Volkswagen Ag

Leybold Durferrit Gmbh

Kyong-Tschong Rie

Albrecht Melber

Frank Schnatbaum

G&uuml;nter Laudien

Swen Biemer

Emilio Rodriguez Cabeo

A method and arrangement for producing a boride layer on a surface by plasma boronizing includes supplying a gas mixture containing a boron-releasing gas to a reactor and generating a glow discharge in the reactor using a pulsed DC voltage. The parameters of the production of the plasma produced by the glow discharge in a treatment chamber of the reactor are selected so that an increased quantity of excited boron particles is generated in the plasma to produce non-porous boride layers, for example, for boride coating of components which need a surface that is highly resistant to wear, for example, gears, camshafts and the like. Parameters with which the production of the boride layer can be controlled are, for example, voltage, pulse-duty factor, frequency, temperature, treatment chamber pressure during the production of the plasma, and the content of boron-releasing gas and of the remaining components in the gas mixture which is fed to the reactor.

Method and arrangement for plasma boronizing

Workpieces of steel are hardened by carburizing the surface and then quenching. The carburizing is performed by means of a plasma discharge in a vacuum, in the presence of gaseous hydrocarbons at voltages between 200 and 2000 volts, preferably between 300 and 1000 volts, and preferably with the admixture of argon. The plasma is produced by means of electrodes operated in a vacuum, the cathode of which serves as workpiece holder and is operated by pulsed operation. In order to achieve a uniform hardness distribution and to reduce the mass flow of carbon, even in the case of irregularly shaped workpieces, the carburization is performed at a total pressure between 14 and 30 mbar, the pulse duration is selected between 110 and 10,000 .mu.sec, and the pause duration is selected between 30 and 10,000 .mu.sec. After the start-up phase has ended, the average power fed to the plasma discharge is reduced either continuously or step-wise by shortening the pulse duration and/or by prolonging the pulse duration, such that, without interruption of the pulsed operation, the carbon content at the surface of the workpiece will at no time exceed the carbon saturation limit of the steel in the austenite region.

Process for hardening workpieces in a pulsed plasma discharge

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Braunschweig, Germany

Kyong-Tschong Rie