Investigation of iron powder friction on tungsten carbide tool wall

In the powder shaping process, friction is often considered as one of the m ain limiting factors since it can be the cause of bad green density distrib utions as well as ejection defects. Therefore, knowledge of this is importa nt for better controlling the compaction stage. This paper makes an attempt to bring out the different process parameters (density, normal stress, sli ding velocity, temperature, and displacement) which influence the friction between a standard iron powder and a tool in tungsten carbide. With this vi ew, a sliding piece device has been built and is described. Several tests h ave been performed; from the results emerge a decrease of the friction coef ficient with increasing density or normal stress, conversely the velocity i ncreases the friction while temperature has no significant role. In this wo rk, particular attention is given to the amplitude of the displacement show ing that it can highly affect friction and wear of green parts. An attempt is made at explaining the observed phenomena and results are correlated wit h an analytical expression. (C) 2001 loM Communications Ltd.