An aft frame assembly for a gas turbine transition piece has a main body with an upstream facing surface, a downstream facing surface, a radially outer facing surface and a radially inner facing surface. A plurality of feed hole inlets are located on the upstream facing surface. Each of the feed hole inlets are coupled to one of a plurality of cooling channels passing through the main body towards the radially inner facing surface. A plurality of microchannels are formed near the radially inner facing surface and extend at least partially along the downstream facing surface. The cooling channels are connected to and terminate in the microchannels. A pre-sintered preform is located on the radially inner facing surface of the main body.