Products
Piston Ring Surface Treatment
Surface Treatments
a.) Phosphating and Ferroxiding
Surface treatment serve to improve the running-in of piston rings and within limits to inhibit
corrosion. This latter feature is only relevant in the case of prolonged storage.
These two processes ensure that running-in occurs and without scuffing.by chemical and
hermal means the surface of a ring is converted respectively to crystalline phosphates and
black iron oxide .
The phosphate layer wears away more easily than the base material of the ring thus achieving
a more rapid running-in.the rubbed off particles of iron oxide are so hard that during the
running-in process they serve as a first class abrasive. Both layers have a limited resistance to
scuffing and in this respect are similar to a nitrided layer.
They are therefore fitted with success to engines in which the level of scuffing is not too high.
b.)Tin and Copper Plating
Thin electrodeposited metallic coatings have a similar protective function. They are somewhat
softer than the material of the cylinder and resist possible seizure by means of a quasi-
lubricating process.
C.)Chrome Plating
An electrodeposited chromium coating has excellence resistance. In addition , its good
resistance without question superior to both uncoated and treated ring. The greatest wear
occurs generally at the top ring at T.D.C. This is due to the inferior running that are present.
As diesel engines have to reach an extremely long life they are usually equipped with more than
or plated piston ring. Even the oil control rings use engines are chrome plated over their running
surface.
D.) Molybdenum Coating
The best method to avoid scuffing is to inlay the Running surface or to coat if completely wit
molybdenum.
This can be accomplished by a flame as flame as well as a plasma spraying process.
This high resistance to scuffing of the molybdenum coating can be related to its high melting
melting point .to its porosity ,and to the lubricating effectiveness of the oxidized molybdenum
layer that can be formed during the breakdown of the oil film.
Resulting from metal spraying acts effectively as an oil reservoir ,and will improve lubrication
under critical running conditions. The face that porosity influences the strength of a small
contacting areas, e,g. oil control rings.
E.)Coatings of ceramic mixtures, cermets and/or metal mixtrres
Coatings of the abovementioned types are extremely wear-resistant.
The coatings uses are for instance ceramic mixtures of aluminium oxide, or cermets consisting
of molybdenum and chromium carbide. Coatings of metal mixtures are combinations of various
metal alloys, mainly molybdenum.