IT202300004266A1 - IMPROVED COMPONENT FOR AN UNDERCARRIAGE ASSEMBLY OF A TRACKED VEHICLE, UNDERCARRIAGE AND TRACK COMPRISING SAID IMPROVED COMPONENT AND METHOD FOR MANUFACTURING AN IMPROVED COMPONENT FOR AN UNDERCARRIAGE ASSEMBLY - Google Patents

Description

IMPROVED COMPONENT FOR AN UNDERCARRIAGE ASSEMBLY OF A TRACKED VEHICLE, UNDERCARRIAGE AND TRACK COMPRISING SAID IMPROVED COMPONENT AND METHOD FOR MANUFACTURING AN IMPROVED COMPONENT FOR AN UNDERCARRIAGE ASSEMBLY

Field of invention

[1] The present invention relates to an improved wear-resistant component of a tracked vehicle such as bulldozers, excavators, loaders, bulldozers, dumpers, road finishers, mobile drills, agricultural tractors, military tanks and a process for manufacturing said improved wear-resistant component.

State of the art

[2] A metal track of a tracked earthmoving machine usually comprises a plurality of bushings, each of which is axially crossed by a pin that transversely connects the two main track link bodies arranged substantially next to each other and hinges two successive main track links to each other, so as to form an articulated chain of a plurality of track links.

[3] During operation, the outer flanks of the bushings slide against the teeth of the undercarriage chain sprockets and are subjected to particularly severe wear.

[4] The inner side of the bushings is also subject to wear caused by friction against their respective pins.

[5] Intermittent contact and sliding between the bushings and the teeth worsens the wear damage of the bushings and also causes fatigue stresses, so these bushings must have sufficient toughness.

[6] These wear and fatigue stresses are among the most severe and bushings have one of the shortest operating lives in an undercarriage.

[7] To resist these stresses, the bushing material must be selected with particular care and, currently, subjected to particular heat and/or chemical treatments.

[8] For example, in a known manufacturing process, the bushing is extruded, carburized and finally quenched and tempered.

[9] An object of the present invention is to overcome the disadvantages described above and in particular to provide a bushing or other undercarriage component capable of withstanding the required wear and other mechanical stresses even if obtained through a simpler and/or more economical manufacturing process than those known.

Summary of the invention

[10] This object is achieved, according to a first aspect of the present invention, with an improved component for an undercarriage assembly of a tracked vehicle having the characteristics according to claim 1.

[11] HVOF treatments and more generally thermal spraying treatments allow to harden only the areas of the bushings of a track - or other improved undercarriage components - that are subject to wear, avoiding hardening other areas that are not affected or are affected to a negligible extent by wear.

[12] These coating processes can be performed at or near the end of the manufacturing process of the bushing or other improved component since they do not substantially alter the size, shape, and hardness of the coated substrate.

[13] More specifically, these coating processes may advantageously be performed after heat treatments and machining of the bushing, more generally and possibly at or near the end of the manufacturing process of the bushing 53 or other improved component.

[14] In this way, if some manufacturing steps are performed by external suppliers, the semi-manufactured components have to be handled fewer times, e.g. packed and unpacked when delivered to or from the external suppliers; furthermore, the main manufacturer's production line has to be retooled fewer times, if at all.

[15] In an improved component according to a particular embodiment of the invention, said thermal spray deposition process is one or more of the following processes: a High Velocity Oxygen Fuel (i.e., High Velocity Oxygen Fuel) process, Plasma spraying (i.e., Plasma spraying), Detonation spraying (i.e., Detonation spraying), Wire arc spraying (i.e., Wire arc spraying), Flame spraying (i.e., High velocity air fuel (HVAF)), Warm spraying (i.e., Cold spraying), Spray and Fuse (i.e., High velocity air fuel (HVAF)), Cold spraying (i.e., Cold spraying), Spray and Fuse (i.e., High velocity air fuel (HVAF)), Plasma spraying (i.e., Detonation spraying), Wire arc spraying (i.e., Wire arc spraying), Flame spraying (i.e., Detonation spraying), Wire arc spraying (i.e., Wire arc spraying), Flame spraying (i.e., Wire arc spraying), High velocity air fuel (HVAF)), Hot spraying (i.e., Cold spraying), Spray and Fuse (i.e., High velocity air fuel (HVAF)), Hot spraying (i.e., Cold spraying), Spray and Fuse (i.e., High velocity air fuel (HVAF)), Hot spraying (i.e., Hot spraying), ...

