Machine component and method for manufacturing it

Abstract

Machine component, used as a component (5, 13) of a crawler track undercarriage, as an excavator tooth (220) or as a tooth (321, 331, 333) of a crusher (300), comprising: a carrier material (100) consisting of a first metal; as well as a coating (90) which is arranged in contact with the substrate material (100) and covers at least part of a surface of the substrate material (100), wherein the coating (90) comprises: a matrix (95) consisting of a second metal; as well as hard particles (91) dispersed in the matrix (95), wherein: the coating (90) has a surface (90A) which is a forged surface; and the hard particles (91) located in a surface region (90B) of the coating (90) are embedded in the coating (90) and arranged side by side, wherein the surface region (90B) of the coating (90) is a region extending from the surface (90A) of the coating (90) to a depth corresponding to an average particle diameter of the hard particles (91).

Description

Technical area

[0001] The present invention relates to machine components and methods for producing the machine components and, in particular, to a machine component containing a coating having hard particles dispersed in a matrix and to a method for producing the machine component. Technical background

[0002] A coating can be applied to a machine component to improve wear resistance and for other purposes. Coatings that can be used to improve wear resistance include a coating comprising hard particles dispersed in a matrix consisting, for example, of steel. Such a coating can be formed, for example, by deposition welding (see, for example, JP 2008 - 000 763 A and JP H08 - 47 774 A).

[0003] JP H09 - 136 136 A describes a process for manufacturing composite machine components requiring increased wear, corrosion, and heat resistance. Components such as video recorder (VTR) drums, brake disc rotors, and engine pistons are described. A base material is covered with a coating of hard particles dispersed in a second metal matrix. This document highlights a drop forging process that improves the bond at the interface through induced material flow parallel to the bond, significantly increasing manufacturing efficiency and component durability by overcoming conventional joining problems with aluminum alloys.

[0004] JP 2013 - 046 928 A deals with a method for manufacturing engine exhaust valves for large diesel engines used in ships, with a focus on improving durability against high-temperature corrosion and wear. It describes a process that involves overlay welding a Ni-Cr-Al-based alloy onto a steel base body, followed by hot forging to shape the component and control the microstructure. The alloy composition is optimized to ensure resistance to sulfur and vanadium attack and to improve the mechanical properties and valve service life under extreme operating conditions. Summary of the inventionTechnical problem

[0005] In a machine component with a coating containing hard particles dispersed in a matrix, the hard particles may fall out of the coating during use. The wear resistance of the machine component with such a coating may be compromised if the hard particles fall out of the coating.

[0006] An object of the present invention is to improve wear resistance of a machine component by preventing the hard particles from falling out of the coating. Solution to the problem

[0007] A machine component according to the present invention is used as a component of a crawler track undercarriage, as an excavator tooth, or as a crusher tooth, and comprises a substrate made of a first metal, and a coating arranged in contact with the substrate and covering at least part of a surface of the substrate. The coating contains a matrix made of a second metal and hard particles dispersed in the matrix. The coating has a surface that is a forged surface. The hard particles located in a surface region of the coating are embedded in the coating and arranged next to one another, wherein the surface region of the coating is a region extending from the surface of the coating to a depth corresponding to an average particle diameter of the hard particles.

[0008] In the machine component of the present invention, the coating surface is a forged surface. The hard particles located in the surface region of the coating are embedded in the coating and arranged adjacent to each other. This prevents the hard particles from significantly protruding from the coating surface. This prevents the hard particles from falling out during use of the machine component, thereby improving the wear resistance of the machine component. Thus, with the machine component of the present invention, it is possible to improve the wear resistance of the machine component. It should be noted that the average particle diameter of the hard particles can be determined by observing a cross section perpendicular to the coating surface with an optical microscope and calculating an average value of the diameters of ten observed hard particles.The machine component of the present invention, which has excellent wear resistance, is suitable for a component of a crawler undercarriage, an excavator tooth, or a crusher tooth, which require high wear resistance.

[0009] In the machine component described above, the hard particles located in the surface area of ​​the coating can be arranged in contact with the surface of the coating. This minimizes the area of ​​a hard particle exposed at the surface of the coating, thereby preventing the hard particle from detaching.

[0010] In the machine component described above, among the hard particles located in the surface area of ​​the coating, any hard particle having an area exposed at the surface of the coating may have an acute central angle (less than 90°) corresponding to the area exposed at the surface of the coating. This makes the area of ​​a hard particle exposed at the surface of the coating small, thereby preventing the hard particle from falling out.

[0011] In the machine component described above, the coating may include a projection in a region that includes an interface between the coating and the substrate material, projecting toward the substrate material. This prevents the coating from detaching from the substrate material.

[0012] In the machine component described above, at least a portion of a hard particle can be accommodated in the projection. This more reliably prevents the coating from detaching from the substrate.

[0013] A method according to the invention for manufacturing a machine component used as a component of a crawler undercarriage, as an excavator tooth, or as a crusher tooth comprises the following steps: manufacturing a support member made of a first metal; forming a coating covering at least a portion of a surface of the support member; and forging the support member on which the coating is formed, so that the coating is machined. The step of forming the coating includes forming the coating containing a matrix made of a second metal and hard particles dispersed in the matrix.

[0014] In the method for manufacturing a machine component of the present invention, the support member on which the coating is formed is forged to process the coating having the hard particles dispersed in the matrix. When the coating is processed by forging, the hard particles protruding from the surface of the coating are pressed into the matrix, which has a relatively low hardness. Thus, the hard particles near the surface of the coating are sufficiently embedded in the coating. This prevents the hard particles from falling out during use of the machine component, thereby improving the wear resistance of the machine component. Thus, with the method for manufacturing a machine component of the present invention, it is possible to improve the wear resistance of the machine component.The method for manufacturing a machine component of the present invention, which can manufacture a component of a crawler undercarriage, an excavator tooth, or a crusher tooth having excellent wear resistance, is suitable for manufacturing these machine components requiring high wear resistance.

[0015] In the method for manufacturing a machine component described above, the step of forging the support member on which the coating is formed may include hot forging the support member on which the coating is formed. When hot forging is used, forging the support member on which the coating is formed may be facilitated. Effects of the invention

[0016] As is apparent from the above description, with the machine component and the method for manufacturing the same of the present invention, it is possible to improve the wear resistance of the machine component by preventing the hard particles from falling out of the coating. Short description of the drawings Fig. 1 is a schematic diagram showing the structure of a crawler traveling device; Fig. Figure 2 is a schematic diagram illustrating the function of a drive wheel and bushings; Fig. 3 is a schematic perspective view showing the structure of a socket; Fig. 4 is a schematic plan view showing the contact state of the drive wheel and a bushing; Fig. 5 is a schematic sectional view along the line VV in Fig. 4; Fig. 6 is a schematic sectional view showing the structure of a coating on and near its surface; Fig. 7 is a schematic sectional view showing the structure at and near an interface between the coating and a substrate; Fig. 8 is a flowchart schematically illustrating a method for manufacturing a machine component; Fig. 9 is a schematic perspective view illustrating a method of manufacturing a drive wheel; Fig. 10 is a schematic perspective view illustrating the method of manufacturing the drive wheel; Fig. 11 is a schematic sectional view illustrating a method of forming a coating; Fig. 12 is a schematic perspective view illustrating the method of manufacturing the drive wheel; Fig. 13 is a schematic perspective view illustrating the method of manufacturing the drive wheel; Fig. 14 is a schematic perspective view illustrating a method of manufacturing a bushing; Fig. 15 is a schematic perspective view illustrating the method of manufacturing the bushing; Fig. 16 is a schematic perspective view showing the structure of a bucket of a hydraulic excavator; Fig. 17 is a schematic plan view showing the structure of a tooth; Fig. 18 is a schematic sectional view along the line XVIII-XVIII in Fig. 17; Fig. 19 is a schematic sectional view showing the structure of a tooth of a comparative example; Fig. 20 is a schematic sectional view illustrating a method of manufacturing a tooth; Fig. Fig. 21 is a schematic sectional view illustrating the method of manufacturing the tooth; Fig. 22 is a schematic perspective view showing the structure of a crusher; Fig. 23 is a schematic perspective view showing the structure of an outer tooth of a fixed portion of the crusher; Fig. 24 is a schematic sectional view along the line XXIV-XXIV in Fig. 23; Fig. 25 is a schematic sectional view along the line XXV-XXV in Fig. 24; Fig. 26 is a schematic perspective view illustrating a method of manufacturing an outer tooth of the fixed portion of a crusher; Fig. 27 is a schematic perspective view illustrating the method of manufacturing the outer tooth of the fixed portion of the crusher; Fig. 28 is a schematic sectional view illustrating the method of manufacturing the outer tooth of the fixed portion of the crusher; Fig. 29 is a schematic sectional view illustrating the method of manufacturing the outer tooth of the fixed portion of the crusher; Fig. 30 is a schematic perspective view illustrating the method of manufacturing the outer tooth of the fixed portion of the crusher; Fig. 31 is a schematic perspective view illustrating the method of manufacturing the outer tooth of the fixed portion of the crusher; Fig. 32 is a schematic sectional view illustrating the method of manufacturing the outer tooth of the fixed portion of the crusher; Fig. 33 is a schematic sectional view illustrating the method of manufacturing the outer tooth of the fixed portion of the crusher; Fig. 34 is a photograph showing a cross-section of a tooth; Fig. 35 is an optical micrograph showing a surface of a coating and its surroundings (example); Fig. 36 is an optical micrograph showing a surface of a coating and its surroundings (comparative example); Fig. 37 is an optical micrograph showing an interface between a coating and a substrate and its surroundings (example); and Fig. Figure 38 is an optical micrograph showing an interface between a coating and a substrate and its surroundings (comparative example). Description of embodiments

