Microstructural Characterization of WC-Co Cemented Carbide Processed Using Selective Laser Sintering

Tungsten Carbide alloy (WC-Co), which is also known as cemented carbide, is used in many industries including manufacturing and mining due to their high hardness and strength Generally, parts made from cemented carbides are produced using the conventional powder metallurgy route which requires a high level of skill, a time-consuming process as well as strenuous post processing techniques to obtain a good part A possible alternative is the use of Powder Bed Fusion (PBF) techniques such as Selective laser melting (SLM) and Selective laser sintering (SLS). The advantage of lesser manufacturing time, flexibility of design, intricacy of parts produced and lightweight structures such as lattice structures makes it even more appealing Yet, PBF techniques do not have widespread adoption in industry because of challenges with parts fabricated using PBF processes. Rough surface finish, residual stresses, porosity, micro cracks, non-equilibrium phases and texture come up as a result of parts being affected by repeated thermal cycles, large temperature gradients and relatively high cooling rates during solidification and solid-state phase transformations upon cooling This affects the microstructural integrity and properties such as fatigue strength, hardness and fracture toughness. Most recently, there has been the need to adopt metal 3D printing for processing cemented carbides using SLM and SLS and evaluating the structure and properties of the processed parts This is challenging because there are currently no approved powders for 3D printing cemented carbides such as WC-Co neither are there any 3D printers licensed to print cemented carbides. The aim of this study is to adopt SLS technique for printing WC-Co cemented carbide and evaluate the microstructural integrity of the as-printed material. An initial study was done to obtain powders for orienting including parametric studies on the optimum printing parameters that gave a relatively good printed part. After, printing, extensive microstructural characterization techniques including electron microscopy and X-ray Diffractometry (XRD) were used to ascertain the structure and properties of the printed material.