Thomas F. Murphy

Improving performance from self-lubricating bronze bearings

In a world where downward pressure on price means much increased pressure on manufacturers, improved performance can be seen as a unique selling point…

The hard facts of carbon and casings

High-performance gearing presents opportunities for case carburising PM components, but successful improvement rests on a proper understanding and interpretation of the microstructure of the carburised area…

A Metallographic Study on the Diffusion Behavior and Microstructural Transformations in Silicon-Containing Powder Metallurgy Steels

The choice of alloying method for ferrous powder metallurgy alloys is often dictated by the oxidation potential of the alloying elements used in powder and compact manufacture. Silicon is effective in improving properties of ferrous PM steels; however, if added to the melt prior to atomization, the likelihood of oxidation is high. Alternatively, Si-rich and more complex particulates can be combined with the base powder, i.e., iron or low-alloy steel, with alloying occurring by solid-state diffusion during sintering. The effectiveness of these additives to improve material properties is dependent on their distribution throughout the material volume, as determined by diffusion of each added element. In this study, the distribution of silicon was quantified using energy-dispersive spectroscopy on an iron-based alloy composition. These data were compared with the volume fraction of the various transformation products in cross sections of hardenability samples using both light and electron microscopy. Predictions on the effects of local chemical composition, cooling rate, and microstructure are made.

Toughening PM gear parts for arduous roles

A study by a major US metal powder manufacturer shows that while surface-densified PM parts can be considered for high attrition areas of automotive engineering such as gearboxes, microstructure is critical to success…