[16] In an improved component according to a particular embodiment of the invention, said hard coating comprises one or more of the following materials: tungsten carbide, molybdenum boride, vanadium carbide, martensitic steel, nickel steel, cobalt or cobalt alloys, chromium carbide.

[17] In an improved component according to a particular embodiment of the invention, said hard coating has one or more of the following substance contents:

- a tungsten carbide content between 50 and 100% by weight;

- a content of cobalt, cobalt alloys, nickel steel between 0 and 30% by weight;

- a molybdenum boride or chromium carbide content of between 0 and 40% by weight;

- a martensitic steel content between 40 and 99% by weight;

- a molybdenum boride or chromium carbide content of between 0 and 40% by weight;

- a vanadium carbide content between 0 and 40% by weight.

[18] In an improved component according to a particular embodiment of the invention, said hard coating has one or more of the following substance contents:

- a tungsten carbide content of between 80 and 90% by weight;

- a cobalt, cobalt alloys, nickel steel or martensitic steel content of between 10 and 14% by weight;

- a molybdenum boride or chromium carbide content of between 5 and 15% by weight;

- a martensitic steel content between 50 and 90% by weight;

- a vanadium carbide content between 5 and 30% by weight.

[19] Due to the above composition, the hard coating has great hardness and wear resistance and can for example reduce the wear of the base material by about 70%.

[20] In an improved component according to a particular embodiment of the invention, said hard coating has a hardness between 50 and 100 HRC.

[21] The above hardness values allow for example a metal bushing connecting several track links of a track to effectively resist wear due to engagement with a chain sprocket of an undercarriage assembly of a tracked vehicle or more generally of a tracked vehicle, while reducing the manufacturing costs of the bushing itself.

[22] In an improved component according to a particular embodiment of the invention, said hard coating has a hardness between 60 and 80 HRC.

[23] These hardness values are an even more optimal balance between wear resistance and reduction of manufacturing costs.

[24] In an improved component according to a particular embodiment of the invention, said hard coating has an average thickness of between 0.1 and 1 millimeter.

[25] This thickness selection is particularly effective both in enhancing wear resistance and in keeping manufacturing costs low.

[26] An improved component according to a particular embodiment of the invention comprises a base piece coated with the hard coating, the base piece comprising a base material selected from the following group:

- a steel that has not previously been carburized or case-hardened;

- a steel having a carbon content of 0.5% by weight or less, or 0.45% by weight or less, or 0.30% by weight or less; - a steel having a carbon content of 0.1% to 0.5% by weight;

- a steel having a carbon content between 0.4 and 0.45% by weight.

[27] Avoiding carburizing or case hardening steps reduces the time and cost to manufacture a track bushing or other improved undercarriage component.

[28] An improved component according to a particular embodiment of the invention is a bushing (53).

[29] In an improved component according to a particular embodiment of the invention, said base piece has a substantially tubular shape.

[30] In an improved component according to a particular embodiment of the invention, the base piece has been formed at least by extrusion.

[31] In a second aspect of the invention, the above-mentioned object is achieved through an undercarriage assembly having the features according to claim 12.

[32] In a third aspect of the invention, the above-mentioned object is achieved through a track having the characteristics according to claim 13.

[33] In a belt according to a particular embodiment of the invention:

- the track (5) comprises a plurality of track links, a plurality of hinge pins 52 and a plurality of pin bushings (53);

- each track link comprises a respective hinge pin (52) and a respective hinge bushing (53), ? fixed and articulated to a subsequent track link by means of the respective hinge pin (52);

- each hinge pin (52) passes axially through a respective pin bushing (53);

- each pin bushing (53) forms flanks;

- the undercarriage frame assembly (3) comprises at least one chain sprocket (32, 34) configured to engage the hinge pins (52) by resting and/or sliding against the sides of the pivot bushings (53); - at least some of the pivot bushings (53), and possibly all, have the features according to claim 10.

