Plasma assisted parts' manufacturing: sintering and surface texturing - part II - influence of inter-cathode distance and gas pressure

Application of Direct Current Plasma Sintering Process in Powder Metallurgy

“…Here, the heating of the part to the sintering temperature is carried out by the fast plasma species bombardment, and the part to be sintered acts as one cathode of the formed hollow cathode discharge. This situation is illustrated in the bottom of Figure 4, in which cylindrical parts to be sintered act as the inner cathode of a typical annular hollow cathode discharge, as presented in references [17][18][19][20][21][22][23]. It is to be noted that, for this configuration, plasma is much more ionized than that obtained in cathode configuration.…”

“…In hollow cathode configuration, for a gas mixture composed of 80% Ar + 20% H 2 , the pressure range usually varies from 1 (133 Pa) to 9 (1200 Pa) Torr, considering pulse voltages on the order of 450 V [5,6,[17][18][19][20][21][22][23]. Here, the heating of the part to the sintering temperature is carried out by the fast plasma species bombardment, and the part to be sintered acts as one cathode of the formed hollow cathode discharge.…”

“…For the cathode configuration, the cylindrical external (hollow) cathode was simply removed, thus leading to a heating condition where only one cathode (the central one) was present in the discharge. For more details, the reader can access the references [17][18][19][20][21][22][23]. In all cases, temperature increment can be expected as the switched-on time of the power supply, and thus the mean power transferred to the plasma is increased.…”

“…Finally, at 0.6 Torr pressure and a = 9 mm, for example, by using a 720 V pulse voltage, for a specific switched-on time of 140 μs, and considering a square wave period of 200 μs (duty cycle of 70%, see Figure 7c), the cathode temperature is increased from about 500°C, at the cathode configuration heating (CCH) to 1100°C, at the hollow cathode discharge (HCD). Being the interest, the reader can access additional details about the HCD in references [17][18][19][20][21][22][23].…”

Effects of the Voltage and Pressure on the Carburizing of Martensitic Stainless Steel in Pulsed DC Glow Discharge

“…Such aspects associated with the inelastic collision processes 49 leading reactive species to be formed summarize how the reactive species density directly influence the physical-chemical interactions in the plasma-surface interface, thus on the thermochemical treatment result. In this case, it is worth mentioning different phenomena occurring such as the edge effect 19,20 , sputtering [42][43][44]50,51 , active species generation 52,53 , and the cathode (samples) heating, which in the practice is a function of the pulse switched-on time or duty cycle (t on ) 51 .…”