Kabushiki Kaisha Riken

Tokusen Kogyo Co., Ltd.

Yuji Shima

Takuma Sekiya

Junya Takahashi

Masaki Moronuki

Masayuki Sato

Yuuichi Murayama

Ryouichi Kamon

Shigeo Inoue

Takashi Kimura

Keiji Honda

Hiroki Saito

Terushige Ueda

A piston ring includes a substrate, and a film covering at least a part of a surface of the substrate. The film includes Si and N. A Si content of the film is in a range of 1.1 to 7.5 at %, a crystallite size of the film is in a range of 10 to 30 nm, and a compressive residual stress of the film is 400 to 800 MPa.

Piston ring, and method for manufacturing same

To provide a piston ring excellent in thermal setting resistance, and also excellent in side surface wear resistance even under such a high-temperature high-pressure environment as to be more than 300&#xb0; C. and up to 400&#xb0; C., the base metal of the piston ring is a steel containing, by mass %, C: 0.30 to 0.65%, Si: 0.80 to 1.20%, Mn: 0.20 to 0.60%, Cr: 4.50 to 5.70%, Cu: 0.01 to 0.5%, and at least one of Mo, V, W, and Co: 0.2 to 5.4%.

Piston ring

To provide a piston ring free from microwelding to a piston while exhibiting excellent wear resistance in side surfaces, for a long period of use in a high-temperature, high-pressure environment, and its production method, a nitride layer is formed on at least one of upper and lower side surfaces of the piston ring, and then subjected to a phosphate chemical conversion treatment, such that the nitride layer has at least one of granular and vermicular surface forms.

Piston ring and its production method

To provide a piston ring of low-alloy steel having excellent nitridability, namely, a piston ring of low-alloy steel having excellent thermal conductivity and capable of being provided with a sufficient nitrided layer, steel comprising by mass 0.45-0.65% of C, 0.15-0.35% of Si, 0.65-1.00% of Mn and 0.60-1.10% of Cr as indispensable alloy elements, and less than 0.35% of Mo, less than 0.25% of V and less than 0.001% of B as optional alloy elements, the total amount of the indispensable alloy elements and the optional alloy elements being less than 3.0% by mass, is formed into a piston ring; and the nitrided layer is formed on its surface.

To provide a price-competitive compression ring having excellent thermal conductivity and thermal sag resistance, which can be used in a high-thermal-load environment of high-compression-ratio engines, steel identified by the material number of SUP10 in JIS G 4801, which contains small amounts of alloying elements, is used, and a piston ring wire is annealed before an oil-tempering treatment such that spheroidal cementite having an average particle size of 0.1-1.5 &#x3bc;m is dispersed in a tempered martensite matrix, thereby suppressing the movement of dislocation and creep even at 300&#xb0; C., and improving thermal sag resistance.

Compression ring and its production method

To provide a price-competitive compression ring having excellent thermal conductivity and thermal sag resistance, which can be used in a high-thermal-load environment of high-compression-ratio engines, steel identified by the material number of SKS93 in JIS G 4404 is used, and a piston ring wire is annealed before an oil-tempering treatment such that spheroidal cementite having an average particle size of 0.1-1.5 &#x3bc;m is dispersed in a tempered martensite matrix.

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.

[Task] The chromium nitride ion-plating coating has a property that it is hard but is liable to peel off. Year by year, the required level of wear resistance and scuffing resistance becomes higher in a diesel engine. The property of a coating is improved to enhance the wear resistance and scuffing resistance and also to improve resistance against peeling off. [Means for Solution] (1) Composition is mainly composed of chromium, nitrogen, and carbon, and the concentration of carbon relative to the total concentration of the main components is from 4 to 8% by weight. (2) The crystal structure is that texture of the CrN (111) plane orientation is from 0.4 to 2.0 in terms of a CrN (111) structural coefficient. (3) Vickers hardness is from Hv 1600 to Hv 2000.

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Kashiwazaki, Japan

Yuji Shima