[34] In a fourth aspect of the invention, the above-mentioned object is achieved through a process for producing an improved component for an undercarriage assembly having the characteristics according to claim 15.

[35] Avoiding carburizing or case hardening of an entire pin bushing of a track or other improved undercarriage component simplifies and reduces the cost of manufacturing; this advantage is particularly noteworthy since carburizing and case hardening are thermochemical processes, that is, special manufacturing processes that require special and expensive systems and equipment.

[36] In conclusion, avoiding carburizing or cementing significantly reduces manufacturing costs while improving - or at least without worsening - the performance of the improved undercarriage components.

[37] The dependent claims are directed to further features of the invention.

[38] The advantages that can be obtained with the present invention will become more evident to the expert reader, from the following detailed description of a particular and non-limiting embodiment, described with reference to the following schematic figures.

List of figures

Figure 1 shows a perspective view of an undercarriage assembly according to a particular embodiment of the present invention;

Figure 2 shows a perspective view of a section of the track of the undercarriage assembly of Figure 1; Figure 3 shows a sectional view, along the section plane passing through the pin axes, of a section of the track of Figure 2;

Figure 4 shows a perspective view of a track pin bushing from Figure 2;

Figure 5 shows a sectional view, along the section plane passing through the pin axis, of a section of the pin bushing of Figure 4;

Figure 5A shows an enlarged detail of Figure 5;

Figure 6 shows a perspective view of a portion of a chain sprocket of the undercarriage assembly of Figure 1.

Detailed description

[39] Figures 1-6 relate to an undercarriage assembly according to a particular embodiment of the invention, indicated by the overall reference 1.

[40] The undercarriage assembly 1 may be part of a tracked vehicle such as bulldozers, excavators, loaders, bulldozers, tippers, road finishers, mobile drills, agricultural tractors, military tanks.

[41] The undercarriage assembly 1 includes an undercarriage frame assembly 3 upon which a track 5 can be assembled so that it is capable of movement relative to the undercarriage frame assembly 3.

[42] The track 5 may comprise a plurality of track links, each of which comprises for example a main track link body 50 and a sole 51 fixed to the latter, and the track links may be articulated together so as to form a chain, preferably a self-contained continuous chain (Figure 1, 2); in this case, the track is preferably and mostly made of steel or another metallic material.

[43] Preferably, the track 5 comprises a plurality of pin assemblies that connect a first track link to a second and subsequent track link; for example, each pin assembly may connect and hinge a first and second main track link body 50 that are part of the first and second and subsequent track link, respectively (Figure 2).

[44] Each pin assembly may include a hinge pin 52 and a pin bushing 53.

[45] The track links may be assembled and hinged together for example by press-fitting the two opposite ends of each hinge pin 52 into two pin holes made in the ends of the main link bodies 50 of an adjacent track link, so as to prevent the hinge pin 52 from rotating relative to the main link bodies 50 of the adjacent track link; in this way, each hinge pin 52 transversely connects the main link bodies 50 of one track link.

[46] Each end of the pin bushing 53 is preferably press fit into a bushing hole of two ends of two respective track links.

[47] Since the hinge pin 52 extends axially through and beyond its respective pivot bushing 53 and is capable of rotation relative to bushing 53, each pin assembly connects and articulates two adjacent track links.

[48] The wall of the pin bushing 53 can have a maximum radial thickness WBS of for example between 5 and 50 millimetres and a minimum radial thickness of for example between 5 and 20 millimetres (Figure 5).

[49] Advantageously, the pin bushing 53 may have an enlarged center section 530 and two mating bushing ends 532 having a smaller mean or maximum diameter than the center section.

[50] The enlarged center section 530 is designed to engage the drive pinion 32 which drives the track 5 and causes the tracked vehicle to move forward and to resist wear caused by the drive pinion during operation.

