Remote crack repair welding in steels using high power Nd:YAG lasers

Abstract

The capabilities of fibre delivered laser power have been demonstrated in many successful manufacturing applications in a wide range of industry sectors. These laser systems also offer significant possibilities for remote processing applications and in particular, repair operations. This paper describes work conducted with a 4 kW continuous wave fibre delivered Nd:YAG laser, to investigate the feasibility of performing an in situ repair, on a low silicon content mild steel component used in the core region of a gas cooled Magnox reactor. Due to the high pressures and temperatures experienced in service, in addition to the environmental conditions, these components are susceptible to oxide build up. The design of the component is such that the oxide can initiate cracking in the arc welds used in the original manufacturing process. Procedures are described which allow the same laser source to both remove the oxide layer from the component and subsequently heal the cracked region. Single pass and weave welding techniques were evaluated as well as the addition of filler wire material in order to provide weld reinforcement. The potential advantages of using such a laser procedure over traditional repair methodologies are outlined.The capabilities of fibre delivered laser power have been demonstrated in many successful manufacturing applications in a wide range of industry sectors. These laser systems also offer significant possibilities for remote processing applications and in particular, repair operations. This paper describes work conducted with a 4 kW continuous wave fibre delivered Nd:YAG laser, to investigate the feasibility of performing an in situ repair, on a low silicon content mild steel component used in the core region of a gas cooled Magnox reactor. Due to the high pressures and temperatures experienced in service, in addition to the environmental conditions, these components are susceptible to oxide build up. The design of the component is such that the oxide can initiate cracking in the arc welds used in the original manufacturing process. Procedures are described which allow the same laser source to both remove the oxide layer from the component and subsequently heal the cracked region. Single pass and weave weldi...