Table 3.
Operating conditions described in early ECAS patents: (i) punch and die materials; (ii) applied pressure, voltage drop (between electrodes), current density, discharging time, sample diameter; (iii) chamber atmosphere and (iv) sintered materials.
| Inventor, nation year, reference | Processing condition and apparatus | Pressure, voltage, current, temperature, discharge time, diameter | Chamber atmosphere | Sintered materials |
|---|---|---|---|---|
| Bloxam, GB1906 [4, 5] | Pressureless sintering by current flow across the sample | 0, (ng), (ng), (ng), (ng), (ng) | Vacuum | Industrial scale production of W and Mo lamp filaments |
| Weintraub, US1913 [62] | Pressure and current sintering | (ng), 110 V, (ng), ≈2000, (ng), ≈2 cm | Vacuum | W, carbides and nitrides |
| Davis, GB1927 [63] | Die made of silica tube Punch made of steel (water cooled) | (ng), (ng), (ng), 1000 °C, <5 min, (ng) | Vacuum | Refractory materials |
| Sherwood, GB1931 [64] Sherwood, GB1933 [65] | Metallic punch and die Easily sintered parts Extraction by lubricants | 30/300 MPa, (ng), (ng), (ng), 30–120 s, (ng) | Inert/reducing atmosphere | Oilfree bearing material made of 89 wt% Cu, 10 wt% Sn and 1 wt% stearic acid |
| Taylor, GB1932 [6] Taylor, US1933 [7] | Die made of graphite or silica punch made of steel; | Assumed 100 MPa, (ng), (ng), 1000 °C; 1–2.5 s, ‘length greater than its diameter’ | Vacuum | 80–97 wt%; 3–20 wt% WC C |
| Hoyt US1932 [66] | Graphite die | 7 MPa, (ng), (ng), 1300–1450 °C, ‘about one to several minutes’, (ng) | Inert/reducing atmosphere | WC 87 wt% Co 13 wt%, from elemental W and C powders |
| Thomson Ltd, GB1935 [68] | Die made of graphite Plungers made of graphite or Mo | (ng), (ng), (ng), 1000 °C, <30 s, 2 cm | (ng) | Abrasive wheels with 10–20 wt% diamond, 3–20 wt% Co and WC |
| Kratky, US1937 [70] | Die made of graphite Punch made of W | Impact loading, 4 V, 800 A, (ng), few minutes, (ng) | Vacuum | Hard bodies especially WC cermets, HSS |
| Willey, US1937 [144] Willey, US1938 [145] | Spot welding machine Die made of graphite Punch made of Mo | 70 MPa, (ng), (ng), (ng), >4 min, (ng) | Air | Diamond-embedded abrading tool, WC and Ni or Co |
| Engle, US1940 [71] | Hybrid heating from inside/outside Homogenous temp. distribution Punch and die made of graphite | (ng), 3–12 V, >3000 A, (ng), >1350 °C, 7.5 cm | Controllable | Cermets |
| Cremer, US1944 [87] | Electrically insulated die Metallic punch | 150–350 MPa, 5–20 V, repetition of 20 kA (pulsed), 1/30 s, 0.7 cm | Air | Cu, Au, Al and other metals, densification time <1/30 s |
| Ross, US1945 [72] | Automatic sintering machine Mica insulating die Metallic punch | Impulsive loading >500 MPa, (ng), (ng), (ng), (ng), (ng) | Air | Steel, cermets |
(ng), not given in the patent.