[51] Each end of coupling bushing 532 is preferably separated from the center section by a shoulder 534.

[52] The ratio LTN/LB between the length LTN of the enlarged central section 530 and the overall length LB of the bushing 530 is preferably between 0.2 and 0.8, more preferably between 0.3 and 0.6 or 0.4 and 0.45.

[53] The ratio DB1/LB between the outside diameter DB1 of the enlarged center section 530 and the overall length LB of the bushing 530 is preferably between 0.2 and 0.8, more preferably between 0.3 and 0.6, 0.4 and 0.5 or 0.45 and 0.5.

[54] The undercarriage frame assembly 3 may comprise, for example, one or more of the following elements:

- a 30 frame;

- wheels such as one or more chain sprockets 32 and one or more idler wheels 34; at least one chain sprocket is preferably a drive wheel 32 or idler wheels 34, such as the idler wheel 34 in Figure 1;

- pulleys, roller assemblies 38, 40 resting against the track 5 and/or above - such as the roller assembly 40 - or under which - such as the roller assemblies 38 - said track 5 rolls and/or moves;

- motors or other actuators, gearboxes or couplings that drive the track 5, power supply lines such as electrical or hydraulic lines that power said motors or other actuators.

[55] The frame 30 may comprise for example welded metal plates, shells and/or beams, each of which has a more or less complex shape.

[56] Preferably, the undercarriage assembly 1 comprises one or more support roller assemblies 38, 40 configured to bear against the track 5 and/or roll over or under the track 5.

[57] In the embodiment of Figure 1, the support roller assemblies 38 roll above the track 5 and the support roller assemblies 40 roll below the track 5.

[58] The roller assemblies 38, 40 are preferably arranged between a chain sprocket 32 and one or more idler wheels 34 - the latter being also referred to as idler gears 34.

[59] Preferably, the roller bodies 44 of the roller assemblies 38, 40 have a smaller outside diameter than the chain sprocket 32 and the idler sprocket or idler sprockets 34.

[60] Preferably, the chain sprockets 32, 34 change the direction of the track 5 substantially more than each roller assembly 38, 40 does.

[61] The undercarriage assembly 1 further comprises a first friction surface 7 and a second friction surface 9 configured to slide against each other (Figure 4, 5).

[62] The first 7 and second friction surfaces 9 are formed by the undercarriage frame assembly 3 and/or the track 5.

[63] For example, the first 7 and the second friction surface 9 may both be formed by the undercarriage frame assembly 3, both by the track 5, or one of them - the first 7 or the second friction surface 9 - by the undercarriage frame assembly 3 and the other of them - respectively the second 9 or the first friction surface 7 - by the track 5.

[64] In accordance with one aspect of the present invention, the undercarriage comprises an improved component 52 which may be included in the undercarriage frame assembly 3 or in the track 5 and forms at least the first friction surface 7.

[65] The first friction surface 7 is made of a hard coating 5301 obtained through a high-speed oxy-fuel process or more generally through a thermal spray deposition process.

[66] These coating processes can be performed at or near the end of the manufacturing process of the bushing or other improved component since they do not substantially alter the size, shape, and hardness of the coated substrate.

[67] More specifically, these coating processes may advantageously be performed after heat treatments and machining of the bushing, more generally and possibly at or near the end of the manufacturing process of the bushing 53 or other improved component.

[68] In this way, if some manufacturing steps are performed by external suppliers, the semi-manufactured components have to be handled fewer times, e.g. packaged and unpacked when delivered to or from the external suppliers; furthermore, the main manufacturer's production line has to be retooled fewer times, if at all.

[69] The chain sprockets 32, 34 preferably form a respective crown of teeth (Figure 5); during operation, said teeth preferably engage the flanks of the pin bushing 53, for example a substantially central section 530 of the flanks.

[70] Said first friction surface 7 may be for example called the central section 530 of the sides of the pin bushing 53, or more generally the whole or a part of the sides of the pin bushing 53.

