Abstract
The manufacturing and performance of ceramic/metal matrix composite (cermet) electrical discharge machining (EDM) electrodes have been investigated. The processing techniques necessary for creating TiB2/Cu, TaC/Cu, TaC/Cu(s), TaC/CuNi, TaC/Al, NbC/Cu, and TiC/CuNi electrodes were developed. The electrodes (anodes) were eroded in an EDM machine using a stainless steel workpiece (cathode) and the performance variables-wear ratio, sink rate, and surface finish-were tracked. TiB2/CU was shown to be a superior EDM electrode to copper, graphite, and W/Cu, and slightly better than Serb/CU- Three methods of enhancing wetting of the metal to the porous ceramic were successfully attempted: (1) the use of alloying elements in the metal infiltrate such as boron or nickel, (2) the use of a 6% hydrogen in argon environment, and (3) the use of an oxygen getter furnace. Using one or a combination of the above three methods allowed for infiltration of ceramics that were previously impossible to infiltrate. Both a high thermal conductivity and a high melting point of the ceramic have been shown necessary for low wear ratios. Cermet electrodes composed of a ceramic such as TiB2, which has a high melting point and low thermal conductivity, did not perform as well as TaC, which has a lower melting point and a higher thermal conductivity. The sink rate of an EDM electrode is dependent upon the radiative properties of the surface of the electrode. The radiative properties were found to be dependent upon both the ceramic and metal infiltrate. TaC, which was previously impossible to infiltrate under non-vacuum environments without cracking was successfully infiltrated. Adding boron to copper resulted in a slight decline in the performance of the electrodes. Voids within the microstructure decreased the performance of the electrodes to a lesser degree than did alloying elements such as boron. An electron microprobe (EM) was used to study the electrodes after EDM. Dot maps, and EDS were used to aid in understanding the erosion mechanisms of the cermet electrodes.
Kim, Eugene Ty (1998). Manufacturing and performance of ceramic/metal matrix composite electrical discharge machining electrodes. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1998 -THESIS -K563.