Fracture behavior of binder jetting 3D printed cemented carbides: Influence of printing direction and testing configuration

Abstract

Cemented carbides exhibit an outstanding performance as materials for tools and components. As applications of these materials become more and more challenging, complex tool geometries are often needed to suit the extreme requirements. Within this context, Additive Manufacturing (AM) has emerged as a popular option, as they combine a group of processing techniques involving layer-by-layer printing. In general, AMed samples are expected to exhibit characteristics linked to the layer-by-layer wise shaping route; and hence, a dependence of the mechanical properties on layer directionality may come out. It is then the main objective of this study to investigate, document and understand the fracture behavior of WC-12_wt.Co samples fabricated via binder jetting printing (BJT), as a function of layer assemblage orientation. In doing so, specimens corresponding to four combinations of two printing directions and two testing configurations were studied. Use of samples micronotched by means of ultrashort pulsed laser ablation allowed to conclude that, similar to microstructure and hardness, fracture toughness of BJT cemented carbides exhibits an isotropic behavior. However, this is not the case for flexural strength, property for which a strong dependence on the relative orientation of layer assemblage is assessed. In this regard, higher strength and wider data dispersion are attained as loading is applied perpendicular to planes containing layer interfaces, as compared to the parallel case. Similar characteristic strength levels together with relatively lower Weibull modulii, as compared to conventionally manufactured WC-Co grades with similar microstructures, are determined. Extensive and detailed fractographic inspection of broken surfaces allows to conclude that specific location, orientation and distribution of flaws intrinsic to layer interfaces as well as printing route followed, depending on testing configuration, are key factors for defining strength level and dispersion in each case.