Experimental investigation and numerical modeling of plasma and laser microwelding processes

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In the growing technological field like micro-electro-mechanical systems (MEMS) and biomedical devices, the microwelding has potential application as encapsulation of miniature components. This thesis work is primarily motivated to develop plasma microwelding system for butt joining of different materials. At first the major efforts are put forward to experimentally investigate the thermo-mechanical and microstructural behavior for joining of titanium alloy, stainless steel and low carbon steel. A comparative study between plasma and laser microwelding on titanium alloy put forward about the fundamental advantages over the processes. Using controlled and regulated arc current, the micro plasma arc welding process is specifically designed where the weld quality is assessed by carefully controlling the process parameters and by reducing the formation of oxides. A process window in terms of welding current and speed is evaluated to predict the defect-free microwelded joint. The plasma current range of 8 – 13 A produces high quality welded joints for all the selected materials. The weld joint quality is affected by specifically designed fixture that controls the oxidation of the joint and introduces high cooling rate. In laser microwelding of titanium alloy, high peak power is actually dampen by pulsation of Nd:YAG laser cratered to use in microwelding process. The feasible range of process parameters like laser scanning speed of 3-7 mm/s and peak power of 1-5 kW produces high quality weld joint.
Supervisor: Swarup Bag