Grain Orientation Texture Control and Its Effects on the Hardness and Abrasion Resistance of Sintered Carbides

Abstract

The objective of this research work is to develop and evaluate a fabrication procedure that enables a degree of control over the surface and sub-surface grain orientation texture of spark plasma sintered carbides and to investigate its effects on the hardness and abrasion resistance of the material. The composite material used in this investigation is a mixture of tungsten carbide (90% WC) and cobalt (10% Co) powders. The fabrication procedure predominantly involves mixing measured weight fractions of WC and Co powders with a temporary binder (polyvinyl alcohol) so that the mixture is malleable into thin sheets, and then subjecting these to multiple high-pressure rolling operations – subjecting these sheets to high-pressure rolling is primarily responsible for partially “aligning” the grains in order to have a dominant orientation. From these sheets, a number of discs were cut, stacked, thermally de-bound (to remove the temporary binder), and then spark plasma sintered to obtain bulk cemented WC-Co samples. The relationships between the degree of orientation texture and the fabrication process conditions were investigated through X-ray diffraction (XRD). Certain mechanical properties of the samples were then characterized, including indentation hardness testing and scratch testing using a diamond engraver, in order to evaluate their comparative hardness and abrasion resistance. Manipulating the grain orientation texture in this manner thus has potential to enable a level of control over numerous mechanical properties of WC-Co hard-material composites.