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Laser welding requires much capital investment comparing with generally employed arc welding. However, the laser welding enables to join very small objects with high accuracy because the laser has high energy density and high controllability. In addition, it is possible to suppress welding deformation due to low heat input. Therefore, the laser welding is employed for various joining processes. This study aims to clarify formation mechanism of weld pool in laser cladding in order to improve incomplete fusion through numerical simulation on laser welding considering deformation of weld pool surface and convective heat transfer in it. Consequently, it was found that the gas pressure plays important role for improve incomplete fusion in laser welding. The higher pressure of gas increases penetration depth by pushing away molten metal at center of the weld pool without changing direction of convection.

Recently, stress corrosion cracking (SCC) has been observed at aged components of nuclear power plants under water environment and high exposure of radiation. Toshiba has been developing both an underwater laser welding directly onto surface of the aged components as maintenance and repair techniques. This paper reports underwater laser cladding and seal welding using INCONEL 52/52M.

Stress corrosion cracking (SCC) is one of the major reasons to reduce the reliability of aged reactor components. Toshiba has been developing underwater laser welding onto surface of the aged components as maintenance and repair techniques. Because most of the reactor internal components to apply this underwater laser welding technique have 3-dimensional shape, effect of welding positions and welded shapes are examined and presented in this report.Copyright © 2006 by ASME

The deterioration of weldability caused by helium is an important issue to be addressed in planning of proactive maintenance of light water reactor core internal components. Helium concentration, generated by neutron irradiation, was calculated to be about 20 appm in a core shroud after the 40-years nuclear power plant operation. The helium bubbles in grain boundaries (GBs) of the weld heat affected zone is one of the causes of weld cracking. In fact, there are some reports that application of conventional Gas Tungsten Arc Welding (GTAW) for neutron irradiated austenitic stainless steels caused cracks1,2. Yttrium-Aluminum-Garnet (YAG) Laser technique is one of the candidate method for surface modification and repair welding of the irradiated stainless steels, because the cooling rate of YAG Laser technique is fairly fast, the helium bubbles could not grow enough in grain boundary during process. Therefore, in the s study, the test of Laser surface modification (LSM) treatment, which is same as Laser de-sensitized treatment (LDT) and Laser repair welding (LRW) for neutron irradiated Type 304 and Type 316L austenitic stainless steels, were conducted. The applicability of LSM and LRW with optimized condition for neutron irradiated to 5E24 n/m2 (>1MeV) was demonstrated. The present study was carried out by the Japan Power Engineering and Inspection Corporation (JAPEIC) as one of the research works entrusted by the Ministry of Economy, Trade and Industry (METI).The deterioration of weldability caused by helium is an important issue to be addressed in planning of proactive maintenance of light water reactor core internal components. Helium concentration, generated by neutron irradiation, was calculated to be about 20 appm in a core shroud after the 40-years nuclear power plant operation. The helium bubbles in grain boundaries (GBs) of the weld heat affected zone is one of the causes of weld cracking. In fact, there are some reports that application of conventional Gas Tungsten Arc Welding (GTAW) for neutron irradiated austenitic stainless steels caused cracks1,2. Yttrium-Aluminum-Garnet (YAG) Laser technique is one of the candidate method for surface modification and repair welding of the irradiated stainless steels, because the cooling rate of YAG Laser technique is fairly fast, the helium bubbles could not grow enough in grain boundary during process. Therefore...