Investigation of Microstructure and Mechanical Properties of Super Alloy C-276 by Continuous Nd: YAG Laser Welding

Abstract

The present work investigates the microstructure and mechanical properties of the alloy C-276 by using continuous neodymium: yttrium aluminum garnet (Nd: YAG) laser welding process. Weldingtrials were carried out by varying the scan speed of the laser beam from 550mm/min to 1200mm/min. The scan speed of 550mm/min was found to give good weld quality with no lack of penetration, and was adopted for the work reported here. The laser power was kept constant at 2 KW. Optical microscope and Scanning Electron Microscope (SEM) were used to study the microstructural features of the weld joint. Energy Dispersive X-ray Spectrometry (EDS) analysis was carried out to study the extent of segregation in the weld joint. Tensile tests were carried out to determine the strength and ductility of weldment. The microstructure in the fusion zone is predominated by fine cellular structure. The higher hardness in the weld zone is believed to be resulting from the fine dendritic structure compared to the relatively coarse grain structure of base metal. Microsegregation in fusion zone was found to be within acceptable limits, but there was evidence for macrosegregation. The weld joints exhibited tensile strength matching well with that of base metal (760MPa) with good ductility (40%).