Frank Palmer and George Luerssen conducted similar research in about six decades ago. They were looking at time requirements rather than energy requirements, but their data might be helpful. They studied the effect of initial furnace temp, surface finish, size, shape, furnace atmosphere, and...
A copper & zinc alloy called "spelter" was often used by blacksmiths of that era for brazing operations on thin sections. Alex Bealer describes the use of spelter to repair saws and shovels in rual Alabama as late as the 1940's & 50's.
Searching for the Path of Least Resistance
