Investigation of the Influence of the Method of Application of Lubricating Coatings on the Process of Compaction of Porous Sintered Blanks in Dynamic Hot Pressing

Abstract

We reveal the differences between the structures of a graphite coating obtained by the traditional technology of lubrication of sintered blanks with a solution of colloidal graphite and a coating produced by applying the proposed vibration treatment. It is shown that, as a result of treatment of this kind, particles of the coating change their globular shape into flat or flaky. The area of contact of particles of the coating with the surface of the blank increases, and the coating is activated. The chaotic arrangement of particles is replaced by their preferential orientation in the direction of plastic deformation caused by the formation of the coating and the boundaries between the particles composing the coating partially disappear. Moreover, the integrity of continuity and the uniformity of its structure become more pronounced. We detected both the amplification of the influence of graphite coating obtained by the vibration treatment of sintered blanks as compared with their immersion in a graphite emulsion and decrease in the total and surface porosities for the identical energy losses. It is shown that the vibration treatment of blanks for 10–20 min leading to the formation of graphite coatings enables one to increase the mean density of the products from 94–97% to a practically porousless state. The optimal time of vibration treatment of blanks with deposition of graphite is 20–40 min.