[0017] Embodiments of the present invention will be described below. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and the description thereof will not be repeated. First embodiment

[0018] A machine component according to a first embodiment, which is an embodiment of the present invention, will be described using a drive wheel and bushings of a crawler traveling device as examples. Fig. 1 is a schematic diagram showing the structure of a crawler track traveling device. Fig. Figure 2 is a schematic diagram illustrating the function of a drive wheel and bushings. Fig. 3 is a schematic perspective view showing the structure of a socket. Fig. 4 and Fig. 5 are schematic sectional views showing the contact state of the drive wheel and a bushing.

[0019] A crawler traveling device 1 in the present embodiment as shown in Fig. 1 is a travel device for a work machine, such as a bulldozer, and includes a crawler track 2, a crawler track frame 3, a deflection sprocket 4, a drive wheel 5 and a plurality (in the present case seven) of track rollers 10 and a plurality (in the present case two) of support rollers 11.

[0020] The crawler track 2 includes a plurality of crawler links 9 connected in an endless manner, as well as crawler plates 6 attached to the corresponding crawler links 9. The crawler links 9 include outer links 7 and inner links 8. The outer links 7 and the inner links 8 are alternately connected.

[0021] The idler sprocket 4, the plurality of track rollers 10, and the plurality of support rollers 11 are mounted on the crawler frame 3 so as to be rotatable about their respective axes. The drive wheel 5 is arranged at one end of the crawler frame 3. A power source, such as a motor, is connected to the drive wheel 5, and the drive wheel 5 rotates about its axis driven by the power source. On an outer peripheral surface of the drive wheel 5, a plurality of projections 51 are arranged, projecting radially outward. The projections 51 engage with the crawler belt 2. The rotation of the drive wheel 5 is thus transmitted to the crawler belt 2. The crawler belt 2, driven by the rotation of the drive wheel 5, rotates in a circumferential direction.

[0022] The idler sprocket 4 is attached to the other end (opposite the end where the drive wheel 5 is arranged) of the crawler frame 3. Furthermore, on the crawler frame 3, in the area enclosed between the drive wheel 5 and the idler sprocket 4, the track rollers 10 and the support rollers 11 are attached, respectively, on the side in contact with the ground and on the side opposite to the side in contact with the ground. The outer peripheral surfaces of the idler sprocket 4, the track rollers 10, and the support rollers 11 each come into contact with the inner peripheral surface of the crawler belt 2. As a result, the crawler belt 2, driven by the rotation of the drive wheel 5, rotates in the circumferential direction while being guided by the idler sprocket 4, the drive wheel 5, the track rollers 10, and the support rollers 11.

[0023] An outer member 7 and an inner member 8 which are adjacent to each other are, as described with reference to Fig. 2, by means of a connecting pin 12 and a bushing 13. Each inner link 8 has two through holes 15 which are formed so as to run in a direction perpendicular to the plane of rotation of the crawler belt 2. One and the other of these two through holes 15 are formed at one end and the other end in the longitudinal direction of the link, respectively. Each outer link 7 has two through holes 15 which are formed so as to run in a direction perpendicular to the plane of rotation of the crawler belt 2. One and the other of these two through holes 15 are formed at one end and the other end in the longitudinal direction of the link, respectively.

[0024] The socket 13 has, as described with reference to Fig. 3, the bushing 13 has the shape of a hollow cylinder. The bushing 13 has a smaller-diameter portion 139 formed at each end, which has a smaller outer diameter. The bushing 13 has an inner peripheral surface 133 that has a constant diameter along its length. In the smaller-diameter portions 139, the thickness of the bushing 13 is reduced.

[0025] Paired outer members 7 are, as described with reference to Fig. 2 and Fig. 3, are arranged so that their two through holes 15 are each aligned, as viewed in the direction perpendicular to the plane of rotation of the crawler track 2. Paired inner links 8 are arranged so that their two through holes 15 are each aligned, as viewed in the direction perpendicular to the plane of rotation of the crawler track 2. An adjacent outer link 7 and an inner link 8 are arranged so that a through hole 15 of the outer link 7 and a through hole 15 of the inner link 8 are each aligned, as viewed in the direction perpendicular to the plane of rotation of the crawler track 2. A bushing 13 is arranged so that it is sandwiched between a pair of inner links 8, and the smaller diameter portion 139 at each end is inserted into a through hole 15 of the corresponding inner link 8.A connecting pin 12 is configured to extend through the through holes 15 of the outer and inner links 7 and 8, which are adjacent to each other, the holes being aligned as viewed in the direction perpendicular to the plane of rotation of the crawler belt 2, and to extend through the space enclosed by the inner peripheral surface 133 of the corresponding bushing 13. The connecting pin 12 is configured to extend through the bushing 13 in the longitudinal direction.

[0026] The drive wheel 5 rotates in a circumferential direction, with its outer peripheral surface 53 engaging with outer peripheral surfaces 131 of the bushings 13 that form the crawler belt 2. The outer peripheral surface 53 of the drive wheel 5 and the outer peripheral surfaces 131 of each bushing 13 must therefore have high wear resistance. The drive wheel 5 is a machine component that slides relative to another component or the bushing 13 and is in contact with the bushing 13 or the outer peripheral surface 53 in the contact area. The bushing 13 is a machine component that slides relative to another component or the drive wheel 5 and is in contact with the drive wheel 5 or the outer peripheral surface 131 in the contact area.

[0027] The drive wheel 5 contains, as described with reference to Fig. 4 and Fig. 5, a base material 50 made of metal (steel) and a coating 52 covering the base material 50 to form the outer peripheral surface 53, which is the contact portion. The outer peripheral surface 53, which is the surface of the coating 52, has been smoothed. Here, the state in which the outer peripheral surface 53, i.e., the surface of the coating 52, is smoothed refers to the state in which the surface profile, which was created by surface tension and the like when the coating 52 was formed in the liquid state, has been removed from the surface of the coating 52. In the present embodiment, the outer peripheral surface 53, which is the surface of the coating 52, is a forged surface. The outer peripheral surface 53, orThe surface of the coating 52, which was formed by surface tension and the like during the formation of the coating 52 in the liquid state, has been smoothed by forging. As the metal constituting the base material 50, for example, carbon steel for machine use or alloy steel for machine use specified according to the JIS standard (e.g., S45C or SCM435, as well as manganese steel (SMn), chromium steel (SCr), or chromium-molybdenum steel (SCM) containing an equivalent amount of carbon) can be used.

