Hardness and indentation fracture toughness of carbides in implantation-modified carbide-metal composite surfaces

Abstract

Microhardness and indentation fracture toughness measurements were made on WC and TiC carbides (105 – 205 μm in size) in two model carbide-metal composite samples prepared by the laser melt particle injection process. High fluence titanium implantation of the composite surfaces resulted in softening of the carbides as well as in a reduced incidence of lateral crack break-out and carbide shattering during indentation fracture. Although the incidence of radial crack trace formation increased at the higher indentation loads (greater than 500 gf), crack length measurements at low load indents indicated an apparent increase in the fracture toughness K c of the carbides with implantation. As a result of these changes, reduced damage and material loss ( i.e. increased wear resistance) during abrasion and erosion are anticipated for implanted carbides. Indentations made on a third sample indicated a fracture resistance dependence on carbide size. TiC carbides (74 – 88 μm) in this sample shattered at indentation loads 1 3 - 1 2 of those used on the samples of larger carbide size.