1986 Volume 4 Issue 1 Pages 187-192
The notch toughness of brazed joints with a gold-18%nickel alloy and an amorphous nickel-base filler metal was investigated. The base metals used were SUS304 stainless steel, SUS420J2 stainless steel, Inconel X-750 nickel-base superalloy and MAS-1 maraging steel. The specimen for the notch toughness test was a rectangular butt-brazed type which finished the standard 2 mm V-notch Charpy specimen after brazing. These specimens were tested at temperature ranging from -196°C to 600°C.
In the 304 stainless steel joint brazed with gold-18% nickel filler metal, the absorbed energy of the joint was low at temperature below room temperature because the strength of the base metal was considerably higher than that of the filler metal.
In the both 304 and 420J2 stainless steel joints brazed with nickel-base filler metal, a brittle eutectic liquated grain boundary formed at and near brazed zone due to the boundary diffusion of boron. The toughness of these joints was reasonably low.
Notch toughness of Inconel X-750 joint brazed with gold-18% nickel filler metal was extremely low over the whole temperature range from -196°C to 600°C. This was the reason why the strength of Inconel X-750 superalloy scarcely decreased up to the temperature of 800°C, compared to appreciably decrease in that of gold-18% nickel alloy. On the other hand, in the joint brazed with nickel-base filler metal for longer than 10 min, the brazed region revealed a homogeneous structure resulting from an isothermal solidification. Therefore, the joint indicated the fairly high toughness.