Two parts moving in contact always generate friction. Plating with lubricity is intended to decrease the friction between the rubbing surfaces and prevent wear or seizing-up of materials. Generally, soft plating films are suitable because conformability and a low friction coefficient are key points for improvement of lubricity.
Recently, such composite plating as highly lubricious particles, like Teflon or molybdenum disulfide, dispersed and co-deposited in hard nickel-phosphorous plating film surface plays an active part under wear environments in which lubricating oil cannot be used.
|Type of plating
||- Silver plating, indium plating, tin plating, tin-lead alloy plating, lead-indium alloy plating
- Conformability and lubricity are excellent.
- Hardness of tin plating film
- Lead and indium are softer than tin.
Sn < Pb < In
|Pistons and piston rings of internal combustion engines, bearings, screws of molding machines, etc.
||- Microporous chromium plating + oil retention
- TEFLOK (product name) with solid lubricant Teflon impregnated in microporous chromium plating film
- Electroless nickel-Teflon composite plating, electroless nickel-molybdenum disulfide composite plating, electroless nickel-graphite fluoride composite plating, electroless nickel-phosphorus-boron nitride composite plating
Appearance photo of chromium plated surfaces
increasing the oil retaining ability
(From “Kuromu Mekki”; Matsuhei Kishi,
Nikkan Kogyo Shimbun Ltd.)
Lubricity is increased by lowering the surface friction coefficient, increasing the oil retaining ability, and improving the conformability, etc. Composite plating is next-generation plating combined with wear resistance, lubricity, corrosion resistance, and so on because hard/soft plating can be selected as a matrix metal, and Teflon particles, graphite fluoride, molybdenum disulfide, etc., having excellent lubricity can be selected as fine particles dispersed and co-deposited.