Method #1 is the most common. Method #2 is easiest, cheapest, most reliable and generally works best. Method #3 can give a little advantage but that is rarely needed in this kind of an application. For more information on Brazing Carbide browse the articles in our Brazing Services, or read our article on Brazing Tungsten Carbide.
1. Put the carbide in the notch with a little clearance. Then heat it and use a fluxed rod and let the alloy wick down into the gaps. This way you get a pretty good layer on each side depending on how carefully the parts are positioned. You get an extremely thin layer or no layer at all on the bottom. Minimal strength and very high susceptibility to heat stress cracking.
2. Lightly flux the sides and bottom of the notch. Put one or more pieces of fluxed brazing alloy wire under the tungsten carbide. Heart until the tungsten carbide settles in place. This gives a nice even layer of brazing alloy on all three sides of the part. This can be pretty well a self-centering operation. The secret is to use as little pressure as possible to hold the part in place while heating. Heat until you get nice, even, thin line of braze alloy around all the edges. This is probably the most efficient and most effective method of the three.
3. In the third method you use a trimetal or solid ribbon material and pre-place it. Then you heat until you see a nice, even, and small flow all the way around. This is the surest method and gives the most protection against cracking from thermal stress. It is also much more expensive than the other two methods in terms of material cost (generally about twice) and labor (generally three to five times.)