1990 Volume 8 Issue 4 Pages 445-450
Essentially, it is impossible to braze graphite with copper filler metal because no wetting occurs. However, when the graphite is combined with iron in copper brazing, the iron base metal dissolves in molten copper. Simultaneously, the dissolved iron is deposited as columnar Fe/9-6%Cu/1.4-1, 6%C alloy phase from the graphite base material interface at a ocnstant brazing temperature-that is, the "dissolution and deposit of base metal" takes place.
By placing the iron foil insert between both graphite base materials, therefore, the columnar phase is deposited from both graphite boundaries toward the foil during heating. As a result, both graphite base materials are united by the columnar phase through the iron foil insert. In the same way, the graphite-to-molybdenum or -tungsten joint can he produced.
The shear strength of the graphite-to-graphite joint at 298K was about 32MPa. Further, in the 4-point bending tests at elevated temperature, the flexural strength of the graphite-to-graphite joint was 35-40MPa over temperature ranges from 298 to 873K.