NITRURATION OR CARBONITRURATION THERMOCHEMICAL TREATMENTS WITH PIECES IMMERSED IN HIGH POWERED PULSED PLASMAS

The description of the present device which is presented in this document is the continuity of previous developments made in the plasma-assisted thermochemical treatments field, referenced in the following patent applications: MX/a/2011/011993, PA/a/2003/009970, MX/a/2015/001058 and MX/a/2016/000586. In the case of the last reference, a device and a procedure for performing thermochemical nitrutation treatments on steel parts is presented; unlike the cited cases, a resource for the plasma formation is also presented; based on the immersion of the pieces to be treated in a medium with active species generated in the plasma. For the development described in the document, the parts to be treated can be taken out of the plasma generation process, being immersed in the active species region generated in the plasma. For the plasma production, high-power sources are used that ponder their intensity with pulses in the micro-seconds domain, avoiding the formation of electric arcs in the medium. As in the patent application presented in document MX/a/2016/000586, the plasma is diagnosed by means of optical emission spectroscopy. Based on the identification of electronic transitions of active and emissive species in plasmas for thermochemical treatment, luminous emissions for special and specific wavelengths are identified, the wavelengths are used as a reference or setpoint to establish the supply of mass flows of gas mixtures in the process, the resource uses information generated in the emission spectrum of the second positive system of the nitrogen molecule. The pressure in the chamber can be affected by the supply of gas mixtures, the same can also be affected by means of a curtain valve located between the vacuum chamber and a pumping group, affecting the conductance of the system. Referring in this document to the device described in the patent application MX/a/2015/001058, corresponds to a cubic chamber of 1.8 m in edge size, in the chamber, the pieces are housed for the thermochemical treatment assisted by a weakly ionized plasma. Unlike previous developments, sources that produce intense pulses in the micro seconds domain are used for plasma formation, then the pulses can be reversed or they can be canceled for periods of milliseconds. During the treatment there is independence between the production of active species and temperature; this feature imposes a means to heat the pieces. Electrical resistances are used in the chamber to establish the temperature