Effect of low-temperature cooling on corrosion properties of laser welding Hastelloy C-276/304 stainless steel with filler wire

To suppress the weld defects and improve corrosion resistance of laser welded joints, the low-temperature cooling was applied to assist laser welding Hastelloy C-276/304 stainless steel with filler wire. And the different low-temperature cooling (-5 degrees C, 5 degrees C, 20 degrees C) were selected for experimental research. Results show that adding low-temperature cooling can increase the cooling rate and solidification rate of weld. And the temperature gradient grows with the increase of solidification rate near the fusion line of weld. Consequently, the content of precipitated phase decreases from 1.75% to 0.71%, reducing by nearly 59.0%. The increase of temperature gradient can reduce the unmixed zone, which decreases from 22.1 mu m to 11.4 mu m, reducing by nearly 48.0%. At the same time the contents of corrosion-resistant elements and the proportion of grain boundaries with small angles increase in the laser weld with low-temperature cooling. As the cooling temperature drops, the effect of microstructure optimization of weld is enhanced. Finally, the corrosion properties of welded joints are obviously improved with the temperature decrease. The corrosion potential of welded joints increases by 24.3%. The corrosion current density of welded joints reduces by 54.3%. The intergranular corrosion sensitivity of welded joints reduces by 76.5%.