Analysis of Wettability Behavior of Brazing Filler Metal Using In–situ Observation and Microstructure

Abstract

Generally, brazing is completed when the brazing filler metal penetrates the gap by uniform wetting. It is believed that the joining process is completed with the formation of joint defects “voids” in the process of uniform wetting. However, previous studies have shown that what occurs when brazing is performed is non–uniform wetting. It is suggested that this non–uniform wetting is the cause of void generation.

Wetting and spreading of brazing filler metal is tested on a metal plate, as described in JIS Z 3191. The resulting angle between the molten brazing filler metal and the base metal surface is substituted into the “Young’s equation”. This is used to investigate the wetting of the brazing filler metal. However, this method does not cover the wetting of the molten brazing material as it moves into the gap.

From the results of the experiment, it was found that there are two types of wetting of molten brazing filler metal：“primary wetting” and “secondary wetting.”