From what I've read, at least in computer applications, the heat pipes used have sintered metal bonded to the inside and they use it since it's very cost effective. But I'm no expert in this area and I'm curious to know what other methods are used in other applications that @freedom_in_4low may know more about.
I've always understood sintered parts to be pressed into a mold and then heated up to bond the particles in place. The parts always have a distinct look that is very smooth but porous. The bubble stones in aquariums are typically sintered as are lots of fuel filters. I got confused by the just dumping in of the metal powder around a mandrel.