[0028] A bushing 13 includes a base material 134 and a coating 132 covering the base material 134, thus forming the outer peripheral surface 131, which is the contact area. The outer peripheral surface 131, which is the surface of the coating 132, has been smoothed. In the present embodiment, the outer peripheral surface 131, which is the surface of the coating 132, is a forged surface. The outer peripheral surface 131, or the surface of the coating 132, which has been affected by surface tension and the like during formation of the coating 132 in the liquid state, has been smoothed by forging. As the metal forming the base material 134, for example, carbon steel for use in machinery or alloy steel for use in machinery specified according to the JIS standard (e.g.S45C or SCM435, as well as manganese steel (SMn), chromium steel (SCr) or chromium-molybdenum steel (SCM), which contains an equivalent amount of carbon).

[0029] In the drive gear 5 and the bushings 13, which are the machine components in the present embodiment, the surfaces of the coatings 52 and 132 forming the contact areas have been smoothed. This prevents a localized increase in contact pressure and other phenomena, so that the components cause less damage to the other components (bushes 13 and drive gear 5).

[0030] The following is a description of the structure of a coating formed on the drive wheel 5 and the bushings 13. Fig. Figure 6 is a schematic sectional view showing the structure of a coating at and near its surface. Fig. Figure 7 is a schematic sectional view showing the structure at and around an interface between the coating and a substrate. A coating 90 (coating 52 and coating 132) formed on the drive wheel 5 and the bushings 13 includes, as described with reference to Fig. 6 and Fig. 7, a matrix 95 consisting of a second metal and hard particles 91 dispersed in the matrix 95. The second metal forming the matrix 95 can, for example, be a mixture of a metal originating from a welding wire and the metal (first metal) forming the carrier material 100 (carrier material 50 and carrier material 134). Particles having a higher hardness than the matrix 95, such as particles made of cemented carbide, can be used as the hard particles 91. The coating 90 has greater wear resistance than the carrier material 100.

[0031] The surface 90A of the coating 90 as shown in Fig. 6 is a forged surface. The hard particles 91 located in a surface area 90B of the coating, which is an area within an average particle diameter of the hard particles 91 from the surface 90A of the coating 90, are embedded in the coating 90 while being arranged adjacent to each other. This prevents the hard particles 91 from being arranged to significantly protrude from the surface 90A of the coating 90. This, in turn, prevents the hard particles 91 from falling out during use of the drive gear 5 and the bushings 13, thereby improving the wear resistance of the drive gear 5 and the bushings 13.

[0032] The hard particles 91 located in the surface area 90B of the coating can, as in Fig. 6, be arranged in contact with the surface 90A of the coating 90. This makes the area of ​​a hard particle 91 exposed at the surface 90A of the coating 90 small, thereby preventing the hard particle 91 from falling out.

[0033] Of the hard particles 91 located in the surface area 90B of the coating, as shown in Fig. As shown in Figure 6, each hard particle 91 having a portion exposed at the surface 90A of the coating 90 must have an acute central angle θ (less than 90°) corresponding to this exposed portion. This makes the area of ​​a hard particle 91 exposed at the surface 90A of the coating 90 small, thereby preventing the hard particle 91 from falling out.

[0034] In a region including an interface between the coating 90 and the carrier material 100, as described with reference to Fig. 7, the coating 90 has protrusions 99 that protrude toward the carrier material 100. The protrusions 99 provide an anchoring effect that prevents the coating 90 from detaching from the carrier material 100. A protrusion 99 receives at least a portion of a hard particle 91. This more reliably prevents the coating 90 from detaching from the carrier material 100. The matrix 95 of the coating 90 is located between the carrier material 100 and the hard particle 91 received in the protrusion 99. The hard particle 91 received in the protrusion 99 is not in contact with the carrier material 100. The center of the hard particle 91 is located outside the protrusion 99 (i.e., a portion of the hard particle 91, which has a volume of less than half of that of the hard particle 91, is received in the protrusion 99). A hard particle 91 is received in a protrusion 99.Each projection 99 has a depth that is smaller than the radius of the hard particle 91 received in the projection 99.

[0035] A method of manufacturing a drive wheel 5, which is the machine component in the present embodiment, will be described below with reference to Fig. 8 to 13 described. Fig. 8 is a flowchart schematically illustrating a method for manufacturing a drive wheel which is the machine component. Fig. 9, Fig. 10, Fig. 12 and Fig. 13 are schematic perspective views illustrating the method of manufacturing the drive wheel. Fig. 11 is a schematic sectional view illustrating a method of forming a coating.

[0036] In the method for manufacturing a drive wheel 5 in the present embodiment, first, as described with reference to Fig. 8, a step for manufacturing a support element is carried out as a step S10. In this step S10, as described with reference to Fig. 9, a support member 61 is manufactured, which becomes a support material 50 of the drive wheel 5. The support member 61 is made of a metal that forms the support material 50. The support member 61 has a cylindrical shape. The support member 61 includes a pair of end surfaces 61B and a side surface 61A connecting the end surfaces 61B.

[0037] Subsequently, a step of forming a coating is carried out as a step S20. In this step S20, as described with reference to Fig. 9 and Fig. 10, a coating layer 63 is formed to cover a part of the side surface 61A of the support member 61 manufactured in step S10. The coating layer 63 is formed over the entire length in the longitudinal direction of the support member 61. The coating layer 63 is formed in a part in the circumferential direction (approximately one half in the circumferential direction) of the support member 61. The coating layer 63 has a structure in which beads 62 extending in the longitudinal direction of the support member 61 are adjacent to each other without gaps between them in the circumferential direction.

[0038] The coating 63 can be formed, for example, by means of deposition welding using CO2 arc welding, as described below. First, an apparatus for forming a coating is described. The apparatus for forming a coating includes, as described with reference to Fig. 11, a welding torch 70 and a nozzle 80 for supplying hard particles. The welding torch 70 includes a welding nozzle 71 having a hollow cylinder shape, and a contact tip 72 disposed inside the welding nozzle 71 and connected to a power source (not shown). A welding wire 73 in contact with the contact tip 72 is continuously supplied to the front end side of the welding nozzle 71. For the welding wire, JIS YGW12, for example, can be used. A gap between the welding nozzle 71 and the contact tip 72 is a flow path for shielding gas. The shielding gas flowing through the flow path is ejected from the front end of the welding nozzle 71. The nozzle 80 for supplying hard particles has a hollow cylinder shape. Inside the hard particle supply nozzle 80, hard particles 91 are supplied and ejected from the front end of the hard particle supply nozzle 80.

[0039] This coating forming apparatus can be used to form a coating 63 using the method shown below. Using a support member 61 as one electrode and the welding wire 73 as the other electrode, voltage is applied across the support member 61 and the welding wire 73. This creates an arc 74 between the welding wire 73 and the support member 61. The arc 74 is shielded from the ambient air by the shielding gas ejected from the front end of the welding nozzle 71 along the arrows β. Carbon dioxide, for example, can be used as the shielding gas. The heat in the arc 74 melts a portion of the support member 61 and also melts the front end of the welding wire 73. The thus melted front end of the welding wire 73 forms droplets that are transferred to the molten portion of the support member 61.This forms a melt pool 92, which is a liquid region in which the molten support element 61 and the molten welding wire 73 are mixed together. The hard particles 91 ejected via the hard particle supply nozzle 80 are supplied to this melt pool 92.

[0040] When the welding torch 70 and the nozzle 80 for supplying hard particles constituting the deposition welding device move relative to the support member 61 in the direction shown by the arrow α, the position at which the molten pool 92 is formed shifts accordingly. The previously formed molten pool 92 solidifies to form a bead 62. The bead 62 contains a matrix 95 formed by solidification of the molten pool 92 and hard particles 91 dispersed in the matrix 95. A plurality of such beads 62 are formed side by side in the width direction without any gap between them, so that a desired area on the side surface 61A of the support member 61 is covered, thus completing the formation of the coating 63 (see Fig. 10). It should be noted that hardfacing can be performed, for example, under the following conditions: welding current of 230 A, welding voltage of 17 V, feed rate of hard particles of 110 g / min, and bead protrusion length of 4 mm. JIS YGW11 can be used as the welding wire. WC- or W2C-based particles can be used as the hard particles.

