Masahiko Mega

Application of YAG laser welding to gas turbine components

An investigation to apply YAG laser welding to gas turbine components was carried out. The materials of gas turbine such as Ni base alloy are difficult to weld by conventional arc welding methods because of large heat affection. But laser welding can reduce heat input compared with conventional methods and keeps the good repeatability. The welding parameter survey was carried out to satisfy the designing requirements. The YAG laser welding under appropriate conditions enables to prevent welding defects such as HAZ cracks and improves the weld joints quality and performance. Tensile test and low cycle fatigue test were carried out. Tensile strength and fatigue life of laser weld joints are same or higher than that of conventional manual TIG weld joints. The Automatic YAG laser welding system was also developed and put into practical use.

Boundary Lubrication Properties of Surface Modified Material Produced by Laser and Electron Beam Surface Alloying

The surface-modified material can be produced by laser and electron beam surface alloying of a plasma-sprayed molybdenum layer on Cr-Mo steel. The boundary lubrication properties and the metal structure of the surface alloy have been investigated. The main points of this study are as follows. 1. The surface alloy is thick, about 5 mm, and of uniform composition. 2. The surface alloy shows good wear resistance and good seizure resistance, in the same level as electroplated chromium and plasma-sprayed molybdenum layers. 3. Good wear resistance is attributable to the metal structure which is composed of hard M6C phase and soft α−Fe phase. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in San Diego, California, October 19–21, 1992