Matéria (Rio de Janeiro)
On-line version ISSN 1517-7076
DIAS, A.M.S.; MIRANDA, J.S. and GODOY, G.C.. Evaluation of fracture toughness by indentation testing in hardmetal tools. Matéria (Rio J.) [online]. 2009, vol.14, n.2, pp. 869-877. ISSN 1517-7076. http://dx.doi.org/10.1590/S1517-70762009000200009.
The Vickers indentation testing is commonly used for hardness surface measurement for different types of materials. This testing method is quite versatile and it is used to evaluate different mechanical properties, such as Young modulus (E) and fracture toughness (KIC), particularly in sintered materials like the tungsten carbide with cobalt (WC-Co). This material is used in the manufacturing of cutting tools, once it has very high surface hardness and also compression strength, although low fracture toughness values, which decreases its service life when submitted to high wear conditions. However, due to those peculiar mechanical properties, the WC-Co presents difficult analysis through conventional testing techniques, mainly considering fracture toughness evaluation. For that reason, the aim of this work was to evaluate experimentally the hardness and fracture toughness in two commercial tools, made of tungsten carbide with cobalt, through Vickers indentation testing. A simple and low cost procedure of sample preparation was used, consisted of a selective polishing, in order to avoid superficial residual stresses. In sequence, the scanning electron microscope (SEM) was used to evaluate the distribution of tungsten carbide in the cobalt matrix. The results of this analysis have shown uniformity in the tungsten carbide dispersion in the cobalt matrix, indicating that the sample preparation process did not create great values of superficial residual stresses. The experimental hardness and fracture toughness values were obtained, which have agreed with the ones found in the literature.
Keywords : Vickers indentation; fracture toughness; SEM.