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3855 |
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Friday, May 23, 2014, Hall H3 9:00 AM New Processes |
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Atmospheric plasmadynamic system in thermal spraying |
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Yuri Chivel* / MerPhotonics, France |
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Progress in the area of particle velocities 2 km/s or more in thermal spraying requires the use of new methods of acceleration them as modern devices using chemical energy exhausted themselves. Electromagnetic plasmadynamic systems are one of the most promising systems for a number of applications: thermal spraying, surface modifications. On the surface these systems provide the same action parameters (i.e., power density, exposure time) as technological lasers, but they have advantages - large action spots, up to ten square centimeters and combined thermal and shock action. These systems are able to accelerate micron particles to speeds of 2 km/s or more. A new two-stage electromagnetic plasmadynamic system with the first stage in the form of a three DC plasma torch with power 7 kW and plasma flow temperature ~ 8000 at atmospheric pressure, and with the second stage in a form of a coaxial plasma accelerator has been devised. At the exit of the accelerator, a large-diameter underexpanded plasma flow is formed which is characterized by high velocity as great as 3 5 103 m/s with the diameter of plasma flow up to 2 -3 cm . As working gas of DC torch nitrogen or air is used with a small amount of argon. The plasma flows with duration 200-300 µs and plasma temperature recorded by the method of relative intensities of the spectral lines of Ar ranges up to 1,5 103K were obtained. Frequencies up to 1-4 Hz were realized at energy of pulsed flow 6 - 24 kJ. The results of the use of this source for the acceleration of particles (10-30 ¼m) and coating as well as for surface hardening of tooling are presented and discussed. 4. Thermal Spray process 4.2 New Process |