[71] Said second friction surface 9 may comprise for example one or more of the following entities: the flanks of the teeth of the chain sprockets 32, 34, the entire or a part of the surface of the recesses present between two adjacent teeth of the chain sprockets 32, 34 and which periodically receive the flanks 530 of the bushings 53 during operation (Figure 5).

[72] Preferably, said hard coating comprises one or more of the following materials: tungsten carbide, molybdenum boride, vanadium carbide, martensitic steel, nickel steel, cobalt or cobalt alloys, chromium carbide.

[73] Preferably, the hard coating has one or more of the following substance contents:

- a tungsten carbide content of 50 to 100% by weight, or 60 to 90% by weight, 70 to 90% by weight, 80 to 90% by weight or 85 to 90% by weight and for example about 88% by weight;

- a cobalt, cobalt alloys or nickel steel content of 0 to 30% by weight, or 5 to 20% by weight, 7 to 15% by weight, 10 to 30% by weight or 10 to 14% by weight and for example equal to 12% by weight;

- a martensitic steel content of between 40 and 99% by weight or between 50 and 95% by weight or 50 and 90% by weight;

- a molybdenum boride or chromium carbide content of 0 to 40% by weight, or 10 to 40% by weight, 5 to 20% by weight, or 5 to 15% by weight; - a vanadium carbide content of 0 to 40% by weight, or 5 to 30% by weight.

[74] Preferably, said hard coating comprises a matrix and one or more enrichment substances.

[75] Preferably, the enrichment substances form between 0 and 30 wt.%, or between 5 and 20 wt.% or 5 and 15 wt.% of the hard coating.

[76] Preferably, the matrix forms the remaining weight content of the hard coating 5301.

[77] The matrix preferably comprises tungsten carbide and/or cobalt or cobalt alloys and/or nickel steel.

[78] Preferably, the enrichment substances comprise one or more of the following substances: martensitic steel, cobalt, e.g. substantially 99% pure cobalt, 90% pure cobalt or other cobalt alloys having a significant amount of cobalt, e.g. at least 50% cobalt, at least 60% cobalt, at least 70% cobalt or at least 80% cobalt, chromium carbide, molybdenum carbide, vanadium carbide.

[79] Preferably, at least one of the enrichment substances comprises one or more of the following substances: tungsten carbide, molybdenum boride, vanadium carbide.

[80] Preferably, said hard coating has a hardness between 50 and 100 HRC, 55 and 90 HRC or 60 and 80 HRC.

[81] Preferably, said hard coating has an average thickness of between 0.2 and 4 millimeters, between 0.5 and 0.4 millimeters, or 0.5 and 3.5 millimeters, 0.5 and 2.5 millimeters, 0.5 and 2 millimeters or 0.2-1 millimeter.

[82] Due to the above composition, the hard coating has great hardness and wear resistance and can for example reduce the wear of the base material by about 70%.

[83] The previous measurements allow to obtain a pin bushing 53 for example through the following procedure:

- a semi-finished bushing is extruded from a metal bar;

- the entire semi-fabricated bushing is induction hardened, by cooling the bushing e.g. from the outer diameter and causing a martensitic transformation e.g. over its entire thickness, preferably at least on its outer and inner surfaces;

- the bushing is induction hardened and cooled from the internal diameter, tempering the previously quenched portion;

- the bushing is then stress relieved, can then be machined and its outer flanks can be coated using the high velocity oxy-fuel process mentioned above or more generally using a thermal spray deposition process.

[84] Preferably, said improved component comprises a base piece 5300 coated by the hard coating 5301 and comprising - possibly consisting of or made mostly of - a base material selected from the following group (Figure 5A):

- a steel or other metal that has not previously been carburized or case hardened, for example because it has never been carburized after the semi-finished product or another semi-fabricated axlebox was produced;

- a steel having a carbon content of 0.5% by weight or less, or 0.45% by weight or less, or 0.30% by weight or less.

[85] The base piece 5300 comprises or is made of a steel having a carbon content preferably equal to or greater than 0.2% by weight, more preferably equal to or greater than 0.25% by weight or 0.3% by weight.

[86] Preferably, the steel forming or otherwise contained in the base piece 5300 has a carbon content of between 0.1 and 0.5% by weight and more preferably between 0.4 and 0.45% by weight.

