Electric-discharge sintering of oxidized metal powders

Conclusions

• 1. An investigation into the effect of various methods of application of electric energy and mechanical load on some characteristics of materials produced by electric sintering has shown that, at a given level of energy consumption, EDS ensures the most homogeneous structure, the highest density, and the best mechanical properties.

• 2. Use of an alternating current leads to more effective sintering of peripheral regions. The reason for this is that sintering with an ac component is accompanied by the evolution of a large quantity of heat in the surface zone as a result of the skin effect. This heat counterbalances the heat lost from peripheral zones, thereby ensuring a more even temperature distribution over the specimen cross section.

• 3. It has been established that the variation of porosity as a function of prepressing pressure has a non-monotonic character. In particular, for an electrolytic nickel powder with a particle size of < 50μ and an oxygen content of 0.06% this function passes through a minimum at a prepressing pressure of 16–20 kg/cm².

• 4. Experiments have shown that there exists a critical value of prepressing pressure above which uniform electric breakdown through interparticle gaps occurs in the whole volume of the compact.