Development of Laser Welding Process for Reduced Activation Ferritic Martensitic Steel for Indian Test Blanket Module

Laser and laser hybrid welding are among the processes chosen for joining Indian reduced activation ferritic martensitic (INRAFM) steel that will be used for fabrication of Indian test blanket modules (TBMs) to be tested in ITER. In the present study, a 3.5 kW slab CO₂ laser in autogenous mode and hybridized mode with MIG were successfully employed to make butt joints in plates 6 mm and 12 mm thick respectively. Initially, bead-on-plate (BOP) experiments were conducted to study the effect of various laser and laser hybrid welding parameters such as laser power, welding speed, MIG torch angle, wire feed rate, composition of torch gas, gas shielding arrangement, stand off, distance between arc and laser, and focal position of the laser with respect to the surface. The resultant weld beads were evaluated for weld penetration, width of the weld, and width of the HAZ. Based on BOP welding studies, parameters were chosen for carrying out butt welding experiments using square butt for 6 mm plates and Y-groove edged configurations for 12 mm thick plates with various root face heights and included angles. The radiography results showed that all the welds were acceptable as per ASME Section III. The welds were also evaluated using hardness tests, metallographic analysis, and tensile, bend, and impact tests.