Piston rings in cast tool steels and process for the manufacture thereof

A piston ring in cast tool steels, comprising:

• a tempered ring including a contact face configured to contact a piston cylinder, the ring having a chemical composition including:
• a concentration of C from 0.80 to 1.40 percent weight;
• a concentration of Cr from 2.50 to 4.20 percent weight;
• a concentration of Mn from 0.10 to 1.00 percent weight;
• a concentration of Mo from 1.00 to 2.00 percent weight;
• a concentration of Nb from 2.50 to 4.50 percent weight;
• a concentration of P of no more than 0.05 percent weight;
• a concentration of S of no more than 0.05 percent weight;
• a concentration of Si from 0.10 to 1.00 percent weight;
• a concentration of Ti from 0.10 to 0.30 percent weight;
• a concentration of V from 1.00 to 3.00 percent weight;
• a concentration of W from 1.00 to 3.00 percent weight;
• and
• a remaining concentration balance of Fe;
• wherein the ring has a microstructure including 1) a matrix of tempered martensite with precipitation of at least one of V2C carbides, VC carbides, Mo2C carbides, MoC carbides, Cr2C carbides, CrC carbides, W2C carbides, and WC carbides having a size of approximately 3 μm or less, and 2) NbC eutectic carbides having a cubic morphology, a volumetric fraction from approximately 1% to 4%, a size from approximately 3 μm to 7 82 m, and a homogeneous distribution, and wherein the ring has a hardness from approximately 400 HV to 800 HV.

A piston ring in cast tool steels, comprising:

• a tempered ring structured of a material having a chemical composition including:
• a concentration of C from 0.80 to 1.40 percent weight;
• a concentration of Cr from 2.50 to 4.20 percent weight;
• a concentration of Mn from 0.10 to 1.00 percent weight;
• a concentration of Mo from 1.00 to 2.00 percent weight;
• a concentration of Nb from 2.50 to 4.50 percent weight;
• a concentration of P of no more than 0.05 percent weight;
• a concentration of S of no more than 0.05 percent weight;
• a concentration of Si from 0.10 to 1.00 percent weight;
• a concentration of Ti from 0.10 to 0.30 percent weight;
• a concentration of V from 1.00 to 3.00 percent weight;
• a concentration of W from 1.00 to 3.00 percent weight;
• and
• a remaining concentration balance of Fe;
• wherein the ring has a microstructure including 1) a matrix of tempered martensite with precipitation of at least one of V2C carbides, VC carbides, Mo2C carbides, MoC carbides, Cr2C carbides, CrC carbides, W2C carbides, and WC carbides having a size of approximately 3 μm or less, and 2) NbC eutectic carbides having a cubic morphology, a volumetric fraction from approximately 1% to 4%, a size from approximately 3 μm to 7 μm, and a homogeneous distribution, and wherein the ring has a hardness from approximately 400 HV to 800 HV and includes at least one surface including a nitridation.