Piston ring
To provide a high-thermal-conductivity piston ring having excellent scuffing resistance and wear resistance, which can be used in a high-heat-load environment in engines, a TiN coating as thick as 10-60 μm, in which the texture coefficient of a (220) plane is 1.1-1.8 in X-ray diffraction on the coating surface, larger than those of (111) and (200) planes, is formed under the optimized ion plating conditions on a peripheral surface of the piston ring. Also, to obtain excellent sliding characteristics with low friction without losing excellent thermal conductivity of TiN, a hard amorphous carbon coating is formed on the TiN coating.
1. A piston ring comprising:
a substrate; and
a TiN coating having a thickness of 10-60 μm on a peripheral sliding surface of the substrate, the texture coefficient of a (220) plane of TiN in the X-ray diffraction of a surface of said TiN coating being 1.1-1.8, larger than those of (111) and (200) planes of TiN, wherein
said TiN coating is formed in a nitrogen atmosphere consisting of N 2 gas.
2. The piston ring according to claim 1 , further comprising a amorphous carbon coating formed on said TiN coating.
3. The piston ring according to claim 2 , wherein said amorphous carbon coating contains substantially no hydrogen.
4. The piston ring according to claim 2 , wherein said amorphous carbon coating has a thickness of 0.5-10 μm.
5. The piston ring according to claim 1 , wherein the substrate of said piston ring has a composition comprising, by mass, 0.50-0.60% of C, 1.20-1.60% of Si, 0.50-0.90% of Mn, and 0.50-0.90% of Cr, the balance being Fe and inevitable impurities.
6. The piston ring according to claim 1 wherein the substrate of said piston ring has a composition comprising, by mass, 0.45-0.55% of C, 0.15-0.35% of Si, 0.65-0.95% of Mn, 0.80-1.10% of Cr, and 0.15-0.25% of V, the balance being Fe and inevitable impurities.
7. The piston ring according to claim 6 , wherein the substrate of said piston ring comprises spheroidal cementite having an average particle size of 0.1-1.5 μm dispersed in an annealed martensite matrix.