Effect of ultrasound oscillations on the consolidation of iron powder in hot pressing

Abstract

1. A comparative investigation of the conditions of vacuum sintering of iron powder according to the method of hot pressing with and without simultaneous ultrasound action was performed. 2. It has been shown that ultrasound oscillations cause intensive shrinkage during the first five to ten minutes of sintering, after which the shrinkage increases at a lower rate. Thus, the ultrasound accelerates the transition from unsteady to steady-state flow of the powder and increases its “activity.” Local heating of a powder exposed to the ultrasound leads, in the final analysis, to a reduction in the hot pressing temperature by 15–20%. No direct effect of ultrasound oscillations on the steady-state powder flow velocity was observed. 3. The cyclic hardness was measured, and the ratio of the cyclic hardness to the Brinell hardness was determined. Our data indicate that, in sintering iron powder with simultaneous exposure to the ultrasound, the cold working is somewhat reduced, and the endurance ratio values change to a slight extent.