Wear mechanisms of WC-Co drill bit inserts against alumina counterface under dry friction: Part 2 — Graded WC-Co inserts

• Published in: International journal of refractory metals & hard materials Vol. 48; pp. 65 - 73
• Main Authors: Yahiaoui, M., Paris, J.-Y., Denape, J., Colin, C., Ther, O., Dourfaye, A.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2015; Elsevier
• Subjects: Alumina counterface; Aluminum oxide; Boride phase; Borides; Cemented carbide; Cemented carbides; Cobalt; Condensed Matter; Friction; Imbibition; Inserts; Materials Science; Phases; Physics; Reactive imbibition; Third body; Cemented carbide; Reactive imbibition; Boride phase; Third body; Alumina counterface
• ISSN: 0263-4368; 2213-3917
• DOI: 10.1016/j.ijrmhm.2014.07.024

The tribological behaviour of innovative graded cemented carbide inserts were studied by using a rotary tribometer and abrasive alumina counterfaces. This work completes the study made on commercial inserts with homogeneous cobalt content. Inserts with three types of graduation processes were considered: inserts with borides WCoB phases, imbibed inserts and inserts combining both processes (i.e. inserts with reactive imbibition). Physicochemical and mechanical measurements show that the WCoB phases increase the hardness towards the active surface and the imbibition increases the insert core fracture toughness. The wear tests indicate that the boride phases lower the friction coefficient. In addition, as for the commercial inserts, cemented carbide volumes with higher cobalt content also reduce the friction coefficient. Concerning the wear results, the boride phases improve the abrasion resistance. By applying a third body approach, the WCoB phases limit the introduction of cobalt binder in the source flow, the cohesion of alumina particles in the internal flow and the formation of an abrasive paste in the contact. The imbibition process, where the cobalt migration is controlled, does not affect the wear resistance by avoiding a cobalt enrichment of the cemented carbide near the active surface. •We study the wear behaviour of graded WC-Co inserts against an alumina counterface.•We describe that the boride phases lower the friction coefficient.•We show that the boride phases improve the abrasion resistance.•We explain that the boride phases avoid the action of an abrasive third body.•A controlled imbibition process does not affect the wear resistance.