Mitsubishi Heavy Industries Limited

Takahiko Hirohata

Mao Takei

Toshinari Nishimura

Masaya Kanikawa

The invention improves reliability of a valve gear in which a cobalt-based alloy is welded by plasma power building up. The valve gear includes a bearinghaving a sliding surface against a valve shaft. The valve gear having a welded layermade of heat-resistant cobalt-based alloy, based on plasma powder building up, formed on the sliding surface against the valve shaft. The welded layerincludes a first welded layerformed on the surface of the bearing, having a dilution ratio of 5 to 25% and a second welded layerformed on the first welded layer, having a dilution ratio of 50% or less of the dilution ratio of the first welded layer. The dilution ratio indicates the penetration amount of the welding metal into the base metal, and is a value obtained by B/A&#xd7;100 (%) wherein A represents the total amount of the welded metal and B represents the amount of the welding metal penetrating into the base metal.

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Hyogo, Japan

Takahiko Hirohata