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: 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.

Abstract: A tip plug is capped on a boss section so as to fit to a hole which is used for detaching a core which is formed in a blade tip section of the gas turbine blade. A butt-section T is melted so as to form a butt-welding section by using a YAG laser beam. Also, parameters such as an interval between the butt-section T, a member for forming the tip plug, condition for a laser welding operation, and a defocus position of the laser beam are optimized.

Abstract: A tip plug is capped on a boss section so as to fit to a hole which is used for detaching a core which is formed in a blade tip section of the gas turbine blade. A butt-section T is melted so as to form a butt-welding section by using a YAG laser beamthere; thus, the hole is plugged by the tip plug. Also, parameters such as an interval between the butt-section T, a member for forming the tip plug, condition for a laser welding operation, and a defocus position of the laser beam are optimized. By doing this, it is possible to control the entering heat amount and prevent the solidification cracking and the liquation cracking reliably. Furthermore, it is possible to melt and weld the butt-welding section more strongly by using a laser having a narrow bead width; thus, it is possible to improve the manufacturing process efficiently and produce a product in uniform quality repeatedly.