Kabushiki Kaisha Riken

Yuuichi Murayama

Masayuki Sato

Takuma Sekiya

Youhei Iwamoto

Masaki Moronuki

Yuji Shima

Junya Takahashi

To provide a piston ring having a hard laminate coating having excellent scuffing resistance, wear resistance and peeling resistance, which can be used in an environment of high mechanical and thermal load in engines, the piston ring is provided on its outer peripheral sliding surface with a CrN-type hard coating as thick as 10-60 &#x3bc;m and comprising a CrN/CrCN laminate coating having hardness Hv of 1000 or more and residual compression stress of 1500 MPa or less, a laminate unit composed of a CrN layer and a CrCN layer being as thick as 30 nm or more; the CrN/CrCN laminate coating being formed by alternately laminating CrN layers and CrCN layers containing C dissolved in CrN by ion plating.

Piston ring

To provide a hard-amorphous-carbon-coated piston ring having low friction and excellent wear resistance and peeling resistance to reduce the fuel consumption of automobiles, an outer peripheral surface of a steel-made piston ring base material is provided with a primary layer constituted by a CrN/Cr laminate coating or a CrN/TiN laminate coating as thick as 10-60 &#x3bc;m, which is obtained by alternately laminating CrN-type chromium nitride and chromium metal or TiN-type titanium nitride, an intermediate layer of chromium metal and/or titanium metal as thick as 0.05-1.0 &#x3bc;m, and then a hard amorphous carbon coating as thick as 0.4-20 &#x3bc;m.

Piston ring and its production method

To provide a piston ring having a hard laminate coating for excellent scuffing resistance, wear resistance and peeling resistance, which can be used in an environment of high mechanical and thermal load in engines, the piston ring is provided with a hard laminate coating as thick as 10-60 &#x3bc;m on its outer peripheral surface, the laminate coating being formed by alternately laminating two types or more of layers made of different compounds, each of the compound layers being made of nitride of at least one metal selected from the group consisting of Ti, Cr, Zr, V, Hf and Al.

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 &#x3bc;m, 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.

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 is provided. Also, to provide a piston ring with low friction for contributing to the improvement of fuel efficiency, a TiN coating as thick as 10-60 &#x3bc;m, in which the texture coefficient of a (111) plane is 1.2-1.65 in X-ray diffraction on the coating surface, with the texture coefficient of a (111) plane&#x3e;the texture coefficient of a (220) plane&#x3e;the texture coefficient of a (200) plane, is formed under the optimized ion plating conditions on a peripheral surface of the piston ring. Further, 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.

Growing community of inventors

Kashiwazaki, Japan

Yuuichi Murayama