[0041] Subsequently, a hot forging step is carried out as a step S30. In this step S30, the support member 61 with the coating 63 formed in step S20 is hot forged. The support member 61 with the coating 63 formed thereon is, as described with reference to Fig. 10 and Fig. 12, heated to a temperature that enables hot forging, and then placed in a mold for forging, which has a cavity corresponding to a desired shape of the drive wheel 5. In the present embodiment, a plurality of arc-shaped parts forming an annular drive wheel 5 are produced by hot forging. The resulting parts are assembled in a later step to produce the annular drive wheel 5. The coating 63 formed in step S20 is processed by hot forging. The support member 61 is hot forged so that the coating 63 covers the outer peripheral surface of the drive wheel 5. Thus, a coating 52 is produced which has a smooth surface on which the surface profile caused by surface tension in the liquid state and the like has been removed. By hot forging, as shown in Fig. 12, ridge 59 is formed. Subsequently, as described with reference to Fig. 12 and Fig. 13, punching is carried out to remove the burr 59, so that a part is created that forms the drive wheel 5 (see Fig. 13).

[0042] When the support member 61 with the coating 63 formed thereon is hot forged, as described with reference to Fig. 11 and Fig. As can be seen in Figure 6, hard particles 91, which protrude from a surface of the coating 63 (beads 62) during the formation of the coating 63, are pressed into the coating 63 (beads 62). As a result, in the drive gear 5, the hard particles 91 located in the surface region 90B of the coating are embedded in the coating 90 and arranged side by side. The hard particles 91 located in the surface region 90B of the coating are arranged in contact with the surface 90A of the coating 90. Of the hard particles 91 located in the surface region 90B of the coating, any hard particle 91 that has a portion exposed on the surface 90A of the coating 90 has an acute central angle θ (less than 90°) corresponding to the exposed portion. This prevents the hard particle 91 from falling out during use of the drive gear 5, thereby improving the wear resistance of the drive gear 5.

[0043] When the support member 61 with the coating 63 formed thereon is hot forged, protrusions 99 are formed in the coating 90 due to the hard particles 91 that were present near the interface between the coating 63 (beads 62) and the support member 61 at the time of formation of the coating 63. At least a portion of a corresponding hard particle 91 is received in each protrusion 99. With the above-described process, the surface portion of the coating 90, which has excellent wear resistance because the hard particles 91 are arranged in contact with the surface 90A, and the protrusions 99 that prevent the coating 90 from separating from the base material 100 are simultaneously formed.

[0044] Subsequently, as explained with reference to Fig. 8, a heat treatment step is performed as a step S40. In this step S40, the pinion 5 (the part constituting the pinion 5) manufactured by hot forging in step S30 is subjected to heat treatment. The heat treatment performed in step S40 is, for example, quenching and tempering. This imparts desired hardness and toughness to the base material 50 of the pinion 5. Subsequently, in order to attach the pinion 5 to a support body (not shown), a portion where no coating 90 has been formed is subjected to machining to improve dimensional accuracy, form a mounting hole, and so on. The pinion 5 (the part constituting the pinion 5) in the present embodiment is thus completed.

[0045] In the following, with reference to Fig. 8, Fig. 14 and Fig. 15, a method of manufacturing a bushing 13, which is the machine component in the present embodiment, is described. Fig. 8 is a flowchart schematically illustrating a method for manufacturing a bushing. Fig. 14 and Fig. 15 are schematic perspective views illustrating the method for manufacturing the bushing. The bushing 13 in the present embodiment can be manufactured using a method similar to that of the drive gear 5 described above.

[0046] In the method of manufacturing a bushing 13 in the present embodiment, as described with reference to Fig. 8, first, a step for manufacturing a carrier element is carried out as a step S10. In this step S10, as described with reference to Fig. 14, a support member 64 is manufactured, which becomes a support material 134 of the bushing 13. The support member 64 is made of a metal that forms the support material 134. The support member 64 has a cylindrical shape. The support member 64 includes a pair of end surfaces 64B and an outer peripheral surface 64A connecting the end surfaces 64B.

[0047] Subsequently, a step of forming a coating is carried out as a step S20. In this step S20, as described with reference to Fig. 14 and Fig. 15, a coating layer 63 is formed to cover part of the outer peripheral surface 64A of the support member 61 formed in step S10. The coating layer 63 is formed in the central portion in the longitudinal direction of the support member 64. No coating layer 63 is formed at both end portions in the longitudinal direction of the support member 64. The coating layer 63 is formed over the entire surface in the circumferential direction of the support member 64. The coating layer 63 has a structure in which beads 62 extending in the longitudinal direction of the support member 64 are juxtaposed with each other in the circumferential direction without gaps between them. The coating layer 63 can be formed, for example, by deposition welding using CO2 arc welding, as in the above-described production of the drive gear 5.It should be noted that the coating 63 may be formed in a part in the circumferential direction of the support member 64 corresponding to the area that comes into contact with the drive wheel 5, for example, over half of the circumference.

[0048] Subsequently, a hot forging step is carried out as a step S30. In this step S30, the support element 64 with the coating 63 formed in step S20 is hot forged. The support element 64 with the coating 63 formed thereon is, as described with reference to Fig. 15 and Fig. 3 to 5, heated to a temperature that enables hot forging, and then placed in a mold for forging, which has a cavity corresponding to a desired shape of the bushing 13. With hot forging, the coating 63 formed in step S20 is processed. The support member 64 is hot forged so that the coating 63 covers the outer peripheral surface 131 of the bushing 13. Thus, a coating 132 is produced that has a smooth surface on which the surface profile caused by surface tension in the liquid state and the like has been removed. The two ends of the support member 64 in the longitudinal direction where no coating 63 has been formed become the smaller diameter portions 139 of the bushing 13. Subsequently, a bolt hole is formed into which a connecting bolt 12 for connecting the links 7 and 8 is inserted (see Fig. 2). The bolt hole is drilled as described with reference to Fig. 3, is formed by the inner peripheral surface 133 and extends in the axial direction.

[0049] When the support member 64 with the coating 63 formed thereon is hot forged, hard particles 91 that protrude from a surface of the coating 63 (beads 62) when the coating 63 is formed are pressed into the coating 63 (beads 62). As a result, in the bushing 13, the hard particles 91 located in the coating surface region 90B are embedded in the coating 90 while being arranged side by side. The hard particles 91 located in the coating surface region 90B are arranged in contact with the surface 90A of the coating 90. Of the hard particles 91 located in the coating surface region 90B, any hard particle 91 that has a portion exposed on the surface 90A of the coating 90 has an acute central angle θ (less than 90°) corresponding to the exposed portion.This prevents the hard particle 91 from falling out during use of the bushing 13, thereby improving the wear resistance of the bushing 13.

[0050] When the support member 64 with the coating 63 formed thereon is hot forged, the bushing 13 develops protrusions 99 in the coating 90 due to the hard particles 91 that were present near the interface between the coating 63 (beads 62) and the support member 64 at the time the coating 63 was formed. At least a portion of a corresponding hard particle 91 is received in a protrusion 99.

[0051] Subsequently, as explained with reference to Fig. 8, a heat treatment step is performed as a step S40. In this step S40, the bushing 13 produced by hot forging in step S30 is subjected to heat treatment. The heat treatment performed in step S40 includes, for example, quenching and tempering. This imparts the desired hardness and toughness to the base material 134 of the bushing 13. Subsequently, the smaller-diameter portions 139 of the bushing 13 are machined to improve dimensional accuracy, reduce surface roughness, etc. The bushing 13 in the present embodiment is thus completed. Second embodiment

[0052] A machine component according to a second embodiment, which is another embodiment of the present invention, will be described below using an excavator tooth of a hydraulic excavator as an example. Fig. 16 is a schematic perspective view showing the structure of a bucket of a hydraulic excavator. Fig. Figure 17 is a schematic plan view showing the structure of a tooth. Fig. 18 is a schematic sectional view along the line XVIII-XVIII in Fig. 17.

