Coating with enhanced sliding properties
The present invention relates to coated sliding parts having coating systems which allow better sliding performance under dry and/or under lubricated conditions. The coating systems according to the present invention being characterized by having an outermost layer which—is a smooth oxide-containing layer in case of sliding applications under lubricated conditions, or—is a self-lubricated layer comprising molybdenum nitride, in case of sliding applications under dry or lubricated conditions, is a selflubricated layer with a structured surface comprising a multitude of essentially circular recesses with diameters of several micrometers or below, the recesses randomly distributed over the surface.
1. Sliding component ( 10 ) having a sliding surface to be exposed to relative movement with respect to another component under lubricated conditions, wherein the sliding surface of the sliding component ( 10 ) is at least partially coated with a coating system ( 1 ) comprising an outermost layer ( 7 ), characterized in that,
the outermost layer ( 7 ) is an oxide-containing layer having mechanical stability at high temperatures and at least mostly comprising a metal oxide, the layer ( 7 ) having an element composition defined by the formula Me 1-b-c X c O b with b>0 and at least twice as large as c and with c>0, where
Me is a metal different from Mo or a combination of metals other than Mo, Me having a concentration in atomic percent of 1−b−c, and
O is oxygen having a concentration in atomic percent of b, and
X is or contains nitrogen and/or carbon, having a concentration in atomic percent of c,
wherein the outermost layer ( 7 ) has a smooth or smoothed surface which exhibits essentially no protrusions but which exhibits recesses, and
wherein the outermost layer ( 7 ) comprises arc-PVD droplets.
2. Sliding component ( 10 ) according to claim 1 , characterized in that the surface of the outermost layer ( 7 ) comprises a multitude of essentially circular recesses with diameters of several micrometers or below, the recesses randomly distributed over the surface.
3. Sliding component ( 10 ) according to claim 1 , characterized in that the surface of the outermost layer ( 7 ) is a polished surface.
4. Sliding component ( 10 ) according to claim 1 , characterized in that, the coating system ( 1 ) comprises additionally:
at least one bonding strength layer ( 3 ) for improving coating adhesion, and
at least one metal nitride containing layer ( 5 ) and
at least one additional oxide-containing layer ( 6 ) arranged under the outermost layer ( 7 ), the additional oxide-containing layer ( 6 ) differing from the outermost layer ( 7 ).
5. The sliding component ( 10 ) according to claim 4 wherein the at least one metal nitride containing layer ( 5 ) is chromium nitride or a molybdenum nitride.
6. The sliding component ( 10 ) according to claim 1 , characterized in that, the coating system ( 1 ) comprises additionally:
at least one metal nitride containing layer ( 5 ) and
at least one additional oxide-containing layer ( 6 ) arranged under the outermost layer ( 7 ), the additional oxide-containing layer ( 6 ) differing from the outermost layer ( 7 ).
7. The sliding component ( 10 ) according to claim 6 wherein that at least one metal nitride containing layer ( 5 ) is chromium nitride or a molybdenum nitride.
8. The sliding component ( 10 ) according to claim 1 , wherein the sliding surface of the sliding component ( 10 ) is disposed in contact with a surface of the component and wherein the sliding component ( 10 ) and the component slide relative to each other.
9. The sliding component ( 10 ) according to claim 1 , wherein X is or contains carbon having a concentration in atomic percent of c.