Effect of oxygen on the wettability of 304L stainless steel by liquid Ag–Cu eutectic alloy

In order to suggest brazing conditions of 304L stainless steel with Ag–Cu eutectic alloy containing oxygen, a wetting test and sandwich brazing test were performed. During the wetting tests, the contact angle slightly decreased with increasing temperature. In addition, as the oxygen content in the Ag–Cu alloy was controlled between 0.0212 and 0.0415 wt%, the contact angle became as low as about 70°–75° at 1093 K. From the sandwich brazing tests, with the oxygen-free Ag–Cu alloy, a number of macroscopic scale defects were observed, whereas the Ag–Cu alloy containing 0.0415 wt% oxygen showed a sound interface with the base metal. This may be caused by the removal or modification of the Cr₂O₃ oxide layer on the stainless steel surface by soluble oxygen and copper. The current experiments suggest that stainless steel brazing is possible with the Ag–Cu eutectic alloy by controlling the oxygen content without high vacuum application.