[0053] A spoon 201 in the present embodiment as shown in Fig. 16, which is attached to a front end of a boom (not shown) of a hydraulic excavator, is used for excavating earth and sand. The bucket 201 includes a main body 210 consisting of a plate-like member and having an opening, a plurality (in the case of Fig. 16 includes three teeth 220 mounted on the main body 210 so as to partially protrude from a periphery 212 of the opening of the main body 210 on its excavation side, and an attachment portion 230 disposed on a side of the main body 210 opposite the side to which the teeth 220 are mounted. The bucket 201 is supported by the arm of the hydraulic excavator via the attachment portion 230. When the bucket 201 is used for excavation work, the teeth 220 first penetrate into soil and sand. The teeth 220 are therefore required to have strong abrasion resistance (wear resistance) to soil and sand.

[0054] A tooth 220 contains, as in Fig. 17, a front end 221 and a rear end 222. The tooth 220 is attached to the main body 210 at the rear end 222 side, with the front end 221 side protruding from the periphery 212 of the opening of the bucket 201. The tooth 220, in use, is in contact with another component, which is the main body 210. The bucket 201 penetrates soil and sand via the front end 221 side of the tooth 220. The front end 221 side of the tooth 220 must therefore have particularly high resistance to abrasion by soil and sand.

[0055] A tooth 220 contains, as described with reference to Fig. 18, a substrate 225 made of a first metal, and a coating 227 arranged in contact with the substrate 225 and covering a covered area 225A that is a part of a surface of the substrate 225. As the first metal for the substrate 225, for example, carbon steel for machine use or alloy steel for machine use specified according to the JIS standard (e.g., S45C or SCM435, as well as manganese steel (SMn), chromium steel (SCr), or chromium-molybdenum steel (SCM) containing an equivalent amount of carbon) can be used.In an edge region 229 of the coating, which corresponds to a boundary between the covered region 225A and an exposed region 225B, which corresponds to an area outside the covered region 225A on the surface of the carrier material 225, the exposed region 225B and a surface 227A of the coating 227 are flush with each other and form a forged surface. The surface 227A of the coating 227 corresponds entirely to the forged surface.

[0056] Fig. 19 is a schematic sectional view showing the structure of a tooth with a coating as a comparative example. When forming a coating for improving wear resistance at or near a leading end of a tooth, the coating is usually formed on a steel base material having a desired shape. Tooth 920 of the comparative example, which is a typical tooth with a coating, includes, as described with reference to Fig. 19, a front end 921 and a rear end 922. A coating 927 is formed on the side of the front end 921 of the tooth 920. The coating 927 is formed, for example, by deposition welding, to cover a covered area 925A of a substrate 925 that has been formed into a desired shape. Thus, at edge portions 929A, 929B, which correspond to boundaries between the covered area 925A and exposed areas 925B, 925C outside the covered area 925A, steps are formed between the exposed areas 925B, 925C and a surface 927A of the coating 927. These steps increase the resistance of the tooth 920 to penetrating soil and sand. Furthermore, the coating 927 is formed after the substrate 925 has been formed. It is difficult to form the coating 927 near the front end 921.Thus, in the area including the front end 921, the front end exposed portion 925C is formed, which is not covered with the coating 927. Due to this front end exposed portion 925C, which has low wear resistance, the progression of wear is accelerated and the frequency of replacement of the tooth 920 increases.

[0057] In the tooth 220 in the present embodiment, as described with reference to Fig. 18, the exposed portion 225B and the surface 227A of the coating 227 are flush with each other in the edge portion 229 of the coating. This can prevent an increase in penetration resistance, which would otherwise be caused by a step in the edge portion 229 of the coating. When the edge portion 229 of the coating is enclosed in the forged surface, the cutting processing step for making the exposed portion 225B and the surface 227A of the coating 227 flush with each other can be omitted. Therefore, the processing of the edge portion 229 of the coating, where the hardness difference is significant, and the processing of the coating 227, whose hardness is high, can be avoided. Thus, in the tooth 220 in the present embodiment, it is possible to avoid a disadvantage that would otherwise occur when forming the coating 227.Furthermore, a coating may be formed on a support member, and then forging may be performed to form a region including the front end 221. Thereby, the region including the front end 221 may be formed as shown in FIG. Fig. 18, can be easily covered with the coating 227, and a tooth 220 having high wear resistance can be manufactured.

[0058] The coating 90 (coating 227) formed on the tooth 220 contains, as described with reference to Fig. 6 and Fig. As can be seen in Figure 7, as in the drive wheel 5 and the bushing 13 in the first embodiment described above, a matrix 95 consisting of a second metal, as well as hard particles 91 dispersed in the matrix 95, can be, for example, a mixture of a metal originating from a welding wire and a metal (first metal) forming the carrier material 100 (carrier material 225). Particles having a higher hardness than the matrix 95, such as particles of cemented carbide, can be used as the hard particles 91. The coating 90 has greater resistance to abrasion by soil and sand (wear resistance) than the carrier material 100.

[0059] The surface 90A of the coating 90 as shown in Fig. 6 is a forged surface. The hard particles 91 located in a surface area 90B of the coating, which is an area within an average particle diameter of the hard particles 91 from the surface 90A of the coating 90, are embedded in the coating 90 while being arranged side by side. This prevents the hard particles 91 from being arranged to significantly protrude from the surface 90A of the coating 90. This, in turn, prevents the hard particles 91 from falling out during use of the tooth 220, thereby improving the wear resistance of the tooth 220.

[0060] The hard particles 91 located in the surface area 90B of the coating can, as in Fig. 6, be arranged in contact with the surface 90A of the coating 90. This makes the area of ​​a hard particle 91 exposed at the surface 90A of the coating 90 small, thereby preventing the hard particle 91 from falling out.

[0061] Of the hard particles 91 located in the surface area 90B of the coating, as shown in Fig. As shown in Figure 6, each hard particle 91 having a portion exposed at the surface 90A of the coating 90 must have an acute central angle θ (less than 90°) corresponding to this exposed portion. This makes the area of ​​a hard particle 91 exposed at the surface 90A of the coating 90 small, thereby preventing the hard particle 91 from falling out.

[0062] The coating 90 contains, as described with reference to Fig. 7, in a region including an interface between the coating 90 and the carrier material 100, protrusions 99 protrude toward the carrier material 100. The protrusions 99 provide an anchoring effect that prevents the coating 90 from detaching from the carrier material 100. A protrusion 99 receives at least a portion of a hard particle 91. This more reliably prevents the coating 90 from detaching from the carrier material 100. The matrix 95 of the coating 90 is located between the carrier material 100 and the hard particle 91 received in the protrusion 99. The hard particle 91 received in the protrusion 99 is not in contact with the carrier material 100. The center of the hard particle 91 is located outside the protrusion 99 (i.e., a portion of the hard particle 91, which has a volume of less than half of that of the hard particle 91, is received in the protrusion 99).A hard particle 91 is housed in a protrusion 99. Each protrusion 99 has a depth that is smaller than the radius of the hard particle 91 housed in the protrusion 99.

[0063] A method for manufacturing a tooth 220 is described below. Fig. 8 is a flowchart schematically illustrating a method for manufacturing a tooth which is the machine component. Fig. 20 and Fig. 21 are schematic sectional views illustrating the method of manufacturing the tooth.

[0064] In the method for manufacturing a tooth 220 in the present embodiment, as described with reference to Fig. 8, first, a step for manufacturing a carrier element is carried out as a step S10. In this step S10, as described with reference to Fig. 20, a support member 250 is manufactured, which becomes a support material 225 of the tooth 220. The support member 250 is made of a first metal. The support member 250 has a cylindrical shape. The support member 250 has a cylindrical shape that includes one end surface 252, another end surface 253, and a side surface 251 connecting the one end surface 252 and the other end surface 253. A first chamfered portion 252A is formed in a region where the one end surface 252 and the side surface 251 are connected. A second chamfered portion 253A is formed in a region where the other end surface 253 and the side surface 251 are connected. The side of the one end surface 252 of the support member 250 corresponds, as described with reference to Fig. 20 and Fig. 18, the side of the front end 221 of the tooth 220, and the side of the other end surface 253 of the support element 250 corresponds to the side of the rear end 222 of the tooth 220.

