# US 2017/0254418 A1 · Piston Ring

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- Number: US 2017/0254418 A1
- Document ID: US20170254418A1
- Status: Published application
- Kind: A1
- Application number: 15/061,181
- Filed: 2016-03-04
- Published: 2017-09-07
- Earliest claimed: 2016-03-04
- Assignees: Mahle International GmbH
- Applicants: Mahle International GmbH
- Inventors: Thomas Stong; Thomas Smith
- Web page: https://patentgrep.com/patent/US20170254418A1

## CPC

- F16J 9/26: characterised by the use of particular materials
- C23C 14/0641: {Nitrides (C23C14/0617 takes precedence)}
- C23C 28/042: {including a refractory ceramic layer, e.g. refractory metal oxides, ZrO2, rare earth oxides}
- C23C 28/044: {coatings specially adapted for cutting tools or wear applications}
- C23C 28/42: {characterized by the composition of the alternating layers}
- F16J: PISTONS {(specially adapted for dampers F16F9/32)}; CYLINDERS; SEALINGS
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)

## Abstract

A piston ring for a piston of a reciprocating internal combustion engine. The piston ring comprises a body having an outer contact surface. A tribological coating is formed on the outer contact surface of the body. The tribological coating comprises a quaternary Cr—V—Ti—N system. In one form, the tribological coating is deposited on the outer contact surface of the body as a stack of multiple layers.

## Claims

### Claim 1

A piston ring comprising:
a body having an outer contact surface; and
a tribological coating overlying the outer contact surface of the body, wherein the tribological coating comprises a quaternary Cr—V—Ti—N system.

### Claim 2 (depends on 1)

The piston ring set forth in claim 1 wherein the quaternary Cr—V—Ti—N system comprises 15-45 at % chromium (Cr), 10-20 at % vanadium (V), 5-15 at % titanium (Ti), and 40-50 at % nitrogen (N).

### Claim 3 (depends on 1)

The piston ring set forth in claim 1 wherein the tribological coating is doped with 0.1-10 at % of at least one doping element selected from the group consisting of oxygen (O), carbon (C), and boron (B).

### Claim 4 (depends on 1)

The piston ring set forth in claim 1 wherein the tribological coating comprises 5-15 at % of at least one element or compound selected from the group consisting of molybdenum (Mo), niobium (Nb), zirconium (Zr), tungsten (W), tantalum (Ta), aluminum (Al), and silicon (Si).

### Claim 5 (depends on 1)

The piston ring set forth in claim 1 comprising:
a nitrided layer formed at an exterior surface of the body, wherein the tribological coating is formed over the nitrided layer.

### Claim 6 (depends on 1)

The piston ring set forth in claim 1 comprising:
an intermediate coating disposed between the body and the tribological coating, wherein the intermediate coating comprises at least one of chromium (Cr), titanium (Ti), and vanadium (V).

### Claim 7 (depends on 1)

The piston ring set forth in claim 1 wherein the tribological coating is formed on the outer contact surface of the body by a physical vapor deposition (PVD) process.

### Claim 8 (depends on 1)

The piston ring set forth in claim 1 wherein the body comprises a split annular body and the tribological coating is formed on an outer circumferential surface of the annular body.

### Claim 9 (depends on 1)

The piston ring set forth in claim 1 wherein the tribological coating has a thickness in the range of 5-100 μm.

### Claim 10 (depends on 1)

The piston ring set forth in claim 1 wherein the tribological coating comprises a stack of multiple layers that includes a first layer and a second layer, with the first layer having a different chemical composition than that of the second layer.

### Claim 11 (depends on 10)

The piston ring set forth in claim 10 wherein at least one of the layers in the stack of multiple layers that make up the tribological coating comprises a quaternary Cr—V—Ti—N system.

### Claim 12 (depends on 10)

The piston ring set forth in claim 10 wherein at least one of the layers in the stack of multiple layers that make up the tribological coating comprises a binary metal nitride.

### Claim 13

A piston ring comprising:
a split annular body having an upper surface, a lower surface, an inner circumferential surface, and an outer circumferential surface extending between the upper and lower surfaces; and
a tribological coating overlying the outer circumferential surface of the annular body, wherein the tribological coating comprises a quaternary Cr—V—Ti—N system and is formed on the outer circumferential surface of the annular body as a stack of multiple layers.

### Claim 14 (depends on 13)

The piston ring set forth in claim 13 wherein the quaternary Cr—V—Ti—N system comprises 15-45 at % chromium (Cr), 10-20 at % vanadium (V), 5-15 at % titanium (Ti), and 40-50 at % nitrogen (N).

### Claim 15 (depends on 13)

The piston ring set forth in claim 13 wherein at least one of the layers in the stack of multiple layers that make up the tribological coating comprises a quaternary Cr—V—Ti—N system.

### Claim 16 (depends on 13)

The piston ring set forth in claim 13 wherein at least one of the layers in the stack of multiple layers that make up the tribological coating comprises a binary metal nitride.

### Claim 17 (depends on 13)

The piston ring set forth in claim 13 wherein the stack of multiple layers includes a first layer and a second layer, with the first layer having a different chemical composition than that of the second layer.

### Claim 18 (depends on 17)

The piston ring set forth in claim 17 wherein the first layer and the second layer are individually and alternately applied to the outer circumferential surface of the annular body at least two times.

### Claim 19 (depends on 13)

The piston ring set forth in claim 13 comprising:
a nitrided layer formed at an exterior surface of the annular body; and
an intermediate coating formed on the outer circumferential surface of the annular body over the nitrided layer,
wherein the tribological coating is formed over the intermediate coating on the outer circumferential surface of the annular body.

### Claim 20 (depends on 13)

The piston ring set forth in claim 13 wherein the quaternary Cr—V—Ti—N system is doped with 0.1-10 at % of at least one doping element selected from the group consisting of oxygen (O), carbon (C), and boron (B).