The gas velocity by the fluid dynamic method (shown in Fig.6 and the expression 2), the temperature distribution (shown in Fig. 14) and the mixing rate of air (as measured by the Orsat apparatus) (shown in Fig. 11) into the jet along the jet axis at various distances from the nozzle under the ordinary operating conditions for spraying process are experimented and some considerations of the results are made. Moreover, the flying velocities of the spraying powders (Al
2O
3, Mo and Nickelbase alloy) in the jet are measured by using the turning disc (shown in Fig. 1).
The results can be summarized as follows.
Under the conditions of the flow rate of operating gas 30l/min and the operating currents 450 and 550 A.
(1) At the 50 mm' distance from the nozzle
(i) Flying velocity of spraying powder
Al
2O
3: 150-160 m/sec
Mo: 100-105 m/sec
Nickel-base alloy: 70 m/sec
(ii) Gas velocity: 120-140 m/sec
(iii) Temperature
under current 550 A: 2, 200°C
under current 450 A: 1.700°C
(iv) Mixing rate of air: 55-65%
(2) At the 100 mm' distance from the nozzle
(i) Flying velocity of spraying powder
A1
2O
3: 140-150 m/sec
Mo: 95-100 m/sec
Nickel-base alloy: 60-70 m/sec
(ii) Gas velocity: 40-50 m/sec
(iii) Temperature (under current 450, 550 A): 800-900°C
(iv) Mixing rate of air: about 90%
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