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Resistance spot welding (RSW) is widely used in the microwave tube industry. There are many parameters employed in the welding processing: weld current, weld time, electrode force, hold time, squeeze time, electrode material, electrode geometry, electric polarity, surface roughness, cover gas, et al. In this study, an attempt is 2 -1 2 R x t made to improve the RSW quality of 5OMo-5ORe refractory foils and to understand the typical characteristics of RSW 5OMo-5ORe.alloys used in high power cathode E|ecrode Force assembly applications...|._____-...._.. WeldC060Ĩ ntroduction 5OMo-5ORe sheets synthesized by powder metallurgy U Tm methods were welded using a Unitek Model DC25 linear 14ue"1iietn4 -Hl" 4 #.DC resistance welder. Different combinations of welding parameters were used. The welding quality was evaluated using tensile-shear tests on a Instron Series IX Testing Figure 1. Principles of Resistance Welding System with a 0.2 mm/min tension rate at room temperature. The characteristics of the welds were examined by optical microscopy and SEM. The peak load of tensile-shear test was obtained from the average value of several samples. Figure 1 illustrates the principles of resistance spot welding. Figure 2 illustrates the effect of electrode geometry on the weld. The grain structure in the affected weld region was typically columnar in shape with significant porosity observed. Some electrode geometries resulted in multiple contact points and uneven current | distribution. Segregation of Mo and Re was observed in _ some welds, Figure's 3 and 4. The effect of hold time did M have an effect on the microstructure of the weld area and the strength of the weld, Figure's 5 and 6. Further work is under way in an attempt to improve the Asymmetrical Current Density Symmetrical Current Densitywelding quality of the 5OMo-5ORe alloy foils. This may lead to design options if it proves feasible to replace some braze joints with optimized RSW joints. Figure 2. Effect of Electrode Geometry