Abstract: A valve gear in which corrosion due to a potential difference does not occur and which can reduce the corrosion occurrence even when loads due to microvibrations are given. The valve gear includes a valve stem and a valve bush that slidably supports the valve stem. The valve stem is formed from a forged part made of a Ni-based superalloy and the valve bush is formed from a cast part made of a Ni-based superalloy. The preferable surface roughness of a sliding surface of the valve stem in contact with the valve bush and the preferable surface roughness of a sliding surface of the valve bush in contact with the valve stem is 100 ?M or less in units of Rz.

Abstract: 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 bearing 2 having a sliding surface against a valve shaft 1. The valve gear having a welded layer 12 made of heat-resistant cobalt-based alloy, based on plasma powder building up, formed on the sliding surface against the valve shaft 1. The welded layer 12 includes a first welded layer 12a formed on the surface of the bearing 2, having a dilution ratio of 5 to 25% and a second welded layer 12b formed on the first welded layer 12a, having a dilution ratio of 50% or less of the dilution ratio of the first welded layer 12a. The dilution ratio indicates the penetration amount of the welding metal into the base metal, and is a value obtained by B/A×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.

Abstract: Provided is a valve gear in which corrosion due to a potential difference does not occur and which can reduce the corrosion occurrence even when loads due to microvibrations are given. The valve gear according to the present invention comprises a valve stem 6 and a valve bush 7 that slidably supports the valve stem 6. The valve stem 6 is formed from a forged part made of a Ni-based superalloy and the valve bush 7 is formed from a cast part made of a Ni-based superalloy. The preferable surface roughness of a sliding surface of the valve stem 6 in contact with the valve bush 7 and the preferable surface roughness of a sliding surface of the valve bush 7 in contact with the valve stem 6 is 100 ?m or less in units of Rz.

Abstract: The reliability of a valve gear in which a cobalt-based alloy is welded by plasma powder building-up welding is improved. Disclosed is a valve gear including a bearing 2 having a sliding surface against a valve shaft 1, the valve gear being characterized in that: a welded layer 12 made of a heat-resistant cobalt-based alloy, based on plasma powder building-up, is formed on the sliding surface against the valve shaft 1; and the welded layer 12 includes a first welded layer 12a formed on the surface of the bearing 2, having a dilution ratio of 5 to 25% and a second welded layer 12b formed on the first welded layer 12a, having a dilution ratio of 50% or less of the dilution ratio of the first welded layer 12a. The dilution ratio is a parameter indicating the penetration amount of the welding metal into the base metal, and means a value obtained by B/A×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.