wt%, and a tensile stress, wherein the second range does not overlap with the first range. The machine component includes an outer surface, and after the machine component has been exposed to a temperature of at least 300°C in an operating environment for at least 3 hours, a third hardness at a first depth of 250 micrometers (μm) from the outer surface is at least 59 HRC, and a fourth hardness at a second depth of 600 μm from the outer surface is less than 53 HRC.

6. The method of claim 5, wherein the carbon content of the steel is in the range of 0.17% by weight to 0.32% by weight.

7. The method according to claim 5, wherein the machine component comprises at least one of a fuel injector nozzle tip (120) and a fuel injector nozzle valve (122).

8. The method according to claim 5, wherein carburizing the rough component further comprises: The crude component is heated to at least 950°C for a predetermined period of time in a carbon-containing environment under partial vacuum.

9. A fuel system for a machine including one or more fuel injection components, wherein at least one of the fuel injection components includes a body having: An outer layer (206), comprising an outer surface (208), having a first hardness of at least 55 Rockwell hardness grade C (HRC) and compressive stress and positioned on the outer surface of the body, wherein the outer layer (206) has a first carbon content in a first range of 0.7 wt% to 1.6 wt% and has a thickness of at least 300 micrometers (μm); and A core layer (204), encapsulated by the outer layer (206), the core layer (204) having a second hardness of less than 55 HRC, a second carbon content in a second range of 0.17 wt% to 0.5 wt%, and a tensile stress, wherein the second range does not overlap with the first range. in, After one or more fuel injection components have been exposed to a temperature of at least 300°C in the operating environment for at least 3 hours, the third hardness at a first depth of 250 micrometers (μm) from the outer surface is at least 59 HRC, and the fourth hardness at a second depth of 600 μm from the outer surface is less than 53 HRC.

10. The fuel system of claim 9, wherein the core layer (204) comprises manganese in the range of 0.2 wt% to 1 wt%, silicon in the range of 0 wt% to 0.3 wt%, phosphorus in the range of 0 wt% to 0.3 wt%, nickel in the range of 0 wt% to 0.01 wt%, chromium in the range of 1.5 wt% to 2 wt%, molybdenum in the range of 1.7 wt% to 2.4 wt%, and vanadium in the range of 0.1 wt% to 1 wt%.

Images