Elaboration de gradients de composition continue dans des taillants PDC

International audienceCemented carbides are composites which possess an excellent compromise between hardness and toughness. For years, to improve one property without decreasing the other one, the concept of graduated structure was widely studied. In this work, we present a process to create one-step continuous gradients of several millimetres within WCCo cermet, by the imbibition method. This process was applied on commercial drilling bit. The effects of this thermal processing are analysed in term of microhardness, cobalt concentration and grains size. The results obtained on PDC drill cutter show gradients of 540HV in WC-Co bit and 350HV in bit covered by the polycrystalline diamond layer. Such gradients have never been reported before to our knowledge

Gradation process by imbibition in WC-Co for mining tools application

International audienceContinuous composition gradients of several millimetres were generated in commercial WC-Co cutters to improve their shock resistance. This important gradation was obtained in one-step by using the imbibition process. The effects of this thermal processing were analysed in terms of microhardness, cobalt concentration and WC grain size. A gradient of a 300 HV amplitude is measured in the 8 mm-height sample treated by the imbibition process in association with a boron-rich coating. This gradient was preserved after the HPHT (high pressure – high temperature) step used for the diamond table deposition on the WC-Co cutter. To our knowledge, such gradients have never before been reported and should certainly increase cutter service life

Process for the production of an element comprising at least one block of dense material constituted by hard particles dispersed in a binder phase : application to cutting or drilling tools

A process is presented which produces at least one block of dense material constituted by hard particles dispersed in a binder phase, it being possible for the dense material to be enriched locally with binder phase by imbibition. The process includes bringing at least one imbibition area of a surface of the block, preferably coated with a coating material, into contact with an imbibiting material which locally enriches the block with binder phase. The block in contact with the imbibiting material is then subjected to a suitable thermal cycle constituted by heating, temperature maintenance and cooling. This serves to bring some or all of the imbibiting material and the binder phase of the block into the liquid state in such a manner that the enrichment with binder phase takes place solely through the imbibition area. The block is used in connection with the building of a drill bit or tool

Procédé pour fabriquer une pièce comprenant au moins un bloc en matériau dense constitué de particules dures dispersées dans une phase liante : application à des outils de coupe ou de forage

Procédé pour fabriquer une pièce comprenant au moins un bloc (1) en matériau dense constitué de particules dures dispersées dans une phase liante, le matériau dense étant susceptible d'être enrichi localement en phase liante par imbibition, procédé selon lequel on met au moins une aire d'imbibition (4) d'une surface (3) du bloc au contact d'un matériau d'imbibition (2) capable d'enrichir localement le bloc en phase liante, puis on soumet le bloc au contact du matériau d'imbibition à un cycle thermique adapté, constitué d'un chauffage, d'un maintien en température et d'un refroidissement, de façon à passer partiellement ou totalement à l'état liquide le matériau d'imbibition et la phase liante du bloc, de telle sorte que l'enrichissement en phase liante se fasse uniquement à travers l'aire d'imbibition

Polymer-based nanocomposites: Overview, applications and perspectives

Polyamide 6 and pristine montmorillonite have been melt blended in an extruder and water was injected into the melt in order to produce polyamide-based nanocomposites. The pristine clay was found to be exfoliated and dispersed homogenously in the polyamide. A mechanism explaining the formation of such nanocomposites is presented. Concentrated systems were achieved and redispersed in polypropylene by reactive processing. It is shown that, by this way, polyamide acts as a "primary" compatibiliser, with the maleic anhydride modified polyolefin playing the role of a "secondary" compatibiliser. (C) 2006 Elsevier B.V. All rights reserved