Coating for a piston ring
A piston ring and method of forming includes a base portion formed of a metallic material, an outer contact surface and an inner contact surface extending between a first face and a second face that is opposite the first face of the piston ring, a chromium coating layer on the second face, the outer contact surface, and the inner contact surface, a layer of diamond-like carbon (DLC) disposed over the chromium coating layer on the outer contact surface, and a phosphate layer on a first face.
1 . A piston ring, comprising:
a base portion formed of a metallic material;
an outer contact surface and an inner contact surface extending between a first face and a second face that is opposite the first face of the piston ring;
a chromium coating layer on the inner contact surface, the outer contact surface, and the second face;
a layer of diamond-like carbon (DLC) disposed over the chromium coating layer on the outer contact surface;
a phosphate layer provided on the first face; and
wherein the phosphate layer is disposed directly on the metallic material of the base portion of the first face between an upper outer corner region and an upper inner corner region of the base portion.
2 . The piston ring of claim 1 , wherein the phosphate layer partially overlaps the DLC at the upper outer corner region of the base portion and partially overlaps the chromium coating layer at the upper inner corner region of the base portion.
3 . The piston ring of claim 2 , wherein the phosphate layer has a diminishing thickness along the upper outer corner region and the upper inner corner region.
4 . The piston ring of claim 1 , further comprising a physical vapor deposition (PVD) chrome interlayer interposed between the DLC and the chromium coating layer along the outer contact surface.
5 . The piston ring of claim 1 , further comprising a polymer layer overlaying the DLC.
6 . The piston ring of claim 1 , wherein the DLC has an approximately constant thickness along the outer contact surface and a diminishing thickness at a lower outer corner region of the base portion and the upper outer corner region of the base portion.
7 . The piston ring of claim 6 , wherein:
the chromium coating layer has an approximately constant thickness along the outer contact surface, the lower outer corner region, the second face, a lower inner corner region of the base portion, and the inner contact surface; and
the chromium coating layer has a diminishing thickness at the upper outer corner region and the upper inner corner region of the base portion.
8 . The piston ring of claim 1 , wherein the chromium coating layer has a thickness of between 10 μm and 20 μm with a thickness variation of equal to or less than 5 μm, and wherein the chromium coating layer has a flatness of equal to or less than 2 μm along the second face and the inner contact surface.
9 . A piston ring, comprising:
a base portion formed of a metallic material, the base portion including an outer contact surface and an inner contact surface extending between a first face and a second face that is opposite the first face;
a chromium coating layer on the inner contact surface, the outer contact surface, and the second face;
a layer of diamond-like carbon (DLC) disposed over the chromium coating layer on the outer contact surface;
a phosphate layer provided on the first face;
wherein the layer of DLC has a diminishing thickness at a lower outer corner region of the base portion and an upper outer corner region of the base portion; and
wherein the phosphate layer partially overlaps the DLC at the upper outer corner region and partially overlaps the chromium coating layer at an upper inner corner region of the base portion.
10 . The piston ring of claim 9 , wherein the layer of DLC has an approximately constant thickness along the outer contact surface.
11 . The piston ring of claim 9 , wherein the chromium coating layer has a diminishing thickness at the upper outer corner region.
12 . The piston ring of claim 11 , the chromium coating layer has an approximately constant thickness along the outer contact surface, the lower outer corner region, the second face, a lower inner corner region of the base portion, and the inner contact surface.
13 . The piston ring of claim 9 , wherein the phosphate layer is disposed directly on the metallic material of the base portion of the first face between the upper outer corner region and the upper inner corner region of the base portion.
14 . The piston ring of claim 9 , wherein the phosphate layer has a diminishing thickness along the upper outer corner region and the upper inner corner region.
15 . The piston ring of claim 9 , further comprising a physical vapor deposition (PVD) chrome interlayer interposed between the DLC and the chromium coating layer along the outer contact surface.
16 . The piston ring of claim 9 , further comprising a polymer layer overlaying the DLC.
17 . The piston ring of claim 9 , wherein the chromium coating layer has a thickness of between 10 μm and 20 μm with a thickness variation of equal to or less than 5 μm, and wherein the chromium coating layer has a flatness of equal to or less than 2 μm along the second face and the inner contact surface.
18 . The piston ring of claim 1 , wherein the chromium coating layer fully covers the inner contact surface, the outer contact surface, and the second face.
19 . The piston ring of claim 1 , wherein the chromium coating layer is further disposed on the upper outer corner region, the upper inner corner region, a lower outer corner region, and a lower inner corner region.
20 . The piston ring of claim 9 , wherein the chromium coating layer fully covers the inner contact surface, the outer contact surface, and the second face.