Adhesion in Powder Metallurgy

In powder metallurgy autohesive and adhesive processes are involved in extrusion and pressing techniques and in the production of finished articles from the original powdered material they also affect the free-running properties of powders. 

Evidently the small particles merge with each other, forming strong aggregates, and this also reduces the running of the powders. Since autohesive forces may be smaller in vacuum than in air ( 16), the best running properties occur for smaller particles under vacuum conditions. 

The volumetric flow of powder is also affected by the roughness of the surface, which in turn affects the adhesion. Thus the 

The running also depends on the autohesion of the powders, particularly on the electrical and molecular components. 

The forces of adhesion and autohesion may be reduced by hy-drophobization of the powder surface ( 10), thus increasing the free-running properties. Hydrophobization of the surface of sand may be effected by treatment with suspensions or solutions of wood pitch [447]. 

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