Coating to reduce coking deposits on steel pistons
A piston for an internal combustion engine is provided. The piston includes a coating applied to a ferrous body portion to reduce or prevent chemical bonding of carbon deposits or coking on the body portion at temperatures ranging from 200 to 400° C. The coating includes a fluoropolymer, such as polytetrafluoroethylene, fluorosilane, fluorocarbon, fluoroplastic resin, and/or perfluoroplastic, and may be hydrocarbon or silicone based. The coating also has a thickness of 25 microns to 1 millimeter. The coating can be disposed on an undercrown surface, ring grooves, ring lands, pin bosses, and/or skirt sections of the body portion.
1. A piston, comprising:
a body portion formed of a ferrous material,
said body portion including a crown presenting a combustion surface and undercrown surface,
a coating disposed on said undercrown surface of said body portion,
said coating including a fluoropolymer,
said coating including at least one of polysilane and polysilazane, and said coating having a thickness of 25 microns to 1 millimeter.
2. The piston of claim 1 , wherein said coating further includes at least one of thermoset resin and silicone.
3. The piston of claim 1 , wherein said fluoropolymer of said coating includes polytetrafluoroethylene, fluorosilane, fluorocarbon, fluoroplastic resin, and/or perfluoroplastic.
4. The piston of claim 1 , wherein said coating reduces chemical bonding of carbon deposits or coking on said body portion at temperatures ranging from 200 to 400° C.
5. The piston of claim 1 , wherein said body portion includes a ring belt region depending from said combustion surface, said body portion includes a pair of pin bosses depending from said crown and spaced from one another by a pair of skirt sections, said coating is disposed on at least one of the following: at least one ring groove of said ring belt region, at least one land of said ring belt region, at least one of said pin bosses, and at least one of said skirt sections.
6. The piston of claim 1 , wherein said body portion includes a cooling gallery extending circumferentially around a center axis between said crown and a lower section of said body portion.
7. The piston of claim 6 , wherein said body portion includes a ring belt region depending from said combustion surface, said body portion includes a pair of pin bosses depending from said crown and spaced from one another by a pair of skirt sections,
said lower section of said body portion includes at least a portion of said ring belt region, said pin bosses, and said skirt sections,
said crown includes an upper rib spaced from said center axis and extending circumferentially around said center axis,
said lower section of said body portion includes a lower rib aligned with said upper rib and extending circumferentially around said center axis,
said upper rib is welded to said lower rib,
said lower section of said body portion includes a lower wall extending radially from said lower rib to said ring belt region, and
said cooling gallery is defined by said ring belt region, said ribs, said undercrown surface, and said lower surface.
8. The piston of claim 1 , wherein said undercrown surface is openly exposed and not bounded by a sealed or enclosed cooling gallery.
9. The piston of claim 8 , wherein said undercrown surface includes a center region disposed at said center axis and between said pin bosses and said skirt sections, and said undercrown surface includes pockets disposed between said pin bosses and said ring belt region.
10. The piston of claim 8 , wherein said undercrown surface is located opposite said combustion surface and radially inwardly of said ring grooves,
said undercrown surface is openly exposed and not bounded by a sealed or enclosed cooling gallery,
said undercrown surface includes a center region disposed at said center axis and between said pin bosses and said skirt sections, and
said undercrown surface includes pockets disposed between said pin bosses and said ring belt region.
11. The piston of claim 1 , wherein said body portion includes a ring belt region depending from said combustion surface, said body portion includes a pair of pin bosses depending from said crown and spaced from one another by a pair of skirt sections,
said ferrous material of said body portion is steel or another iron-based material,
said body portion extends around said center axis and longitudinally along said center axis from an upper end to a lower end,
said crown presents said combustion surface at said upper end for exposure to a combustion chamber of an internal combustion engine,
said combustion surface includes a combustion bowl extending toward said center axis from an outer rim and includes an apex at said center axis,
said ring belt region includes a plurality of ring grooves spaced from one another by lands,
said ring belt region is located at an outer diameter of said body portion and extends circumferentially about a center axis of said body portion,
said pin bosses and said skirt sections extend from said crown to said lower end,
said pin bosses define a pin bore for receiving a wrist pin,
said coating is disposed on at least one of said undercrown surface, at least one of said ring grooves, at least one of said lands, at least one of said pin bosses, and at least one of said skirt sections, and
said coating reduces chemical bonding of coking deposits on said body portion at temperatures ranging from 200 to 400° C.
12. A piston, comprising:
a body portion formed of a ferrous material,
a coating disposed on at least a portion of an undercrown surface of said body portion, and
said coating including a fluoropolymer,
said coating including polysilane, and
said coating having a thickness of 25 microns to 1 millimeter.
13. The piston of claim 12 , wherein said coating further includes at least one of thermoset resin and silicone.
14. The piston of claim 12 , wherein said fluoropolymer of said coating includes polytetrafluoroethylene, fluorosilane, fluorocarbon, fluoroplastic resin, and/or perfluoroplastic.