Gas/Solid Interactions In The Evolution Of Graded Microstructures In Hardmetals

摘要

Five industrial hardmetal alloys were investigated by various analytical methods (DTA, DIL, EGA and CGHE). They show different melting, shrinkage and outgassing behaviour with respect to the fcc/WC ratio and N content dependent on the atmosphere. High N_2 pressure may cause a decrease of the liquidus point temperature due to eutectic reactions including carbon. Shrinkage behaviour can be divided into two types, which can be controlled by the N_2 pressure. Maximum CO evolution occurs at a temperature where nearly no N_2 is evolving. This is confirmed by N content measurements of samples from interrupted heating cycles. From these measurements optimisation of sintering parameters could be achieved.