[0065] Subsequently, a step of forming a coating is carried out as a step S20. In this step S20, as described with reference to Fig. 20 and Fig. 21, a coating 260 is formed in contact with a covered area 251A, which is a part of a surface of the support member 250 manufactured in step S10, to cover the covered area 251A. The coating 260 is formed to cover a desired area of ​​the support material 225 when hot forging is performed, which will be described later. The covered area 251A can be determined in advance through a simulation of the hot forging, for example, using a finite element method. In the present embodiment, as described with reference to Fig. 21, the coating 260 is formed to cover the side of the one end surface 252 of the side surface 251, the first chamfered portion 252A, and the one end surface 252. The coating 260 can be formed by deposition welding using CO2 arc welding, as in the first embodiment described above.

[0066] Subsequently, a hot forging step is carried out as a step S30. In this step S30, the support element 250 with the coating 260 formed in step S20 is hot forged. The support element 250 with the coating 260 formed thereon is, as described with reference to Fig. 21 and Fig. 18, is heated to a temperature that enables hot forging, and then placed in a mold for forging, which has a cavity corresponding to a desired shape of the tooth 220. This hot forging machines a region of the support member 250 that includes an edge portion 259 of the coating. Through the hot forging, the edge portion 259 of the coating becomes the edge portion 229 of the coating of the tooth 220. With the edge portion 259 of the coating machined during the hot forging, the tooth 220 is produced, which has the exposed region 225B and the surface 227A of the coating 227, which are flush with each other, in the edge portion 229 of the coating.In the edge portion 229 of the coating, the exposed area 225B and the surface 227A of the coating 227 form a flush forged surface corresponding to the area of ​​the surface of the mold used in the hot forging, in which the edge portion 225B of the coating is machined. In the edge portion 229 of the coating, the exposed area 225B and the surface 227A of the coating 227 form a flush surface corresponding to the shape of the forging die. The edge portion 229 of the coating is enclosed in the forged surface.

[0067] When the support member 250 with the coating 260 formed thereon is hot forged, hard particles 91, which protruded from a surface of the coating 260 during the formation of the coating 260, are pressed into the coating 260. As a result, in the tooth 220, the hard particles 91 located in the surface region 90B of the coating are embedded in the coating 90 and arranged next to each other. The hard particles 91 located in the surface region 90B of the coating are arranged in contact with the surface 90A of the coating 90. Of the hard particles 91 located in the surface region 90B of the coating, any hard particle 91 that has a region exposed on the surface 90A of the coating 90 has an acute central angle θ (less than 90°) corresponding to the exposed region (see Fig. 6). This prevents the hard particle 91 from falling out during use of the tooth 220, thereby improving the wear resistance of the tooth 220.

[0068] When the tooth 220 has its carrier element 250 hot-forged with the coating 260 formed thereon, projections 99 are formed in the coating 90 due to the hard particles 91 that were located near the interface between the coating 260 and the carrier element 250 at the time of formation of the coating 260. At least a portion of a corresponding hard particle 91 is received in a projection 99 (see Fig. 7).

[0069] Subsequently, as explained with reference to Fig. As can be seen in Figure 8, a heat treatment step is performed as step S40. In this step S40, the tooth 220 produced by hot forging in step S30 is subjected to heat treatment. The heat treatment performed in step S40 consists, for example, of tempering. This imparts the desired hardness and toughness to the carrier material 225 of the tooth 220. Using the method described above, the tooth 220 is completed in the present embodiment. Third embodiment

[0070] Hereinafter, a machine component according to a third embodiment, which is another embodiment of the present invention, will be described using a tooth of a crusher as an example. Fig. Figure 22 is a schematic perspective view showing the structure of a crusher. Fig. 23 is a schematic perspective view showing the structure of an outer tooth of a fixed portion of the crusher. Fig. 24 is a schematic sectional view along the line XXIV-XXIV in Fig. 23. Fig. 25 is a schematic sectional view along the line XXV-XXV in Fig. 24.

[0071] A crusher 301 in the present embodiment as shown in Fig. 22 and is attached to a front end of an arm of a work machine, is used to crush concrete or other materials to be crushed. The crusher 301 includes a main frame 310, a fixed portion 320 attached to the main frame 310, and a movable portion 330 rotatably mounted on the main frame 310 so that it can be opened and closed with respect to the fixed portion 320. The movable portion 330 is connected to a hydraulic cylinder (not shown) arranged in the main frame 310. The movable portion 330, driven by the hydraulic cylinder, rotates and is thus opened and closed with respect to the fixed portion 320.

[0072] The fixed portion 320 has a front end to which a plurality (three in the present embodiment) external fixed portion teeth 321 are mounted in a spaced relationship. A breaker plate 322 is positioned on the fixed portion 320 at the portion facing the movable portion 330 when the movable portion 330 is closed with respect to the fixed portion 320. The breaker plate 322 has a plurality of through-holes formed therein, and recesses 323 are formed in the portions of the fixed portion 320 exposed through the respective through-holes. The movable portion 330 has a front end to which a plurality (two in the present embodiment) external movable portion teeth 331 are mounted in a spaced relationship.In the movable portion 330, a plurality of movable portion inner teeth 333 are arranged in the area facing the fixed portion 320 when the movable portion 330 is closed with respect to the fixed portion 320. When the movable portion 330 is closed with respect to the fixed portion 320, the two movable portion outer teeth 331 respectively enter the two spaces formed by the three fixed portion outer teeth 321. When the movable portion 330 is closed with respect to the fixed portion 320, the movable portion inner teeth 333 enter the corresponding recesses 323 in the fixed portion 320.In the crusher 301 thus constructed, concrete or other materials to be crushed are fed between the movable section 330 and the fixed section 320 in the state where the movable section 330 is open with respect to the fixed section 320, and then the movable section 330 is closed with respect to the fixed section 320, so that the materials are crushed. When the materials are crushed, the outer teeth 321 of the fixed section, the outer teeth 331 of the movable section, and the inner teeth 333 of the movable section directly contact the concrete or other materials to be crushed. The outer teeth 321 of the fixed section, the outer teeth 331 of the movable section, and the inner teeth 333 of the movable section, which are the teeth of the crusher, therefore need to have high wear resistance.To improve wear resistance, coatings can be formed on the crusher teeth, or the outer teeth 321 of the fixed section, the outer teeth 331 of the movable section, and the inner teeth 333 of the movable section. The structure of an outer tooth 321 of the fixed section is described below as an example of the crusher tooth.

[0073] An outer tooth 321 of the fixed portion has, as described with reference to Fig. 23, a front end surface 321A which is a flat surface on the front end side, a rear end surface 321D which is a flat surface on the rear end side, a first side surface 321B which is a flat surface connecting the front end surface 321A and the rear end surface 321D and to face the movable portion 330 side, a second side surface 321E which is a curved surface connecting the front end surface 321A and the rear end surface 321D and disposed opposite to the first side surface 321B, and two third side surfaces 321C, each of which is a flat surface connecting the front end surface 321A and the rear end surface 321D and also connecting the first side surface 321B and the second side surface 321E. The outer tooth 321 of the fixed portion is attached to the fixed portion 320 at the rear end surface 321D.

[0074] The outer tooth 321 of the fixed portion includes, as described with reference to Fig. 24 and Fig. 25, a carrier material 325 consisting of a first metal, and a coating 327 arranged in contact with the carrier material 325 and covering part of the surface of the carrier material 325. The coating 327 covers the entire extent of the front end surface 321A and a part of each of the first side surface 321B, the second side surface 321E, and the third side surfaces 321C. Larger parts of the surface of the first side surface 321B and the second side surface 321E are covered by the coating 327 than of the third side surfaces 321C.

[0075] No coating 327 is formed on the rear end surface 321D. For the first metal forming the substrate 325, for example, carbon steel for machine use or alloy steel for machine use specified according to the JIS standard (e.g., S45C or SCM435, as well as manganese steel (SMn), chromium steel (SCr), or chromium-molybdenum steel (SCM) containing an equivalent amount of carbon) can be used.

[0076] The coating 90 (coating 327) formed on the outer tooth 321 of the fixed portion contains, as described with reference to Fig. 6 and Fig. As can be seen in Figure 7, as with the drive wheel 5 and the bushings 13 in the first embodiment described above, a matrix 95 consisting of a second metal and hard particles dispersed in the matrix 95. The second metal forming the matrix 95 can, for example, be a mixture of a metal originating from a welding wire and the metal (first metal) forming the carrier material 100 (carrier material 325). Particles having a higher hardness than the matrix 95, such as particles made of cemented carbide, can be used as the hard particles 91. The coating 90 has greater wear resistance than the carrier material 100.

