Manipulation of Strength During Sintering as a Basis for Obtaining Rapid Densification without Distortion

Abstract

Sintering to full density enables powder metallurgy products to compete with castings and forgings. Subsieve powders with high inherent sinterability provide one means to attain densification, but at a substantial cost penalty when compared with readily available coarse compaction grade powders. Unfortunately, for large powders the sintering stress that causes densification is small and often insufficient to overcome the inherent compact strength that resists rapid densification. In such cases, only slow diffusion-controlled densification occurs. The current analysis identifies an option for sintering densification of large particles based on a comparison of the sintering stress and component strength during heating. Rapid densification occurs when the in situ strength is reduced to levels comparable to the sintering stress. On this basis, alloy systems are identified for full density sintering using thermal softening concepts.