Feasibility of underwater laser forming of laminated metal composites

Abstract

Laminated metal composites are of great interest in various industries. Previous studies demonstrate undesired mechanical or microstructural changes in these composites during the laser forming process due to rapid temperature gradient. In this research, underwater laser forming is proposed to minimize this effect. This process could also be an effective method for on-site forming or repairing of large metal/composite sheets used in underwater applications, such as marine equipment, ships, and lake/sea-based offshore oil platforms. The underwater laser forming process is performed experimentally on a three-layered stainless steel/copper/stainless steel composite and compared with the results of in-air tests. Total forming time, bending rate, and microstructural changes are compared for both underwater and in-air conditions. The effects of forming parameters, such as the number of irradiations, laser beam velocity, diameter, and power, are also compared and discussed. It is shown that the bending angle per irradiation in underwater forming is significantly lower in comparison with in-air condition, but the production time is less due to the elimination of cooling time. Also, the microstructure of stainless steel at heat-affected zone was unchanged, and the hardness of upper layer experienced smaller changes when formed under water. The underwater laser forming process is demonstrated to be feasible and can be applied for underwater applications with a high degree of reliability.