[0077] The surface 90A of the coating 90 as shown in Fig. 6 is a forged surface. The hard particles 91 located in a coating surface area 90B, which is an area within an average particle diameter of the hard particles 91 from the surface 90A of the coating 90, are embedded in the coating 90 while being arranged side by side. This prevents the hard particles 91 from significantly protruding from the surface 90A of the coating 90. This, in turn, prevents the hard particles 91 from falling out during use of the fixed-section outer tooth 321, thereby improving the wear resistance of the fixed-section outer tooth 321.

[0078] The hard particles 91 located in the surface area 90B of the coating can, as in Fig. 6, be arranged in contact with the surface 90A of the coating 90. This makes the area of ​​a hard particle 91 exposed at the surface 90A of the coating 90 small, thereby preventing the hard particle 91 from falling out.

[0079] Of the hard particles 91 located in the surface area 90B of the coating, as shown in Fig. As shown in Figure 6, each hard particle 91 having a portion exposed at the surface 90A of the coating 90 must have an acute central angle θ (less than 90°) corresponding to this exposed portion. This makes the area of ​​a hard particle 91 exposed at the surface 90A of the coating 90 small, thereby preventing the hard particle 91 from falling out.

[0080] In a region including an interface between the coating 90 and the carrier material 100, as described with reference to Fig. 7, the coating 90 has protrusions 99 that protrude toward the carrier material 100. The protrusions 99 provide an anchoring effect that prevents the coating 90 from detaching from the carrier material 100. A protrusion 99 receives at least a portion of a hard particle 91. This more reliably prevents the coating 90 from detaching from the carrier material 100. The matrix 95 of the coating 90 is located between the carrier material 100 and the hard particle 91 received in the protrusion 99. The hard particle 91 received in the protrusion 99 is not in contact with the carrier material 100. The center of the hard particle 91 is located outside the protrusion 99 (i.e., a portion of the hard particle 91, which has a volume of less than half of that of the hard particle 91, is received in the protrusion 99). A hard particle 91 is received in a protrusion 99.Each projection 99 has a depth that is smaller than the radius of the hard particle 91 received in the projection 99.

[0081] A method for manufacturing an outer tooth 321 of the fixed portion will be described below. Fig. 8 is a flowchart schematically illustrating a method for manufacturing an outer tooth of the fixed portion which is the machine component. Fig. 26 and Fig. 27 are perspective views illustrating a method of manufacturing an outer tooth of the fixed portion of a crusher. Fig. 28 and Fig. 29 are schematic sectional views illustrating the method of manufacturing the outer tooth of the fixed portion of the crusher. Fig. 28 is a schematic sectional view taken along the line XXVIII-XXVIII in Fig. 27. Fig. 29 is a schematic sectional view along the line XXIX-XXIX in Fig. 28. Fig. 30 and Fig. 31 are schematic perspective views illustrating another method of manufacturing the outer tooth of the fixed portion of the crusher. Fig. 32 and Fig. 33 are schematic sectional views illustrating the other method of manufacturing the outer tooth of the fixed portion of the crusher. Fig. 32 is a schematic sectional view taken along the line XXXII-XXXII in Fig. 31. Fig. 33 is a schematic sectional view taken along the line XXXIII-XXXIII in Fig. 32.

[0082] In the method of manufacturing an external tooth 321 of the fixed portion in the present embodiment, first, as described with reference to Fig. 8, a step for manufacturing a support element is carried out as a step S10. In this step S10, as described with reference to Fig. 26, a support member 350 is fabricated, which becomes a support material 325 of the outer tooth 321 of the fixed portion. The support member 350 is made of a first metal. The support member 350 has a cylindrical shape including a first end surface 350A, a second end surface 350D, and a side surface 350F.

[0083] Subsequently, a step of forming a coating is carried out as a step S20. In this step S20, as described with reference to Fig. 27 to 29, a coating layer 360 is formed to cover the first end surface 350A and a portion on the side of the first end surface 350A of the side surface 350F of the support member 350 manufactured in step S10. The coating layer 360 may be formed with a plurality of ridges 362 as in the first embodiment. The first end surface 350A is completely covered by the coating layer 360. No coating layer 360 is formed on the second end surface 350D. On the side surface 350F, a portion within a predetermined distance from the portion connected to the first end surface 350A in the axial direction is covered with the coating layer 360. Although the coating layer 360 on the side surface 350F has a substantially uniform length in the axial direction, it has a shorter length in paired portions that are symmetrical with respect to the central axis.Corresponding to these regions, protruding exposed regions 350G are formed on the side surface 350F, which are not covered with a coating and protrude toward the first end surface 350A. The coating 360 can be formed by deposition welding using CO2 arc welding, as in the first embodiment described above.

[0084] Subsequently, a hot forging step is carried out as a step S30. In this step S30, the support element 350 with the coating 360 formed in step S20 is hot forged. The support element 350 with the coating 360 formed thereon is, as described with reference to Fig. 27 to 29 and Fig. 24 and Fig. 25, it is heated to a temperature that enables hot forging, and then placed in a mold having a cavity corresponding to a desired shape of the outer tooth 321 of the fixed portion for forging. Hot forging processes the coating 360 formed in step S20. Through hot forging, the first end surface 350A and the second end surface 350D become regions corresponding to the front end surface 321A and the rear end surface 321D of the outer tooth 321 of the fixed portion, respectively.On the side surface 350F, the areas in the circumferential direction where the protruding exposed portions 350G have been formed become the third side surfaces 321C of the external tooth 321 of the fixed portion, and the areas outside the areas where the protruding exposed portions 350G have been formed become the first side surface 321B and the second side surface 321E of the external tooth 221 of the fixed portion.

[0085] When the support member 350 with the coating 360 formed thereon is hot forged, hard particles 91, which protruded from a surface of the coating 360 during the formation of the coating 360, are pressed into the coating 360. As a result, in the outer tooth 321 of the fixed portion, the hard particles 91 located in the surface area 90B of the coating are embedded in the coating 90 and arranged next to each other. The hard particles 91 located in the surface area 90B of the coating are arranged in contact with the surface 90A of the coating 90 (see Fig. 6). Of the hard particles 91 located in the coating surface area 90B, any hard particle 91 having a portion exposed on the surface 90A of the coating 90 has an acute central angle θ (less than 90°) corresponding to the exposed portion. This prevents the hard particle 91 from falling out during use of the outer tooth 321 of the fixed portion, thereby improving the wear resistance of the outer tooth 321 of the fixed portion.

[0086] When the support member 350 with the coating 360 formed thereon is hot forged, projections 99 are formed in the coating 90 at the outer tooth 321 of the fixed portion due to the hard particles 91 that were located near the interface between the coating 360 and the support member 350 at the time of formation of the coating 360. At least a portion of a corresponding hard particle 91 is received in a projection 99 (see Fig. 7).

[0087] Subsequently, as explained with reference to Fig. 8, a heat treatment step is performed as a step S40. In this step S40, the fixed portion outer tooth 321 manufactured by hot forging in step S30 is subjected to heat treatment. The heat treatment performed in step S40 is, for example, quenching and tempering. This imparts desired hardness and toughness to the base material 325 of the fixed portion outer tooth 321. Subsequently, the areas where no coating 360 has been formed are subjected to machining to improve dimensional accuracy, etc. The fixed portion outer tooth 321 in the present embodiment is thus completed.

[0088] It should be noted that in the steps described above, in order to facilitate hot forging after forming the coating 360, preforming may be carried out before forming the coating 360. That is, a support member 350 having a cylindrical shape is formed as described with reference to Fig. 26 and Fig. 30, in step S10, and then the side of the first end surface 350A is subjected to preforming. With this preforming, the first end surface 350A is formed into a rectangular shape, and first chamfered portions 350B and second chamfered portions 350C are formed, which are connected to the long sides and the short sides of the first end surface 350A, respectively.

