Relationship between physical structure and machinability of green compacts

Abstract

The dependence of green machinability on compact density and strength was investigated for room temperature and warm compacted steel powder compacts containing two different types of lubricant. Brazilian disc compression tests were employed to determine green strength, while machinability was assessed in terms of response to drilling.

For the room temperature compacted materials, it was found that high compact densities and strength were not, in most cases, associated with improvements in machinability. Furthermore, it was shown that lubrication (both type and quantity) and compaction pressure plays a critical role in determining the level of breakouts observed. In contrast, the use of warm compaction, in conjunction with specially designed lubricants, has been shown to be a suitable method of producing high density, high strength compacts while retaining good green machining characteristics. Mechanisms responsible for the observed behaviours of both the room temperature and warm compacted specimens have been forwarded in the present paper.