Investigation of iron powder friction on tungsten carbide tool wall

In the powder shaping process, friction is often considered as one of the main limiting factors since it can be the cause of bad green density distributions as well as ejection defects. Therefore, knowledge of this is important for better controlling the compaction stage. This paper makes an attempt to bring out the different process parameters (density, normal stress, sliding velocity, temperature, and displacement) which influence the friction between a standard iron powder and a tool in tungsten carbide. With this view, a sliding piece device has been built and is described. Several tests have been performed; from the results emerge a decrease of the friction coefficient with increasing density or normal stress, conversely the velocity increases the friction while temperature has no significant role. In this work, particular attention is given to the amplitude of the displacement showing that it can highly affect friction and wear of green parts. An attempt is made at explaining the observed phenomena and results are correlated with an analytical expression. (C) 2001 loM Communications Ltd.