[0089] Subsequently, in step S20, as described with reference to Fig. 31 to 33, a coating 360 is formed to cover the first end surface 350A, the first beveled portions 350B, and the second beveled portions 350C of the preformed support element 350. The first end surface 350A is completely covered with the coating 360. No coating 360 is formed on the second end surface 350. The coating 360, which extends in the axial direction, is in the areas that extend beyond the first beveled portions 350B (see Fig. 33), longer than in the areas extending over the second beveled sections 350C (see Fig. 32). Then, in step S30, hot forging is performed so that the first end surface 350A and the second end surface 350D become the regions corresponding to the front end surface 321A and the rear end surface 321D of the fixed portion outer tooth 321, respectively. The regions where the coating 360 is short in the axial direction become the third side surfaces 321C of the fixed portion outer tooth 321, and the regions where the coating 360 is long become the first side surface 321B and the second side surface 321E of the fixed portion outer tooth 321.

[0090] In each of the methods for manufacturing the machine components in the first to third embodiments described above, when forming the coating on the base member, a surface portion of the base member corresponding to the area of ​​the base member where the coating is to be formed may be removed in advance, or a stepped portion may be formed on the base member before forming the coating. This reduces the degree of deformation of the coating during forging, thereby preventing, for example, wrinkling of the forged coating. Examples

[0091] A tooth 220 was manufactured using a similar manufacturing process to the manufacturing method described in the second embodiment, and the resulting tooth was subjected to a test to examine the coating structure and the like (Example). For comparison purposes, a tooth was manufactured using a similar manufacturing process, but the coating forming step (step S20) was omitted, and a coating was formed by build-up welding after heat treatment. The resulting tooth was subjected to a similar test (Comparative Example). The dies used for hot forging had the same shape in the Example and the Comparative Example.

[0092] Fig. 34 is a photograph showing a cross section of the tooth 220 of the example. The edge portion 229 of the coating, the exposed area 225B and the surface 227A of the coating 227 are, as described with reference to Fig. 34, are flush with each other and form a forged surface. This confirms that the tooth 220 in the second embodiment can be manufactured using the manufacturing method in the second embodiment. No cracking is observed between the coating 227 and the substrate 225. No problems occur during hot forging performed after the coating is formed.

[0093] Fig. Figure 35 is an optical micrograph obtained by imaging a surface of the coating of the example and its surroundings. Fig. Figure 36 is an optical micrograph obtained by imaging a surface of the coating of the comparative example and its surroundings. In the coating of the comparative example, which was formed by deposition welding and subsequently not processed by forging, as shown in Fig. 36, hard particles 91 protrude significantly from the surface 90A of the coating. In the coating of the example, which was formed and then machined by forging, hard particles 91 located in the surface area, as shown with reference to Fig. 35, are embedded in the coating (matrix 95) and arranged side by side. The hard particles 91 are aligned in contact with the surface 90A of the coating. A hard particle 91 having a portion exposed at the surface 90A of the coating 90 has an acute central angle θ (less than 90°) corresponding to the exposed portion. This is presumably because, during the process of forging the coating, the hard particles 91 protruding from the surface 90A of the coating are pressed into the matrix 95, which has a relatively low hardness.

[0094] Fig. Figure 37 is an optical micrograph obtained by imaging an interface between the coating and the support material of the example and its surroundings. Fig. Figure 38 is an optical micrograph obtained by imaging an interface between the coating and the substrate of the comparative example and its surroundings. In the comparative example, in which the coating was formed by deposition welding and subsequently not processed by forging, as shown in Fig. 38, the interface between the coating (matrix 95) and the substrate 100 is flat. In the example that was processed by forging after the coating was formed, in the area that includes the interface between the coating (matrix 95) and the substrate 100, as described with reference to Fig.37, projections 99 are formed with the coating (matrix 95) that project toward the substrate 100. Each projection 99 accommodates a portion of a corresponding hard particle 91. It is assumed that the projections 99 were formed due to the presence of the hard particles 91 near the interface with the substrate while the coating was being forged. A hard particle 91 that contributed to the formation of a projection 99 has at least a portion accommodated in the projection 99. Description of reference symbols

[0095] 1: Crawler track traveling device; 2: Crawler track; 3: Crawler track frame; 4: Idler sprocket; 5: Drive wheel; 6: Crawler plate; 7: Outer link; 8: Inner link; 9: Crawler link; 10: Idler roller; 11: Support roller; 12: Connecting pin; 13: Bushing; 15: Through hole; 50: Backing material; 51: Projection; 52: Plating; 53: Outer peripheral surface; 59: Burr; 69: Backing member; 61A: Side surface; 61B: End surface; 62: Bead; 63: Plating; 64: Backing member; 64A: Outer peripheral surface; 64B: End surface; 70: Welding torch; 71: Welding nozzle; 72: Contact tip; 73: Welding wire; 74: Arc; 80: Nozzle for feeding hard particles; 90: Coating; 90A: Surface; 90B: Surface area of ​​the coating; 91: Hard particle; 92: Melt pool; 95: Matrix; 99: Projection; 100: Substrate; 131: Outer peripheral surface; 132: Coating; 133: Inner peripheral surface; 134: Substrate; 139: Smaller diameter portion; 201: Spoon; 210: Main body; 212: Periphery of the opening; 220: Tooth;221: front end; 222: rear end; 225: backing material; 225A: covered area; 225B: exposed area; 227: coating; 227A: surface; 229: edge portion of the coating; 230: attachment portion; 250: backing member; 251: side surface; 251A: covered area; 252: one end surface; 252A: first chamfered portion; 253: other end surface; 253A: second chamfered portion; 259: edge portion of the coating; 260: coating; 301: breaker; 310: main frame; 320: fixed portion; 321: outer tooth of the fixed portion; 321A: front end surface; 321B: first side surface; 321C: third side surface; 321D: rear end surface; 321E: second side surface; 322: breaker plate; 323: recess; 325: carrier material; 327: coating; 330: movable portion; 331: outer tooth of the movable portion; 333: inner tooth of the movable portion; 350: carrier member; 350A: first end surface; 350B: first chamfered portion;350C: second chamfered portion; 350D: second end surface; 350F: side surface; 350G: protruding exposed portion; 360: coating; and 362: bead;

Claims

[1] Machine component, used as a component (5, 13) of a crawler track undercarriage, as an excavator tooth (220) or as a tooth (321, 331, 333) of a crusher (300), comprising: a carrier material (100) consisting of a first metal; and a coating (90) arranged in contact with the carrier material (100) and covering at least part of a surface of the carrier material (100), the coating (90) containing: a matrix (95) consisting of a second metal; and hard particles (91) dispersed in the matrix (95), wherein: the coating (90) has a surface (90A) which is a forged surface; and the hard particles (91) located in a surface region (90B) of the coating (90) are embedded in the coating (90) and arranged next to one another, wherein the surface region (90B) of the coating (90) is a region extending from the surface (90A) of the coating (90) to a depth corresponding to an average particle diameter of the hard particles (91). [2] A machine component according to claim 1, wherein the hard particles (91) located in the surface region (90B) of the coating (90) are arranged in contact with the surface (90A) of the coating (90). [3] A machine component according to claim 1, wherein, of the hard particles (91) located in the surface region (90B) of the coating (90), any hard particle (91) having a region exposed at the surface (90A) of the coating (90) has an acute central angle (θ) corresponding to the region exposed at the surface (90A) of the coating (90). [4] Machine component according to one of claims 1 to 3, wherein in a region which includes an interface between the coating (90) and the carrier material (100), the coating (90) contains a projection (99) which projects towards the carrier material (100). [5] Machine component according to claim 4, wherein at least a part of a hard particle (91) is received in the projection (99). [6] Method for producing a machine component used as a component (5, 13) of a crawler track undercarriage, as an excavator tooth (220) or as a tooth (321, 331, 333) of a crusher (300), comprising the following steps: manufacturing a support element (64) consisting of a first metal; Forming a coating (63) covering at least part of a surface (64A) of the carrier element (64); and Forging the support element (64) on which the coating (63) is formed so that the coating (63) is machined, wherein: the step of forming the coating (63) includes forming the coating (63) which contains a matrix (95) consisting of a second metal and hard particles (91) dispersed in the matrix (95). [7] A method of manufacturing a machine component according to claim 6, wherein the step of forging the support member (64) on which the coating (63) is formed includes hot forging the support member (64) on which the coating (63) is formed.

Images