PECULARITIES OF COMPOSITE POWDERS PLASMA SPRAYING PREPARED BY MECHANICAL ALLOYING

Résumé
Cet article présente les avantages du "mélange mécanique" par rapport aux autres méthodes de préparation des poudres de matériau composites destinées à la projection plasma. Des composites constituées de NiCr-ZrO₂, NiCr-Cr₂C₃, W-Cu sont présentés comme exemple.

Abstract
In the present paper the main advantages of mechanical alloying compared to the other methods of composite powders preparing are discussed from the point of view both of powder quality and structure and properties of sprayed coatings. As an example on the base of NiCr-ZrO₂-, NiCr-Cr₂C₃-, W-Cu- compositions it is shown, that prepared powders are characterized by high particles composition homogeneity, fine disperse components distribution in particles volume, high values of bound strength and components contact area, high flowability, particles shape, grain size distribution etc. It is established that compared to any composite powder the powders prepared by mechanical alloying are characterized by a sufficient amount of accumulated energy caused by intensive particles peening, high internal stresses, and disperse strengthening effect. During the spraying process the accumulated energy is educed providing reliable composite particles melting not only in the axis plasma jet region but on the periphery too. It results in the increase of material use coefficient in plasma spraying, in the change of spraying distance, in a coatings quality improvement.