Tandem laser brazing of heat-resistant alloys using precious filler metals

Abstract

The diode laser brazing of heat-resistant alloys with precious filler metals has been conducted using the tandem beam which consisted of preheating beam and main brazing beam. The 1mm thick plates of Inconel 600 and A286 alloys were butt-brazed using the 0.5mm diameter Au-18%Ni, Ag-10%Pd and Ag-21%Cu-25%Pd filler metals with a brazing flux. The processing parameters of the tandem laser powers and the brazing clearance were varied. The sound butt joints could be obtained by using the tandem beam with the laser powers of 400-500W/100-150W even at the narrow gap brazing below 0.2mm wide where the melted filler metal did not infiltrate completely into the joint gap by only using the main brazing beam (single beam brazing). Fracture strength of braze joint using Ag-Pd filler metal increased with decreasing the brazing clearance and attained about 70% of the base metal strength at the brazing clearance of 0.1mm, while those using Au-Ni and Ag-Cu-Pd filler metals were comparable to the base metal strength at any brazing clearance between 0.1-1.5mm. The preheating effect during the tandem beam brazing resulted in the superior brazability in the situation from the narrow gap to the wide gap brazing because of the improvement in wettability, spreadability of melted filler metal and the erosion resistance of base metal by depressing the extremely rapid cooling rate and steep temperature distribution in the base metal.The diode laser brazing of heat-resistant alloys with precious filler metals has been conducted using the tandem beam which consisted of preheating beam and main brazing beam. The 1mm thick plates of Inconel 600 and A286 alloys were butt-brazed using the 0.5mm diameter Au-18%Ni, Ag-10%Pd and Ag-21%Cu-25%Pd filler metals with a brazing flux. The processing parameters of the tandem laser powers and the brazing clearance were varied. The sound butt joints could be obtained by using the tandem beam with the laser powers of 400-500W/100-150W even at the narrow gap brazing below 0.2mm wide where the melted filler metal did not infiltrate completely into the joint gap by only using the main brazing beam (single beam brazing). Fracture strength of braze joint using Ag-Pd filler metal increased with decreasing the brazing clearance and attained about 70% of the base metal strength at the brazing clearance of 0.1mm, while those using Au-Ni and Ag-Cu-Pd filler metals were comparable to the base metal strength at any...