Investigation on the Effect of Pulsed Frequency on Microstructure and Hardness of Alloy C-2000 by Current Pulsing 2020-28-0420
The objective of the study is to investigate the effect of current pulsation frequency on the weld bead microstructure, segregation, and hardness of Hastelloy C-2000 weldments. Bead on Plate (BoP) welds was made by using the Pulsed Current Gas Tungsten Arc Welding method (PCGTAW) at eleven different frequencies. The weld bead width and depth of penetration was measured with the help of Dinolite macro analyzer. The microstructure of weldments is further examined through an optical microscope and Scanning Electron Microscopy (SEM) to identify the type of grain, grain coarsening and extent of the Heat Affected Zone (HAZ). The grain structure turns into finer and equiaxed in all cases and there was an optimum frequency range over which the significant grain refinement was observed. Microsegregation of alloying elements was computed with the aid of Energy Dispersive X-ray Spectroscopy (EDS). Vickers Hardness Tester was used to measure the hardness of the weld samples at ambient conditions. The same optimum frequency range matched with maxima in hardness. The excellent blend of metallurgical characteristics and hardness was realized for the weldments fabricated with 20Hz pulse frequency.