Track pin bushing having a metallurgically bonded coating

A track pin bushing for cooperating with a track pin in an endless track, the track pin bushing comprising:

• a tubular body formed of an iron-based alloy with a first end and a second end, an outer surface that is case-hardened in at least a section thereof, and an inner surface having an inner diameter, wherein the inner diameter defines the circumference of an axial bore extending from the first end to the second end and at least a portion of the outer surface has been removed to a depth sufficient to expose a non-carburized layer of the iron-based alloy;
• and
• a wear-resistant coating metallurgically bonded to said non-carburized layer, the wear-resistant coating comprising a fused, hard metal alloy comprising at least 60% iron, cobalt, nickel, or alloys thereof,
• wherein said portion of the outer surface that has been removed corresponds to a contact surface adapted to engage with a drive sprocket in the endless track of a track-type machine.

A track pin bushing for cooperating with a track pin in an endless track, the track pin bushing comprising:

• a tubular body formed of an iron-based alloy with a first end and a second end, an outer surface that is case-hardened in at least a section thereof, and an inner surface having an inner diameter, wherein the inner diameter defines the circumference of an axial bore extending from the first end to the second end and at least a portion of the outer surface has been removed to a depth sufficient to expose a non-carburized layer of the iron-based alloy;
• and
• a wear-resistant coating metallurgically bonded to said non-carburized layer, the wear-resistant coating comprising a fused, hard metal alloy comprising at least 60% iron, cobalt, nickel, or alloys thereof,
• wherein a Vickers hardness of the wear-resistant coating is greater than 950 HV.

A track pin bushing for cooperating with a track pin in an endless track, the track pin bushing comprising:

• a first end and a second end;
• an inner surface having an inner diameter, wherein the inner diameter defines the circumference of an axial bore extending from the first end to the second end;
• an outer surface having a varying diameter;
• and
• a wear-resistant coating disposed on a first portion of the outer surface and metallurgically bonded to the track pin bushing, the wear-resistant coating comprising a fused, hard metal alloy comprising at least 60% iron, cobalt, nickel, or alloys thereof,
• wherein the wear resistant coating has a thickness of approximately 1.5 mm,
• wherein the varying diameter of the outer surface includes a first outer diameter at a first end section and a second end section and a second outer diameter at a middle section therebetween, wherein the second outer diameter is greater than the first outer diameter,
• wherein the outer surface includes an annular groove located in at least a portion of said middle section and extending over a majority of an axial length of said middle section and wherein the wear resistant coating is disposed in said annular groove, and
• wherein the track pin bushing is an iron-based alloy and at least the middle section in which the annular groove is not located is carburized and quenched and the annular groove has a depth sufficient to expose a non-carburized layer of the iron-based alloy.

A method for hardfacing with a wear-resistant coating a metal surface of a carburized metal part, the method comprising the steps of:

• removing the carburized metal from at least a portion of the metal surface to a depth sufficient to expose a non-carburized layer of the metal, the portion defining an area to be coated;
• coating the area with a slurry comprising a fusible, hard metal alloy with at least 60% iron, cobalt, nickel, or alloys thereof in the form of a finely divided powder and polyvinyl alcohol;
• and
• forming a metallurgical bond between the area and the coated slurry to form the wear-resistant coating.

A method for hardfacing a metal surface of a track pin bushing with a wear-resistant coating, the track pin bushing comprising an outer surface having an outer diameter, an inner surface having an inner diameter, a first end and a second end, wherein the inner diameter defines the circumference of an axial bore extending from the first end to the second end and cooperating with a track pin in an endless track, the method comprising the steps of:

• carburizing at least a portion of the track pin bushing to produce a surface having a carburized depth;
• preparing at least a portion of the carburized surface of the track pin bushing in an area to be coated by removing the carburized metal to a depth sufficient to expose a decarburized layer;
• coating the exposed decarburized layer of the track pin bushing with a slurry comprising a fusible, hard metal alloy with at least 60% iron, cobalt, nickel, or alloys thereof in the form of a finely divided powder and polyvinyl alcohol;
• forming the wear-resistant coating by metallurgically bonding the exposed decarburized layer and the slurry;
• and
• case hardening a non-prepared and carburized surface of the track pin bushing by quenching.

A method for hardfacing a metal surface of a track pin bushing with a wear-resistant coating, the method comprising:

• forming the track pin bushing having a first end and a second end, an inner surface having an inner diameter, wherein the inner diameter defines the circumference of an axial bore extending from the first end to the second end, an outer surface having a first outer diameter at a first end section and a second end section and a second outer diameter at a middle section therebetween, the second outer diameter being greater than the first outer diameter;
• carburizing the track pin bushing to produce a carburized outer surface, inner surface and first and second end sections, each with a carburization depth;
• removing carburized steel from at least a portion of said middle section to reduce the second diameter by at least the carburization depth,
• coating said middle portion in the area of the reduced diameter with a slurry comprising a fusible, hard metal alloy with at least 60% iron, cobalt, nickel, or alloys thereof in the form of a finely divided powder and polyvinyl alcohol;
• adjusting a thickness of the slurry to have an outer surface that is concentric with the axial bore, wherein the thickness of the concentric outer surface is from 1.67 to 2.0 times a final thickness of the wear-resistant coating;
• forming the wear-resistant coating by metallurgically bonding said portion of said middle portion and the slurry;
• and
• case hardening at least the inner diameter and first and second ends.

A track pin bushing for cooperating with a track pin in an endless track, the track pin bushing comprising:

• a tubular body formed of an iron-based alloy with a first end and a second end, an outer surface that is case-hardened in at least a section thereof, and an inner surface having an inner diameter, wherein the inner diameter defines the circumference of an axial bore extending from the first end to the second end and at least a portion of the outer surface has been removed to a depth sufficient to expose a non-carburized layer of the iron-based alloy;
• and
• a wear-resistant coating metallurgically bonded to said non-carburized layer, the wear-resistant coating comprising a fused, hard metal alloy comprising at least 60% iron, cobalt, nickel, or alloys thereof,
• wherein said portion of the outer surface that has been removed is on a circumferential surface of the outer surface.