[87] The base piece 5300 may for example be or comprise said semi-finished product or semi-fabricated bushing or a part thereof.

[88] The base piece 5300 may for example form a larger part of the finished bushing 53, and for example form at least half the weight of the finished bushing, or at least 0.7 times, at least 0.8 times, at least 0.9 times or at least 0.75 times the weight of the finished bushing.

[89] Where the improved component is a pin bushing 53, its base piece is preferably a substantially tubular blank or other substantially tubular body.

[90] Avoiding carburizing or case hardening steps reduces the time and cost to manufacture bushings 53 or other improved undercarriage component.

[91] More generally, a further aspect of the present invention relates to a method for producing bushing 53 or other improved component for a tracked vehicle undercarriage assembly, comprising the following steps:

- provide a semi-finished base piece, for example by extrusion, and made of or otherwise comprising steel which has not previously been carburized or case hardened;

- coating at least a part of the semi-finished base piece through a high-speed oxy-fuel process or more generally through a thermal spray deposition process so as to create the hard coating forming the first friction surface 7;

wherein said process for producing the improved component does not include the step of carburizing or cementing the semi-finished base piece or the finished base piece.

[92] Avoiding carburizing or case hardening of the entire pin bushing 53 or other improved component 53 simplifies and makes the manufacturing process less expensive; this advantage is particularly noteworthy since carburizing and case hardening are thermochemical processes, i.e. special manufacturing processes that require special and expensive systems and equipment.

[93] HVOF treatments and more generally thermal spraying allow to harden only the areas of the bushing 53 - or other improved components - that are subject to wear, avoiding hardening other areas that are not affected or are affected to a negligible extent by wear.

[94] In conclusion, avoiding carburizing or cementation significantly reduces manufacturing costs while improving - or at least without worsening - the performance of the improved components.

[95] The embodiments described above may be modified in various ways without departing from the scope of the present invention.

[96] For example, an improved component according to the present invention may be not only a pin bushing 53, but for example also a component of the roller assemblies 38, 40, the sole teeth 510 or the track link track.

[97] An improved component according to the present invention may be coated or more generally obtained not only through a high velocity oxy-fuel process, but for example through plasma spraying (i.e. Plasma spraying), detonation spraying (i.e. Detonation spraying), wire arc spraying (i.e. Detonation spraying), flame spraying (i.e. Detonation spraying), high velocity air fuel (HVAF), warm spraying, cold spraying, spray and fuse (i.e. Detonation spraying).

[98] Any reference in this specification to "An embodiment", "an embodiment", "exemplary embodiment", etc. indicates that a particular feature, structure or peculiarity described in connection with the embodiment is included in at least one embodiment of the invention.

[99] Occurrences of such expressions at various points in the specification do not necessarily all refer to the same embodiment.

[100] Further, where a particular feature, structure or particularity is described in connection with any embodiment, it is understood that it is within the skill of one skilled in the art to implement such feature, structure or particularity in connection with other of the embodiments.

[101] All construction details can be replaced with technically equivalent elements.

[102] A statement such as "A comprises B, C, D" or "A is made of B, C, D" should be understood as including and disclosing the particular case of "A is made up of B, C, D".

[103] Wordings such as "A includes an element B", unless otherwise specified, should be understood as "A includes one or more elements B".

[104] Mentions of a "first, second, third? nth entity?" are simply meant to distinguish entities from one another, but the mention of an nth entity does not necessarily imply the existence of a first, second, third.

? (n-1)-th entity?.

[105] Examples and lists of possible alternatives are not intended to be exhaustive.

