Piston ring and method of manufacture
A piston ring may include a split annular body having a plurality of exterior surfaces, an intermediate coating disposed on and directly contacting at least one exterior surface of the split annular body, and a tribological coating. The tribological coating may include a first layer disposed on and directly contacting the intermediate coating, and a second layer disposed on and directly contacting the first layer. The first layer may have a first hardness and a first porosity. The second layer may have a second hardness and a second porosity. The second hardness may be less than the first hardness. The second porosity may be greater than the first porosity.
1 . A piston ring, comprising:
a split annular body having a plurality of exterior surfaces;
an intermediate coating disposed on and directly contacting at least one surface of the plurality of exterior surfaces;
a tribological coating including:
a first layer disposed on and directly contacting the intermediate coating, the first layer having a first hardness and a first porosity; and
a second layer disposed on and directly contacting the first layer, the second layer having a second hardness and a second porosity;
wherein the second hardness is less than the first hardness;
wherein the second porosity is greater than the first porosity;
wherein the first layer has a first material composition; and
wherein the second layer has a second material composition that is the same as the first material composition.
2 . The piston ring of claim 1 , wherein:
the plurality of exterior surfaces includes a lower surface; and
the intermediate coating is disposed on and directly contacts the lower surface.
3 . The piston ring of claim 2 , wherein:
the plurality of exterior surfaces further includes an outer circumferential surface, an inner circumferential surface, and an upper surface; and
the intermediate coating is further disposed on and directly contacts the outer circumferential surface.
4 . The piston ring of claim 1 , wherein the first layer and the second layer each include a nitride of titanium, a nitride of zirconium, a nitride of vanadium, a nitride of niobium, a nitride of chromium, a nitride of molybdenum, and/or a nitride of tungsten.
5 . The piston ring of claim 1 , wherein the intermediate coating includes chromium, nickel, cobalt, titanium, and/or vanadium.
6 . The piston ring of claim 5 , wherein the intermediate coating includes chromium.
7 . The piston ring of claim 1 , wherein a ratio of the second hardness to the first hardness is from 0.5:1 to 0.7:1.
8 . The piston ring of claim 1 , wherein the first layer and the second layer includes an amorphous carbon-based material, a diamond-like carbon-based material, and/or a metal nitride.
9 . The piston ring of claim 1 , wherein an outermost surface of the second layer of the tribological coating is free of any further coating material such that the tribological coating forms an outermost coating of the split annular body.
10 . A piston ring, comprising a split annular body having a plurality of exterior surfaces, wherein:
at least one surface of the plurality of exterior surfaces includes a first intermediate coating layer disposed directly thereon;
at least one other surface of the plurality of exterior surfaces includes a second intermediate coating layer disposed directly thereon, a first tribological coating layer disposed on and directly contacting the second intermediate coating layer, and a second tribological coating layer disposed on and directly contacting the first tribological coating layer;
the first tribological coating layer has a first hardness;
the second tribological coating layer has a second hardness;
the second hardness is less than the first hardness; the first tribological coating layer has a first material composition; and
the second tribological coating layer has a second material composition that is the same as the first material composition.
11 . The piston ring of claim 10 , wherein:
the plurality of exterior surfaces includes an outer circumferential surface, an inner circumferential surface, a lower surface, and an upper surface;
the at least one surface of the plurality of exterior surfaces includes the lower surface; and
the at least one other surface of the plurality of exterior surfaces includes the outer circumferential surface, the inner circumferential surface, and/or the upper surface.
12 . The piston ring of claim 10 , wherein:
the at least one surface of the plurality of exterior surfaces includes a first surface;
the at least one other surface of the plurality of exterior surfaces includes a second surface; and
the first intermediate coating layer disposed on the first surface and the second intermediate coating layer disposed on the second surface are portions of a continuous intermediate coating formed over the first surface and the second surface.
13 . The piston ring of claim 10 , wherein:
the first intermediate coating layer is formed by a first deposition process; and
the second intermediate coating layer is formed by a second deposition process.
14 . The piston ring of claim 13 , wherein the first deposition process and the second deposition process are the same deposition process such that the first intermediate coating layer disposed on the first surface and the second intermediate coating layer disposed on the second surface are formed together as portions of a continuous intermediate coating.
15 . The piston ring of claim 10 , wherein:
the first tribological coating layer has a first thickness; and
the second tribological coating layer has a second thickness that is less than the first thickness.
16 . The piston ring of claim 15 , wherein the second thickness of the second tribological coating layer is
5% to 30% of an overall thickness of the first tribological coating layer and the second tribological coating layer.