Laser welding of dissimilar alloys

Optimized design of a device, which is used to generate very low temperature in an enclosed mass of helium, requires several joints between stainless steel 304-Pemendur-49 and SS 304-Kovar combinations. All the joints have different thickness and have to qualify mechanical-, He leak- and acceleration tests. A pulsed Nd –YAG laser has been used to experimentally optimize the laser welding parameters on constituent alloys prior to welding of the device. Important results of the parametric study including microstructures and tensile strengths of the welds of above combinations have been presented and discussed from the application point of view. A glass component adjacent to one of the joints has been cracking during welding of a module. An abridged analysis of the problem and the solution developed and adopted to circumvent the same has also been included.