THE CHEMICAL TRANSPORT MECHANISM OF EMITTER MICRO-PARTICLES PARTICLES IN TUNGSTEN ELECTRODES- A METALLURGICAL STUDY

Abstract

A metallurgical study has been conducted on the erosion mechanism of pure tungsten electrodes and 1.5% La2O3 doped tungsten electrodes, used in Tungsten Inert Gas (TIG) welding. The behavior of micro-emitter particles in Lanthana doped electrodes has been studied from the points of view of in-process electrode consumption, topographical changes on electrode, the formed phases evaluation and electrode temperature profile estimation by using various materials characterization techniques. The results show various characteristics zones on the surface of tungsten electrode tip, which signifies the difference in the migration and evaporation of lanthana emitter particles. Due to difference in working temperature inside the electrode, variation in grain growth occurred in both type of electrodes. Also, it has been observed that the Lanthana doped electrode durability decreases with time due to consumption of emitter particles and temperature dependant grain coarsening of tungsten matrix.