SPARK-PLASMA SINTERING VS. HIGH VOLTAGE ELECTRIC DISCHARGE CONSOLIDATION: COMPARATIVE ANALYSIS

摘要

Spark-Plasma Sintering (SPS) is a low-mode field assisted sintering technique, which consists essentially of conjoint application of fast heating rates, axial pressure and DC-pulsed low voltage - high current assisted sintering. High-Voltage Electric Discharge Consolidation (HVEDC) includes the axial pressure and discharge of the electrical energy stored in capacitors, thus enabling a nearly instantaneous, large potential difference across the powder specimen. The inter-particle neck temperature kinetics is comparatively assessed for the two considered technologies. It is shown that for both techniques there is an upper level for the local Joule heating of the inter-particle contacts beyond which the processing instability may occur. It is shown that an optimum current amplitude and pulse time are necessary to generate sufficient heat for producing strong inter-particle joining and to avoid local overheating phenomena. While for HVEDC the duration of a single pulse is a process controlling parameter, SPS apparently can be controlled by multiple pulse on and off frequency.