Abstract: A piston ring with a coated outer surface is provided. The coating is disposed on end sections of the outer surface adjacent a gap. Typically, a middle section of the outer surface located between the end sections is not coated. The coating can be formed of CrN or DLC, and the CrN coating can be applied by physical vapor deposition (PVD). The end sections of the outer surface, upon which the coating is applied, are rough. For example, the outer surface can be blasted or otherwise textured to achieve the rough surface. The rough surface retains oil and distributes stress better than a smooth surface, and thus reduces crazing and flaking of the coating.

Abstract: A piston ring with a coated outer surface is provided. The coating is disposed on end sections of the outer surface adjacent a gap. Typically, a middle section of the outer surface located between the end sections is not coated. The coating can be formed of CrN or DLC, and the CrN coating can be applied by physical vapor deposition (PVD). The end sections of the outer surface, upon which the coating is applied, are rough. For example, the outer surface can be blasted or otherwise textured to achieve the rough surface. The rough surface retains oil and distributes stress better than a smooth surface, and thus reduces crazing and flaking of the coating.

Abstract: A coated piston ring for a piston is provided. The piston ring includes a running surface, a flank surface, and a transition surface therebetween. The transition surface curves or extends at an angle between the running surface and the flank surface. A running layer is disposed over the running surface and over at least a portion of the transition surface. A flank layer is disposed over the flank surface and over at least a portion of the transition surface. The running layer is applied by physical vapor deposition, and the running layer is applied by galvanic deposition. The running layer is formed of chromium nitride, and the flank layer is formed of chromium. A portion of the flank layer overlaps and is disposed outward of a portion of the running layer. During operation of the piston, the overlapping portion is spaced from both the piston and the cylinder.

Abstract: A piston ring with a coated outer surface is provided. The coating is disposed on end sections of the outer surface adjacent a gap. Typically, a middle section of the outer surface located between the end sections is not coated. The coating can be formed of CrN or DLC, and the CrN coating can be applied by physical vapor deposition (PVD). The end sections of the outer surface, upon which the coating is applied, are rough. For example, the outer surface can be blasted or otherwise textured to achieve the rough surface. The rough surface retains oil and distributes stress better than a smooth surface, and thus reduces crazing and flaking of the coating.

Abstract: A piston ring with a coated outer surface is provided. The coating is disposed on end sections of the outer surface adjacent a gap. Typically, a middle section of the outer surface located between the end sections is not coated. The coating can be formed of CrN or DLC, and the CrN coating can be applied by physical vapor deposition (PVD). The end sections of the outer surface, upon which the coating is applied, are rough. For example, the outer surface can be blasted or otherwise textured to achieve the rough surface. The rough surface retains oil and distributes stress better than a smooth surface, and thus reduces crazing and flaking of the coating.