Claims (15)

1) Improved component (53) of an undercarriage assembly (1) of a tracked vehicle, wherein: - the undercarriage assembly (1) comprises an undercarriage frame assembly (3) onto which a track (5) can be assembled so that it is capable of moving relative to the undercarriage frame assembly (3); - the undercarriage assembly (1) further comprises a first friction surface (7, 540) and a second friction surface (9, 560) configured to slide against each other; - the first (7) and second friction surfaces (9) are formed by the undercarriage frame assembly (3) and/or the track (5); - the improved component (53) is included in the undercarriage frame assembly (3) or in the track (5) and forms at least the first friction surface (7); - the first friction surface (7) is made of a hard coating obtained through a thermal spray deposition process. 2) Improved component according to claim 1, wherein said thermal spray deposition process is one or more of the following processes: a high velocity oxy-fuel process, i.e. High Velocity Oxygen Fuel, plasma spraying, i.e. Detonation spraying, i.e. Wire arc spraying, i.e. Flame spraying, i.e. High velocity air fuel, HVAF, i.e. Warm spraying, i.e. Cold spraying, i.e. Spray and Fuse. 3) Improved component according to claim 1 or 2, wherein said hard coating comprises one or more of the following materials: tungsten carbide, molybdenum boride, vanadium carbide, martensitic steel, nickel steel, cobalt or cobalt alloys, chromium carbide. 4) Improved component according to one or more preceding claims, wherein said hard coating has one or more of the following substance contents: - a tungsten carbide content of between 50 and 100% by weight; - a content of cobalt, cobalt alloys, nickel steel between 0 and 30% by weight; - a molybdenum boride or chromium carbide content of between 0 and 40% by weight; - a martensitic steel content between 40 and 99% by weight; - a vanadium carbide content between 0 and 40% by weight. 5) Improved component according to one or more preceding claims, wherein said hard coating has one or more of the following substance contents: - a tungsten carbide content of between 80 and 90% by weight; - a cobalt, cobalt alloys, nickel steel or martensitic steel content of between 10 and 14% by weight; - a molybdenum boride or chromium carbide content of between 5 and 15% by weight; - a martensitic steel content between 50 and 90% by weight; - a vanadium carbide content between 5 and 30% by weight. 6) Improved component according to one or more preceding claims, wherein said hard coating has a hardness between 50 and 100 HRC. 7) Improved component according to claim 6, wherein said hard coating has a hardness between 60 and 80 HRC. 8) Improved component according to one or more preceding claims, wherein said hard coating has an average thickness between 0.1 and 1 millimetre. 9) Improved component (53) according to one or more preceding claims, comprising a base piece coated by the hard coating, the base piece comprising a base material selected from the following group: - a steel that has not previously been carburized or case-hardened; - a steel having a carbon content of 0.5% by weight or less, or 0.45% by weight or less, or 0.30% by weight or less; - a steel having a carbon content of 0.1% to 0.5% by weight; - a steel having a carbon content between 0.4 and 0.45% by weight. 10) Improved component according to one or more preceding claims, said improved component being a bushing (53). 11) Improved component according to claim 9 or 10, wherein said base piece has a substantially tubular shape. 12) Undercarriage assembly (1) comprising an improved component (53) according to one or more of the preceding claims. 13) Track (5) comprising an improved component (53) according to one or more of the preceding claims. 14) Track (5) according to claim 13, wherein: - the track (5) comprises a plurality of track links, a plurality of hinge pins 52 and a plurality of pin bushings (53); - each track link comprises a respective hinge pin (52) and a respective hinge bushing (53), ? fixed and articulated to a subsequent track link by means of the respective hinge pin (52); - each hinge pin (52) passes axially through a respective pin bushing (53); - each pin bushing (53) forms flanks; - the undercarriage frame assembly (3) comprises at least one chain sprocket (32, 34) configured to engage the hinge pins (52) by resting and/or sliding against the sides of the pivot bushings (53); - at least some of the pivot bushings (53), and possibly all, have the features according to claim 10. 15) Method for producing an improved component (53) for an undercarriage assembly (1) of a tracked vehicle according to one or more claims 1-11, comprising the following steps: - provide a semi-finished base piece made of or otherwise comprising steel which has not previously been carburized or case hardened; - coating at least a part of the semi-finished base piece through a thermal spray deposition process so as to produce a hard coating forming a first friction surface (7); - wherein said process for producing the improved component (53) does not include the step of carburizing or cementing the semi-finished base piece or the finished base piece.