Characterization of pre-alloyed tin bronze powder prepared by recycling machining chips using jet milling

Abstract

In this study jet milling has been used as a novel method to recycle bronze machining chips into bronze powder suitable for making powder metallurgy components. This method has been compared with ball milling process to make an assessment of its efficiency as a recycling route. The size reduction rate, morphological, physical and mechanical properties of the bronze powders produced was investigated. It was found that, jet milling was a much less time consuming method compared to ball milling to pulverize bronze machining chips. The oxygen content of the ball milled product was increased during ball milling and reached 0.58% after 24h while, the Jet milled powder was approximately free of oxides. In addition, jet milling produced powders with irregular shape and low work hardening compared to ball milled powders and hence better green properties for the former were observed. Although, for the ball milled powders only at 700MPa compacts with adequate handling properties could be made, it was possible to make sound compacts of the jet milled powders at all the compacting pressures used and green density of 6.5–8g/cm3 was achieved by increasing the compaction pressure from 200 to 700MPa.