The Influence of Residual Stresses Induced by Grinding on the Fracture Toughness of Cemented Tungsten Carbide

Grinding of cemented tungsten carbide blanks for cutting tools is responsible for the inducement of residual stress, which affects crack formation and propagation, influencing their lifetime. However, the direct measurement of residual stress is cost intensive and an alternative is proposed in this work, in which a mathematical relation (logistic function) between x-ray diffraction measurements and fracture toughness obtained by hardness measurements is generated for cemented tungsten carbide ground with different conditions. By means of statistical methods, a strong correlation (Pearson correlation coefficient higher than 0.85) between both variables was demonstrated. Moreover, it was found that higher values of fracture toughness as well as of compressive residual stresses can be obtained with the application of higher single grain chip thicknesses until a critical value of 0.25 µm is achieved, from which a stable behavior is observed. Grinding process can lead to an increase in the fracture toughness from ~ 7 to ~ 12 MPa m^1/2, while compressive residual stresses change from ~ 300 to ~ 900 MPa.