Fracture toughness determination of alumina and cemented carbide with different testing methods

Fracture toughness of a sintered alumina and two tungsten carbide-cobalt materials was determined using four-point-bend specimens with straight through and chevron notches and with the short rod specimen. With the specimens with a straight through notch a lower Ksub(k) was measured for Al2O3 and a higher for WC-Co compared to the chevron-notched specimens. This behavior was explained by the different shapes of the crack growth resistance curves and the different critical notch radii. For Al2O3 a steeply rising crack growth resistance curve and of notch width on the evaluated toughness is discussed. (orig.)