THE EFFECT OF COPPER POWDER SIZE AND MORPHOLOGY ON PROEUTECTOID CEMENTITE NETWORK FORMATION IN PM VALVE SEAT INSERT

摘要

The Valve Seat Insert (VSI) is one of the most important automotive parts that are manufactured by Powder Metallurgy process. Based on CN10CU standard (Powder Selection), carbon content is higher than eutectoid and therefore increases the possibility of cementite network formation on grain boundaries. This network is undesirable and decreases the mechanical properties like radial crushing strength, ultimate tensile strength, elasticity and impact resistance. Reasons for cementite network formation in sintered parts are very complicated. In this research, the effects of main factors such as base materials and sintering parameters on cementite network formation are studied. Due to the large amount of copper (8-12%) and its effect on sintering mechanism, this investigation is implemented using both electrolytic and atomized copper powder.