EFFECTS OF SURFACE-ROUGHNESS ON THE FLEXURAL STRENGTH OF A HARDMETAL

A detailed study to assess the effect of surface roughness on three-po int flexural strength of a WC-Co hardmetal was undertaken. Eight diffe rent types of surface finish were investigated; R-parameters were dete rmined and Weibull statistics were applied to analyse the fracture str ength results. It was concluded that the highest values of rupture str ess and Weibull modulus are obtained when the surfaces and the edges o f the specimens are submitted to careful and gradual, step-by-step, su rface-finishing operations and a 1 mum diamond paste is used as the fi nal abrasive. Only when very fine finish is attained may the results o f rupture stress then represent the intrinsic behaviour of the materia l.