Patent ID: 8561998

Claim:
Nitrided piston ring ( 100 , 100 ′) equipped with a metallic base composed fundamentally of iron to which one first layer ( 1 ) is associated, wherein the ring further comprises one second layer ( 2 ) positioned between the base ( 3 ) and the first layer ( 1 ), the first layer ( 1 ) having at least 2% of nitrogen in weight and a hardness of, at the most, 800 Vickers varying in a substantially linear manner until a minimum hardness of 400 Vickers at a depth of 85 microns (μm) counted as of the most external portion of the first layer, the second layer ( 2 ) having a percentage of carbon in weight at least fractionally superior to the percentage of carbon in weight present in the base ( 3 ) and thickness at least one of higher or equal to at least 15 microns (μm).