Operating performance of steel punch electrodes for electric discharge sintering

Conclusions

• 1. It has been established that a punch electrode contact surface of Class 4–5 finish provided with a coating with a coverage of 60% adheres to metal powders during their electric discharge sintering.

• 2. It is shown that titanium carbide and chromium carbide diffusion coatings on 3Kh2V8F steel reduce the extent of interaction between punch electrodes and copper, aluminum, and titanium powders during their EDS compared with coatings applied by the electric spark and detonation processes. In addition, diffusion coatings adhere most strongly to a steel substrate.

• 3. The interaction is influenced to a large extent by the nature of the metal powder. Of the three powders investigated, Ti, Al, and Cu, titanium powder reacts most strongly, and copper least strongly, with punch electrodes.

• 4. In contact with copper powder the best performance is given by a titanium carbide coating. In the EDS of aluminum powder under a prepressing pressure of less than 2 tons/cm² local passage of electric current is observed leading to welding between the punch electrodes and the sintered specimen; consequently, in the sintering of aluminum powder with punch electrodes coated with chromium carbide and titanium carbide prepressing pressures of not less than 2 tons/cm² should be employed. TIC coatings are unsuitable for operation in contact with titanium powder.