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, and in the change of spraying distance. A more intensive interaction between spraying particles and gases of plasma jet and environment is revealed. Typical structure features of mechanically alloyed composite particles as well as their behaviour during the spraying process allow to deposite coatings with higher quality which can not be achieved for sprayed coatings of the same composition by ordinary methods.
