Effects of Different Shielding Gases and Power Waveforms on Penetration Characteristics and Porosity Formation in Laser Welding of Inconel 690 Alloy
A high power Nd-YAG laser was used to perform bead-on-plate (BOP) welding on high viscosity Inconel 690 alloy plates of 3 mm in thickness with three different shielding gases (Ar, He, and N<SUB>2</SUB>). Adopting a rectangular laser power waveform, four different peak-base power differentials (Δ<I>P</I>) were applied with a constant average power of 1.5 kW. A comprehensive investigation was performed into the influences of the shielding gas, the flow rate, and the value of Δ<I>P</I> on the characteristics of the resulting welds, including the weld morphology, the penetration depth, the plume volume, and the porosity formation. The results showed that the weld penetration depth, the depth-to-width ratio, the weld surface roughness and the degree of weld spattering all increased with increasing Δ<I>P</I>. The choice of shielding gas had a significant effect on the porosity ratio (<I>P</I><SUB>r</SUB>) of the weld. The weld formed under Ar shielding had the highest <I>P</I><SUB>r</SUB>, while that formed under N<SUB>2</SUB> shielding had the lowest. Under He shielding, the gas flow rate had a significant effect on the porosity ratio. However, under the higher density gases of Ar and N<SUB>2</SUB>, the porosity appeared to be insensitive to the flow rate. Finally, an increased Δ<I>P</I> yielded a significant reduction in <I>P</I><SUB>r</SUB> for the welds with higher porosity.
- Materials transactions
Materials transactions 48(2), 219-226, 2007-02-01
The Japan Institute of Metals and Materials