Comparative study on laser brazing and furnace brazing of Inconel 718 alloys with silver based filler metal

Laser brazing and furnace brazing of Inconel 718 alloy with silver based filler metal are investigated in this study. Laser brazing was performed using a 400 W pulsed Nd: TAG laser with varying laser powers, speeds and pulse widths. A central composite design (CCD) including five levels of factors was employed to design the experiments. Furnace brazing was performed in vacuum pressure 5 x 10(-5) mbar at 710 degrees C. The cross sections of brazed joints were examined using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction analyzer (XRD). Microhardness and tensile test were performed for investigation of mechanical properties. The results indicate that laser brazed joints consist of alpha-Ag solid solution, alpha-Cu solid solution surrounded by the a-Ag solid solution and eutectic structure while the furnace brazed joints mainly consist of a-Ag solid solution and alpha-Cu solid solution. The furnace brazed joints show the average tensile strength of 348.5 MPa. However, maximum tensile strength of laser brazed joints was 338 MPa, which is approximately 3% lower than furnace brazed joints. The average microhardness for laser brazed joint was 150 HV compared to 120 HV for furnace brazed joint. This higher value of hardness can be attributed to existence of eutectic phase in laser brazed test pieces. (C) 2014 Elsevier Ltd. All rights reserved.